Insights and Perspectives

• Mechanisms of High Cadmium Accumulation by Wheat Grown in Alkaline Soils and Prospects for Mitigation Strategies

  GAO Yan, FAN Guangping, LI Yuntao, SHI Gaoling, TONG Fei, LI Jiangye, Chen Wei, GE Chenghao, ZHOU Dongmei

  2026,63(4):995-1006, DOI: 10.11766/trxb202502060046

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  Abstract:

  Wheat, serving as a staple food for one-third of the global population, has long been overlooked in terms of its grain cadmium (Cd) accumulation capacity and the resulting dietary exposure risks. By integrating analyses of global literature and our recent research findings, this study preliminarily clarified that wheat grown in contaminated alkaline soils exhibited high Cd accumulation capacity with elevated risks of exceeding food safety thresholds. In rice-wheat rotation farmland systems, the Cd enrichment factor of wheat grains at the same sampling points was significantly higher than that of rice. Remarkably, wheat grains exceeded China’s food safety standard in alkaline soils even when the Cd contents remained below the national risk screening threshold. Elevated soil pH levels induced a pronounced increase in wheat's contribution to adult daily dietary cadmium intake, while concurrently reducing rice’s contribution, demonstrating that alkaline soil conditions amplify Cd exposure risks specifically through wheat-derived dietary pathways. The article further discussed the Cd speciation in alkaline soils and their influencing factors, analyzed the mechanisms related to Cd migration and its chemical binding forms at the root-soil interface, and explored the interaction effects between Cd and trace elements during uptake and translocation by wheat. In order to develop wheat-safe production technologies adapted to the characteristics of alkaline Cd-contaminated soils, future research should strengthen investigations into the molecular mechanisms of Cd interface processes in the wheat rhizosphere and Cd-trace elements interactions on uptake and translocation by roots.

Reviews and Comments

• Research Progress and Future Perspectives on Soil Nitrogen Cycling in Tropical Croplands of Hainan

  JU Xiaotang, ZHANG Chong, ZHANG Limei, SONG Xiaotong, LI Tingyu, LIU Shuoran, LIU Siyi

  2026,63(4):1007-1017, DOI: 10.11766/trxb202503020097

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  Abstract:

  Hainan is the only province in China entirely situated within the tropical region, characterized by abundant light, heat, and water resources, making it the most typical tropical agricultural production base in China. However, restrictive factors such as "poor, acidic, and leaky" soils, coupled with high nitrogen (N) fertilizer inputs in crop cultivation, led to significant risks for N loss in farmlands and severe environmental pollution. The agricultural non-point source pollution situation in Hainan is severe, N and phosphorus discharged from agriculture enter nearshore waters via short transport pathways, leading to serious degradation of coral reefs and seagrass beds. However, the generally weak foundation of research on N cycling in Hainan's tropical farmland soils hindered the development of scientific and targeted N regulation measures. In response to the characteristics of tropical agricultural resources, we propose that future research should focus on four key areas: the characteristics of N transformation, the fate and loss pathways of N, the mechanisms of efficient N utilization in crops, and the principles and regulation measures for reducing N fertilizer application while enhancing efficiency. More attention should be paid to the effects of organic matter-mediated soil fertility and acidity improvement on soil N transformation in Latosols, the mechanisms underlying high ammonia emissions in acidic soils and nitrate accumulation in deep soil profiles, as well as the impact of organic material inputs on nitrous oxide emissions. We emphasize the need to clarify the relationship between the transformation and migration characteristics of N in farmland soils and crop N use efficiency, and to elucidate the mechanisms by which soil carbon (C) pool expansion affects N transformation, migration, retention, and loss prevention. Thus, to propose a principle for reducing N fertilizer application while enhancing efficiency, centered on "increasing C to retain N, coupling C and N, controlling losses, and coordinating N supply". This approach will form an innovative theory and solution. The finding would provide scientific and technological support for the development of efficient and green tropical agriculture and offer a scientific basis for understanding regional differences in N cycling across global climate-soil zones.

• Research Progresses and Future Prospects on Soil Pipe Erosion

  XU Ximeng, LIANG Wenqian, ZHENG Fenli

  2026,63(4):1018-1030, DOI: 10.11766/trxb202507020322

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  Abstract:

  Soil pipe erosion is a special erosion process caused by the formation and expansion of underground soil pipes. It makes important contributions to the development process of gully erosion and the gravitational erosion processes, such as landslides and collapse. It mainly affects the runoff-erosion-sediment transport process of the slope and watershed by changing the near-surface soil hydrological conditions. However, due to its concealment and complexity of genesis, related quantification research faces great challenges. Based on the bibliometric analysis method, this paper systematically reviews the development history of soil pipe erosion research and identifies the hot spots and development directions in the field of soil pipe erosion research. Aiming at the current research focus, this paper overviews the dynamic process of soil pipe formation, summarizes the multiple factors affecting soil pipe erosion, and analyzes the dynamic mechanism and harm of soil pipe erosion. In the future, it is necessary to innovate the monitoring methods of soil pipe erosion, clarify the dynamic mechanism of soil pipe erosion, quantify the contributions of key influencing factors, and develop a water erosion prediction model containing the processes of soil pipe erosion. This will provide a scientific basis for soil pipe erosion risk assessment and optimization of governance measures.

Research Articles

• Comparative Study on Soil Spatial Provenance Based on Soil Property Similarity Clustering and Pedogenic Environment Inference

  SHEN Yun, LIU Feng, LI Decheng, ZHENG Guanghui, PAN Qifeng, ZENG Rong

  2026,63(4):1031-1044, DOI: 10.11766/trxb202505280243

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  Abstract:

  【Objective】Soil spatial traceability has significant application value in forensic soil science and judicial identification.【Method】This study, based on 265 surface soil samples from Anhui Province, compares two soil provenance strategies: (1)a similarity-matching and spatial clustering approach, which filters similar samples using spectral and physicochemical property similarities and applies the DBSCAN algorithm to determine the potential source area of unknown samples; and(2)an inverse inference approach based on pedogenic environmental factors, which employs a random forest model to predict environmental variables such as soil parent material, land use, topography, climate, and vegetation, and infers provenance by integrating spatial distribution maps. By simulating provenance analysis, the accuracy and applicability of the two strategies were evaluated. 【Result】The results indicate that the similarity-matching strategy achieves higher localization accuracy under conditions of strong spatial proximity and well-established databases, while the inverse pedogenic environment inference strategy demonstrates superior spatial constraint capabilities in regions with limited databases or strong spatial heterogeneity. 【Conclusion】Each strategy has its own advantages, and their integrated application holds promise for further improving the accuracy and resolution of soil spatial provenance analysis.

• Manganese Speciation in Hangzhou’s Agricultural Soils: Distribution Patterns and an Artificial Neural Network Predictive Model

  YI Zun, MA Jun, ZHENG Panrui, ZENG Huili, CHEN Baoliang, XIAO Xin

  2026,63(4):1045-1056, DOI: 10.11766/trxb202506100271

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  Abstract:

  【Objective】The speciation of metal elements in soil determines their environmental functions and effects. Developing predictive models for element speciation based on soil properties is an important approach to enrich the informational value of such data and reduce the number of required analytical indicators. This is of great significance for data mining under conditions of limited information. Most metal elements, as important trace elements in soils, are widely present and affect crop growth and soil ecosystem health. Their forms and valence state have significant effects on their migration and transformation mechanisms on the surface and underground. Therefore, studying the metal forms in soil helps to understand their geochemical cycles and facilitate the evaluation of their impact on soil electronic networks, providing scientific basis for developing natural soil remediation methods and supporting the green, efficient, and sustainable use of soil. 【Method】This study selected manganese (Mn), a representative trace metal and redox-active element in soils, as the target. A total of 29 surface agricultural soil samples from different locations in the urban area of Hangzhou were collected and analyzed. The samples were characterized for their physicochemical properties, including total organic carbon (TOC), pH, total Mn content, and cation exchange capacity (CEC). The classical Tessier sequential extraction method was used to determine five Mn fractions in the soil: exchangeable, carbonate-bound, Fe-Mn oxide-bound, organic matter and sulfide-bound, and residual, and their correlation with soil physicochemical properties was evaluated. A neural network-based weight analysis method was then applied to predict Mn using soil physicochemical properties as input variables. 【Result】The results show that the soil pH was mainly alkaline, with abundant CEC and organic matter content. However, CEC exhibited high variability and was probably unevenly distributed and may be easily affected by external factors. Further analysis revealed that the average total Mn content in Hangzhou soils was 1.46 g·kg^-1, higher than the background value for Zhejiang Province. Among the Mn fractions, Fe-Mn oxide-bound and residual forms were dominant, followed by organic/sulfide-bound, while exchangeable and carbonate-bound forms were the least abundant. Spatial distribution showed a layered pattern for exchangeable and carbonate-bound Mn, decreasing from north to south. Significant positive correlations were observed among most Mn fractions, except for the residual form. Among the physicochemical factors, pH showed the strongest correlation with Mn speciation, particularly a highly significant negative correlation with the exchangeable and carbonate-bound species. CEC was positively correlated with carbonate-bound and organic-bound Mn, while soil organic matter showed no significant correlation with any Mn fraction. Also, the neural network modeling demonstrated that using three parameters: total Mn, pH, and CEC, yielded the best prediction performance, with the coefficient of determination (R²) improving from 0.41 to 0.85, and prediction error reducing from 65% to 16%. 【Conclusion】The findings of this study provide theoretical support for predicting metal speciation in soils based on the observed distribution patterns of Mn and its relationships with soil physicochemical properties. The neural network-based modeling approach proposed herein offers a feasible strategy for deep mining of conventional soil survey data and enables rapid estimation of specific metal species. This contributes to a better understanding of the behavior of Mn in the soil redox network.

• Effects of Straw Mulching and Biochar Interlayer on the Water and Salt Movement in Newly Reclaimed Cultivated Land in Coastal Areas

  LE Lige, CHENG Jieyu, HUANG Zhonghui, LÜ Yihao, XIE Wenping, LIN Jinshi, JIANG Fangshi, HUANG Yanhe, ZHANG Yue

  2026,63(4):1057-1070, DOI: 10.11766/trxb202505210233

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  Abstract:

  【Objective】The key to achieving sustainable utilization of newly reclaimed cultivated land in coastal areas is to control the upward accumulation of soil salinization. In this context, mulching and subsoil interlayer placement are widely adopted measures to mitigate salt accumulation in the surface soil. However, the combined effect of straw mulching with a biochar interlayer on soil water and salt transport in the southeastern coastal regions remains unexplored.【Method】This study considered a newly reclaimed cultivated land in the coastal areas of Fujian Province as the research object, and explored the impacts of biochar salt-barrier layer(with burial depths of 25 cm and 45 cm)combined with straw mulching on the distribution of water and salt during the water infiltration and evaporation processes of saline soils.【Result】The results demonstrated that the incorporation of a biochar interlayer significantly decelerated the wetting front advancement during the leaching process. Among all treatments, T3-25 (straw mulching combined with a biochar interlayer at 25 cm depth) exhibited the most pronounced effect, reducing the migration distance by 4.07% compared to the control (CK) after 73 hours of infiltration. As the leaching time prolonged, the salt content of the leachate in all treatments gradually decreased. On the first day of leaching, the T3-45 treatment (surface straw mulching + 45 cm biochar interlayer)had the highest leachate salt content, reaching 16.24 g·L^-1. In terms of total desalination amount, CK outperformed all interlayer treatments due to the absence of interlayer obstruction; it also had the highest pH value (8.07) after leaching. In the 0～45 cm soil layer, a significant reduction in soil salt content was observed across all treatments. The control (CK) treatment exhibited the highest desalination rate at 68.68%, while the T3-45 treatment demonstrated a superior desalination effect compared to T3-25. Regarding specific ions, the T3-25 treatment showed the most pronounced decrease in Na⁺ content, with an average reduction of 74.76%. Also, under the evaporation condition with a groundwater table depth of 65 cm, the soil water content in the 0～45 cm layer was significantly higher in both T3-0 (straw mulching only) and T3-45 treatments than in CK. Following 45 days of evaporation, a notable increase in both total salt and Na⁺ content was detected in the 0～45 cm soil layer for all treatments. Additionally, the T3-45 treatment displayed the lowest increments in the salt accumulation rate and Na⁺ content, at 3.49% and 14.06% respectively, relative to pre-evaporation levels. In contrast, the CK treatment exhibited the most severe salt accumulation, with corresponding increases of 54.21% and 150.19%. By the end of the evaporation stage, the soil pH in all treatments had increased significantly compared to both pre-evaporation values and the CK, with the relative increase over CK ranging from 0.71% to 3.57%.【Conclusion】Based on the experimental results, the combined application of straw mulching with a biochar interlayer at 45 cm depth proved most effective. It not only reduces water evaporation but also achieves the best performance in promoting desalination and inhibiting the salinization of coastal saline soil. This study found that the effects of the T3-25 treatment and the T3-45 treatment are similar. In practical applications where upfront cost-effectiveness is a consideration, the improvement measure of straw mulching with a biochar interlayer buried at a 25 cm depth can be considered for newly reclaimed coastal farmlands in the southeast region.

• Interactive Effects of Poly-γ-Glutamic Acid and Irrigation Quota on Saline-Alkali Soil Properties and Cotton Yield

  WANG Shan, ZHANG Jinzhu, WANG Zhenhua, ZHANG Jihong, LIU Mengjie, MA Zhanli, ZHENG Jiliang

  2026,63(4):1071-1084, DOI: 10.11766/trxb202506130284

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  Abstract:

  【Objective】To establish scientifically grounded, synergistic regulatory approaches for the comprehensive mitigation of the persistent challenge of saline-alkali soil degradation in cotton-growing systems, this study conducted a controlled field experiment during the 2024 cotton season on moderately saline-alkali soils in Manas County, Xinjiang. The objective was to elucidate how the integrated application of poly-γ-glutamic acid (γ-PGA) and regulated irrigation influences soil biochemical processes, cotton physiological performance, yield formation, and fibre quality under field conditions.【Method】A two-factor randomized block design was established, involving three γ-PGA rates (F1: 7.5 kg·hm^-2; F2: 15 kg·hm^-2; F3: 22.5 kg·hm^-2) and two irrigation quotas (W1: 4 000 m³·hm^-2; W2: 4 500 m³·hm^-2). Comprehensive measurements included soil physicochemical indices (Electrical conductivity (EC)-based salinity and pH variations across growth stages), key enzymatic activities (polyphenol oxidase, catalase, urease, sucrase), root morphological traits (length, diameter, biomass ratios), organ-specific dry matter accumulation, and yield and fibre parameters (boll number, lint percentage, composite quality index).【Result】Compared with F1 and F2, the F3 treatment effectively suppressed peak soil salinity and pH, concurrently elevating enzymatic activity, particularly urease, which increased by 30.13%-35.22 %. Nevertheless, the response plateaued beyond the F3 level, suggesting diminishing returns under higher γ-PGA concentrations. Enhanced enzymatic activity and improved rhizosphere conditions promoted root proliferation and biomass accumulation, resulting in a moderate but statistically significant yield increase (3.02%-27.96 %). Likewise, a higher irrigation quota (W2) alleviated surface salt accumulation and improved enzyme activities by 9.16%-48.33%, although excessive irrigation risked secondary salinization through capillary rise and nutrient leaching. Also, multivariate analyses (Principal component analysis and Pearson correlation) revealed a strong positive correlation (P < 0.05) between enzyme activity and yield traits. At the same time, soil salinity and alkalinity showed negative correlations with fibre quality indices, emphasizing the trade-off between osmotic stress alleviation and fibre maturation under saline conditions.【Conclusion】The combined application of 22.5 kg·hm^-2 γ-PGA with 4 500 m³·hm^-2 irrigation proved the most efficient configuration within the tested range, primarily by ameliorating the rhizosphere microenvironment (lower EC/pH and enhanced enzymatic turnover) and optimizing photosynthate allocation to reproductive organs. However, the overall improvement remains conditional on soil salinity thresholds, long-term stability, and economic feasibility. Thus, while the integrated γ-PGA-irrigation strategy significantly enhances cotton yield and fibre quality in saline-alkali soils, its scalability and sustainability under variable climatic and hydrological regimes warrant further investigation.

• Screening of Alkali-Producing Strains and Their Amendment Effect on Acidic Soil

  LIU Chong, LIU Yang, WANG Dan, LU Yusheng, GU Jun, ZHU Xiaoxuan, WEN Shuheng, WANG Yong, ZHU Zixin, LI Yaying, GU Wenjie

  2026,63(4):1085-1096, DOI: 10.11766/trxb202505230237

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  Abstract:

  【Objective】Managing soil acidification in farmland soils is of great significance to ensure national food security and sustainable agricultural development. Microorganisms have important application value in soil improvement. However, the research on alkali-producing microorganisms and the mechanism of improving acid soil is still lacking. This study aimed to systematically explore the mechanisms of acidified soil remediation by alkali-producing microorganisms, with a focus on overcoming the limitations of functional microbial resource scarcity and field application technology gaps. 【Method】Systematic screening was employed to isolate alkali-producing microorganisms from acidic soils in South China. Indoor simulation experiments evaluated its pH elevation capacity through repeated inoculation. Genomic analysis revealed its urease gene cluster (ureABCEFGD), and field trials assessed the effects of single-dose application on soil pH and crop yield. 【Result】We screened 109 alkali-producing bacterial strains (65% belonging to Bacillus spp.) and 24 fungal strains (33% Trichoderma spp.). The alkali-producing ability and stability of alkali-producing bacteria were generally stronger than those of fungi, with Lysinibacillus fusiformis LW-3 identified as a key strain. Within 15 weeks of continuous culture, repeated inoculation of L. fusiformis elevated soil pH by 1.5 units, reduced exchangeable aluminum by 23.46%, and decreased hydrolytic acid by 31.80%. Genomic analysis revealed that L. fusiformis LW-3 carried a complete urease gene cluster (ureABCEFGD). Lysinibacillus fusiformis LW-3 could ameliorate acid soil by enhancing soil urease and protease activities, metabolizing ammonia, consuming hydrogen ions through bicarbonate, and reducing the content of active and potential acids in soil. Field application confirmed that soil pH stably increased by 0.2 units and enhanced Chinese cabbage yield by 11.6%. 【Conclusion】This study elucidated a multi-pathway synergy mechanism for acidified soil remediation, including alkali production, enzymatic activity regulation, and acid speciation transformation. These findings indicate that the strain L. fusiformis LW-3 has good application prospects in acid soil amendment, providing technical support for alkaline-producing microbiome-driven soil acidification management.

• Effect of Soil Aggregates on Stoichiometry Characteristics Nutrient Under Different Land Use Types

  YANG Qian, LIU Muxing, XU Jiapan, YI Jun, WANG Chuantao, DING Shuting

  2026,63(4):1097-1109, DOI: 10.11766/trxb202506030256

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  Abstract:

  【Objective】 Land-use change is a primary driver of soil structure alteration and nutrient cycling in ecosystems. In subtropical hilly areas of China, which are ecologically fragile and experience significant land-use pressure, understanding the interplay between soil physical structure and biogeochemical cycles is crucial for sustainable land management. The stability of soil aggregates and the ecological stoichiometry of nutrients serve as critical indicators for evaluating ecological restoration and soil quality. Thus, this study aims to elucidate the mechanism by which typical land use practices in subtropical hilly areas influence nutrient variations through alterations in the distribution characteristics of soil aggregates. 【Method】 We examined soils from three representative land use types(forestland, tea garden, and cultivated land)in Yingshan County, Hubei Province. Key stability indices, including the mean weight diameter (MWD), geometric mean diameter (GMD), soil erodibility (K), and fractal dimension (D), were calculated. Utilizing both stoichiometric methods and multivariate statistical models, we analyzed the relationship between aggregate stability levels and the distribution patterns of soil organic carbon, total nitrogen, and total phosphorus. 【Result】 The results revealed that: (1) The content of >5 mm aggregates in forestland soils was 4.11 and 1.89 times higher than that in tea garden and cultivated land, respectively. Both the mean weight diameter (MWD) and geometric mean diameter (GMD) followed the order: forestland > cultivated land > tea garden. The tea garden soil exhibited the highest erodibility (K) value and fractal dimension (D) value. (2) The soil organic carbon content in forest land was significantly higher than in other plots, reaching 10.22 g·kg^-1. Total nitrogen content followed the order of forest land > tea garden > cultivated land, while total phosphorus content exhibited the opposite trend. Both C: P and N: P ratios were highest in forestland soils, followed by cultivated land and tea garden. (3) Aggregate characteristics were significantly correlated with nutrient indicators (P< 0.05), with the macroaggregates (> 5 mm) playing a major role in shaping C: P and N: P ratios. Also, the partial least squares path modeling (PLS-PM) showed good fit(goodness-of-fit > 0.61)and the path coefficients indicated that the influence pathways of aggregate particle size on nutrient stoichiometric ratios varied under different land use types, with the direct effect being most pronounced in forested areas. 【Conclusion】 This study illustrates that changes in land use significantly affect the relationship between soil structure and nutrient cycling. Forestland, which experiences minimal disturbance, encourages the creation of stable macroaggregates. This process enhances long-term nutrient sequestration and maintains a balanced stoichiometric environment. On the other hand, intensive management practices in tea gardens and cultivated lands can disrupt aggregate stability. This disturbance leads to structural degradation and a notable stoichiometric imbalance. Therefore, it is crucial to preserve forestland and implement sustainable soil practices in managed lands. This approach will significantly improve soil quality and promote ecological sustainability in subtropical hilly areas.

• Long-term Soil Volumetric Water Dynamics and Driving Factors of Typical Vegetation Restoration Types in the Loess Hilly-Gully Region

  YAN Yaru, FENG Tianjiao, LIU Yabo, WU Tianyu, WANG Ping

  2026,63(4):1110-1125, DOI: 10.11766/trxb202510090489

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  Abstract:

  [Objective]To curb the trend of soil degradation and improve ecological environment quality, large-scale and long-term vegetation restoration projects have been carried out in the Loess Plateau region. However, the long-term variations in soil volumetric water under typical vegetation restoration types, especially the variability and differences in soil moisture, have not been given in-depth attention. [Method]Therefore, this study selected typical artificial forests (Pinus tabuliformis, Platycladus orientalis, Robinia pseudoacacia) and natural forests (Quercus mongolica secondary forest) in the Loess Plateau remnant gully area as the subject focus. Based on a long-term sequence (2006—2025) of 0～200 cm soil volumetric water dynamics, combined with multi-phase soil physicochemical properties and vegetation growth attribute data, this study used one-way analysis of variance, principal component analysis, and Mantel test to explore the effects of soil physicochemical properties and vegetation growth parameters on the soil hydrological dynamics in long-term vegetation restoration. [Result]The results show that: (1) Significant soil moisture differences exist between vegetation restoration types: compared to artificial forests, the natural forest has a higher overall soil volumetric water content, with an average of 16.8%and a peak of 30.4%, and greater moisture stability, with an average coefficient of variation of 12.89%; (2) Significant differences exist in soil physicochemical properties and vegetation attributes among different vegetation restoration types. The natural forest has higher nitrogen (236.428 mg·kg^-1), phosphorus (488.575 mg·kg^-1), and organic carbon content (14.903 g·kg^-1) than the three artificial forests. The biomass and height of the tree and shrub layers are lower in the natural forest than in the artificial forests; (3)Principal component analysis and Mantel test analysis show that soil moisture differences are mainly influenced by both tree and understory vegetation attributes, while soil moisture variability is predominantly influenced by understory vegetation attributes. [Conclusion]This study can provide a theoretical basis for the conservation of natural forests in the region, the optimization of understory vegetation in plantations, the enhancement of water conservation capacity through the cultivation of understory vegetation, and the management of soil and water conservation.

• Study on Colloidal Properties of Purple Soil and Its Aggregation Kinetics Under Different Fertilization Treatments

  ZHANG Yiwei, Tian Rui, WU Wenfei, BI Linna, LÜ Runzhe, LI Hang

  2026,63(4):1126-1138, DOI: 10.11766/trxb202411010420

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  Abstract:

  【Objective】The aggregation and dispersion of soil colloids influence macroscopic phenomena such as soil structure, soil erosion, soil nutrients, and pollutant transport. This study aims to explore the process of purple soil colloid aggregation and its ion-specific effects under different fertilization treatments. Specifically, the study aims to elucidate the interactions and microscopic mechanisms from the perspective of the effect of fertilization on mineral composition, surface properties, and aggregation kinetics of purple soil colloids. 【Method】In this study, four fertilization treatments, no fertilizer (CK), urea alone (N), organic fertilizer replacing 10% urea nitrogen (LM), and organic fertilizer replacing 30% urea nitrogen (HM) were set up on a purple soil in Southwest China. After 60 d of incubation, the effect of fertilization on the colloid aggregation kinetics of purple soils and their causes were investigated by determining the colloid quantity, clay mineral composition and surface properties, and soil colloid aggregation process. 【Result】The colloids used in this study contained mainly hydromica, chlorite, montmorillonite, vermiculite, and kaolinite, and the short-term fertilization treatments had no significant effect on the colloid content and mineral composition. Compared to CK, the N treatment induced the highest surface charge density to the purple soil colloids, with the greatest electrostatic repulsion between particles whereas LM and HM treatments decreased the surface charge density, and the degree of decrease was directly proportional to the amount of organic fertilizer added. The aggregation kinetics of soil colloids differed under different fertilizations and the critical coagulation concentration (CCC) decreased in the order of N > CK > LM > HM. Under the same fertilization treatment, the CCC values of purple soil colloids showed an ion-specific effect, decreasing in the order of Na⁺, K⁺, Mg²⁺, and Ca²⁺. Also, correlation analysis showed that there was a strong positive correlation between the CCC values of purple soil colloids and the surface charge density and a strong negative correlation with the specific surface area and organic matter content. 【Conclusion】Different fertilization treatments affect the interaction force between soil particles mainly by influencing the surface chemical properties of purple soil colloids, thus, affecting the aggregation and dispersive behaviors of the colloids.

• Regulatory Effects of Key Components of Purple Soil on the Bioavailability of Cadmium

  LI Jie, HE Huayong, WEI Shiqiang

  2026,63(4):1139-1154, DOI: 10.11766/trxb202506120278

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  Abstract:

  【Objective】 Soil components serve as the material basis determining soil properties and heavy metal behaviors. However, the effects and mechanisms of different soil components on cadmium (Cd) adsorption performance, speciation, and bioavailability in purple soil remains elusive. 【Methods】This study employed selective removal and exogenous addition methods, combined with adsorption-desorption experiments, sequential chemical extraction, and pot bioassays, to investigate the effects of core components of OM (humic acid, HA and fulvic acid, FA), iron oxides, and manganese oxides on Cd adsorption performance, speciation, and bioavailability in purple soil.【Results】 The results showed that there were significant differences in the effects of the various components of purple soil on soil properties: the removal of organic matter (ROM) and iron oxides (RFe) significantly increased soil pH and specific surface area (SSA), while the removal of manganese oxides (RMn) had the opposite effect; the removal of each component significantly reduced soil cation exchange capacity (CEC), charge quantity (SCN), and density (σ₀), with the effects of RFe and RMn being the greatest; the addition of exogenous components had a significantly weaker effect on soil properties than component removal, and only the addition of organic matter-containing components (AHA and AFA) could increase soil pH and CEC, but significantly reduce SSA; the addition of manganese oxides (AMn) significantly increased SSA. The changes in soil components and properties regulated the environmental behaviors of Cd: ROM and RFe significantly enhanced the adsorption capacity and strength of soil Cd, while RMn had no significant effect; in the component addition treatments, only AHA and AMn could enhance the Cd adsorption capacity by soils. The availability of Cd (Avail-Cd) in purple soil was constrained by its occurrence form and had no significant correlation with adsorption capacity; among the various forms of Cd in the soil, only exchangeable Cd(EX-Cd) positively contributed to Avail-Cd, while carbonate-bound (CA-Cd), organic-bound (OM-Cd), and iron-manganese-bound (FeMn-Cd) all showed negative contributions. ROM and RFe, as well as AHA, promoted the transformation of EX-Cd to above less labile forms, thereby reducing soil Avail-Cd contents by 39.30% to 96.80%; while RMn, RFe-Mn, and AFA treatments acted the opposite, significantly increasing Avail-Cd contents by 2.38 times to 2.91 times.【Conclusion】 The pot experiment confirmed that the accumulation of Cd in pakchoi (Brassica chinensis L.) is mainly regulated by the availability of soil Cd. Changes in soil components altered the biological availability of Cd mainly by adjusting soil pH, CEC, OM, SSA and thereby the distribution of Cd forms in soils. This study clarifies the regulatory effects and mechanisms of soil key components on Cd bioactivity, providing a theoretical bases for soil pollution remediation and management.

• Phytic Acid-modified Biochar Reduces Soil Cd Release by Regulating pH and Aggregates Structure

  DI Dongliu, XIAO Jiang, GAI Xu, LI Pujun, CHEN Guangcai

  2026,63(4):1155-1166, DOI: 10.11766/trxb202507010321

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  Abstract:

  【Objective】Phytic acid-modified biochar exhibits excellent adsorption capacity for cadmium (Cd) in aqueous solution; However, its effectiveness and mechanisms in remediating Cd-contaminated soils remain unclear. This study systematically analyzes the dynamic impacts of phytic acid-modified biochar on soil properties, and Cd release in soil, and reveals the key mechanisms underlying biochar regulation of Cd movement in soil. 【Method】 Soil incubation experiments were conducted to systematically evaluate the remediation and amelioration effects of bamboo biochar (BBC), phytic acid-modified bamboo biochar (PABC), and sodium phytate-modified bamboo biochar (SPBC) on Cd-contaminated soils over various incubation periods (0, 10, 20, 60, 120, and 180 days). 【Result】The addition of biochar significantly altered the pH of both soil and soil solution and increased the electrical conductivity (EC). SPBC exhibited the highest EC and total carbon concentration in the soil solution, while PABC showed a distinct advantage in supplying total phosphorus, particularly in the short term. During the early and mid-phases (0-120 days), biochar treatment significantly reduced the Cd concentration in soil solution(24.60%-99.35%), with a significant dose-response effect, and SPBC exhibited the most effective remediation. In addition to their inherent adsorption mechanisms, biochar also inhibited Cd release indirectly by affecting the chemical (pH, total phosphorus, and total carbon), physical (aggregate structure), and biological properties (urease and acid phosphatase) of the soil and soil solution, with soil pH and micro-aggregate content identified as key factors influencing Cd release. In the later phase (120-180 days), enhanced soil aggregate stability further facilitated the remediation process, as biochar increased the activity of urease and acid phosphatase. 【Conclusion】 Phytic acid-modified biochar demonstrates strong potential for both Cd remediation and soil improvement in heavily contaminated soils, offering significant application value.

• Analysis of Research Progress and Development Trends of Land Reclamation at Home and Abroad Based on CiteSpace

  CAO Yin, ZHOU Xian, WANG Jian

  2026,63(4):1167-1179, DOI: 10.11766/trxb202504020154

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  Abstract:

  【Objective】This study examines the evolution and core issues of domestic and international research on homestead land reclamation.【Method】Using “homestead reclamation” and “homestead soil reconstruction” as search terms, relevant literature was retrieved and screened, and visual bibliometric analysis was performed with CiteSpace.【Result】Domestic studies emphasized land-use optimization, urban-rural integration, ecological protection, market mechanisms, and policy interactions with a practical “problem-countermeasure” orientation. However, international literature favored case studies, technological innovation, and mechanistic analyses of reclamation impacts. Nevertheless, both recognized soil quality as critical to reclamation success.【Conclusion】Future research should foster interdisciplinary collaboration, carry out long-term empirical studies, and support incentive-compatible policy frameworks so that rural land reclamation yields sustainable, mutually beneficial outcomes across ecological, social, and economic dimensions.

• Spatiotemporal Variation Characteristics of Agricultural Environmental Costs Under Fertilizer Input in Northeast China

  ZHANG Xilun, WANG Ping, LIU Yalong, WANG Jingkuan

  2026,63(4):1180-1190, DOI: 10.11766/trxb202505200230

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  【Objective】Northeast China is an important grain production base, and it is also one of the largest fertilizer consumption markets. Over the years, the application of many chemical fertilizers has led to increasingly prominent negative impacts on the agricultural ecological environment. Using the application rate of chemical fertilizer in Northeast China in the past three decades, it was estimated environmental cost (EC) from different potential pollution, and their comprehensive environmental cost(CEC)and environmental cost load (ECL). This research will provide a scientific basis for realizing agricultural sustainable development in Northeast China and ensuring China 's food security. 【Method】Combining energy analysis and disability-adjusted life year assessment, the spatial and temporal distribution characteristics of EC from different potential pollution sources, and their CEC and ECL were analyzed in Northeast China from 1990 to 2022. The EC in different provinces and cities and their potential causes were evaluated, and countermeasures and suggestions for reducing EC were put forward. 【Result】(1) From 1990 to 2022, the CEC of fertilizer application in Northeast China gradually increased, from 42.12 million yuan to 3 200.55 million yuan, an increase of 76 times, with an average annual growth rate of 14.49%. The growth rates of the 1990s, 2000s, and 2010s were 22.69%, 16.67%, and 7.78%, respectively, which gradually slowed down. (2) In 2022, the total EC of air, water, and soil pollution caused by chemical fertilizer application was 542.37 million yuan, 749.36 million yuan, and 1908.8 million yuan, respectively. Ammonia and nitrate, respectively, contributed the most to air, water, and soil pollution. Their ECs respectively were 467.92 million yuan, 691.76 million yuan, and 1 485.17 million yuan, reaching 82.64% of the total EC. (3) The largest change in CEC was mainly concentrated in the line from Jiamusi to Chifeng, while the smaller change was concentrated in the line from Yanbian to Dalian. The largest changes in ECL were mainly concentrated in most areas of Liaoning Province, Tongliao, Shuangyashan and the surrounding areas of Jixi, while the smaller changes were mainly in Siping, Yichun, Daxing'anling, and Xilinguole. 【Conclusion】 In the past three decades, the CEC of chemical fertilizer application in Northeast China has increased year by year, but the growth rate has gradually slowed down, indicating that the impact of chemical fertilizer application on the environment has been significantly alleviated. In addition, the EC and ECL showed obvious spatial distribution characteristics, which indicates that the impact intensity of the southern and southern coastal areas was stronger than the northern inland areas. In future research, it is recommended that the focus should be directed towards typical black, brown, and other types of soil in Northeast China, as well as typical cultivated areas such as the corn belt and miscellaneous grain area in Northeast China, to further explore the spatial differences of CEC. Although chemical fertilizer input can increase grain yield, it also brings high EC, which requires scientific fertilization measures according to local conditions. It is necessary to continue to promote scientific fertilization and reasonable intercropping/rotation to improve the utilization efficiency of chemical fertilizers. Finally, the effect of reducing fertilizer application and being environmentally friendly will be realized to ensure the sustainable development of agricultural production in Northeast China.

• Responses of Soil Nutrients and Microbial Communities to Elevated Ozone Concentrations across Different Rice Cultivars

  JI Yang, DU Yiming, ZHAO Mengying, ZHANG Yijia, LI Yuxin, SHANG Bo, FENG Zhaozhong

  2026,63(4):1191-1205, DOI: 10.11766/trxb202502060048

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  【Objective】Elevated near-surface ozone (O₃) concentrations are an increasing threat to rice production, but the mechanisms and dose effects on below-ground ecosystems, including soil nutrient cycling and microbial communities, remain poorly understood. 【Method】This study targeted three major rice cultivars (HuaiDao 5, NanJing 5055, and WuYunJing 27) in the Yangtze River Delta. Using open-top chambers, we conducted an 84-day fumigation experiment with four ozone concentration gradients, including [NF(ambient air), NF20(ambient air + 20 nmol·mol^-1 O₃), NF40 (ambient air + 40 nmol·mol^-1 O₃), and NF60 (ambient air + 60 nmol·mol^-1 O₃)], to systematically analyze the dose-response effects of elevated O₃ concentration on soil nutrients and microbial communities in paddy fields. 【Results】The results showed that increasing O₃ concentration significantly altered soil NO₃^--N and available phosphorus (AP) contents, as well as the abundances of methanotrophs (pmoA gene) and archaea during the rice filling stage, whereas no significant effects were observed for soil DOC, total carbon (TC), available potassium (AK), bacterial or methanogen (mcrA gene) abundances. The interaction between O₃ fumigation and rice cultivar significantly affected soil NH₄⁺-N, NO₃^--N, and AP contents. Specifically, O₃ fumigation significantly reduced NO₃^--N contents in HuaiDao 5 and WuYunJing 27, although the inhibitory effect weakened with increasing O₃ concentration. In contrast, NH₄⁺-N content in NanJing 5055 significantly increased under the highest O₃ treatment (NF60). Similarly, NH₄⁺-N in HuaiDao 5 decreased under O₃ stress but the effect weakened at higher concentrations, whereas NH₄⁺-N in WuYunJing 27 increased under NF60. AP content in HuaiDao 5 exhibited a negative correlation with O₃ concentration, whereas no significant effects were observed in the other two cultivars. O₃ fumigation significantly increased the abundance of pmoA gene in NanJing 5055 and WuYunJing 27, with the promoting effect intensifying under higher O₃ concentrations. Soil bacterial community analysis revealed cultivar-specific responses, the relative abundance of Bacteroidota in WuYunJing 27 and Chloroflexi in NanJing 5055 was positively correlated with O₃ concentration, while the relative abundance of Bacteroidota in NanJing 5055 and Desulfobacterota in HuaiDao 5 showed significant negative correlations. Moreover, the abundance of carbon and nitrogen metabolic pathways in NanJing 5055 and WuYunJing 27 exhibited nonlinear dose-response relationships with increasing O₃ concentrations. 【Conclusion】Our findings demonstrate that soil nutrient dynamics and microbial community responses to O₃ stress are highly cultivar-specific, with evidence suggesting the existence of threshold concentrations for O₃ sensitivity. However, accurately quantifying the mechanisms underlying O₃-induced alterations in below-ground elemental cycling and identifying key ecological thresholds will require long-term in situ observations. These findings offer critical insights for assessing the ecological risks of ozone pollution in rice paddies and guiding the selection of ozone-tolerant cultivars.

• Response of Dissolved Organic Matter Content and Quality in Greenhouse Soils to the Application of Organic Fertilizers with Various Carbon Components

  XU Yehong, BA Wenwen, WANG Xuanqing, LU Chao, LUO Jia, MA Yan

  2026,63(4):1206-1218, DOI: 10.11766/trxb202411190446

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  【Objective】Dissolved organic matter (DOM) is the most active functional component in the soil carbon pool, and the application of organic fertilizer is an effective measure for carbon sequestration and soil fertility improvement in greenhouse soils. However, the response of DOM content and quality in greenhouse soils to organic fertilizer is still unclear, which hinders the elucidation of the regulation mechanisms of the active carbon pool in greenhouse soils and the development of precise application technologies for organic fertilizers.【Method】This study was conducted in situ and five treatments were included: no fertilization as control (CK), chemical fertilizer only (F), and three organic fertilizers with different carbon components replacing 30% of chemical N fertilizer (composted straw replacing 30% of chemical N, FMs; chicken manure replacing 30% of chemical N fertilizer, FMc; and spent mushroom replacing 30% of chemical N fertilizer, FMm). The content of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) were studied in the surface and subsurface layers of greenhouse soils under vegetable cultivation. Combined with three-dimensional fluorescence spectroscopy technology and parallel factor analysis method, the fluorescence spectral characteristic parameters and chemical composition of DOM in soil were analyzed.【Result】Compared with CK, the F treatment had no significant effect on the DOC content in both the surface and subsurface soil; it only significantly increased the DON content in the subsurface soil, with an increase of 1.22-folds. The results showed that compared with F, the FMc organic fertilizer with the highest content of labile carbon components significantly increased the DOC and DON content by 44.2% and 78.1%, respectively, in the surface soil. However, only the DON content in the surface soil significantly increased under the FMs and FMm treatments. Compared with CK, the application of chemical and organic fertilizers significantly reduced the DOC/DON ratio in the surface and subsurface soils, and the humification index (HIX) of DOM in the surface soil significantly increased by 1.06 to 2.07-folds, reaching the highest in the FMc treatment. Also, the fluorescence spectral characteristics of DOM in the subsurface soil did not significantly respond to fertilization. In addition, the content of DOC and DON were significantly negatively correlated with fulvic acid-like components with low molecular weight, while significantly positively correlated with humic acid and aromatic components with high molecular weight.【Conclusion】In summary, the application of chicken manure rich in labile carbon components can more effectively increase the content of DOC and DON and the humification degree of DOM in the surface soil, and increase the proportion of refractory components of DOM in the subsurface soil. Thus, it is more beneficial to apply chicken manure to achieve the "double improvement" of the content and quality of labile carbon pools in the entire tillage layer of greenhouse soils under vegetable cultivation.

• Pelletized Straw Input Promoted Soil Carbon and Nitrogen Sequestration by Enhancing Organic Carbon Fraction in Sandy Soil

  ZHANG Yan, ZHANG Ruimin, ZHANG Pengcheng, LI Hongxu, PANG Huancheng

  2026,63(4):1219-1229, DOI: 10.11766/trxb202504290200

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  【Objective】To combat the depletion of organic carbon and poor water-fertilizer retention in the Horqin Sandy Land, this study examines the mechanisms by which pelletized straw incorporation enhances soil organic carbon and its active fractions.【Method】Through a controlled incubation experiment, the study established treatments with different application rates of pelletized straw: a control with no straw addition (CK), 75 t·hm^-2 pelletized straw (PS75), and 150 t·hm^-2pelletized straw (PS150). Additionally, the experiment included duration treatments consisting of single-year application and two consecutive years of application.【Result】 Compared to the CK treatment, pelletized straw application significantly increased soil organic carbon (SOC) and total nitrogen (TN) contents by 217.52%～749.15% and 197.78%～679.25%, respectively. With increasing application rates and duration of pelletized straw incorporation, the carbon and nitrogen retention capacity of sandy soil was significantly enhanced. Application of pelletized straw consistently elevated the C/N ratio of the sandy soil, with the most significant increase observed in the PS150-1a treatment (P<0.05). Also, the addition of pelletized straw significantly enhanced particulate organic carbon (POC), mineral-associated organic carbon (MAOC), and labile organic carbon (LOC) contents (P<0.05). The contents of POC, MAOC, and LOC increased significantly with higher application rates of pelletized straw and longer amendment duration. Moreover, POC, LOC, and MAOC all showed highly significant positive correlations with total SOC content (P<0.01). Notably, the 150 t·hm^-2 pelletized straw treatment with two consecutive years of application significantly increased the proportion of POC to total SOC by 31.81% (P<0.05), suggesting a preferential accumulation of this active carbon fraction. Nevertheless, pelletized straw application significantly reduced bulk density while improving water-holding capacity and porosity in sandy soil. The study found a statistically significant positive correlation (P<0.01) between the water-holding capacity of sandy soil and the duration of pelletized straw application. Moreover, the improved water retention in sandy soils resulted from synergistic physical adsorption and chemically mediated retention from pelletized straw decomposition. According to redundancy analysis, soil physicochemical properties explained 98.90% of the variability in SOC, TN, and C/N. Besides, MAOC was the primary driver, highlighting mineral association as a fundamental mechanism for soil carbon and nitrogen stabilization. Partial least squares path modeling demonstrated that the cumulative addition of pelletized straw directly promoted SOC sequestration by significantly increasing the contents of both LOC and MAOC (P<0.01). The model further confirmed the dominant role of MAOC in SOC stabilization, highlighting the importance of mineral protection mechanisms for carbon retention in sandy soils. The accumulation of SOC significantly increased TN content (P<0.01), indicating a coupled carbon and nitrogen sequestration effect in the sandy soil. Furthermore, increasing the application rate of pelletized straw significantly reduced soil bulk density and enhanced water holding capacity (P<0.01). In summary, the study demonstrated that SOC fractions served as the key mediator for carbon-nitrogen coupled stabilization in sandy soils. The establishment of this regulatory mechanism provides a theoretical foundation for carbon sequestration management in arid sandy soils.【Conclusion】The study demonstrates that pelletized straw incorporation effectively enhances sandy SOC fractions, promotes carbon-nitrogen synergistic sequestration, and improves soil physical properties, with the optimal effects achieved at 150 t·hm^-2 with two consecutive years of application.

• Effects of Biochar Application on Organic Carbon Composition of Different Density Fractions in Paddy Soil

  ZHU Mengtao, MA Ruiling, CAI Ying, YI Qi, JIANG Shuo, LIU Zhiwei, BIAN Rongjun, ZHANG Xuhui, ZHENG Jufeng, LI Lianqing

  2026,63(4):1230-1242, DOI: 10.11766/trxb202502170063

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  【Objective】Soil organic carbon (SOC) sequestration in agricultural ecosystems is critical for mitigating climate change and maintaining soil fertility, with mineral-associated organic carbon (MAOC) playing a central role in long-term C stabilization. Paddy soils with higher SOC density exhibit distinct biogeochemical cycles due to periodic flooding and anaerobic conditions, making their SOC dynamics particularly complex. While biochar amendment has emerged as a promising strategy to enhance SOC storage, the specific mechanisms by which biochar interacts with soil mineral fractions and modulates native SOC stability remain poorly understood. Previous studies have primarily focused on total SOC changes, overlooking the differential responses of mineral-bound C pools to biochar input. This knowledge gap hinders accurate assessments of biochar's long-term C sequestration potential in paddy systems. The present study aimed to address this gap by investigating how biochar amendment affects SOC distribution across density-based mineral fractions and alters native SOC dynamics through advanced spectroscopic and isotopic tracing techniques.【Method】In this study, a field experiment was established in a typical paddy soil in southern China, with two treatments: biochar application at 15 t·ha^-1 (C15) and no biochar (C0). After two years of rice cultivation, soil samples were collected from the 0-15 cm depth and subjected to sequential density fractionation using sodium polytungstate solutions with gradient densities (1.65, 1.85, 2.05, 2.25, 2.45, 2.65 g·cm^-3). Each fraction was characterized for SOC content, stable isotope composition (δ¹³C), and chemical functional group via Fourier-transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) was used to visualize particle morphology and elemental composition, while X-ray diffraction (XRD)identified dominant mineral phases in each fraction. Isotopic mixing models were applied to quantify biochar-derived C versus native SOC contributions across density gradients.【Result】The results showed that (1) Based on SOC content and soil minerals categories, density fractionation successfully separated soil into three functionally distinct pools: particulate organic carbon(POC, <1.85 g·cm^-3), clay mineral-associated C (1.85～2.45 g·cm^-3), and primary mineral-bound C (>2.45 g·cm^-3). XRD analysis confirmed that the 1.85～2.45 g·cm^-3 fraction was enriched in 2: 1 phyllosilicate (e.g., montmorillonite, illite) and Fe/Al oxides, whereas the >2.45 g·cm^-3 fraction contained quartz and feldspars. Fourier-transform infrared spectroscopy (FTIR) demonstrated that the intensities of O-H stretch (2 923 cm^-1) for aliphatic structures and C=C stretch (1 610 cm^-1) for aromatic compounds gradually decrease in both biochar application (C15) and non-application of biochar (C0) treatments with increasing density, while SOC stability progressively increased.(2)SOC content of density-specific changes varied under biochar amendment: Contribution of SOC in the <1.65 g·cm^-3 fraction increased by 150.1%, driven by biochar particles, while the 1.65～1.85 g·cm^-3 fraction showed a 60.9% increase, due to biochar-derived C adsorption onto clay minerals. Conversely, the 1.85～2.05 g·cm^-3 clay fraction exhibited a 37.4% reduction in SOC contribution. δ¹³C analysis confirmed biochar-C presence across all fractions, with the highest incorporation (64.5%) in the <1.65 g·cm^-3 fraction. Native SOC depletion was observed in five density intervals, with the most severe loss (-41.2%) in the <1.65 g·cm^-3 fraction, indicating strong positive priming. Notably, priming extended to the 1.85～2.25 g·cm^-3 clay fraction (-14.6%), suggesting biochar-induced microbial activity stimulated decomposition of relatively stable mineral-protected C.【Conclusion】This study demonstrates that biochar amendment effectively enhances total SOC content in paddy soil within two years, but its C sequestration efficiency is offset by priming-induced native SOC losses across labile and mineral-protected pools. The findings highlight the need to account for biochar-microbe-mineral interactions when evaluating long-term C sequestration. By linking density fractionation with spectroscopic and isotopic tools, this research advances understanding of mineral-mediated C stabilization in biochar-amended soils, providing a basis for optimizing biochar application strategies (e.g., feedstock selection, application rate) to maximize C sink capacity in rice-based systems. Future work should focus on long-term monitoring of priming effects and microbial community shifts to refine sustainable soil C management practices.

• Impact Characteristics and Mechanisms of Warming on the Decomposition of Soil Organic Carbon Three Pools in Grasslands of the Loess Plateau

  FENG Junhao, LIU Xiaowei, JING Yudu, LIANG Ke, YU Qiang, GUO Liang

  2026,63(4):1243-1255, DOI: 10.11766/trxb202411150440

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  【Objective】Grasslands play an important role in regulating the global carbon cycle through the decomposition of soil organic carbon (SOC) pools. However, the effects of global warming on SOC decomposition dynamics, and the underlying microbial and enzymatic regulatory mechanisms remain unclear. This study aims to investigate how warming alters the decomposition dynamics of active, slow, and passive SOC pools, with a focus on microbial community composition and extracellular enzyme stoichiometry. 【Method】This study was conducted using surface soil collected from semi-arid grasslands on the Loess Plateau in a long-term incubation experiment. Soil samples were incubated at two controlled temperatures (15 ℃ and 25 ℃) under constant temperature and humidity for 553 days (～1.5 year). During the incubation, soil respiration rates, microbial biomass carbon (MBC), extracellular enzyme activities, and microbial community compositions were systematically monitored. 【Result】The results showed that incubation at 25 ℃ significantly increased soil respiration rates, cumulative carbon emissions, and the decomposition rates of the three SOC pools (active, slow, and passive) compared to 15 ℃. However, the magnitude of this enhancement diminished over time. Among the SOC pools, the active pool exhibited the most rapid decline in respiration rate, followed by the slow pool, with the passive pool showing the slowest decline. Additionally, microbial biomass carbon and bacterial diversity decreased more rapidly at 25 ℃, accompanied by significant shifts in microbial community composition. The relative abundance of copiotrophic microorganisms, such as Proteobacteria and Ascomycota, decreased during the incubation, whereas oligotrophic microorganisms, including Actinobacteria and Ascomycota, increased. Notably, copiotrophic microorganisms were more dominant at 15 ℃, while oligotrophic microorganisms were more prevalent at 25 ℃. Microbial oxidative metabolism, nitrogen demand, and phosphorus demand increased progressively throughout the incubation, with overall higher levels observed at 25 ℃ compared to 15 ℃. Furthermore, the response of the three carbon pool decompositions to temperature increase was regulated by extracellular enzymes and microbial community composition. Stepwise linear regression showed that under 15 ℃ incubation, MBC and oxidases were positive regulatory factors for the decomposition of the active and slow carbon pools, respectively. Under 25 ℃ incubation, β-1, 4-N-acetylglucosaminidase, and alkaline phosphatase were positive regulatory factors for the decomposition of the passive carbon pool. The partial least squares path model analysis indicated that incubation temperature and time significantly regulated microbial community composition. The microbial community composition positively regulated extracellular enzyme activity and exerted negative and positive regulation on the decomposition of the slow and passive carbon pools, respectively. Also, extracellular enzymes, as key regulatory factors for the decomposition of the active and passive carbon pools, exerted negative and positive regulation on the decomposition of these pools, respectively.【Conclusion】This study reveals that shifts in microbial community composition, particularly the shift in species with different ecological strategies, play a key role in regulating extracellular enzyme activities and stoichiometry, thereby mediating temperature-induced changes in SOC decomposition dynamics. These findings provide critical insights into the microbial and enzymatic mechanisms that drive SOC turnover under warming conditions, offering valuable evidence to enhance our understanding of global carbon cycling and its feedback to climate change.

• Deciphering and Predicting the Soil Priming Effects Driven by Carbon Substrate Complexity

  YANG Qingrun, LIU Kai, XU Yuzhi, FENG Xinyu, SUN Lin

  2026,63(4):1256-1268, DOI: 10.11766/trxb202507040325

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  【Objective】The priming effect(PE)is a key process in regulating soil organic carbon dynamics, but its mechanism is complex and substrate dependent, which limits the accuracy of model predictions. Therefore, it is necessary to clarify its regulatory mechanism. 【Method】This study is based on 2 122 sets of global observational data, combined with meta-analysis, process-based model analysis, sensitivity testing, and random forest methods, to systematically analyze the mechanism, dynamic process, and main controlling factors of PE under different carbon substrate conditions. 【Result】The results show that: 1) Both simple and complex carbon inputs induce significant positive PE, but the intensity varies significantly among ecosystems, with farmland PE intensity (about 65%) significantly higher than forest ecosystems (about 33%). Multivariate analysis reveales that this difference is mainly due to the coupled variation of climate, soil physicochemical properties, and microbial community structure characteristics along environmental gradients. 2) The priming pathway exhibits significant substrate specificity. Simple carbon input mainly induces strong positive PE through microbial triggering effects, while complex carbon input mainly inhibits the decomposition of native soil organic matter and generates negative real PE through the substrate priority utilization mechanism. 3) The results based on the process model further indicate that the dynamic process of PE is controlled by substrate quality. Simple carbon inputs exhibit two patterns: “continuous positive” and “transient”, while complex carbon input is dominated by a “high apparent-negative real” pattern. Also, parameter sensitivity analysis shows that this model is mainly constrained by microbial maintenance metabolism, reflecting the differences in energy allocation strategies of microorganisms under different substrate conditions. 4) Besides, the main controlling factors of PE have hierarchical differentiation characteristics, and the apparent PE is mainly driven by microbial biomass carbon and soil carbon-to-nitrogen ratio. Moreover, the main controlling factors of real PE depend on substrate type. In simple carbon scenarios, soil organic carbon content and pH are dominant, while in complex carbon scenarios, the governing factors shift to soil carbon-to-nitrogen ratio and exogenous carbon addition. 【Conclusion】By elucidating the controlling mechanisms of PE under different carbon substrate input conditions, this study provides evidence for the accurate prediction of soil organic carbon and the assessment of soil carbon balance in the context of global climate change.

• The Carbon-Iron Coupling Mechanism of Organic Carbon Mineralization in the Rice Root Zone Under Redox Gradients

  LIU Siyang, LI Yan, LI Yulin, GAO Wei, Hu Teng, CHEN Xiangbi, ZHOU Ping, GUO Xiaobin, WU Jinshui

  2026,63(4):1269-1283, DOI: 10.11766/trxb202507020324

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  【Objective】Carbon cycling in paddy soils is crucial for carbon sequestration and soil fertility enhancement. The rice root zone, being the most active site of this cycle, exhibits carbon turnover processes that are closely linked to soil redox conditions and iron phase transformations. However, the iron-mediated organic carbon mineralization process under redox gradients remains unclear, and the carbon-iron coupling mechanism requires systematic elucidation.【Method】In this study, it is established a simplified rhizosphere microcosm system by using soil columns equipped with artificial roots. Four redox potential gradients of the soil column were constructed by adjusting water conditions (60%, 80%, and 100% of soil water saturation capacity, plus 3 cm flooding), and ¹³C-labeled glucose was used as a model root exudate, for investigating the effects of iron phase transformation on total organic carbon mineralization and priming effect in the root zone under different redox states.【Result】The results showed that: (1) Both soil Eh reduction and exogenous glucose input significantly increased the cumulative emissions of CH₄ and CO₂. Under water-saturated conditions, the incremental emission of CH₄ was significantly higher than that of CO₂ in the glucose-amended treatments, and vice versa in the unsaturated water content. (2) In both glucose-amended and non-amended treatments, soil dissolved organic carbon (DOC) content generally decreased compared to pre-incubation levels, but the aromaticity of DOC increased under saturated conditions. Eh reduction and glucose input stimulated ferrous iron (Fe²⁺) reduction and iron-associated organic carbon (Fe-OC) release, with Fe-OC content variations showing significant correlations with iron speciation and CO₂ emission rates. (3) The activities of carbon cycle hydrolase and oxidase were significantly affected by the redox gradient and glucose input. Cellobiohydrolase (CBH) activity decreased with decreasing Eh and showed a negative correlation with CH₄+CO₂ emission rates. Moreover, phenol oxidase activity was higher in the saturated water treatments than in the unsaturated water treatments and was positively correlated with the rate of gas emission. Glucose addition significantly increased the activities of phenol oxidase and catalase oxidase. 【Conclusion】Both the “iron gate” and “enzyme latch” mechanisms synergistically regulated CH₄ and CO₂ emissions. The findings provide critical parameters and a scientific basis for predicting rhizodeposited carbon sequestration potential in subtropical iron-rich paddy soil, and optimizing water management strategies to enhance carbon storage and mitigate greenhouse gas emissions in rice cultivation systems.

• Effects of Long-term Different Fertilization Treatment on Soil Organic Nitrogen Fractions in Weibei Dryland Apple Orcharrds

  CHEN Yumeng, ZHAO Zhiyuan, YI Shusheng, ZHENG Zhaoxia, ZHENG Bangyu, FENG Tianyu, ZHENG Wei, ZHAI Bingnian

  2026,63(4):1284-1298, DOI: 10.11766/trxb202405090192

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  【Objective】Soil organic nitrogen directly reflects the nitrogen supply capacity of soil. Therefore, it is important to clarify the mechanism of the effect of organic fertilizer on soil organic nitrogen components. 【Method】This study was based on the long-term positioning experiment started in 2008, and four fertilization treatments were set up (no fertilization CK, single application of organic fertilizer M, single application of chemical fertilizer NPK, and combined application of organic and inorganic fertilizer MNPK) to explore the effects of long-term different fertilization on the content of soil organic nitrogen components in apple orchards on the Weibei dryland. Besides, the key mechanism of increasing organic fertilizer to improve soil organic nitrogen content was studied through soil organic nitrogen component determination and metabolomics analysis of nitrogen metabolites. 【Result】The results showed that compared with NPK treatment, the contents of soil water, available phosphorus, available potassium, soluble organic nitrogen, and microbial biomass nitrogen in MNPK were increased by 4%, 33.8%, 41.7%, 8.2%, and 21.7%, respectively. Also, the content of acid hydrolyzed total nitrogen and acid ammonium nitrogen increased by 10.1% and 8.9%, respectively. The amino acid nitrogen content of M treatment was significantly higher than those of other treatments during the whole growth period, followed by MNPK, and CK was the lowest. Soil organic nitrogen components were significantly positively correlated with soil total nitrogen, microbial biomass nitrogen, and available nutrients (available phosphorus and available potassium). Except for non-acid hydrolyzable nitrogen, each organic nitrogen component was significantly positively correlated with acid-hydrolyzed total nitrogen. Metabolome results showed that the nitrogenous organic compounds in MNPK treatment were significantly higher than those in other treatments, and the proportion of amino acid nitrogen in the application of organic fertilizer treatment was higher than those in other treatments. Compared with NPK and CK treatments, amino acids accounted for an important proportion of nitrogenous organic compounds upregulated by MNPK treatment, and 8 amino acids were included in 45 nitrogenous organic compounds. The relative abundance was significantly positively correlated with available phosphorus, available potassium and soluble organic nitrogen. 【Conclusion】 The results showed that the improvement of soil physicochemical properties with increased application of organic fertilizer was conducive to organic nitrogen decomposition and turnover of amino acid nitrogen.

• Legacy Effects of Biochar and Organic Fertilizer Application on Soil N₂O Emissions

  YANG Pizhen, JI Cheng, DONG Caixia, LI Shijin, DING Zihao, XU Cong, NING Yunwang, LIANG Dong, ZHANG Yongchun, WANG Jidong

  2026,63(4):1299-1311, DOI: 10.11766/trxb202507010318

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  【Objective】Nitrous oxide (N₂O) is a potent greenhouse gas with a global warming potential 296 times that of carbon dioxide (CO₂). Microbial-driven nitrification and denitrification are major processes contributing to N₂O production. While numerous studies have explored the combined effects of biochar and organic fertilizer, most have been short-term, and the legacy effects of aged biochar on soil N₂O emissions remain poorly understood. The interactive effects of its combined application with organic fertilizers necessitate further investigation. 【Method】Soil samples were obtained from a seven-year field experiment comprising four distinct treatments: (1) control (urea application, F); (2) one-time basal application of biochar (FB); (3) annual application of organic fertilizer (OF); and (4) combined annual application of organic fertilizer and one-time basal biochar (OFB). In the organic fertilizer treatments, 25% of the urea nitrogen was substituted with organic fertilizer nitrogen. A laboratory incubation experiment was conducted to measure cumulative N₂O emissions, quantify the abundances of key functional genes (including nirS, nirK, and nosZ), and partition the relative contributions of fungal and bacterial pathways to N₂O emissions. 【Result】The result showed that compared to the control, cumulative N₂O emissions were significantly reduced by 49.4% in the biochar treatment (FB), 38.4% in the organic fertilizer treatment (OF), and 59.3% in the combined treatment (OFB). Biochar significantly decreased the fungal contribution to N₂O emissions (FDC) by 11.4% and increased the bacterial contribution (BDC) by 5.8%. Organic fertilizer reduced the contribution of ammonia-oxidizing bacteria (AOB) by 15.3% but increased the bacterial contribution by 12.1%. The combined application of biochar and organic fertilizer decreased the fungal contribution by 9.7% and increased the bacterial contribution by 15.7%. Structural equation modeling (SEM) indicated that biochar directly reduced FDC and enhanced BDC, organic fertilizers significantly enhance BDC and reduce (nirS+nirK)/nosZ, thereby decreasing N₂O emissions. 【Conclusion】These results demonstrate the sustained potential of biochar and organic fertilizer amendments in reducing greenhouse gas emissions from agricultural soils and provide mechanistic insights into how these amendments regulate microbial processes governing N₂O production. This research outcome provides scientific support for in-depth analysis of the legacy effects of biochar and organic fertilizer application on soil and their microbiological mechanisms offering scientific guidance for optimizing fertilization practices to achieve the goal of reducing N₂O emissions from farmland soils.

• Effect of Organic Substitution on Crop-Soil-Microbial Stoichiometric Characteristics and Soil Phosphorus Fractions

  HUA Mingxiu, HU Can, CHEN Hao, CHEN Guanglei, WANG Lei, WANG Shenqiang, WANG Yu

  2026,63(4):1312-1324, DOI: 10.11766/trxb202412120486

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  【Objective】The substitution of organic fertilizer for chemical fertilizer is becoming a popular practice for improved crop productivity. However, there is limited understanding of the nutrient stoichiometric relationships among crops, soil, and microorganisms under different proportions of organic fertilizer substitution for chemical fertilizers in a rice-wheat rotation system. 【Method】This study utilized a five-year field experiment at the Yixing experimental site of the Changshu Agro-Ecological Experimental Station, Chinese Academy of Sciences, to investigate the effects of organic fertilizer substitution on crop-soil-microorganism stoichiometric ratios and phosphorus availability under equivalent nitrogen, phosphorus, and potassium inputs. Five treatments were established: no phosphorus fertilizer (CK), conventional chemical phosphorus fertilizer (CF), 30% substitution of chemical phosphorus fertilizer with organic fertilizer (TM), 50% substitution (FM), and 100% substitution (HM). 【Result】Results from ten consecutive cropping seasons over five years revealed no significant differences in the grain and straw yields of rice and wheat or the total carbon, nitrogen, and phosphorus stoichiometric ratios among treatments. The stoichiometric ratios of available nutrients in the soil, including dissolved organic carbon: available nitrogen, dissolved organic carbon∶ available phosphorus, and available nitrogen∶ available phosphorus, ranged from 7.08-7.39, 23.1-26.8, and 3.59-4.06, respectively, under the TM, FM, and HM treatments. Compared with CF, these treatments did not significantly alter the total nutrient stoichiometric ratios in the soil but significantly increased the soil organic phosphorus fractions by 49.7%-58.2%, dominated by moderately labile organic phosphorus (NaOH-P_o). Additionally, soil microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus(MBP)in soil increased by 14.3%-61.1%, 4.37%-36.2%, and 46.4%-50.8%, respectively. The microbial stoichiometric ratios under all treatments were as follows: MBC∶MBN(11.6-14.5), MBC∶MBP(68.3-106), and MBN∶MBP(5.32-7.32). The TM and FM treatments significantly reduced the stoichiometric ratio of enzyme activity (EEA_(C∶N)) but did not affect the overall soil-microorganism stoichiometric balance. 【Conclusion】These findings demonstrate that substituting 30% of chemical fertilizers with organic fertilizers can maintain crop yields while effectively enhancing soil available phosphorus content. This study underscores the critical importance of scientifically regulating the substitution ratio of organic fertilizers to optimize soil nutrient management, improve soil fertility, and promote sustainable agricultural development.

• Effects of Bridge Construction on Mangrove Soil Fungal Diversity and Co- Occurrence Networks

  GAO Guifeng, MA Cheng, YAN Subo, SONG Luyao, CHU Haiyan

  2026,63(4):1325-1335, DOI: 10.11766/trxb202412090480

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  【Objective】Bridge construction strongly affects the structure and function of soil microbial communities in coastal wetlands. However, its specific impacts on mangrove soil fungal communities have not been given much attention. This study aimed to investigate the impacts of bridge construction on mangrove soil fungal communities, focusing on two common construction methods (Steel casing pipe, SC; Sheet pile cofferdam, SP) compared to undisturbed areas (UD), providing insights for ecological conservation and sustainable management.【Method】Soil fungal communities across SC, SP, and UD habitats were investigated using high-throughput sequencing, functional guild annotation, and co-occurrence network analysis. Key soil properties were measured to identify environmental drivers.【Result】The results showed that the main fungal biomarkers in the soils of the UD and SC habitats were Ascomycota, whereas the SP habitat was dominated by Basidiomycota. Also, the species richness of the soil fungi in the SP habitat was significantly (P< 0.01) higher than that in the SC and UD habitats. In addition, the species richness of saprotrophic fungi was significantly (P <0.05) higher in SP than in SC and UD, and the relative abundance of saprotrophic fungi was significantly (P < 0.05) higher in SC than in UD. The soil C/N ratio, TN, and pH were the main environmental drivers affecting fungal guilds. Fungal co-occurrence network analysis showed that the network complexity (avgK = 1.94) was higher in the UD habitat than in the SC and SP habitats.【Conclusion】This study reveals that bridge construction methods differentially alter mangrove soil fungal communities through soil physicochemical alterations. These findings highlight the need for method-specific environmental assessments and offer a scientific basis for balancing coastal wetland conservation with construction activities.

• Effects of Different Organic Fertilizers on Rhizosphere Microbial Carbon Source Utilization, Nematode Community, and Nutrient Absorption of Jackfruit

  CHEN Hongxing, MO Yuncong, XU Yadong, SU Lanxi, BAI Tingyu, WU Gang, XUN Weibing, XU Zhihui, ZHAO Qingyun

  2026,63(4):1336-1347, DOI: 10.11766/trxb202506120277

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  【Objective】This study aimed to investigate the regulatory differences of various organic fertilizers on the rhizosphere microorganisms, nematode communities, and nutrient absorption of jackfruit, so as to select suitable organic fertilizers to construct a healthy soil microecology, and provide a theoretical basis for targeted regulation of soil quality.【Method】Malaysian No.1 grafted seedlings were used as experimental materials, and the latosol formed by granite was used as test soil in this study. The experiment was designed to have six treatments: CK(no fertilizer), DF(soybean flour), YF(sheep manure), JF(chicken manure), NF(cow manure), and CF(chemical fertilizer only), for comparing the effects of different fertilizers on the biomass accumulation, nutrient absorption, and soil microenvironment of jackfruit. 【Result】The application of organic fertilizer generally promoted the biomass accumulation and nutrient absorption of jackfruit, and increased the soil pH and organic matter. NF significantly improved the proportion of soil organic matter, available nitrogen, and potassium nutrients, but significantly reduced the proportion of soil available phosphorus compared to other treatments. The application of JF also significantly increased the contents of soil available nitrogen, phosphorus, and potassium; however, YF treatment induced the weakest effect among all organic fertilizer treatments. Also, the YF treatment had the highest number of soil nematodes and nematode abundance in each trophic group, followed by the NF treatment. The Shannon-Weiner diversity index and evenness index of soil nematodes in the organic fertilizer treatment were significantly higher than those in the CK and CF treatments. In addition, the soil microbial communities under different fertilization treatments all exhibited relatively active metabolism towards carbohydrates, amino acids and carboxylic acids, while their metabolic capabilities towards polymers, phenolic acids, and amides were weaker. The diversity and evenness index of soil microbial community structure in the DF treatment were significantly higher than those in other organic fertilizer treatments. Mantel analysis showed a significant correlation between plant biomass, nematode community, nematode trophic groups, microbial carbon source utilization, and soil pH. Also, the Mantel analysis of nematode community, bacterial-feeding nematode, and omnivorous/predacious nematode with soil organic matter showed significant correlation. 【Conclusion】The application of organic fertilizer can promote the growth and nutrient absorption of jackfruit, increase soil organic matter, and improve soil microecology. Moreover, organic fertilizers from sheep and cow manure is beneficial for increasing the total number of soil nematodes and the number of nematodes in each trophic group, while soybean flour can enhance the activity of rhizosphere microorganisms and promote carbon source utilization. For practical applications, specific organic fertilizers or their combinations can be selected based on the basic soil conditions for targeted regulation of soil health, providing a theoretical basis for high crop yield and efficient resource utilization.

• Effects of Soil Microbial Diversity on Soil Multifunctionality Under Sustained Intensive Forest Management

  HUANG Cheng, WU Lin, LI Xu, FU Songling, FENG Chun, WANG Zhaocheng, LIU Hua

  2026,63(4):1348-1360, DOI: 10.11766/trxb202505240239

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  【Objective】Soil microorganisms serve as crucial mediators, bridging organic and inorganic environmental factors. They play a significant role in regulating multiple soil functions. Forest management represents the primary anthropogenic disturbance to forest soils, yet the mechanisms through which soil microorganisms influence soil multifunctionality (SMF) under continuous intensive management remain unclear. 【Method】This study investigated Carya cathayensis var. dabeishansis secondary forests in the Dabie Mountains to explore the mechanisms by which soil microbial diversity affects SMF under sustained intensive forest management. The authors analyzed 45 plots under varying management durations (0, 3, 8, 15, 20 years) and management metods (CK: no management; EM: extensive management; IM: intensive management)in Jinzhai County, Anhui Province. The soil microbial diversity (amplicon sequence variant, ASV) number, Simpson index, Shannon-Wiener index, and Chao1 richness index for bacterial and fungal communities) and 15 indicators related to four soil functions: nutrient supply (alkali-hydrolyzable nitrogen (AN), available phosphorus (AP), available potassium(AK), microbial biomass nitrogen(MBN), microbial biomass phosphorus (MBP)); nutrient storage(total nitrogen (TN), total phosphorus (TP), total potassium (TK)); nutrient cycling (acid phosphatase (ACP), urease (UE), sucrase (SC), β-1, 4-glucosidase (BG), protease (Pro)); and carbon storage (soil organic carbon, SOC), microbial biomass carbon (MBC)) were measured. SMF was calculated using both the single-function approach and the averaging method. Two-way ANOVA was employed to compare management effects, while Pearson correlation, Mantel tests, and random forest models identified key functional indicators. Structural equation modeling (SEM) was constructed to analyze regulatory pathways. 【Result】The results indicated that short-term management (3 years) significantly enhanced soil microbial diversity and SMF(bacterial Shannon index peaked under IM at year 3; SMF increased by 0.94 compared to CK). However, both declined significantly with prolonged management, with bacterial ASV number and Shannon index decreasing by 19.63% and 3.46% after 20 years of intensive management, respectively. Management duration exerted a significantly greater impact on microbial diversity and SMF than management regime (P< 0.001), and IM amplified this temporal effect (e.g., carbon storage, nutrient cycling, and supply functions under IM-15 were significantly lower than CK). Random forest analysis identified SOC, TP, MBC, AN, TK, MBN, SC, and BG as key indicators of SMF (P< 0.05). SEM revealed that microbial diversity influenced SMF by indirectly regulating soil nutrients and enzyme activities (explaining 57.4% of the variation): bacterial diversity positively drives nutrient and carbon storage. In contrast, fungal diversity governed nutrient cycling and carbon storage. Nutrient supply and storage functions were the core contributors to SMF, where TP and TK indirectly affected SMF by regulating AN, MBN content, and SC/BG enzyme activities. Moreover, long-term management induced soil acidification, SOC loss, and phosphorus limitation (TP significantly decreased after 15 years), impairing microbial community function. This subsequently reduced enzyme activities (e.g., SC, BG) and nutrient turnover efficiency, ultimately leading to SMF degradation.【Conclusion】 This study revealed that the loss of soil microbial diversity is a key factor in SMF degradation under long-term intensive forest management. Thus, optimizing management strategies (supplementing carbon/phosphorus fertilizers, reducing nitrogen fertilizer application, decreasing understory vegetation clearance frequency)to maintain soil ecological functions is highly recommended. These findings provide a theoretical basis for the sustainable management of economic forests in mountainous regions.

• The Effects of Magnetically Treated Water Irrigation on Soil Bacterial Community Characteristics and Functions in Three Types of Greenhouse Vegetables

  WANG Qi, JING Ruyan, WU Yifei, BAI Yuqian, YAN Tianlong, DING Xinjing

  2026,63(4):1361-1371, DOI: 10.11766/trxb202505200231

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  【Objective】Soil bacterial communities are key drivers of ecosystem functions in facility-based agriculture. However, the regulatory effects of magnetized water (MTW) irrigation on the structure and function of soil bacterial communities under facility cultivation remain unclear. 【Method】In this study, soils from eggplant, cucumber, and pepper cultivation plots were used as research objects. The experimental design comprised irrigation treatments using MTW and non-magnetized water (NMTW). Employing high-throughput sequencing technology combined with functional prediction analysis (FAPROTAX), the study systematically evaluated the impact of MTW irrigation on bacterial community composition, diversity, and key environmental driving factors.【Result】The results demonstrated that MTW irrigation significantly increased the abundances of Proteobacteria and Actinobacteria bacteria in soils of all vegetable cultivation plots by 7.43%-61.94% and 1.95%-11.79%, respectively, while decreasing the abundance of Chloroflexi and Gemmatimonadetes by 3.98%-27.42% and 7.89%-9.62%, respectively. At the genus level, MTW irrigation increased the relative abundance of Streptomyces and Chryseolinea in plot soils across all vegetable cultivation systems. Moreover, alpha diversity analysis showed that MTW irrigation significantly increased the Chao1, ACE, and Shannon indices of bacterial communities in pepper cultivation plots by 21.27%, 26.74%, and 12.22%, respectively, while no significant changes in bacterial community diversity were observed in eggplant and cucumber cultivation plots. Also, the redundancy analysis (RDA) revealed that MTW irrigation altered the environmental factors influencing soil bacterial communities, with soil pH, available phosphorus, and total phosphorus being the key factors regulating the abundance of dominant bacterial phyla. Functional prediction (FAPROTAX) showed that MTW irrigation significantly promoted the enrichment of functional bacteria related to cellulolysis and nitrogen fixation, while reducing the abundance of functional bacteria associated with human pathogens.【Conclusion】This study elucidates the multidimensional impacts of MTW irrigation on soil bacterial communities in facility agriculture systems, specifically addressing compositional, functional, and ecological network characteristics. The findings establish a theoretical foundation for regulating soil bacterial structure and metabolic functions, optimizing microbial ecological networks, and promoting sustainable soil management in protected cultivation.

• The Behaviors and Influencing Factors of Reactive Oxygen Species Generation at the Soil-Water Interface Containing Biochar Under Simulated Solar Illumination Conditions

  WANG Haowei, HOU Yucheng, YAO Jiayi, LI Mengwei, FANG Jing, SHAN Shengdao

  2026,63(4):1372-1383, DOI: 10.11766/trxb202506200296

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  【Objective】Reactive oxygen species (ROS) at the soil-water interface play a crucial role in carbon/nitrogen cycling and pollutant transformation. However, it is still unclear how biochar influences the formation of ROS at the soil-water interface. Thus, this study aims to explore the formation behaviors and factors influencing ROS generation at the soil-water interface containing biochar. 【Method】Under simulated solar illumination conditions, the probe capture method was used to quantitatively analyze the generation kinetics and mechanisms of three typical ROS (hydroxyl radical ·OH, hydrogen peroxide H₂O₂, and superoxide radical (O₂^·-) at the 10 g·kg^-1 biochar-amended soil-water interface. The effects of biochar pyrolysis temperature, dissolved biochar carbon (DBC), clay minerals (kaolinite), and dissolved organic matter (fulvic acid) on ROS formation were also examined at such interfaces. 【Result】The results showed that under light, substantial ·OH and H₂O₂ were generated at the biochar-containing soil-water interface, with concentration ranges of 0.43-0.83 μmol·L^-1 and 21.12-30.93 μmol·L^-1, respectively, which were 1.39-2.65 times and 1.31-1.91 times higher than those at the biochar-free interface (control group). In contrast, O₂^·- concentration was low (< 0.2 μmol·L^-1), significantly lower than that in the control. DBC played an important role in the formation of ROS, and after removing DBC, the generation of H₂O₂ in the water-soil interface containing biochar was significantly inhibited, but the generation of ·OH was not affected. Also, kaolinite significantly inhibited the capacity of biochar to mediate ROS generation at the soil-water interface under light (except for high-temperature biochar) and reduced the conversion efficiency of H₂O₂ to ·OH. Fulvic acid significantly enhanced H₂O₂ generation at the light-irradiated, biochar-containing soil-water interface but decreased ·OH concentration.【Conclusion】Light plays a critical role in mediating ROS formation at the biochar-amended interface: it not only promotes H₂O₂ generation and transformation, but also facilitates ·OH production and O₂^·- conversion. However, biochar-mediated ROS generation at the interface is not entirely dependent on light. The generation of ROS at the light-irradiated, biochar-amended soil-water interface is collectively determined by biochar surface persistent free radicals, oxygen-containing functional groups, as well as dissolved organic carbon and Fe²⁺ contents at the interface. These findings provide an important reference for understanding the formation and distribution of ROS in biochar-amended soils.

• Fe Isotopic Compositions of the Soils and Fe-Mn Nodules in the Different Climatic Zones of Eastern China and Its Implications for Pedogenesis

  JIA Yuting, LIU Tingxiao, CAI Tianle, NIE Daling, HU Xuefeng

  DOI: 10.11766/trxb202602110094

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  【Objective】This study aimed to investigate the possible contribution of Fe isotopic composition to weathering and pedogenic processes and the formation of Fe-Mn nodules.【Method】Representative soil profiles were established in the warm-temperate, subtropical, and tropical zones in eastern China. The physical and chemical properties, geochemical characteristics, and Fe isotopic compositions of the soils and Fe-Mn nodules were analyzed. 【Result】The results indicated that the degree of pedogenic weathering of the soils from the different climatic zones was mainly controlled by climatic factors, and was also related to the parent materials. The ferromanganese nodules produced in the different climatic zones were all enriched in Fe and Mn, but varied greatly in geochemical characteristics. The ferromanganese nodules developed from tropical basalt have total Fe (Fet) and free Fe (Fed) content of 353.7 mg·g-1 and 293.5 mg·g-1, respectively. These were significantly higher than those of the nodules formed from the Quaternary red clay in the subtropical and the eluviated cinnamon soil in the warm-temperate zone. However, the Fe isotopic composition in the red or cinnamon soils developed from the different climatic zones and different parent materials was similar, and their δ56Fe value varied between 0.018‰ and 0.120‰, all close to the baseline of the continental crust igneous rock. In contrast, the δ56Fe value of the ferromanganese nodules formed in the three climatic zones was all negative, with an average of -0.330‰, which was significantly enriched in light Fe isotopes. 【Conclusion】These results showed that there was a trend of lightening in Fe isotopes of the ferromanganese nodules from the tropical to the subtropical to the warm-temperate zones.

• Differential Responses of Paddy Soil Multifunctionality in Topsoil and Subsoil to Microbial Diversity Loss

  ZHANG Bin, WEN Yang, WEI Zhanbo

  DOI: 10.11766/trxb202511180552

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  【Objective】This study aimed to examine the impacts of microbial diversity loss on paddy soil multifunctionality, and elucidate the regulatory roles of abundant, moderate, and rare microbial taxa. 【Method】Microbial diversity gradients (D0, D1, D3, D6) were established via the dilution-to-extinction approach and functional genes involved in C, N, P, and S cycling in topsoil (0-20 cm) and subsoil (40-60 cm) of a paddy field were quantified using high-throughput quantitative PCR. Soil multifunctionality was assessed using both the averaging and multi-threshold methods. High-throughput sequencing was employed to analyze the diversity, community structure, and co-occurrence network properties of the three microbial taxa and their relationships with soil multifunctionality. 【Result】Results showed that the responses of soil multifunctionality in topsoil and subsoil to microbial diversity loss were different. Compared with the original soil (D0), the averaging method indicated that different dilution levels (D1, D3, D6) significantly reduced topsoil multifunctionality. The reduction rates were 75.8%-85.8%, 74.6%-80.0%, and 59.8%-64.8% under the rice-fallow (RF), rice-wheat (RW), and rice-milk vetch (RM) cropping systems, respectively, with no significant differences among the dilution levels. In contrast, although subsoil multifunctionality showed minor fluctuations (ranging from 0.05 to 0.28), no significant differences were observed between different dilution levels and the original soil except for the D3 treatment under the RM cropping system. This pattern was further verified by the multi-threshold method. Although the diversity of all three taxa significantly decreased with increasing dilution, the community structure of rare taxa remained relatively stable. Co-occurrence network analysis revealed that topological properties (degree, clustering coefficient) of all three taxa decreased significantly in topsoil under dilution. In contrast, rare taxa in subsoil maintained stable network properties despite dilution. Correlation analysis further indicated that topsoil multifunctionality was closely linked to the diversity, composition, and network topology of all three microbial taxa, while subsoil multifunctionality was primarily associated with the degree and clustering coefficient of rare taxa, which underscores the key role of rare taxa in sustaining subsoil multifunctionality in the face of microbial diversity loss. 【Conclusion】Microbial diversity loss induces differential responses of soil multifunctionality in topsoil and subsoil, which is closely related to the diversity, community structure, and co-occurrence networks of microbial subcommunities in different soil layers.

• Hot-moment and Differences in Nitrification and N2O Production Potential Between Greenhouse and Open-field Vegetable Soils

  LIANG Linhao, WANG Xiaomin, FENG Xueying, HE Jian, YAN Xiaoyuan, SHAN Jun

  DOI: 10.11766/trxb202510100491

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  【Objective】Greenhouse vegetable systems, characterized by greenhouse covering, intensive fertilization, and frequent irrigation, create a semi-closed, warm, and humid microenvironment that more readily intensifies nitrification-driven nitrogen losses and greenhouse gas emissions compared with open-field vegetable systems. Greenhouse and open-field vegetable systems differ markedly in their environmental conditions, which may lead to variations in the intensity of nitrification and the level of nitrous oxide (N2O) production. However, the seasonal dynamics of nitrification activity and N2O production, as well as the underlying community response mechanisms under different management practices, remain poorly understood. 【Method】Soil samples were collected bimonthly (January to November) from representative greenhouse and open-field vegetable systems in Changshu, Jiangsu Province, China. Meanwhile, in situ N2O was collected from the vegetable field using the static chamber method. A microcosm experiment with combined inhibitors was employed to quantitatively assess the annual dynamics of nitrification activity and N2O production driven by complete ammonia-oxidizing bacteria (Comammox) and conventional ammonia-oxidizing microorganisms (Ammonia-oxidizing bacteria, AOB and Ammonia-oxidizing archaea, AOA). The absolute abundances of these microbial groups were determined using quantitative real-time PCR (qPCR) targeting the amoA gene. Additionally, high-throughput sequencing of the amoA gene was conducted to characterize the seasonal shifts in community structure and their responses to different management regimes. 【Result】Results showed that in situ N2O flux in greenhouse vegetable soils was significantly higher than that in open-field vegetable soils, with a pronounced “hot-moment effect” in March and May, contributing 71.23%±25.50% of the annual total flux. Soil nitrification activity exhibited a pronounced “hot-moment” effect in July and September, accounting for 52.41%±1.59% of the annual total, which coincided with the highest N2O production potential (61.35%±9.24% of the annual release). Functionally, the nitrification process and N2O production were predominantly mediated by AOB in greenhouse vegetable soils, whereas AOA dominated in open-field vegetable soils. The greenhouse vegetable system promoted the accumulation of Comammox abundance but suppressed its nitrification function, whereas both the abundance and activity of AOB were significantly enhanced. Correlation analysis revealed that soil temperature, dissolved organic carbon (DOC) and soil pH were the primary drivers of nitrification, while nitrate and DOC were the main factors shaping microbial community composition. 【Conclusion】This study elucidates the influence of differentiated management practices on the nitrification processes of soil nitrifying microorganisms, and demonstrates that the shift from open-field to greenhouse vegetable systems may increase AOB-driven N2O production. These findings provide a scientific foundation for optimizing nitrogen management and developing N2O mitigation strategies in vegetable cultivation systems.

• Soil Extracellular Enzyme Activity and Stoichiometry Along an Elevation Gradient in Southern Subtropical Mountainous Forests

  OU Mengfei, LIU Yanyan, HUANG Xinting, LI Zhiliang, PEI Guangting, SUN Zhaolin, ZHANG Jianbing, LI Zhongguo, SU Hongxin, WEI Haiyong, CHAO Lin

  DOI: 10.11766/trxb202511070532

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  【Objective】Determining the patterns of regulatory factors of soil extracellular enzyme activity along elevational gradients is critical for understanding microbial nutrient limitation and metabolic processes. This contributes to predicting the responses of soil biogeochemical cycles to global change. However, knowledge of the elevational patterns in soil extracellular enzyme activity and their stoichiometry, as well as their drivers, remains limited. 【Method】Soil samples (0-10 cm) were collected from different elevation gradients on Jinzhongshan Mountain in Guangxi, China. These samples were used to investigate the elevational patterns of soil physical and chemical properties, extracellular enzyme activities, and microbial nutrient limitations. Also, the major factors influencing microbial extracellular enzyme activities and their stoichiometry were evaluated. 【Result】 The results indicate that (1) soil water content (SWC), soil nutrient content, stoichiometric ratios, and microbial biomass content increased with increasing elevation. However, soil bulk density (BD), pH, and available phosphorus (AP) content decreased with increasing elevation. (2) The activities of carbon and nitrogen degradation-related enzymes, including β-glucosidase (BG), N-acetylamino glucosidase (NAG), and leucine aminopeptidase (LAP), exhibited no clear pattern with increasing elevational gradient. In contrast, acid phosphatase (ACP) activity initially increased, then decreased along with elevation, presenting a unimodal pattern. Vector analysis of ecoenzyme activities revealed that vector lengths were larger at middle and high elevations (1 429-1 691 m), suggesting an enhanced carbon limitation for soil microorganisms. Additionally, all vector angles were greater than 45°, indicating a widespread phosphorus limitation for soil microbes in the study region. (3) Compared with soil enzyme activity data at the global scale and in Chinese regions, soil enzyme activities related to carbon, nitrogen, and phosphorus cycling in Jinzhongshan, which is located in the transition zone from the eastern humid region to the western semi-humid and semi-arid region, were generally low. This suggested that soil microorganisms in this area were subject to relatively greater N and P limitations. Furthermore, compared to soils in humid regions, the activities of C-, N-, and P-cycling enzymes were lower, whereas the activities of enzymes associated with C and P cycling were relatively higher when compared with arid regions. (4) Mantel test results indicated that soil extracellular enzyme activity and their stoichiometry were significantly correlated with SWC, NO3--N, and microbial biomass nitrogen (MBN). Redundancy analysis (RDA) revealed that NO3--N and microbial biomass phosphorus (MBP) were the key factors driving variations in soil extracellular enzyme activities, whereas soil enzyme stoichiometry was primarily regulated by NO3--N, total phosphorus (TP), C:N, and MBP. (5) Partial least squares path modeling (PLS-PM) demonstrated that soil physical properties and microbial biomass directly influenced soil extracellular enzyme activities, whereas soil physicochemical properties together with microbial biomass exerted direct effects on enzyme stoichiometry.【Conclusion】Elevation affected extracellular enzyme activities mainly through regulating soil physical properties and microbial biomass, but indirectly modulated enzyme stoichiometry via altering soil physicochemical properties and microbial biomass. These findings contribute to enhancing the mechanistic understanding of how soil extracellular enzyme activities and their stoichiometric patterns respond to elevation gradients in mountain forest ecosystems under global climate change.

• Effects of Biochar Coupled with Cropping Patterns on Mollisol Soil Organic Carbon Fractions, Humus Characteristics, and Crop Yield

  LIU Zhihua, ZHANG Xinyu, GAO Ruichun, ZHOU Xin, WANG Yuchao, ZHANG Luyang, SONG Jiejiaen, JIANG Zhenfeng, LI Deping

  DOI: 10.11766/trxb202509190459

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  【Objective】This study aimed to explore the effects of the coupling of different biochar application depths and cropping patterns on the soil carbon pool and crop yield. 【Method】A long-term stationary experiment established in 2019 was adopted, with cropping pattern as the main plot and biochar application method as the subplot. Three cropping patterns were designed: soybean-maize rotation (SM), continuous soybean cropping (S), and continuous maize cropping (M). Three treatments were set up: biochar mixed application at 0-20 cm (B1), biochar mixed application at 0-40 cm (B2), and no biochar application (CK). Soil samples were collected from the 0-20 cm and 20-40 cm soil layers at the crop maturity stage in 2023, and the soil carbon fractions, humus components, and crop yield were determined. 【Result】The results showed that: the contents of soil carbon fractions (e.g., soil organic matter (SOM) and microbial biomass carbon (MBC)) in the rotation system were significantly higher than those in continuous cropping systems, and the SOM content under continuous soybean cropping was significantly higher than that under continuous maize cropping. The application of biochar at 4 500 kg?hm-2 had no significant effect on SOM content in the 0-20 cm soil layer, but it increased the activity of MBC in the 0-20 cm soil layer (by 11.3%-33.7%), optimized humus properties (humic acid (HA) content increased by 6.7%-25.7% while fulvic acid (FA) content decreased by 0.4%-22.5%). This treatment also improved crop yield (soybean yield increased by 24.2%-32.4% and maize yield increased by 13.0%-24.3%). Under the synergistic effect of rotation and biochar application, MBC content increased by 22.8%-33.7%, dissolved organic carbon (DOC) content increased by 17.6%-31.1%, readily oxidizable organic carbon (ROC) content increased by 14.9%-26.6%, HA content increased by 14.5%, FA content increased by 11.8%-15.5%, and the humus quality index (PQ) increased by 11.7%-17.4%.【Conclusion】The coupling of biochar application and crop rotation is beneficial for improving the soil carbon pool, enhancing carbon activity, optimizing humus properties, and increasing crop yield. This practice is expected to play an important role in future agricultural production and soil environment improvement.

• Effect of Foliar Application of Sorbitol-Chelated Potassium on Leaf Physiological, Biochemical Traits, and the Phyllosphere Bacterial Community in Wheat

  ZHENG Ruili, HAN Chuanhao, ZHAO Li, MA Zongbin, ZHANG Mingxia, ZHOU Minxue, JIANG Yuhan, HUANG Mingli, YAN Dongyun

  DOI: 10.11766/trxb202509040438

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  【Objective】This study aimed to elucidate the mechanism by which sorbitol-chelated potassium (SK) promoted nutrient uptake and utilization in wheat leaves.【Method】In this study, sorbitol-chelated potassium was used as the test foliar fertilizer and wheat cultivar Tainong 108 as the experimental material to elucidate the effects of foliar application of different potassium forms on leaf physiological and biochemical traits as well as phyllosphere microbial community structure. Structural equation modeling (SEM) was further employed to quantify the contribution of each factor to wheat yield, thereby providing a theoretical basis for the yield-enhancing mechanisms of chelated potassium fertilizers.【Result】Results from two consecutive field seasons showed that, compared with potassium chloride (K) and a mixture of sorbitol and potassium chloride (S+K), the SK treatment significantly affected wheat leaf physiological and biochemical characteristics and bacterial richness. (1) Mean yield increases were 24.74% and 18.76%, respectively. (2) Grain Mn concentration increased by 16.14% and 12.12%, grain K by 45.68% and 21.96%, late grain-filling stage leaf K by 81.01% and 24.44%, and maturity satge leaf C by 2.52% and 1.95%. (3) Activities of catalase, peroxidase and superoxide dismutase were better maintained, while malondialdehyde content decreased by 25.65% and 7.51%; the activities of protein synthesis enzymes (nitrate reductase, glutamine synthetase and glutamate-pyruvate transaminase) were sustained during mid-to-late grain filling satge. (4) Relative abundance of Firmicutes rose by 57.36% and 50.00%, whereas Actinobacteria declined by 21.63% and 4.26% and Cyanobacteria by 36.05% and 62.03%.【Conclusion】SK treatment enhanced yield and grain quality through the synergistic regulation of wheat leaf element content, antioxidant capacity and protein synthesis enzyme activities. SEM further demonstrated that all measured indicators were directly or indirectly linked to final grain yield.

• Functional Traits of Leaves and Adaptation Strategies of Antioxidant Enzymes in Different Rainfall Conditions of Fraxinus malacophylla Seedlings to Karst Habitats

  ZHENG Shaojie, WANG Lin, SHI Shunrou, LI Lehao, ZHANG Tao, GOU Rongxin, ZHANG Chengmeng, CHEN Yaoyi, DONG Qiong

  DOI: 10.11766/trxb202510180503

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  【Objective】This study aimed to explore the response of functional traits of leaves and the antioxidant enzymes of Fraxinus malacophylla seedlings to rainfall characteristics in different rocky desertification habitats.【Method】This study focused on 2-year-old F. malacophylla seedlings and adopted a two-factor randomized block design. Different karst habitats were set up, including no stone whole soil S0 (all soil layers), half stone half soil S1/2 (upper 1/2 was soil layer, lower 1/2 was Karst layer), and more stone less soil S3/4 (upper 1/4 was soil layer, lower 3/4 was Karst layer), as well as different rainfall time intervals of 3 days (I3d), 6 days (I6d), and 9 days (I9d). During the experiment, the growth and physiological changes characteristics of F. malacophylla seedlings in different Karst habitats were analyzed.【Result】The results showed that under the same rainfall time interval, the root biomass of F. malacophylla seedlings increased with the increase of rock coverage (P<0.05), while the stem and leaf biomass showed a trend of first increasing and then decreasing. As the thickness of Karst increases, the biomass accumulation of various organs from high to low was in the order of roots, stems, and leaves. Under a 3-day rainfall treatment, the leaf area, leaf circumference, leaf length, leaf width, and potassium (K+), calcium (Ca2+), sodium (Na+), and magnesium (Mg2+) contents in various organs of F. malacophylla seedlings increased with the increase of rock coverage (P<0.05). Also, the S3/4 Karst habitat with 6-day and 9-day interval rainfall significantly inhibited the leaf traits and accumulation of K+, Ca2+, Na+, and Mg2+contents in F. malacophylla seedlings. F. malacophylla seedlings adapt to different Karst habitats through various physiological and biochemical regulation strategies, including biomass allocation optimization, interorgan nutrient transport strategies such as Na? transfer to stems, Ca2?/Mg2? enrichment in leaves, reduction of leaf number (LN), activation of superoxide dismutase (SOD), and peroxidase (POD) enzyme activities, and increase soluble protein (SP) content.【Conclusion】In summary, a 6-day rainfall interval and a half stone and half soil habitat (I6dS1/2) are the optimal combination for seedling growth. This study provides a theoretical basis for the cultivation and promotion of F. malacophylla seedlings under different levels of rocky desertification in the southwestern Karst region. It is recommended to adopt a water replenishment interval of about 6 days for afforestation and nurturing in areas with moderate rocky desertification.

• Study on Thermal Desorption Difference and Mechanism of Typical Petroleum-contaminated Clay Minerals

  WANG Jixing, XU Baozhu, LI Qiang, DU Wenqiang, LI Jufeng, ZHANG Xiaofei, WENG Yibin, XU Feng, GUO Shuhai, ZOU Jiajing, XIANG Geng, SHAO Zhiguo

  DOI: 10.11766/trxb202507080334

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  【Objective】Thermal desorption technology is widely applied in the remediation of petroleum-contaminated soil. However, the significant differences in the thermal desorption characteristics due to different types of clay mineral, significantly impact the setting of process parameters and the efficiency of thermal desorption. Thus, this study aims to clarify the differences in thermal desorption mechanisms among various petroleum-contaminated clay minerals and to guide the determination of application parameters for thermal desorption engineering.【Method】In this study, contaminated soil with typical clay minerals including montmorillonite, chlorite and kaolinite were prepared to investigate the thermal desorption kinetic properties, and characterize their microstructures to explore the differences in thermal desorption and the influencing factors. 【Result】The results showed that the thermal desorption of three contaminated soil could be divided into three stages. Phase I (30 ℃-110 ℃), in this phase, montmorillonite and chlorite exhibited a three-dimensional diffusion desorption mechanism, while kaolinite followed a first-order kinetic desorption mechanism. The activation energies (Ea) were 58.64, 124.96 , and 75.22 kJ mol-1, respectively. Phases II (110 ℃-370 ℃) and III (370 ℃-520 ℃) followed a first-order kinetic mechanism. 【Conclusion】The physicochemical properties and microstructure of clay minerals are the main parameters accounting for the differences in their thermal desorption characteristics. Montmorillonite mainly relied on azeotropic stripping, diversion diffusion, catalytic cracking, and interlayer structure adsorption, which promoted the thermal desorption of petroleum hydrocarbons. The influencing mechanism of chlorite involved physical barrier and catalytic cracking, showing an inhibitory effect at temperatures <200 ℃. However, thermal desorption of petroleum hydrocarbons was promoted when the temperature was >200 ℃. The influencing mechanism of kaolinite was mainly chemical adsorption, which generally inhibited the thermal desorption of petroleum hydrocarbons. This study provides theoretical guidance for determining the thermal desorption process parameters of petroleum-contaminated soils containing different types of clay minerals.

• Quantum Regulationof Pb2+ Adsorption by Electric Field at the Mineral Surfaces: Polarization and Polarization-induced Covalent Interaction

  QU Jiawen, TANG Yuting, XI Shuning, LIU Xinmin

  DOI: 10.11766/trxb202509090444

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  【Objective】The interactions between heavy metals and mineral particles play a key role in the passivation/activation of heavy metals, significantly impacting on soil health, food safety and ecological stability. However, quantitative characterization of the type and intensity of these interactions remains challenging. 【Method】Based on orbital hybridization theory, this study quantitatively evaluated the polarization, polarization-induced covalent interactions and Coulomb interactions of the heavy metal Pb2+ on mineral surfaces.【Result】The results show that: (1) The surface charge number follows the order: montmorillonite > silica > kaolinite > hematite. However, the order of surface negative charge density and electric field strength is kaolinite > silica > montmorillonite > hematite, due to differences in specific surface area. (2) The adsorption capacity of Pb2+ depends on the surface charge number, consistent with its trend, while the adsorption strength is governed by the surface electric field. (3) Effective charge coefficients of Pb2+ on soil mineral surfaces, quantified using orbital hybridization theory, averaged as follows: kaolinite (1.848 ± 0.038) > montmorillonite (1.782 ± 0.062) > silica (1.615 ± 0.029) > hematite (1.516 ± 0.036). Based on the effective charge coefficient, the type and intensity of the adsorption force of Pb2+ on mineral surfaces could be assessed. (4) The adsorption of Pb2+ on the surfaces of montmorillonite, kaolinite, and silica is primarily driven by Coulombic forces, which account for more than half of the total adsorption energy. In contrast, adsorption on the surface of hematite is mainly governed by covalent interactions, contributing approximately 65%. Additionally, polarization effects depended on the surface electric field and polarization-induced covalent interactions play a crucial regulatory role in the adsorption of Pb2+. (5) Infrared spectroscopy analysis revealed that the absorption peak of the Si-O bond on the surface of silicon-containing minerals shifted to higher frequencies (blue shifts) as the surface electric field increased. This shift indicates an enhanced polarization-induced covalent interaction between O atoms and Pb2+ on the mineral surfaces. Also, the strong electric field on the surface of hematite enhances the polarization of the -OH group and H2O molecules, leading to the formation of covalent interactions between Pb2+ and -OH groups. Consequently, the Fe-O-Fe bonds are strengthened as the pH increases. 【Conclusion】This study demonstrates that the adsorption of Pb2+ on the surface of soil minerals has polarization and polarization-induced covalent effects, and quantitatively evaluates its contribution. The effective charge coefficient of Pb2+ increases with the increase of surface electric field strength, and the polarization and polarization-induced covalent interaction between mineral surface and Pb2+ increase with the increase of pH. This indicates that polarization and polarization-induced covalent interaction have an important influence on the interaction between Pb2+ and the mineral surface. Additionally, this research establishes a theoretical foundation for the directional regulation of heavy metal passivation/activation in soils through modulation of interfacial forces.

• Research Progress in Numerical Modeling and Simulation of Biofilm Growth in Porous Media

  CHEN Xiaowei, LI Xueying, YANG Xiaofan

  DOI: 10.11766/trxb202505120216

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  The growth and evolution of biofilms in porous media involve complex coupled physicochemical and biological processes. Their pronounced multi-scale characteristics, heterogeneity of the media, and uncertainties in model parameterization have led to fundamental divergences in the theoretical frameworks of numerical models across different scales. This poses significant challenges for the accurate characterization and prediction of biofilm dynamics. In recent years, advances in computational techniques have driven substantial progress in pore-scale, continuum-scale, and cross-scale coupled numerical modeling and simulation of biofilm growth. However, considerable bottlenecks remain in model development, validation, and utilization. These include difficulties in characterizing three-dimensional microscopic pore structures, the complexity of constructing biofilm growth dynamics models, the lack of quantitative standards for cross-scale multiprocess coupling strategies, and the scarcity of experimental data required for model parameterization. Based on the mechanisms of biofilm growth dynamics in porous media, this paper reviews the research progress of pore-scale, continuum-scale, and multi-scale coupling numerical models, analyzes the theoretical foundations, numerical algorithms, application cases, applicability, and limitations of biofilm growth models at different scales. It also summarizes the application potential of three-dimensional imaging technologies, outlines the emerging trends in mechanistic representation of the complete biofilm growth processes, and explores the optimization pathways for cross-scale coupling modeling strategies. This review provides a theoretical basis for the selection and improvement of biofilm growth models, and offers technical support for the engineering application of soil microbial technologies in environmental pollution control and ecological restoration.

• Micro-CT Analysis and Agronomic Effects of Organic-inorganic Amendment Mulching on the Regulation of the Pore Architecture in Saline-Alkali Topsoil

  HU Xinhui, WANG Lu, LIU Fangfang, GUO Honghai, JIA Xi

  DOI: 10.11766/trxb202506090267

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  【Objective】This study aimed to clarify the effects of organic-inorganic regulating material mulching on the pore structure of saline-alkali topsoil and select suitable mulching materials for crop seed germination.【Method】Four experimental treatments were set up, namely CK (native soil), JX1 (composted cow dung + (a mixture of HA, CaO, MgO, SiO₂, and Na₂SeO₃)), JX2 (spent substrate + (a mixture of HA, CaO, MgO, SiO₂, and Na₂SeO₃)), and JX3 (composted straw + (a mixture of HA, CaO, MgO, SiO₂, and Na₂SeO₃)). A field operation involving digging V-shaped ditches→sowing→applying amendments→rolling was adopted. Soil structure and its pore characteristics were analyzed using micro-computed tomography (micro-CT) scanning, combined with field experiments and mathematical statistical analysis.【Result】The results showed that all treatments reduced soil bulk density and improved soil water capability and saturated hydraulic conductivity. Specifically, the saturated hydraulic conductivity of JX2 and JX3 was 2.4 times that of CK, and their soil water capability increased by 17.8%–19.5%. In terms of pore structure, different mulching material significantly affected the quantity and distribution characteristics of soil pores: The JX2 and JX3 showed significantly increased total porosity and connected porosity, while JX1 had lower total porosity; JX3 was dominated by macropores with fewer micropores, whereas JX2 had a more balanced pore size distribution. Comparison of pore structure parameters revealed that JX2 and JX3 had similar values of fractal dimension, anisotropy, and circularity ratio, but the Euler number of JX2 was significantly lower than that of JX3. This indicated that both treatments enhanced the complexity and stability of the pore structure, and JX2 had better pore connectivity. These pore structure optimizations significantly improved the microenvironment for seed germination, thereby increasing the emergence rate and improving the seedling growth traits of foxtail millet, with JX2 showing particularly notable effects.【Conclusion】In conclusion, Organic-inorganic amendment mulching can enhance soil structural performance by optimizing the pore characteristics of saline-alkali soil and create a suitable soil microenvironment for crop seed germination. Among the tested materials, the spent mushroom substrate residue-based (JX2) and straw-based (JX3) regulating materials showed showed the most significant effects.effects, These combinations are effective technical approaches for efficiently regulating the microenvironment of coastal saline-alkali soil and breaking surface soil compaction.

• Digital Mapping of Soil Argillic Horizon Thickness in Northeast China

  HUANG Pu, HUANG Qing, WANG Jingtian, SHI Yuhan, CAI Shenghong

  DOI: 10.11766/trxb202507040326

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  【Objective】The argillic horizon is a subsurface secondary layer formed by the accumulation of soil clay particles, and its thickness exerts a crucial regulatory effect on soil processes and vegetation growth in Alfisols. Understanding its spatial distribution is critical for effective land management, particularly in agriculturally important regions such as Northeast China. However, there is still limited knowledge of the spatial variability in argillic horizon thickness, and predictive studies on this topic are scarce. Traditional understanding has largely relied on extensive field surveys combined with geostatistical methods, which are often resource-intensive and may not be efficient over large regions. This study aims to develop a robust predictive model to map the spatial distribution of argillic horizon thickness across the three northeastern provinces of China by integrating limited soil profile observations with a rich set of environmental covariates. 【Method】A total of 311 soil profile samples with argillic horizons were collected in Northeast China. These samples incorporated data from recent field surveys and historical soil records. Consistent with the SCORPAN framework, 71 environmental covariates were selected to correspond to relief, climate, organism, and soil factors. Dual feature selection was conducted via Pearson correlation analysis and the Boruta algorithm. The quantile regression forest (QRF) model was then adopted for spatial modeling, cross-validation, and uncertainty estimation. Rigorous evaluation of model performance and uncertainty estimation was conducted through 50 repetitions of 10-fold cross-validation, and accumulated local effects (ALE) plots were generated to interpret the relationship between key predictors and the target variable. 【Result】The average results from 50 iterations showed that the model achieved a coefficient of determination (R2) of 0.32, a root mean square error (RMSE) of 24.34 cm, and a mean absolute error (MAE) of 19.47 cm. This performance is significantly superior to that of most regional and national scale soil thickness prediction studies (R2 = 0.11–0.41). The prediction interval coverage percentage (PICP) was 86.2%, which is close to the predefined 90% prediction interval (PI), indicating high reliability of the uncertainty estimation. Soil and climate factors were generally more influential than organism and relief factors, with soil thickness (ST) identified as the most critical driving factor. The spatial prediction results indicated a distinct decreasing trend in argillic horizon thickness from the southwest to the northeast. The western and southwestern regions of the study area exhibited the thickest argillic horizons (mostly over 80 cm, with some regions ranging from 100 to 125 cm), while the northern, eastern, and southeastern regions had thinner ones (mostly 20–35 cm, with some regions below 20 cm). High prediction uncertainty was concentrated in mountainous and hilly regions with sparse soil survey points. 【Conclusion】This study confirms the feasibility of mapping argillic horizon thickness using a machine learning approach combined with environmental covariates, even in large, complex landscapes with limited soil observations. Future research could focus on integrating proxies for parent material and pedogenic age to enhance model accuracy, as well as exploring the spatial prediction of other argillic horizon properties (e.g., upper boundary and compactness). This study not only addresses the gap in argillic horizon thickness prediction in Northeast China, but also offers valuable insights for optimizing regional land management strategies.

• Assessment of Three Amendments for Improving Acid-Red Soil Using Ecosystem Multifunctionality

  WAN Fang, MING Runting, NA Liping, GU Yuyu, WANG Wei, HU Hongqing, TAN Wenfeng, WU Yupeng

  DOI: 10.11766/trxb202508050382

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  Abstract: 【Objective】This study aimed to comprehensively evaluate the ameliorative effects of amendments application on acid red soil. 【Method】A field trial was conducted in an acid red soil region of Zhuji City, Zhejiang Province. Three acid soil amendments were tested: a vermicompost-oyster shell powder-biochar composite amendment (C), a high-alkalinity biochar amendment (B), and a silicon-calcium-potassium-magnesium amendment (S), with an untreated control (CK). Through the measurement of twenty specific indicators selected from four major categories (soil acidity, nutrient supply, microbial community characteristics, and plant productivity) that reflect fundamental ecological processes, we analyzed the effects of different treatments on ecosystem multifunctionality (EMF). 【Result】The results showed that compared with CK, three amendments significantly reduced soil acidity, with B treatment demonstrating the most pronounced acid-reducing effect (61.81% decrease in exchangeable Al3+ and 62.23% decrease in exchangeable acidity). C treatment elevated total nutrients and available phosphorus content by 14.99%-22.43% relative to CK. Compared with CK, all amendments significantly increased bacterial diversity and evenness, while C and S treatments further enhanced bacterial community stability. Regarding plant productivity, B and C treatments increased yields by 26.87% and 25.47%, respectively, compared with CK, while treatment S enhanced aboveground biomass by 27.30% relative to CK. Evaluation of ecosystem multifunctionality revealed that C, B, and S treatments improved EMF by 112.38%, 95.98%, and 129.71%, respectively, compared with CK. 【Conclusion】These findings demonstrate that while amendments significantly enhanced EMF in acid soil, their effects on specific ecological indicators vary. Therefore, during practical implementation, suitable soil amendments should be selected and applied based on the characteristics and types of the acid soil.

• Effects of Salinity and Fertilization Interactions on Short-Term Transformation Processes of Soil Organic Carbon in Coastal Saline-Alkali Soils and Their Microbial Mechanisms

  JIANG Yuhan, YAO Yao, XU Lixin, SOHAIL Aslam, WAN Dan, LIU Congqiang, YU Guanghui

  DOI: 10.11766/trxb202510050483

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  【Objective】 Coastal saline-alkali lands represent a critical yet fragile ecosystem where soil carbon dynamics are simultaneously influenced by natural salinity stress and anthropogenic management practices. Clarifying this interactive mechanism is essential for understanding carbon sequestration potential and for developing adaptive management practices in coastal agroecosystems under salinity stress. Specifically, we sought to determine how different fertilization strategies modulate the response of soil carbon pools and microbial processes to varying degrees of salt stress over a short temporal scale. Thus, the specific objective was to clarify the effects of the interaction between salinity and fertilization on the short-term turnover of soil organic carbon in coastal saline-alkali soils and to elucidate the underlying microbial driving mechanisms.【Method】 The soil used for this study was collected from a typical coastal saline area in the Bohai Rim region and subjected to a 30-day controlled pot experiment. Three salinity gradients (0 g·kg-1, 2 g·kg-1, and 4 g·kg-1 NaCl) were established and combined with four fertilization treatments: control (CK), chemical fertilizer (NPK), chemical fertilizer plus straw (NPKS), and bio-organic fertilizer (BF). A systematic analysis was carried out, encompassing measurements of soil carbon fractions (such as dissolved organic carbon and mineral-associated carbon), peroxidase activity, microbial community structure (via high-throughput sequencing), and the expression of key functional genes related to the carbon cycle. 【Result】 Significant interactive effects between salinity and fertilization were observed across most of the measured soil and microbial parameters. Compared to the non-saline condition, the NPKS treatment under moderate salinity (2 g·kg-1) significantly increased soil dissolved organic carbon content (about 39%) and enhanced peroxidase activity, suggesting a stimulated decomposition of added organic materials. Concurrently, this treatment shifted the microbial community structure, favoring r-strategists over K-strategists, indicating a microbial functional adaptation towards faster growth and resource exploitation under the combined input of organic substrate and mild salt stress. In contrast, higher salinity (4 g·kg-1) markedly compromised the stability of iron-bound organic carbon, with its content decreasing by over 50% in the control treatment, highlighting a severe disruption of mineral-organic matter associations under strong saline conditions. The microbial r/K strategy composition showed a strong correlation with soil pH, which was itself modulated by the fertilization treatments. Furthermore, the expression of carbon cycle functional genes exhibited a clear non-linear response to salinity, reaching its peak at the 2 g·kg-1 salinity level, which points to a hormesis-like effect where low-level stress temporarily enhances microbial metabolic potential.【Conclusion】 The results demonstrate that the combined application of chemical fertilizer and straw can facilitate the transformation of active carbon pools in the short term by modulating microbial community function towards a more metabolically active state. However, elevated salinity constrains carbon stability primarily by weakening mineral protection mechanisms, thereby potentially offsetting the benefits of organic amendments in highly saline environments. This study provides insights into the short-term microbial regulation of carbon cycling in saline environments and highlights the importance of integrated management strategies that consider salinity thresholds. The findings imply that tailoring fertilization practices, such as straw incorporation, to specific salinity levels could optimize short-term carbon turnover and contribute to the sustainable management of coastal saline-alkali soils.

• Synergistic Effects of Combined Application of Organic Materials and Calcium-Based Amendments on Soil Fertility and Crop Growth in Newly Reclaimed Red Soil

  XUE Ya, ZHANG Congzhi, MA Xuewei, ZHAO Zhanhui, MA Zhiwei, CHEN Zhuo, WANG Yaru, ZHANG Nan, PAN Hui, FAN Beibei, NIU Xiaoni, SHEN Weishou, ZHANG Jiabao

  DOI: 10.11766/trxb202510270512

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  【Objective】Newly reclaimed red soils are generally characterized by high acidity and low organic matter content, which severely constrain soil fertility improvement and crop productivity. This study aimed to evaluate the effects of combined application of organic materials and calcium-based amendments (lime and calcium salts) on soil fertility enhancement and acidification control in newly reclaimed red soil.【Method】A field experiment was conducted in Ji’an, Jiangxi Province (since 2023) with six treatments: chemical fertilizer alone (CK); CK plus natural humic material (9 000 kg·hm?2), biostimulant (1 500 kg·hm?2), organic fertilizer (7 500 kg·hm?2), and 1 500 kg·hm?2 calcium salt (T1); CK plus the same organic materials combined with 3 000 kg·hm?2 calcium salt (T2); CK plus the same organic materials combined with 1 500 kg·hm?2 lime (T3); CK plus the same organic materials combined with 3 000 kg·hm?2 lime (T4); and CK plus the same organic materials combined with 7 500 kg·hm?2 fermented residue (T5). Soil physicochemical properties, carbon fractions, and crop growth were analyzed using physical fractionation, scanning electron microscopy, and multivariate statistical methods.【Result】The addition of lime and calcium salts significantly regulated soil acidity, with soil pH increasing by up to 16.2%, and markedly enhanced phosphorus availability, as available phosphorus increased by more than six fold. Application of natural humic materials rapidly increased soil carbon pools, with soil organic carbon and particulate organic carbon increasing by up to 84.0% and 263.9%, respectively. However, the sole application of fermented residue aggravated soil acidification and reduced carbon stability. Microscopic observations and multivariate analyses further demonstrated that the combined application of natural humic materials with low rates of lime or calcium salts synergistically improved soil pore structure, increased microbial biomass carbon and dissolved organic carbon (by up to 94.6% and 122.7%, respectively), and substantially promoted both aboveground and belowground biomass of rapeseed (increases exceeding 7-fold).【Conclusion】The combined application of organic materials and calcium-based amendments effectively regulates soil acidification, enhances carbon stability, and promotes coordinated improvement of soil fertility and crop growth in newly reclaimed red soil. This strategy provides a scientific basis and technical reference for the rapid improvement of soil quality in newly reclaimed farmland.

• Effects of Nano CeO2 Seed Soaking on Seed Germination and Physiological Characteristics of Alfalfa Under Drought-Salinity Stress

  YANG Jinhui, TONG Yuhua, WANG Xiaotong, MA Yonglong, YU Dongwen, LI Shuxia

  DOI: 10.11766/trxb202510290517

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  【Objective】In arid and semi-arid regions, the coexistence of drought and high salinity imposes severe constraints on crop establishment, impairing seed germination and early seedling growth, consequently causing substantial agricultural losses. Seed priming with nanoparticles represents an emerging, economically viable, and environmentally sustainable approach to enhance crop performance under adverse conditions. Thus, harnessing this new approach in developing sustainable strategies to improve plant stress resilience is imperative.【Method】This study investigated the efficacy of cerium oxide nanoparticles (CeO2 NPs) as a seed priming agent in alleviating the detrimental effects of combined drought-salinity stress (simulated by 60 000 mg·L-1 polyethylene glycol (6% PEG-6000) and 50 mmolL-1 saline-alkali (NaCl：Na2SO4=9：4，pH adjusted by NaHCO3)) on alfalfa (Medicago sativa L.). Seeds were treated with CeO2NP suspensions (0, 1.0, 2.5, 5, 10, 15, and 20 mg·L-1) for 12 h and subsequently subjected to stress conditions for 14 d.【Result】The results demonstrated that drought-salinity stress significantly suppressed germination and seedling growth. However, priming with CeO2 NPs notably mitigated these inhibitory effects in a concentration-dependent manner, with the most pronounced improvements observed at 5 mg·L-1. At this optimal concentration, significant enhancements were recorded in germination potential, germination rate, germination index, vigor index, root length, shoot height, and fresh biomass compared to the non-primed stress group. Also, 5 mg·L?1 CeO2NP treatment also reduced membrane damage, as indicated by lower relative electrical conductivity (REC) and malondialdehyde (MDA) content, and decreased hydrogen peroxide (H2O2) accumulation under combined stress. Concurrently, it elevated the activities of antioxidant enzymes (catalase and ascorbate peroxidase) and the concentrations of osmoregulatory compounds (proline and soluble sugars). Correlation analysis revealed strong positive associations among growth parameters, which were negatively correlated with membrane injury indices. These findings suggest that CeO2 NP priming strengthens the synergistic interaction between the antioxidant system and osmotic adjustment, thereby preserving membrane integrity and promoting germination and seedling growth under combined stress. 【Conclusion】In conclusion, seed priming with 5 mg·L?1 CeO2 NPs effectively improves alfalfa establishment under drought-salinity stress conditions, offering a promising nano-agronomic strategy for sustainable crop production in marginal environments.

• Effects of Long-term Straw and Straw Ash Return on Rice Yield and Soil Potassium Supplying Capacity

  ZHOU Yiting, WU Zheng, WEI Xuejiao, YUAN Weiqi, WEI Zongqiang, ZENG Yanhua, WU Jianfu1

  DOI: 10.11766/trxb202508090386

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  【Objective】This study aimed to evaluate the effects of long-term straw and straw ash application on rice yield and soil potassium (K) supply capacity.【Method】Based on a long-term field experiment initiated in 2010 in Jinxian, Jiangxi Province, four treatments were established: no straw return and no fertilizer (CK), chemical fertilizer alone (NPK), full straw return combined with chemical fertilizer (NPK+RS), and full straw ash return combined with chemical fertilizer (NPK+RA). Soil samples (0-20 cm) were collected after the late rice harvest in 2023 to determine total K and different K fractions, K content at different adsorption sites of clay minerals, K release kinetics, and quantity/intensity (Q/I) relationship, and rice yield was analyzed accordingly.【Result】Fertilization significantly increased rice yield and soil K content. Under equal NPK nutrient inputs, NPK+RS and NPK+RA increased average annual yields of early rice by 5.22% and 3.53%, and late rice by 3.68% and 2.41%, respectively, compared with NPK. Water-soluble K showed little variation among fertilization treatments. Compared with NPK, non-exchangeable K in NPK+RS and NPK+RA increased by 13.16% and 17.12%, respectively. NPK+RA significantly enhanced exchangeable K, effective K, and total K by 5.41%, 2.87%, and 3.09%, respectively, and its exchangeable and effective K contents were 7.88% and 4.99% higher than those under NPK+RS. Fertilization significantly increased K contents at clay mineral adsorption sites. Compared with NPK, K contents at the mineral surface (p sites), edge (e sites), and interlayer (i sites) increased by 45.07%, 10.09%, and 6.27%, respectively, under NPK+RS; the corresponding increases under NPK+RA were 49.46%, 16.97%, and 11.91%. During K release, no significant differences were observed among fertilization treatments in the rapid-release stage. In the slow-release stage, compared with NPK, cumulative K release increased by 19.69% and 9.07%, and the release rate increased by 19.66% and 9.09% under NPK+RS and NPK+RA, respectively, with NPK+RS showing significantly higher values than NPK+RA. In addition, Q/I analysis indicated that both NPK+RS and NPK+RA optimized soil K supply capacity and intensity more effectively than NPK.【Conclusion】Under equal NPK nutrient inputs, straw and straw ash return combined with chemical fertilizer were superior to chemical fertilizer alone in improving rice yield and enhancing soil K supply capacity. Considering the adverse environmental impacts of straw burning, direct straw return combined with chemical fertilizer is recommended for preferential promotion.

• Comparison of the Influence of 18S-rRNA Gene Primer Selection on the Assessment of Eukaryotic Biodiversity in Urban Soil: A Case Study of Ningbo City

  MA Shangfei, GONG Xin, SHANGGUAN Huayuan, YAO Haifeng, SUN Xin

  DOI: 10.11766/trxb202507260360

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  【Objective】Soil eukaryotes are key indicator organisms for soil health in ecosystems, and changes in their diversity and community structure can effectively reflect the evolution of soil quality. In high-throughput sequencing-based studies on eukaryotic diversity, the selection of amplification primers directly affects the number of sequences of detected taxa, thereby determining the accuracy of biodiversity assessment. However, the impact of primer selection on the assessment of soil eukaryotic diversity remains timidly explored.【Method】 This study focused on soils from seven typical urban land use types in Ningbo City. Amplification was only conducted for two pairs of widely used 18S-rRNA gene V4 region primers (NF1F_18Sr2bR, TAReuk454FWD1F_TAReukREV3R). The study systematically compared the effects of different primers on the assessment of soil eukaryotic community composition and diversity, and analyzed the differences between two bioinformatic methods: Amplicon sequence variants (ASVs) and operational taxonomic units (OTUs). 【Result】That the proportion of amplification in eukaryotes for the NF1F_18Sr2bR primer was significantly higher than that of TAReuk454FWD1F_TAReukREV3R. Different primers exhibited a preference for specific soil eukaryotic taxonomic groups. Specifically, at the ASVs level, the NF1F_18Sr2bR primer preferred fungi, protozoa, nematoda, arthropoda, and annelida; at the OTUs level, the TAReuk454FWD1F_TAReukREV3R primer preferred protozoa and arthropoda, while the NF1F_18Sr2bR primer preferred nematoda, and annelida. Among the primers, NF1F_18Sr2bR was more appropriate for detecting rare species. The rare species of fungi, nematoda, and annelida amplified by this primer accounted for 12.09%, 38.31%, and 58.33% of their total sequences, respectively. In contrast, TAReuk454FWD1F_TAReukREV3R was more suitable for detecting shared species, as it detected 804 shared species OTUs across different land use types, which was higher than that detected by the other primer. Both primer selection and analytical methods collectively determine the differences in α-diversity assessment, but they do not determine the variations in β-diversity or the effects of environmental factors on community structure. In terms of α-diversity, for both primer pairs, the differences in α-diversity among different land uses were greater at the ASV level than at the OTU level. With respect to β-diversity, the explanatory power of the OTUs level for community diversity was higher than that of the ASVs level. 【Conclusion】This study revealed the critical impact of primer selection on the assessment of soil eukaryotic diversity. In future studies, primers and analytical methods should be selected appropriately based on target taxa and research objectives to ensure the accuracy of community structure and diversity assessment.

• The Impact Mechanism of Different Soil Cover Thicknesses on Soil Erosion and Nutrient Loss in Open-pit Coal Mine Dump

  XIONG Shuzhen, ZHANG Yanan, ZHANG Taiyu

  DOI: 10.11766/trxb202507310367

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  【Objective】The thickness of soil cover is a key factor determining the ecological restoration effectiveness of the open-pit coal mine dump. A reasonable reclamation thickness directly affects the effects of soil erosion control, nutrient retention, and vegetation restoration.【Method】Taking the dump of Fushun West Open-pit Mine as the research object, a platform-slope model with a height of 50 cm, a platform width of 40 cm, and a slope of 25°was constructed. An indoor simulated rainfall test was conducted, and the rainfall duration was 120 min. During the rainfall process, to record the development process of the rill, one section was taken along its longitudinal direction at the top, middle, and bottom, respectively. The width and depth of the trench were measured with a steel ruler, and the length of the trench was recorded simultaneously. The average values were respectively taken as the morphological characteristic parameters of the rill. The measurement time was from the beginning of the self-generated flow. Within the first 20 min, measurements were taken every 2 min, and from 20 to 120 min, measurements were taken every 6 min. Meanwhile, the runoff and sediment yield were collected every two min using the runoff bucket. After 12 h of sedimentation, the supernatant was collected, and the flow rate was measured with a graduated cylinder. The sedimentary soil was dried in an oven at 105℃ to a constant weight, and the moisture content was measured. Afterwards, the runoff volume was estimated as the sum of the water volume measured by the graduated cylinder and the soil moisture content, while the sediment yield was considered as the dry weight of silt and sand. After determining the sediment yield, nutrient con-tent analysis was conducted. Soil organic matter was determined by the potassium dichromate external heating method, total nitrogen was determined by the Kjeldahl nitrogen analyzer method, and available phosphorus and available potassium were determined by ICP-MS. By analyzing the obtained data, the influence mechanism of different soil cover thicknesses on the sediment yield characteris-tics and nutrient loss process of the waste dump was revealed.【Result】(1) Under different soil cover thicknesses, rill erosion was dominant. The process can be divided into the rill head formation stage, the rill erosion development and evolution stage, and the stable stage. The maximum development rates were 0.65-3.0 cm∙min-1, 1.5-16.75 cm∙min-1, and 0.38-1.25 cm∙min-1, respectively. The soil cover thickness was linearly and positively correlated with the time of the maximum sediment yield rate and the time of the maximum sediment content, with R2≥0.93. That is, increasing the soil cover thickness can effectively delay the occurrence of erosion and reduce the output of sediment. (2)Also, the rate of soil nutrient loss decreased with the increase in soil cover thickness. Under the conditions of 10 cm, 20 cm, and 30 cm soil cover, it was 4.34%-55.11%, 4.97%-46.78%, and 2.61%-40.93%, respectively. The overall degree of nutrient loss followed available phosphorus > total nitrogen > available potassium > organic matter. (3) The dynamics of nutrient loss and the rate of sediment yield and flow showed a synergistic change pattern. The cumulative contribution ratios of sediment yield and flow in the first, second, and third stages of erosion ditch development were 2.3%-3.4%, 55%-71%, and 31%-43%, respectively, and the cumulative contribution ratios of sediment yield were 0.7%-3%, 47%-88%, and 13%-52%, respectively. Additionally, the contribu-tion ratios of cumulative nutrient loss were 0.61%-4.8%, 35.10%-81.48%, and 14.48%-63.98%, respectively. The second stage of fur-row development was the main stage of sediment yield and nutrient loss, but the peak loss rate was delayed with the increase of soil cover thickness.【Conclusion】Based on the goal of controlling soil erosion and nutrient loss, it is recommended that in the reclamation project of dumps under similar climate-soil conditions, the soil cover thickness be set at 30 cm.

• Hyperspectral Soil Salinity Inversion and Interpretability Analysis Based on CR-FOD Transform and XGBoost Model

  YANG Jicun, GUO Bing, HAN Baomin

  DOI: 10.11766/trxb202508020373

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  【Objective】Under the global context of climate change and anthropogenic impacts, soil salinization has become increasingly severe. However, traditional salinization monitoring suffers from being time-consuming, labor-intensive, and costly. Hyperspectral-based salinization monitoring often relies on single mathematical transformations and one-dimensional spectral information, while also exhibiting poor model interpretability. Research utilizing combined spectral transformations to construct spectral indices for salinization estimation urgently requires in-depth exploration. Thus, this study aims to fully exploit spectral information, enhance data sensitivity, and establish a high-precision, interpretable salinization inversion model based on spectral indices.【Method】Dongying City was selected as the study area, where hyperspectral datasets were collected through field surveys, and soil samples were analyzed in the laboratory for salinity determination. The samples were divided into training and testing sets in a 7:3 ratio based on salinity gradients. Spectral data were preprocessed using Savitzky-Golay (S-G) filtering and Multiplicative Scatter Correction (MSC). Four spectral transformations were applied: Reflectance (R), Reciprocal (1/R), Logarithm of Reciprocal (log(1/R)), and Continuum Removal (CR). The Fractional Order Derivative (FOD) transformation was subsequently performed on each form. Ten types of two-dimensional spectral indices were constructed from the combined transformed data at each derivative order. Optimal band combinations and differential orders were identified by assessing correlation coefficients with soil salt content (SSC). Using these spectral indices as features and measured salinity as the dependent variable, four machine learning models—Partial Least Squares Regression (PLSR), Convolutional Neural Network (CNN), eXtreme Gradient Boosting (XGBoost), and Support Vector Machine (SVM)—were constructed. The hyperparameters of all models were optimized using the Bayesian Optimization (BO) algorithm, which iteratively fitted a probabilistic surrogate model to guide the search for hyperparameters that minimize cross-validation error. Each model was trained and tuned via ten-fold cross-validation. Performance was evaluated using the Coefficient of Determination (R2), Root Mean Square Error (RMSE), and Residual Prediction Deviation (RPD). The best-performing model was further interpreted using SHapley Additive exPlanations (SHAP) to identify influential spectral features. 【Result】Results demonstrated that:(1) FOD effectively enhances spectral sensitivity by highlighting gradient information during spectral curve variations; (2) Mathematical transformations combined with FOD significantly improve correlations between spectral data and SSC; (3) The 2-order NDI index after CR treatment achieved the highest absolute correlation coefficient (|r|=0.91) with SSC; (4) The CR-FOD-XGBoost model delivered optimal accuracy (testing set: R2=0.94, RMSE=0.85 g·kg?1, RPD=4.33); (5) In the optimal model, GDI1 contributed most significantly while DI clusters adjacent to zero contributed minimally. 【Conclusion】Collectively, this study demonstrates that combining spectral transformations to construct indices with Bayesian-optimized XGBoost modeling effectively improves soil salinity inversion accuracy, providing scientific foundations for salinization control and ecological sustainability. Future research should focus on enhancing spectral sensitivity responsiveness to further improve model performance, thereby advancing theoretical frameworks for sustainable land-use and environmental conservation strategies.

• Progress and Prospects of Layered Double Hydroxides in In-situ Passivation of Heavy Metals in Agricultural Soil

  DING Changfeng, YIN Jibin, HE Liqin, DU Jiufang, WANG Xingxiang

  DOI: 10.11766/trxb202509010430

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  Heavy metal contamination in agricultural soils in China is severe, posing a significant threat to the safety of agricultural products. The development of long-lasting and stable in-situ passivation materials has become a current research hotspot for the safe utilization of contaminated farmland. Layered double hydroxides (LDHs) possess unique advantages such as large specific surface area, strong ion-exchange capacity, tunable structure, and super-stable mineralization, offering a new pathway to overcome the limitations of traditional materials. This article systematically reviews the research progress of LDHs in the in-situ passivation of heavy metals in farmland soils from three perspectives: mechanisms of action, material design, and stability evaluation. Firstly, it analyzes the mechanisms by which LDHs synergistically passivate heavy metals through multiple pathways, including isomorphous substitution, ion exchange, adsorption–precipitation, and redox–precipitation. Secondly, it summarizes the effectiveness of both pure LDHs and their composite materials in the in-situ passivation of heavy metals in farmland soils, and discusses the “molecular engineering” design achieved by regulating layer cations, functionalizing interlayer guests, and composite design to enhance targeting capability. Finally, the long-term stability of their passivation effects is evaluated from chemical, physical, and biological perspectives, revealing their potential to resist environmental interference. The article concludes by analyzing current challenges in LDH research and outlining future research directions, aiming to provide insights for the targeted design, precise application, long-term effectiveness, and safety evaluation of LDHs in the in-situ passivation of heavy metals in farmland soils.

• Spectral Prediction of Soil Organic Matter in Typical Black Soil Regions by Combining Fractional-Order Derivatives and Spectral Indices

  XIE Pingru, HONG Yongsheng, XU Xianghua, YAN Guojing, ZHANG Chao, TIAN Kang, FAN Yanan, CHEN Jian, HU Wenyou

  DOI: 10.11766/trxb202506250309

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  【Objective】Rapid and accurate estimation of soil organic matter (SOM) is crucial for assessing soil fertility, guiding sustainable agricultural management, and supporting carbon accounting at regional and global scales. SOM is a key indicator of soil quality, influencing nutrient cycling, microbial activity, crop productivity, and soil carbon sequestration potential. While reliable, traditional chemical analysis methods are costly, time-consuming, and destructive, making them unsuitable for large-scale or repeated monitoring. Visible and near-infrared (Vis-NIR) spectroscopy provides a rapid, non-destructive, and environmentally friendly alternative for SOM assessment. However, the effectiveness of Vis-NIR spectroscopy is often limited by spectral noise, baseline drift, and low sensitivity to absorption features associated with organic components. Therefore, developing advanced spectral transformation and modeling strategies that can enhance weak spectral signals and extract effective features related to SOM is essential. This study aims to construct a collaborative modeling framework combining fractional-order derivative (FOD) transformation and spectral indices to improve the interpretability and predictive accuracy of Vis-NIR spectral data from typical black soil regions in Northeast China.【Methods】A total of 227 soil samples were collected from representative farmland in the black soil region, an important grain-producing area in Northeast China. The reflectance spectra and SOM content were obtained in the laboratory. The spectral data were processed with FOD ranging from 0 to 2.0 (increment by 0.1 at each step). Two-dimensional (2D) and three-dimensional (3D) spectral indices were calculated to explore the interaction information between different wavelength combinations. The correlation between each spectral index and SOM content was analyzed to determine the most sensitive index. Two machine learning algorithms—random forest (RF) and Cubist—were used to construct prediction models. The input datasets were divided into two categories: (1) FOD-transformed reflectance (FOD dataset); and (2) spectral indices that were most strongly correlated with SOM (index dataset). Four models were thus constructed: FOD-RF, Index-RF, FOD-Cubist, and Index-Cubist. Ten-fold cross-validation was used to evaluate the performance of the model, and the determination coefficient (R²) and root mean square error (RMSE) were used as evaluation indexes. In addition, this study also analyzes the importance of model characteristics to determine the key wavelength or exponential combination that is helpful for SOM prediction.【Results】FOD transform significantly improved the spectral interpretability and enhanced the detection of weak organic absorption characteristics in the Vis-NIR band. The Cubist model with the 0.3-order derivative spectrum exhibited the best performance and provided a validation R² of 0.74. The RF model performs best at higher derivatives (1.6-1.9), and the R² value remains between 0.63 and 0.65. In addition, the correlation between 3D spectral index and SOM is stronger than that of 2D index, and 3D spectral index improves the interpretability of features. The characteristic importance analysis showed that the most sensitive spectral regions predicted by SOM were located within 1410-1880 nm and 2200-2350 nm, corresponding to the overtone and combined vibration of C-H, N-H and O-H functional groups.【Conclusion】The combination of FOD preprocessing and spectral index provides a robust, flexible and scalable framework for estimating SOM using Vis-NIR spectroscopy. This study emphasizes a promising direction in the field of intelligent soil remote sensing monitoring and information technology, and provides methodological progress for digital soil mapping, precise nutrient management and sustainable land management. Its application potential is not only limited to the prediction of SOM, but also extended to a wider range of soil property assessment, which provides a theoretical and technical basis for the construction of intelligent soil information system to support the sustainable development of agriculture in major grain producing areas such as northeast China.

• Prediction of Soil Fertility Properties in Cropland Using Multi-temporal Synthetic Remote Sensing Image: A Case Study of Youyi Farm in Sanjiang Plain

  MA Haiyi, WANG Changkun, LIU Jie, GUO Zhiying, YUAN Ziran, YAO Chengshuo, WANG Xiaopan, PAN Xianzhang

  DOI: 10.11766/trxb202507090338

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  【Objective】 The Northeast of China is one of the most important grain production base for China. In recent years, unreasonable use of cultivated land in this region has caused a decline in soil fertility, posing a severe threat to the nation’s food security. To ensure sustainable agricultural practices, it is important to develop a rapid and reliable method for monitoring variations in soil physicochemical properties. 【Method】This study focused on the Youyi Farm in the Sanjiang Plain as the research area, aiming to evaluate the feasibility of Sentinel-2 multi-temporal remote sensing imagery in predicting key soil fertility properties. A total of 103 surface soil samples in cropland were collected, and Sentinel-2 images acquired during the potential bare-soil periods (April, May, and June) from 2019 to 2023 were selected to build a Random Forest regression model for predicting soil organic matter, total nitrogen, total phosphorus, and total potassium. To investigate the temporal effects of images on the prediction performance and to identify optimal temporal combinations for high-precision prediction of these soil fertility properties, the images were organized along two temporal axes. First, the images were divided into seven-year groups (five single-year groups: 2019, 2020, 2021, 2022, and 2023, and two multi-year groups: 2020—2022 and 2019—2023). Then, within each year-group, the images were further divided into four month-groups (three single-month-groups: April, May, and June, and one multi-month-group: April—June). Finally, the combination of the seven year-groups and four month-groups produced 28 distinct year–month temporal groupings. For each grouping, all available Sentinel-2 images were synthesized by median compositing to produce 28 synthetic images that served as inputs to the Random Forest model. 【Result】The results indicate that soil organic matter was predicted with the highest accuracy among the four fertility properties, with an R² of 0.62 and an RMSE of 6.58 g·kg-1. The prediction accuracy of soil total nitrogen was similar to that of organic matter, with an R² of 0.58 and an RMSE of 0.34 g·kg-1. Total phosphorus predictions were not sufficiently accurate for practical applications, with the highest accuracy of an R² of 0.13 and RMSE of 0.01 g· kg-1. The total potassium achieved a relatively high prediction accuracy of an R² of 0.53 and RMSE of 1.55 g·kg-1. 【Conclusion】The results in different year-groups and month-groups indicated that (1) multi-year synthetic images outperformed single-year synthetic images in prediction accuracy, and (2) the synthetic images from May showed the highest prediction accuracy among the monthly groupings. These findings demonstrate that careful temporal selection and multi-temporal synthesis of Sentinel-2 imagery can improve the prediction accuracy of soil organic matter, total nitrogen, and total potassium in the cultivated land of Northeast China. In contrast, Sentinel-2 spectral bands alone are difficult to effectively predict total phosphorus content. Integrating auxiliary environmental variables (such as topography, climate, or cultivation management) or employing alternative remote sensing data may be necessary to achieve higher accuracy. Overall, this study provides methodological guidance and technical support for regional-scale soil fertility monitoring and mapping in the Sanjiang Plain.

• Prediction of Cu Fractions in Intact Soil Profiles of Mining Areas Using Hyperspectral Imagining and Machine Learning

  LIU Dong, WANG Shihang, ZHAO Mingsong, LIU Feng, XU Shengxiang

  DOI: 10.11766/trxb202510090490

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  【Objective】Hyperspectral remote sensing technology holds considerable research value for monitoring and assessing heavy metal contamination in soils. However, it is unclear how this technology can be used to detect different heavy metal fractions in soil. 【Method】This study collected 22 intact soil profile samples with depths of approximately 100 cm from farmland soils in the Le""an River Basin, Jiangxi Province, China. The samples were used to investigate the potential of hyperspectral imaging (HSI, 400-1010 nm) for predicting five copper (Cu) fractions in intact soil profiles, including total Cu, weak acid-extractable Cu (F1), reducible Cu (F2), oxidizable Cu (F3), and residual Cu (F4). After the spectral data and Cu contents of the soil profile samples were measured, prediction models for soil Cu contents were established. Several modeling methods were applied to investigate the effect of different spectral preprocessing techniques on prediction accuracy, including partial least squares regression (PLSR), random forest (RF), Cubist regression tree (Cubist), Gaussian process regression (GPR), and Support vector machine (SVM). 【Result】The results show that the four machine learning algorithms, namely RF, Cubist, GPR, and SVM, generally outperformed the linear PLSR model in terms of R², demonstrating higher predictive accuracy. After preprocessing with the combined absorbance transformation and first derivative method (Abs+FD), the SVM-based model achieved relatively good predictive performance for the five soil Cu fractions in the independent validation set (F1: R2p = 0.78, RMSEp = 0.56 mg·kg-1; F2: R2p = 0.78, RMSEp = 0.40 mg·kg-1; F3: R2p = 0.67, RMSEp = 1.33 mg·kg-1; F4: R2p = 0.70, RMSEp = 2.91 mg·kg-1; Total Cu: R2p = 0.67, RMSEp = 3.64 mg·kg-1). 【Conclusion】These findings indicate that HIS combined with machine learning can effectively predict multiple heavy metal fractions in soil profiles, which is of great significance for improving our understanding of the migration and transformation of heavy metals in soil and for conducting regional soil pollution risk assessments.

• Research Progress on Synergistic Regulation of Soil-Borne Diseases by Rhizosphere Microbiome and Root Exudates

  WU Jinping, ZHOU Jie, BAI Yafan, KUANG Yidi

  DOI: 10.11766/trxb202510140494

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  Against the backdrop of global population growth and environmental changes, intensive agriculture under continuous cropping systems has exacerbated the frequent occurrence of soil-borne diseases and continuous cropping obstacles, while traditional chemical control methods are increasingly incompatible with the demands of green and sustainable agricultural development. Healthy soil serves as the foundation for crop disease resistance and stable productivity. As the core microdomain for “soil-plant-microbe” interactions, the rhizosphere relies on the bidirectional dynamic and synergistic regulation between the rhizosphere microbiome and root exudates as the core intrinsic mechanism of soil-borne disease defense. Root exudates directionally regulate the functional gene expression of the rhizosphere microbiome through specific signaling molecules. This can either drive the enrichment of beneficial microbial communities and the activation of disease-resistant functions, or selectively enrich pathogens to form malignant interactions under continuous cropping conditions. In return, the rhizosphere microbiome feeds back to plant roots via metabolites, optimizing the composition and secretion rhythm of root exudates, and together they constitute a dynamic balance network of “beneficial interaction-malignant interaction”. Soil physicochemical properties such as texture, pH, and organic matter content play key mediating roles in this process, directly affecting interaction efficiency and disease control effects. This review systematically summarizes the core pathways of their synergistic disease resistance: root exudates directly inhibit pathogens or directionally recruit beneficial microorganisms through “concentration/type-dependent” mechanisms; the rhizosphere microbiome suppresses diseases through multiple pathways, including direct antagonism, nutrient competition, immune activation, and autotoxin degradation. On this basis, the paper synthesizes technological innovations such as the construction of synthetic microbial communities, optimization of agricultural practices, gene editing, and synthetic biology, and analyzes the current bottlenecks in the field promotion of these technologies. The study proposes that future research should focus on constructing a “soil type-metabolite-receptor-gene” precision regulation network and establishing a “short term-medium term-long term” three-level ecological risk assessment system. This study aims to provide theoretical support and technical pathways for resolving the contradiction between crop productivity guarantee and ecological security under continuous cropping obstacles, while offering references for the synergistic inhibition of other types of plant diseases through rhizosphere microecological regulation.

• Research Progress on the Mechanisms of Vegetation Restoration Affecting Soil Fe-Bound Organic Carbon

  DONG Lingbo, DENG Lei, LÜ Qingzi, HAN Keyu, SHANGGUAN Zhouping

  DOI: 10.11766/trxb202509220463

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  Soil iron-bound organic carbon (Fe-OC) is a quantitatively important and exceptionally stable fraction of the soil organic carbon (SOC) pool. Owing to its relatively high proportion and stability, it plays a key role in mediating the soil carbon cycle and sustaining long-term carbon sequestration. As an effective strategy for enhancing soil carbon sequestration capacity and alleviating the adverse impacts of climate change, vegetation restoration has garnered increasing attention regarding its impacts on soil carbon dynamics and the underlying mechanisms. This review systematically synthesized recent research findings pertaining to the influences of vegetation restoration on soil Fe-OC. First, it sorted out the basic characteristics of Fe-OC, clarifying that Fe-OC binds to iron oxides primarily through adsorption and coprecipitation processes, and meanwhile identified two major formation pathways: microbial-mediated transformation of organic substrates and direct adsorption of plant-derived dissolved organic matter. On this basis, it elucidated the dynamic patterns of Fe-OC under vegetation restoration, its changes are regulated by soil texture and vegetation type (Fe-OC tends to accumulate in coarse-textured soils but decreases in fine-textured soils, and forestland exhibits a stronger Fe-OC accumulation effect than grassland and shrubland). Further, it analyzed key influencing factors, including the composition and molecular properties of SOC, the speciation and reactivity of iron oxides, as well as soil microbial traits, and interpreted the coupled regulatory mechanisms through which vegetation restoration governs the formation, accumulation, and stability of Fe-OC from physical processes (soil aggregate formation and soil moisture regime regulation), chemical reactions (shifts in SOC molecular structure and iron valence transformation), and biological activities (microbial metabolic processes and organic acid exudation). Also, this review identified the existing knowledge gaps and limitations in current research, and proposed that future studies should expand the coverage of diverse climatic zones, accurately quantify the relative contribution ratios of plant- and microbe-derived carbon to Fe-OC pools, strengthen the analysis of the role of soil microbial functions in the formation and stabilization of Fe-OC, and integrate the complex drivers of global change to simulate Fe-OC dynamics under multifactorial scenarios. Only through such comprehensive and interdisciplinary approaches can the intricate mechanistic responses of Fe-OC to vegetation restoration be fully unveiled. This review delineates prospective research directions for the study of soil Fe-OC dynamics under vegetation restoration, facilitates a more comprehensive understanding of the impacts of vegetation restoration on the soil carbon cycle, and provides an important scientific basis for formulating soil carbon sink management strategies to address global climate change.

• Research Progress on Soil Aggregate Stability Driving Greenhouse Gas Emissions in Agroforestry Systems

  YANG Hongbing, LEI Lei, ZENG Lixiong, LIU Juntao, HUANG Zhilin, ZHU Jianhua, XIAO Wenfa

  DOI: 10.11766/trxb202508250415

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  Abstract:

  Agroforestry systems enhance soil structural stability and optimize carbon-nitrogen coupling through the vertical hierarchical configuration and spatiotemporal complementarity of trees, shrubs, grasses, and crops. This increases their potential for greenhouse gas (GHG) mitigation and carbon sequestration. However, the mechanistic attribution and cross–scale upscaling of GHG fluxes remain constrained by heterogeneity in soil aggregate structure and microhabitats. As a key driver of GHG emissions, soil aggregate stability governs substrate availability, microbial activity, and gas diffusion by shaping pore networks and oxygen-water distribution patterns, which in turn regulate CO2 mineralization, CH4 production and oxidation, and N2O generation via nitrification and denitrification pathways. From the perspectives of hierarchical aggregate theory and micro–ecological process modeling, this review systematically synthesizes the biotic (roots, arbuscular mycorrhizal fungi, microbial mucilage/exudates), physicochemical (organo–mineral associations; iron and aluminum oxides and hydroxides), and management (intercropping, biochar, tillage) drivers of aggregate stability in agroforestry systems, as well as the key pathways and scenario–dependent differences (climate, soil type, and management) through which they affect GHG emissions. Future research directions in this field should focus on elucidating the regulatory effects of root-microbe-aggregate interactions on GHG metabolism; establishing cross-scale research frameworks that integrate in-situ observations with mechanistic models; validating site-specific carbon sequestration and emission reduction technologies through long-term experiments; and predicting the impacts of extreme events and future climate scenarios on system emissions.

• Interactions Between Rhizosphere Microorganisms and Plant Cell Walls and Their Role in Aluminum Tolerance in Acidic Soils

  LIANG Yuting, Xu Wen, ZHANG Li, ZHANG Hui, DING Jixian, ZHAO Yuan, MA Zhiyuan, JIANG Meitong

  DOI: 10.11766/trxb202510220506

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  As a critical interface between plants and microorganisms, the cell wall frequently undergoes compositional or structural alterations during its interactions, a process known as cell wall modification. Such modifications not only influence plant-microbe interactions but also play a regulatory role in enhancing plant tolerance to aluminum toxicity in acidic soils. Therefore, investigating whether microorganisms can alleviate aluminum toxicity through the modulation of plant root cell wall properties holds significant scientific importance and practical application potential. This review summarizes the regulatory mechanisms of microbial action on root cell walls with respect to root cell wall dynamics, focusing on the patterns and characteristics of microbial-induced root cell wall modifications. Furthermore, it discusses potential sites and molecular pathways involved in this process that contribute to improved plant resistance to aluminum toxicity under acidic conditions. The review aims to provide a theoretical foundation for a deeper understanding of plant-microbe interaction mechanisms and to offer novel insights for the development of a synergistic system integrating "aluminum-tolerant crops" with functional microorganisms.

• Effects of Equal Replacement of Chemical Fertilizer by Organic Fertilizer on Soil Properties, Bacterial Community, and Rice Yield

  GUO Shimeng, LI Yimeng, LIU Jiaxin, WANG Yue, WU Zhouzhou, WANG Shu, ZHOU Chanchan†, MU Jingyi, LIU Junfeng, LIANG Chao

  DOI: 10.11766/trxb202507300365

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  【Objective】This study aimed to investigate the effects of equal replacement of chemical fertilizer by organic fertilizer on rice microbial community and yield. 【Method】 A long-term field experiment was conducted in Liaoning from 2019 to 2023. In this experiment, two rice cultivars, Shendao47 (SD47) and Shendao505 (SD505), were grown in the field with four fertilization treatments at same N, P, K rate: CF (100% chemical fertilizer), OR10 (10% organic fertilizer + 90% chemical fertilizer), OR20 (20% organic fertilizer + 80% chemical fertilizer), OR30 (30% organic fertilizer + 70% chemical fertilizer). 【Results】The results revealed the following: (1) Organic fertilizer substitution increased rice yield mainly by enhancing effective panicles, grain filling rate, and 1000-grain weight, with OR20 treatment achieving the highest yield; (2) Organic fertilizer substitution significantly improved soil fertility by increasing organic matter, total nitrogen, and available nutrient content (alkali-hydrolyzable nitrogen, available phosphorus, and available potassium) in plow layer (0-20 cm); (3) Organic fertilizer substitution significantly enhanced the activity of urease, protease, sucrase, and nitrate reductase in both rhizosphere and bulk soil; (4) Organic fertilizer substitution significantly increased the Chao1 index (richness) and Shannon index (diversity) of bacterial communities in the rhizosphere, whereas its effect on bulk soil bacterial diversity was not statistically significant; (5) At the phylum level, organic fertilizer substitution improved the relative abundance of carbon and nitrogen cycling bacterial phyla such as Proteobacteria, Bacteroidetes, reduced the abundance of oligotrophic bacterial phyla such as Acidobacteria, and optimized the bacterial community structure in bulk and rhizosphere soil; (6) Functional prediction analysis indicated that organic fertilizer treatments enhanced transcription and carbohydrate transport and metabolism in bulk soil, and strengthened metabolism pathways such as amino acid transport and metabolism, inorganic ion transport and metabolism, and lipid transport and metabolism in rhizosphere soil.【Conclusion】In conclusion, under equivalent nutrient input, partial substitution of chemical fertilizer with organic fertilizer could improve the soil microenvironment, enhance key enzyme activities, and optimize the structure and function of soil microbial communities. These changes synergistically promote soil nutrient availability and supply capacity, ultimately increasing rice yield. This practice represents a sustainable fertilization strategy suitable for paddy fields in Northeast China.

• Comprehensive Toxicity Assessment of Biochar on Earthworms in Soil and Its Molecular Mechanism

  GAO Xuan, ZHANG Xiaonan, LI Chao, ZHU Hongxia, FANG Jing

  DOI: 10.11766/trxb202510240509

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  Abstract:

  【Objective】The potential impact of biochar on key soil animals, especially earthworms, is an important aspect in evaluating its environmental safety. Although previous studies have confirmed the toxic effects of biochar on earthworms, there is still a lack of systematic understanding of how preparation conditions regulate its toxicity and the specific sources of toxicity. Thus, this restricts the screening and application of low-risk biochar. 【Method】The effects of biomass sources (rice straw and perishable waste) and pyrolysis temperature (350 ℃, 500 ℃, and 650 ℃) on the toxicity of biochar to earthworms were systematically investigated. Also, the toxicity differences between biochar and its extract solution were compared. Moreover, the common Eisenia fetida was used as the test subject, and multiple indicators were employed, such as individual survival rate, enzyme activity, histopathological observation, and transcriptomics, to evaluate the effect of biochar on the earthworm’s survival. 【Result】The main results indicated that: (1) The toxic effects of biochar on earthworms exhibited significant feedstock specificity and dose dependence. At an exposure dose of 2.5 g·kg-1, perishable waste biochar (PWB) significantly reduced the relative survival rate of earthworms, while the same dose of rice straw biochar (RSB) had no significant effect; when the dose increased to 5 g·kg-1, both types of biochar showed obvious lethal effects on earthworms. (2) The response of the oxidative stress system showed that biochar stimulated the antioxidant defense mechanism of earthworms. Moreover, as the pyrolysis temperature increased, the oxidative stress in the earthworms showed a decreasing trend. The integrated biomarker response further indicated that the ecological risk of PWB was higher than that of RSB, and the toxicity risk of biochar pyrolyzed at a lower temperature was stronger. (3) Histopathological analysis indicated that biochar can induce damage to the epidermis and midgut of earthworms, with the damage caused by PWB being more severe. Transcriptomics revealed that several key physiological pathways such as protein digestion and absorption, extracellular matrix (ECM)-receptor interaction, and vitamin digestion and absorption in earthworms, were affected under the exposure to biochar, and PWB induced more differentially expressed genes. (4) Biochar extract solution exhibited toxic tendencies to earthworms in the soil at a dosage of 5 g·kg-1, while the toxicity was lower than that of the solid biochar. This indicated that both the chemical composition toxicity of its extract solution and the physical characteristic risks of its solid particles should be considered for a comprehensive assessment of the ecological safety of biochar. 【Conclusion】Based on the above results, the toxic effects of biochar on earthworms in the soil are influenced by multiple factors such as the feedstock, pyrolysis temperature, dosage, and components of biochar. Thus, this study provides an important reference for research aimed at better assessing the environmental risks of biochar and provides a theoretical basis for the safe application of biochar in soil.

• The Influence of Biological Nitrification Inhibitors on the Yield and Quality of Organic Chrysanthemum morifolium Ramat cv. ‘Hangbaiju’ and Its Synergistic Mechanism

  SONG Qi, LIU Xiaofei, DONG Gangqiang†, LU Yufang, LU Weiwei, MIN Ju†, SHI Weiming

  DOI: 10.11766/trxb202510200504

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  【Objective】The combined application of biological nitrification inhibitors (BNIs) with chemical nitrogen (N) fertilizers reduces N loss and enhances nitrogen use efficiency (NUE). However, research on their combined use with organic N fertilizers remains limited, and their yield-enhancing effects and underlying mechanisms remain unclear. 【Method】This study employed organic Chrysanthemum morifolium Ramat cv. ‘Hangbaiju’ in field trials, establishing four treatments: no nitrogen application (-N), fish protein organic water-soluble fertilizer (N), N+50 g·kg-1 methyl 3-(4-hydroxyphenyl) propionate (MHPP), and N+50 g·kg-1 salicylic acid (SA). The research investigated the effects of combining BNIs with organic N fertilizers on chrysanthemum yield, quality, and the underlying synergistic mechanisms. 【Result】 Results indicated that the N+SA treatment yielded the highest harvest at 6 154 kg·hm-2, achieving a 40.2% increase in yield (P < 0.05), a 9.1% rise in total flavonoids (P < 0.05), and a 75.0% improvement in NUE (P < 0.05) compared to the N treatment. Compared with the N treatment, N+MHPP showed a trend of increasing yield and enhancing NUE. N+SA significantly increased total root length by 147.7% and fresh root biomass by 127%, with root-promoting effects significantly superior to N+MHPP. Principal component analysis indicated positive correlations between Chrysanthemum morifolium Ramat cv. ‘Hangbaiju’ yield and NUE with root length, root surface area, and root volume. It is speculated that the application of SA may achieve synergistic effects of “increased yield, enhanced efficiency, and improved quality” by optimizing the root architecture of Chrysanthemum morifolium Ramat cv. ‘Hangbaiju’, enhancing nitrogen uptake, and potentially exhibiting growth-promoting activity.【Conclusion】This study confirms the significant potential of BNIs in boosting yield, efficiency, and quality within organic water-soluble fertilizer systems, providing a new pathway for green and efficient fertilization of organic medicinal crops.

• Bordetella petrii B35 Enhances Rice Growth Promotion by Sphingomonas sp. HJY via Siderophore Mediation

  WANG Zhongyang, LI Mei, WAN Qun, CAO Yaoyao, MA Liya, FENG Fayun, GE Jing, YU Xiangyang

  DOI: 10.11766/trxb202508290425

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  【Objective】The intricate interactions between introduced plant growth-promoting rhizobacteria (PGPR) and the indigenous microbial community are pivotal determinants of inoculation efficacy and plant health. While the direct mechanisms of PGPR are well-studied, the role of resident microbes in modulating their activity remains less understood. This study focuses on Sphingomonas sp. HJY, a known growth-promoting bacterium for rice, aims to elucidate how specific indigenous bacteria influence its plant growth-promoting capacity and to uncover the fundamental mechanisms behind this interaction. Clarifying this synergy is crucial for advancing the knowledge of rhizosphere ecology and optimizing microbial inoculation strategies. 【Method】A batch of bacteria was isolated from rice rhizosphere soil, and indigenous bacterial helpers that promoted the growth of HJY were screened by both co-culture assay and supernatant-culture assay. The bacterium with the most pronounced promotion effect was selected as a representative and identified by full?length 16S rRNA gene sequencing. To elucidate the mechanism of facilitation, the selected helper strain was cultured under iron-rich and iron-limited conditions. Its siderophore production was quantified using the Chrome Azurol S (CAS) assay. Subsequently, the impact of its filter-sterilized supernatant from both iron conditions on HJY growth was compared. Finally, a pot experiment with natural soil was conducted to assess the influence of the indigenous bacterial helper on the ability of HJY to promote rice growth. 【Result】The results showed that the indigenous bacterium labeled B35 exhibited the most significant promotion effect on HJY growth. The biomass of HJY was increased by 71.2% and 95.4% by B35 cells and its sterile supernatant, respectively, with the latter being significantly more effective. This strain was identified as Bordetella petrii. Under iron?limited conditions, the siderophore secretion by B35 was significantly higher than under iron?sufficient conditions. Moreover, the iron?limited supernatant enhanced the growth?promoting effect on HJY by 13.89% compared with the iron?sufficient supernatant, indicating that siderophores secreted by B35 were one of the main factors promoting HJY growth. Soil inoculation experiments demonstrated that, at 18 days, the plant height, fresh biomass, chlorophyll content, and root length of rice treated with HJY + B35 sterile supernatant were increased by 5.9%, 11.6%, 12.7%, and 21.2%, respectively, compared with those treated with HJY alone. In contrast, the corresponding indices for rice treated with HJY + B35 cells were increased by 4.4%, 7.6%, 5.1%, and 8.0% compared with HJY alone. These results indicated that both B35 and its sterile supernatant could enhance the growth?promoting effect of HJY on rice, with the supernatant treatment showing a superior effect to the bacterial cell treatment. Inoculation with B35 alone or its supernatant alone had no significant effect on rice growth. 【Conclusion】 In conclusion, this study demonstrates that the indigenous bacterium Bordetella petrii B35 enhances the plant growth-promoting activity of Sphingomonas sp. HJY through a facilitative interaction driven largely by siderophore production. This interaction significantly improves HJY"s efficacy in promoting rice growth in natural soil, with the direct application of the helper"s metabolites yielding the strongest effect. These findings provide novel insights into the complex network of rhizosphere microbial interactions, highlighting how targeted exploitation of specific facilitative relationships—such as cross-feeding via siderophores—can be a crucial strategy for optimizing the performance of PGPR inoculants. This study, therefore, offers a theoretical foundation for designing more effective and stable synthetic microbial consortia for sustainable agriculture.

• Profile Distribution of Ammonia-Oxidizing Microorganisms and Their Role in N2O Emissions in Typical Farmlands of Southern China

  TAO Huake, WANG Xiaomin, HAN Zongyang, MAO Xinyu, YAN Xiaoyuan, SHAN Jun

  DOI: 10.11766/trxb202508290423

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  【Objective】This study aimed to investigate the effects of different land use types and soil profiles on ammonia-oxidizing microorganisms and nitrogen (N) cycling processes, with a focus on the community distribution and functional roles of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and complete ammonia oxidizers (Comammox) in agricultural soils under different management regimes.【Method】Soil samples (0-100 cm) were collected from three typical farmland ecosystems in Changshu, Jiangsu Province, including rice-wheat rotation, orchard, and vegetable fields, during both spring and summer. Soil physicochemical properties were determined, and microbial community composition and abundance were analyzed using quantitative PCR and high-throughput sequencing. In addition, microcosm incubation experiments with nitrification inhibitors were conducted to determine nitrification and N2O production rates, enabling clear quantification of microbial contributions to soil nitrogen transformations.【Result】The ammonia oxidation rate and N2O emission rate of the surface soil are the highest, with mean values of 6.1 ± 1.0 mg·kg-1·d-1 (calculated by N, the same as below) and 17.9 ± 6.1 ng·kg-1·d-1, respectively, and both declined significantly with depth. The N2O emission rate in rice–wheat soils (17.5 ± 5.6 ng·kg-1·d-1) was significantly higher than that in vegetable soils (1.5 ± 0.5 ng·kg-1·d-1). Within the rice–wheat system, summer exhibited a significantly higher N2O emission potential than spring. Among ammonia oxidizers, AOB contributed most to nitrification, accounting for 56.6% in surface soils and up to 64.9% in subsurface layers, while the contribution of Comammox increased with depth. Microbial functional gene abundance and diversity showed pronounced vertical heterogeneity and were strongly influenced by land use type. Correlation analysis indicated that microbial gene abundance was significantly positively correlated with nitrification rates, and that ammonium nitrogen and dissolved organic carbon were the key factors regulating both nitrification and N2O emissions. Structural equation modeling further revealed that AOB gene abundance was a major determinant of ammonia oxidation rates and that ammonia oxidation processes were positively linked to N2O emissions.【Conclusion】This study systematically evaluated the effects of land use and soil profile on the functional differentiation of ammonia-oxidizing microorganisms. The findings demonstrated that AOB dominate ammonia oxidation across soil layers, while Comammox play an increasingly important role in deeper soils, and that both groups jointly regulate the potential mechanisms of N2O emissions. These results provide theoretical support for developing microbe-oriented strategies for agricultural nitrogen management.

• Microscopic Mechanisms Mediating N2O Production and Emission in Soil-Straw System Pore Structures: A Review

  LU Yuanchuang, LIU Ying, WANG Gang, ZHU Kun

  DOI: 10.11766/trxb202508180403

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  Nitrous oxide (N2O) is a potent greenhouse gas; thus, understanding its emission mechanisms from agricultural soils is a critical research priority. Previous studies have largely focused on macro-scale drivers like climate and management, leaving a gap in the systematic understanding of how micro-scale soil pore heterogeneity regulates N2O dynamics. This review addresses this gap by synthesizing current knowledge. It first examines how dynamic changes in soil pore characteristics (e.g., porosity, pore-size distribution, connectivity) govern the transport of water, gases (O2, N2O), and solutes, thereby creating distinct microenvironments for N2O production and diffusion. A key focus is the scenario of straw incorporation. The analysis details how straw management, encompassing application methods, duration, and straw type—interacts with soil physical structure and moisture regimes (particularly wetting-drying cycles) to reshape pore network heterogeneity. Building on this physical foundation, the review then analyzes the consequential biogeochemical effects. It highlights how pore-scale heterogeneity in the distribution and accessibility of carbon/nitrogen substrates and oxygen critically regulates microbial nitrogen transformation processes (e.g., nitrification and denitrification), ultimately controlling N2O production pathways and the emergence of emission “hotspots.” Furthermore, this synthesis consolidates potential micro-scale mitigation strategies that leverage pore structure manipulation. These include optimizing straw treatment (e.g., biochar production, particle size reduction) and targeting microbial communities to design microenvironments that suppress N2O formation or enhance its reduction to N2. In summary, by developing an integrated framework that links pore structure dynamics with microbial biogeochemistry, this review advances the mechanistic understanding of N2O emissions under straw incorporation. It provides a novel, pore-centric perspective and a theoretical basis for designing innovative farmland management practices aimed at reducing greenhouse gas emissions while supporting sustainable agriculture.

• Assessment of Soil Resilience in China

  WU Kening, CHEN Xingyu, CHEN Anqi, FENG Zhe

  DOI: 10.11766/trxb202507010320

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  【Objective】Soil resilience refers to the ability of soil to restore its original properties and functions after being disturbed by anthropogenic or climate change. It is an important ecological indicator for achieving the sustainable utilization of soil resources. This paper aims to construct a soil resilience evaluation system suitable for large-scale applications and assess the spatial distribution characteristics of soil resilience in China. 【Method】Based on existing research results, this study refines the logic of index construction, determines four dimensions: soil properties, climatic factors, topographic influences, and biological characteristics, and sets a total of nine specific indicators. The Analytic Hierarchy Process (AHP) is used to determine the weights of the indicators, and weighted superposition analysis is conducted to form a national spatial distribution map of soil resilience. 【Result】The results show that soil resilience in China presents a spatial pattern that gradually increases from West to East and from North to South. Nationwide, soils with high and relatively high resilience account for 25% and 39%, respectively, mainly concentrated in South and Southwest China. The areas with relatively low resilience include the Gansu and Xinjiang regions and the Loess Plateau Area. 【Conclusion】The research provides technical support and decision-making basis for establishing the evaluation of specific soil functions at the macroscopic scale in China at the theoretical and methodological level.

• Soil Magnesium Status and Magnesium Fertilizer Application in the Chinese Agriculture

  ZHANG Fusuo, CHEN Zhichang, WU Liangquan, LI Chunjian, LIU Donghui, TIAN Xinyue, HAO Yanshu, Muhammad Atif MUNEER, MA Yifei, LU Zhenya, HE Dongdong

  DOI: 10.11766/trxb202511090534

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  Abstract:

  Magnesium (Mg) is an essential mineral element for plants, playing critical roles in photosynthesis, nutrient transport, stress responses, and nutrient use efficiency. However, the long-term ignorance of Mg fertilizers in China"s agricultural production has led to widespread soil Mg deficiency, which constrains crop yield, quality, and the potential for further improvement in nutrient use efficiency. This study provides a comprehensive assessment of soil exchangeable Mg status and Mg fertilizer use in China, based on integrated data from national surveys and field experiments conducted by the National Mg Network. It also evaluates the effects of Mg fertilizers in improving crop quality and nutrient use efficiency. In addition, it analyzes the national demand and usage of Mg fertilizers, thereby advancing the understanding of the fundamental physiological functions and agronomic roles of Mg in crop production. Survey results indicate that soil exchangeable Mg concentrations are generally higher in the northern regions (average 271.7 mg kg-1) compared to the southern regions (174.6 mg kg-1). The application of Mg fertilizers remains below 9%, with application rates far below than crop requirements. Mechanistic studies demonstrate that Mg directly participates in the light reactions of photosynthesis and carbon fixation, and regulates the circadian rhythms of photosynthesis. It also promotes nitrogen uptake and assimilation through improved carbon allocation and signaling pathways. Moreover, Mg exhibits multiple protective mechanisms under aluminum toxicity, salinity, and high-temperature stress, and activates plant immune responses to enhance disease resistance. Field trials show that appropriate Mg application can increase average crop yield by 14.6%. It also significantly improves the nutritional and sensory quality of agricultural products while improving the efficiency of nitrogen, phosphorus, and potassium fertilizer use. The estimated Mg fertilizer demand in China"s agricultural production is 2.81–4.40 million tons (as MgO), yet the current application of Mg fertilizer is just 150000 tons. The insufficient development and diversification of Mg fertilizer products remain a major bottleneck for the green development of Chinese agriculture. In the future, it is necessary to strengthen the basic and applied research on plant Mg nutrition, expand the production and supply chains of Mg fertilizers, and enhance policy support to promote large-scale adoption. These efforts will contribute to higher yield, better quality, improved nutrient use efficiency, and the sustainable development of Chinese agriculture.

• Optimization of Virus Enumeration in Epifluorescence Microscopy for Farmland Soil

  WANG Feng, LIU Lingzhi, LIU Rui, GUO Bingqing, MENG Ao, CHEN Meihui, AN Tingting, WANG Jingkuan

  DOI: 10.11766/trxb202508310429

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  【Objective】Viruses play a crucial role in regulating soil microbial community and host dynamics. However, the efficient extraction and enumeration of soil viruses remain challenging due to the complexity of soil environments. This study aimed to enhance the efficiency of soil virus detection by optimizing both the viral extraction protocol and epifluorescence microscopy observation conditions. 【Method】Soil samples were collected from the long-term brown soil fertilization experimental station at Shenyang Agricultural University. Three key factors affecting soil virus extraction efficiency and enumeration results were evaluated: (1) antifade agents (the commercial anti-quenching agent Fluoromount-G? and a laboratory-prepared antifade agent); (2) disruption methods (blender, vortex mixer, ultrasonic cell disruptor, and water bath shaker); and (3) soil-to-liquid ratios (30:100 and 50:100; mass: volume). Viral particles were stained using SYBR Green I and enumerated under an epifluorescence microscope. The optimized protocol was subsequently applied to brown soil, black soil, and meadow soil to validate its general applicability. 【Result】Without an antifade agent (Fluoromount-GTM or laboratory-prepared antifade agent), viral particles were difficult to observe under the 100× objective. The application of Fluoromount-GTM significantly increased virus counts to 3.75 × 108 virus-like particles (VLPs)?g-1, outperforming the laboratory-prepared antifade agent. The disruption method significantly affected virus extraction efficiency (P < 0.05). The blender (650 W, 50 Hz) treatment for 3 minutes achieved the highest extraction efficiency, significantly surpassing the vortex mixer and water bath shaker, whereas no viral particles were observed with the ultrasonic cell disruptor treatment. In addition, increasing the soil-to-liquid ratio also significantly enhanced virus extraction efficiency (P < 0.05), with the 50:100 ratio resulting in a 1227.10% increase in virus counts compared to the 30:100 ratio. The validation results demonstrated that the optimized method consistently yielded stable and reliable viral counts across all three soil types, with significant differences in viral abundance observed among them, confirming its broad applicability. 【Conclusion】In summary, this study established an efficient, stable, and widely applicable epifluorescence microscopy method for soil virus enumeration through the systematic optimization of the disruption method, soil-to-liquid ratio, and antifade agent. The optimized method significantly enhances the extraction efficiency and counting accuracy of soil viruses, thereby providing robust technical support for soil viral ecology research.

• Research Progress on Extracellular Electron Transfer in Heterotrophic Fe(III)-Reducing Archaea

  ZHAO Feng, MIAO Yijing, YANG Fan

  DOI: 10.11766/trxb202509230465

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  Dissimilatory Fe(III) reduction represents a fundamental microbial respiratory process in anoxic soils and sediments, exerting profound influence on the biogeochemical cycling of iron, carbon, and sulfur. In recent years, accumulating evidence has revealed that under specific environmental conditions, metabolically active archaea can outnumber bacteria in certain soil ecosystems, indicating their non-negligible contribution to global carbon and nitrogen cycling. Compared with bacteria, however, the study of Fe(III)-reducing archaea remains in its infancy. Existing research has demonstrated that these archaea are capable of utilizing Fe(III) (hydr)oxides as terminal electron acceptors for anaerobic respiration via both direct and indirect electron transfer pathways. This review provides a comprehensive overview of the diversity of Fe(III)-reducing archaea and their distinctive extracellular electron transfer (EET) mechanisms. Direct EET appears primarily reliant on multiheme c-type cytochromes, but may also involve archaea-specific key components such as molybdopterin oxidoreductases (MoOR), heterodisulfide reductases (HdrDE), and methanophenazines (MP). Indirect pathways may involve the secretion of yet-unidentified endogenous electron shuttles or the utilization of exogenous redox mediators that facilitate long-range electron transfer to extracellular Fe(III) oxides. Also, distinct archaeal groups, including hyperthermophiles, methanogens, and anaerobic methanotrophic archaea (ANME), exhibit remarkable variation in substrate utilization, electron acceptor preference, and ecological distribution. These differences reflect both the metabolic versatility and evolutionary innovation of archaeal electron transfer systems. Despite these advances, the mechanistic understanding of archaeal Fe(III) reduction remains limited, largely due to challenges in cultivation and genetic manipulation. Future research should prioritize the development of efficient archaeal genetic systems, and the establishment of genetically tractable model organisms to uncover novel uncultivated Fe(III)-reducing archaeal taxa. Analyzing the molecular mechanisms and ecological roles of archaeal Fe(III) reduction will provide critical insights into the evolutionary diversification of microbial respiration and the functioning of redox processes in natural ecosystems. Moreover, quantifying the ecological impact of these archaea in global Fe-C coupling will enhance our understanding of nutrient dynamics and redox regulation in soils and sediments. Ultimately, these efforts will contribute to a more comprehensive and mechanistic model of archaeal participation in Earth’s biogeochemical networks.

• From Regulating Rhizobiont to Green Intelligent Fertilizer: Innovation and Application of Green Nematode Disease Control Products Driven by Root Exudates

  GU Shaohua, WANG Kunguang, MA Jing, CUI Dongming, ZHANG Fusuo, ZUO Yuanmei

  DOI: 10.11766/trxb202509020434

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  Abstract:

  The rhizobiont can improve nutrient utilization efficiency and reduce soil-borne diseases through a cascade of plant-microbe-soil interactions, thereby maintaining the health of the soil-plant system. Developing green intelligent fertilizers based on this theory that target and regulate rhizosphere processes is a key breakthrough in achieving sustainable agricultural development. In the face of this challenge, this article focuses on the agricultural losses caused by nematode diseases and the ecological and environmental problems caused by chemical control. From a new perspective of the rhizobiont, it systematically explores new green control methods for soil-borne diseases driven by root exudates. The article first provided a detailed theoretical explanation of the rhizobiont, focusing on the key role of plant root exudates as a core driving force in shaping rhizosphere microbial communities, mediating multispecies synergistic interactions, and maintaining soil-plant health. Furthermore, it analyzed the molecular mechanisms by which different plant-derived functional substances recruit beneficial microorganisms and target the regulation of plant parasitic nematodes. Finally, the technical conception, product development, and effect verification of transforming these basic ecological principles into green intelligent fertilizer were further discussed. The key future research directions in this field in the future were prospected, thereby providing a practical example for the development of green intelligent fertilizer products based on the theory of rhizobiont, and providing an innovative theoretical and technical basis for the development of sustainable agriculture and food security.

• Effect of Salinization Degree on the Sequestration of Exogenous Organic Carbon in Soil Aggregates

  ZHAO Lixia, CHENG Kun, BIAN Qing, ZHU Lingyue, ZHENG Jie, WANG Xiaoyue, JIANG Yuji

  DOI: 10.11766/trxb202511060529

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  Abstract:

  【Objective】Saline-alkali soils have enormous potential for carbon sequestration, and straw inputs in these soils strongly influence the microorganism-mediated sequestration of soil organic carbon (SOC). Nevertheless, the mechanisms and effects of different salinization degrees on the sequestration of straw-derived carbon in soil aggregates remain unexplored. 【Method】A 90-day laboratory experiment using continuous 13C labeling combined with amino sugars microbial biomarkers technology was conducted to investigate the effects of saline-alkali degrees on the content and distribution of straw-derived carbon and its contribution rate to soil organic carbon. Also, the content of microbial necromass carbon and its contribution rate to 13C-SOC at aggregate sizes in different saline-alkali soils was evaluated.【Result】(1) From the perspective of aggregate size fractions, the straw-derived carbon was primarily distributed in the 2~0.25 mm aggregate, and its content was higher than that in other aggregate size fractions. In contrast, the >2 mm aggregate exhibited the lowest content of straw-derived carbon. With the increase of soil salinization degrees, significant increase in the distribution content of straw-derived carbon was observed in the >2 mm and < 0.25 mm aggregate, but the distribution content of straw-derived carbon in the 2~0.25 mm aggregate significantly decreased. (2) At the aggregate scale, in saline-alkali soils, fungal necromass carbon dominated within microbial necromass carbon, accounting for approximately 84.74% to 95.29% of the microbial necromass carbon. The content of 13C-fungal and 13C-bacterial necromass carbon was the highest in the <0.25 mm aggregate, while the highest ratio of 13C-fungal necromass carbon and 13C-bacterial necromass carbon was in the >2 mm aggregate. The content of 13C-fungal necromass carbon and the ratio of 13C-fungal necromass carbon and 13C-bacterial necromass carbon significantly increased with increasing salinization degrees, but the content of 13C-bacterial necromass carbon showed a opposite trend. (3) Contribution rate of straw-derived carbon to SOC and 13C-microbial necromass carbon to 13C-SOC increased gradually with decreasing aggregate sizes in soil aggregates. In addition, soil salinization degrees significantly increased the contribution rate of straw-derived carbon to SOC in each aggregate size and the contribution rate of 13C-fungal necromass carbon and 13C-microbial necromass carbon to 13C-SOC in the 2~0.25 mm and <0.25 mm aggregate. However, a significant decreased was observed for the contribution rate of 13C-microbial necromass carbon to 13C-SOC in the >2 mm aggregate and the contribution rate of 13C-bacterial necromass carbon to 13C-SOC in each aggregate size.【Conclusion】This study clarifies the microbial mechanism of straw-derived carbon sequestration processes at aggregate sizes in different saline-alkali soils, which provides important theoretical guidance for regulating soil organic caron sequestration processes in saline-alkali soils ecosystems through straw-returning practices.

• Effects of Soil Microbial Diversity and Environmental Factors on Aboveground Biomass

  Yang Yi, Li Yan, Sun Jibin, Qiu Kaiyang, Wang Guohui, Zheng Xiang, Hai Xuying, Xue Bin, Guo Yanju, Ma Yulong, Xie Yingzhong

  DOI: 10.11766/trxb202505230236

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  Abstract:

  【Objective】 Plant-soil microbe interactions are the cornerstone of grassland ecosystem function and stability. Elucidating the relationship between plant biomass and soil microbial diversity, along with its environmental dependencies, is essential for understanding ecosystem maintenance mechanisms and predicting future dynamics. However, most studies focus primarily on bulk soil microbes, while integrated investigations examining the effects and relative contributions of both bulk and rhizosphere soil microbes on plant biomass remain scarce. Therefore, this study aimed to elucidate the effects of soil microbes on aboveground biomass (AGB) under the combined influence of biotic and abiotic factors.【Method】 This study was conducted in the desert steppe on the eastern foothills of the Helan Mountains. The characteristics of soil microbial communities in both bulk soil and the rhizosphere soil of dominant plants across different plant communities were analyzed. The effects of soil microbes on aboveground biomass (AGB) under the combined influence of biotic and abiotic factors were elucidated. 【Result】 The results revealed that: 1) No significant difference was observed in microbial alpha diversity between bulk and rhizosphere soils (P > 0.05), whereas beta diversity showed significant differences (P < 0.05). The absolute abundance of both bacteria and fungi in the rhizosphere soil of all dominant plants was higher than that in the corresponding bulk soil, except for bacterial abundance in the rhizosphere of Stipa breviflora. Stochastic processes dominated the microbial community assembly in both bulk and rhizosphere soils. 2) AGB was significantly positively correlated with the biotic factors of plant diversity and Faith’s phylogenetic diversity of fungi in bulk soil, as well as the abiotic factors of ectorhizosphere soil pH and total nitrogen content (P < 0.05). Conversely, it was significantly negatively correlated with mean annual temperature, soil moisture content, and available phosphorus in bulk soil (P < 0.05). 3) Plant diversity was the primary factor explaining the variation in AGB, accounting for 41.5% of the explained variance, followed by soil physicochemical properties. 4) In contrast to rhizosphere microbes, bulk soil microbial diversity acted as the key mediator linking environmental factors to AGB. The effects of climatic and soil physicochemical factors on AGB were primarily indirect, transmitted through this mediating pathway. 【Conclusion】 In conclusion, the diversity of plant and bulk soil microbiomes is a key biological regulator in maintaining plant AGB of the desert steppe ecosystem, a role that is modulated by climatic factors and soil physicochemical properties.

• Effects and Mechanisms of Phoebe bournei Litter Input on Soil Priming Effect Based on Organ and Carbon to Nitrogen Ratio Differences

  MAO Zixi, GAN Ziying, XIE Jiangtao, QIU Qingyan†, HU Yalin

  DOI: 10.11766/trxb202507200353

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  【Objective】Litter quality is a key factor regulating the intensity and direction of the soil priming effect. However, it remains unclear whether inputs of litter from different organs of the same plant or litter with different carbon to nitrogen ratios (C/N) from the same organ differentially impact soil priming effect, as well as the underlying mechanisms.【Method】To address this gap, 13C-labeled seedlings of Phoebe bournei were used as study materials. Through fertilized and non-fertilized treatments, leaf, stem, and root tissues with low and high C/N ratios were obtained to investigate the effects of litter inputs with different C/N ratios on soil priming. Soil microbial biomass, enzyme activity, and soil available nitrogen contents (NH4+-N and NO3--N) were measured concurrently to elucidate the underlying mechanisms.【Result】After 180 days of incubation, the addition of high and low C/N ratio leaf litter and low C/N ratio root litter inhibited the mineralization of soil organic carbon (SOC) by about 11.09%, 9.05% and 8.07%, respectively, inducing a significant negative priming effect. However, the other treatments did not cause significant priming effects. The influence of different C/N ratios in the same organ of Phoebe bournei on soil priming effect was primarily observed within the first 8 days of incubation, with high C/N ratio litter inducing a stronger negative priming effect than low C/N ratio litter. The reason is that high C/N ratio litter input caused microbial nitrogen (N) immobilization, reducing soil available N content, which led to N limitation and suppressed microbial activity, thereby decreasing SOC decomposition. In the later stages of incubation, the effects of different C/N ratio litter on soil microbial biomass carbon and carbon metabolism-related enzyme activities were not significant, so the influence of C/N ratio on soil priming gradually diminished. Among different plant organs, leaf litter induced a stronger negative priming effect than root litter. Specifically, the negative priming effect induced by leaf addition weakened over time, while root addition continuously induced a negative priming effect. Stem addition caused a priming effect that fluctuated between positive and negative, but the cumulative effect offset, resulting in no significant change in SOC decomposition.【Conclusion】The impact of Phoebe bournei litter input on soil priming effect varied significantly among organs, whereas the influence of litter C/N ratio on soil priming effect was mainly concentrated in the early stages of litter decomposition. The main mechanism by which leaf litter induced a negative priming effect was through reducing soil available nitrogen, which inhibited microbial activity, thereby decreasing SOC decomposition. In contrast, the negative priming effect induced by low C/N ratio roots was because their high lignin content and low bioavailability, causing C limitation for microorganisms during decomposition, leading to reduced SOC decomposition.

• Characteristics of Cultivated Land Soil Acidity and Main Controlling Factors in the Typical Black Soil Region of Northern Songnen Plain

  LIN Ziyi, WU Huayong, SONG Xiaodong, ZHAO Yuguo, ZHANG Ganlin

  DOI: 10.11766/trxb202509040439

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  Abstract:

  【Objective】 Soil acidification is a prominent issue in the typical black soil region of the northern Songnen Plain, which hinders the sustainable development of regional agriculture. Thus, exploring the characteristics of soil pH, exchangeable acidity, and their influencing factors in the cultivated soils of the typical black soil region can provide a scientific basis for the zoning and classification of soil acidification improvement measures. 【Method】 In this study, surface soils of cultivated land in Bei""an City and Wudalianchi City, Heilongjiang Province, were taken as the research object. Soil samples from 119 soil sites were collected to determine soil acidity and related soil properties, while data on relevant environmental and anthropogenic factors were collected. Pearson correlation analysis and random forest model were used, combined with the theory of soil acid-base buffering, to explore the main controlling factors affecting the spatial variation of soil pH, exchangeable H⁺, and exchangeable Al³⁺ contents. 【Result】 The results showed that the surface soils of cultivated land in the study area were dominated by strongly acidic and acidic soils. The spatial variability of soil pH was low, while the spatial variability of soil exchangeable acid content was high. There were no significant differences in soil pH and exchangeable acidity contents between dark brown soils, black soils, marsh soils, and meadow soils. Pearson correlation analysis indicated that soil pH was extremely significantly and positively correlated with the contents of exchangeable Ca²⁺ and Mg²⁺, clay fractions, and mean annual temperature, and significantly negatively correlated with soil organic matter content, silt content, aluminum saturation, mean annual precipitation, and elevation. Soil exchangeable H⁺ and Al³⁺ contents were extremely significantly and positively correlated with soil organic matter content, silt content, aluminum saturation, mean annual precipitation, and elevation, and extremely significantly and negatively correlated with the contents of exchangeable Ca²⁺ and Mg²⁺, clay fractions, and mean annual temperature. The random forest model showed that the 15 influencing factors explained 84.38% and 71.61% of the variations in soil pH and exchangeable acids, respectively. Among these factors, soil factors contributed the most (65.67% and 56.19%), followed by environmental factors such as annual average precipitation (18.57% and 13.87%), whereas the contribution of anthropogenic factors was negligible with respect to the spatial variation of soil pH and exchangeable acid (0.14% and 1.55%). 【Conclusion】 The typical black soil region in northern Songnen Plain has a high acid buffering capacity due to its high base saturation and abundant feldspar minerals, which is significantly different from the soil in typical red soil regions. The main controlling factors for the spatial variation of soil acidity are soil exchangeable base ions (Ca²⁺ and Mg²⁺) contents, aluminum saturation, and annual average precipitation.

• Penetration Resistance Characteristic Model of Red Soils and Influencing Factors

  WANG Jinqiang, CHENG Chaofan, TIAN Zhengchao, HE Yangbo, LIN Lirong, CHEN Jiazhou

  DOI: 10.11766/trxb202507150348

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  Abstract:

  【Objective】High soil penetration resistance (PR) limits global crop growth and sustainable agricultural productivity. Heavy soil texture, low soil organic matter, and low topsoil water content during summer significantly increase PR under a subtropical monsoon climate in southern China. However, the specific mechanisms controlling these processes remain elusive. Thus, the objectives were to investigate the applicability of various penetration resistance characteristic models in red soils with different parent materials and identify key influencing factors, and assess the ameliorative effects of mechanical- and bio-tillage on PR in Ultisols. 【Methods】This study investigated four red soils derived from different parent materials in China’s humid subtropical climate, including granitic (GS), Quaternary red clayey (CS), argillaceous shale (AS), and red sandstone red soil (SS). Key parameters measured included soil PR, water content (SWC), bulk density (), organic matter (SOM) and texture. We evaluated the performance of five PR models (soil water content model, soil matric potential model, soil water content and bulk density model, soil matric potential and bulk density model, and saturated stress model) and identified their influencing factors in red soils, assessed the ameliorative effects of mechanical- and bio-tillage on PR in Ultisols, and determined the PR threshold for four red soils using the least limiting water range. 【Results】Among the five characteristic models of soil PR, the saturated stress model provided a better fit (lower SSE and higher R²) for the four red soils, followed by the soil water content model, the soil water content and bulk density model, and the soil matric potential model. PR in red soils increased with decreasing water content, exhibiting a sharp increase once the water content fell below a critical value (~ 0.32 cm³·cm-³). The PR of low bulk density soils (1.3 g· cm-³) experienced a sharp increase at low water contents, whereas that of high bulk density soils (1.5 g·cm-³) showed a dramatic increase at high water contents. Soil texture (clay content) was a primary factor influencing PR of different parent material red soils, while SOM had negligible effects. When the soil water content was 0.25 cm³·cm-³, mechanical tillage (deep tillage with 30 cm ploughing depth) reduced PR by ~1 034 kPa in the 0~40 cm depth compared to control treatment (no-tillage), whereas bio-tillage achieved a reduction of ~785 kPa in the same depth and reduced PR (~1 500 kPa) in the subsoil. The critical PR thresholds of the four red soils exceeded 2 500 kPa, and thresholds for clayey red soils were higher than those for sandy red soils. 【Conclusion】The saturated stress model proved highly effective for predicting red soil PR in of southern China. SWC,  and texture played the primary factors influencing PR across different parent material red soils, with clayey red soils (CS and AS) exhibiting higher PR thresholds than sandy red soils (GS and SS). This research provides a scientific basis for identifying the occurrence of seasonal drought and rationally selecting tillage practices for drought prevention in subtropical red soil regions of China through the lens of soil penetration resistance.

• Effects of Different Green Manure Plantations on Runoff and Sediment Yield in Sloped Citrus Orchards with Purple Soil and Their Underlying Mechanisms

  ZHAO Yanting, WANG Xiaoyan, HE Hui, CHEN Zhanpeng, CHEN Fangxin, SHAN Qiao

  DOI: 10.11766/trxb202508030377

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  【Objective】Green manure cultivation in orchards plays a positive role in improving soil physicochemical properties, such as soil structure, and in reducing soil erosion. However, the mechanisms by which green manures mitigate soil erosion in sloping orchard systems remain unclear. 【Method】This study was conducted using runoff plots in a citrus orchard to systematically monitor runoff and sediment yield under natural rainfall conditions in plots planted with ryegrass (Lolium perenne), hairy vetch (Vicia villosa), and white clover (Trifolium repens), compared with bare tilled (bare soil) control plots. The effects of green manure plant characteristics, stem thickness, plant height, root length, and vegetation cover, on soil structural properties (porosity, bulk density, average infiltration rate) and organic matter content, as well as their relationships with runoff and sediment production, were analyzed. 【Result】The results showed that (1) Green manure plant traits significantly improved from initial to peak flowering. Hairy vetch exhibited the greatest plant height and root length, ryegrass had the optimal stem thickness, and white clover achieved the highest vegetation cover. (2) Soil bulk density and porosity were closely correlated with green manure root length: more developed root systems were associated with lower bulk density and higher porosity (P < 0.05). At peak flowering, green manure plots showed a significant decrease in bulk density and notable increases in porosity and average infiltration rate compared to the seedling stage, whereas the bare tilled control exhibited opposite trends. Organic matter content increased in all plots from seedling to peak flowering, but the smallest increase occurred in the bare control. Among treatments, hairy vetch showed the greatest reduction in bulk density (–8.69%) and the largest increases in porosity (+8.22%) and organic matter (+45.88%). Also, ryegrass demonstrated the best infiltration performance, followed by white clover. (3) Root length exerted strong influences on subsurface flow (effect strength = 0.66) and sediment yield (0.71), while plant height and vegetation cover primarily affected surface runoff (0.62) and sediment yield (0.61) by dissipating rainfall energy and resisting overland flow. Over a full annual cycle, including growth, residue decomposition, and tillage periods, the average runoff and sediment yields followed the order: bare tillage > hairy vetch > white clover > ryegrass, clearly indicating the superior overall erosion control by ryegrass. Although the hairy vetch plots recorded the lowest sediment concentration in runoff, temporal analysis revealed distinct performance patterns. Specifically, white clover was most effective in reducing runoff and sediment during the early growth stages (seedling/initial flowering) due to its rapid establishment, whereas ryegrass performed best during peak flowering, decomposition, and the non-growing season, owing to its persistent biomass and robust root system. 【Conclusion】Intercropping ryegrass and white clover in sloping citrus orchards provides the most effective control of soil and water loss. These findings provide theoretical support for the strategic mixing and temporal scheduling of green manure species, tailored to specific ecological functions in different agroecological zones.

• Effects and Driving Mechanisms of Leguminous Green manure on Soil Ecosystem Multifunctionality in Apple Orchards

  WANG Ju, YU Jintao, LI Mingjun, YANG Peizhi, ZHAI Bingnian, LI Ziyan

  DOI: 10.11766/trxb202509110448

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  【Objective】Intensive orchard management in semi-arid regions has caused soil quality degradation and declining ecosystems’ multifunctionality, thereby threatening production sustainability. While green manure mulching shows promise for sustainable orchard management, the mechanistic impact on soil quality and ecosystem multifunctionality remain unclear.【Method】This study investigated the impact of four green manure mulching treatments- no mulching, gramineae monoculture (ryegrass, Lolium perenne L.), legume monoculture (white clover, Trifolium repens L.), legume-gramineae mixture (1:1) on soil quality and ecosystem multifunctionality in semi-arid orchards.【Result】The results revealed that green manure mulching substantially enhanced soil quality, with legume monoculture showing superior performance (89.0% and 88.5% increases versus grass and mixed systems, respectively). All treatments stimulated soil enzyme activities and alleviated microbial limitations (carbon: 5.8%-8.6%; nitrogen: 5.0%-14.7%), collectively increasing ecosystem multifunctionality by 87.4%-100.2%.【Conclusion】This study reveals that green manure mulching effectively enhances soil ecosystem multifunctionality in semi-arid orchards, with legume-based systems (monoculture or mixed) recommended for implementation.

• Research Progress of Pelletized Straw Incorporation

  WANG Xiquan, WANG Peixin, QIAN Chunrong, PANG Huancheng

  DOI: 10.11766/trxb202510100492

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  Straw incorporation poses a persistent challenge while remaining fundamental to soil fertility management in modern Chinese agriculture. However, traditional straw incorporation methods are characterized by slow decomposition, inefficient soil organic matter enhancement, and significant yield reduction. To combat these drawbacks, we proposed and developed straw pelletization technology as a novel alternative for efficient straw utilization over 14 years, providing a novel solution for land conservation and intensive utilization. This review synthesized the research progress in straw pelletization and incorporation, with the aim of providing a theoretical foundation and technical guidance for its high-quality development. This review commenced with a retrospective analysis of the conceptual foundation of straw pelletization and incorporation, which involves secondary crushing and pelletizing of straw to simultaneously tackle decomposition and field incorporation challenges. Subsequently, based on previous practices, the study delineated ten major advantages, such as markedly increased incorporation rates, rapid soil organic carbon sequestration, and stable yield improvements. It also identifies three salient scientific questions, the mechanism of accelerated decomposition, carbon turnover processes, and carbon sequestration thresholds, while envisioning the application potential of pelletized straw returning in intensive agriculture, organic agriculture, medium- and low-yield fields, and reserve croplands. Finally, to bridge the gap in large-scale and widespread adoption, two essential supporting measures were proposed: the optimization and widespread deployment of integrated straw crushing and pelletizing machinery, and the establishment and development of a straw pellet trading platform. In summary, straw pelletization and incorporation enable the simultaneous improvement of soil fertility and crop yield, thereby supporting the national strategies of the Two Stores (storing grain in the land and through technology) and the Dual Carbon (Carbon Peak and Carbon Neutrality).

• Spatio-Temporal Variations of Soil Total Nitrogen and Nitrogen Use Efficiency in Farmland of A Typical County in Cinnamon Soil Area

  HE Ningbo, SU Xinyue, BAI Kaidong, WANG Hengfei, LI Jianhua, XU Minggang

  DOI: 10.11766/trxb202504130178

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  Abstract: 【Objective】 Optimizing nitrogen management of the farmland is critical to achieve the strategy of reducing fertilizer input and improving efficiency, as well as advance the agricultural green development. This study aims to explore the spatio-temporal variations of soil total nitrogen (TN) and nitrogen use efficiency (NUE) in typical county of cinnamon soil region over the past four decades, which can provide the scientific basis for enhancing farmland nitrogen management. 【Method】 Based on the farmland soil properties (soil nutrients, etc.) in Shouyang County, Shanxi Province in 1983, 2010, and 2023, and the agricultural production statistical data (planting area, crop yields, fertilizer types and application rates, livestock breeding quantity, etc.) from 1980 to 2023, classical statistics and geostatistics were employed to analyze the spatiotemporal dynamics of TN. The farmland nitrogen balance model was used to estimate nitrogen use efficiency (NUE) and nitrogen surplus. Random-forest analysis was applied to identify the key factors that affected the variations of TN. 【Result】 From 1983 to 2023, the farmland TN content in Shouyang County increased significantly, rising from 0.66 g·kg-1 to 1.02 g·kg-1. The most notable increase in TN occurred in Pingtou Town, Yinlingzhi Town, and the eastern part of Chaoyang Town. Over the past four decades, the NUE showed a pattern of first decreasing and then increasing, which declined from 48.63% in the 1980s to 33.08% in the 2000s and subsequently rose to 43.75% in the 2010s. Spatially, the farmland NUE value ranged from 30.66% to 50.99% among various regions during the 1980s to 2000s, which showed no significant difference. While in the 2010s, the NUE in the northern region (45.52%) was significantly higher than that in the central (36.84%) and southern regions (36.80%). The Random-forest analysis identified that soil organic carbon and nitrogen fertilizer amount were the key influencing factors to the changes of TN, with the relative importance of 33.95% and 10.57%, respectively. Currently, the farmland NUE and nitrogen surplus in Shouyang County were 45.78% and 97.2 kg·hm-2, respectively, which were still outside the optimal nitrogen management level. The northern region exhibited a relatively high NUE but a substantial nitrogen surplus, while Jingshang Town and Xiluo Town in the southern region recorded extremely low NUE and high nitrogen surplus. 【Conclusion】 Overall, although the farmland nitrogen management in Shouyang County has been improved over the past four decades, it still falls short of the optimal level. It is recommended that the entire Shouyang County, especially the Jiechou Town in the northern region, the Chaoyang Town in the central region, and the Jingshang Town and Xiluo Town in the southern region should prioritize rational nitrogen fertilizer amount to enhance farmland NUE, reduce nitrogen surplus, and ultimately achieve the optimal nitrogen management level.

• Effects of Earthworms on Nitrogen Utilization and Loss with Different Fertilizer Applications

  Cheng Yihan, Ouyang Yi, Zhao Jiaxin, Pei Xiangyu, Zhang Lin, Lu Yaoxiong, Wu Yupeng

  DOI: 10.11766/trxb202503290146

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  【Objective】The application of organic fertilizers in agricultural soils increases the density of earthworms. However, it remains unclear how earthworms change the fate of soil nitrogen under different fertilizer applications. 【Method】Using a pot experiment, the present study explores the effects of earthworms on soil nitrogen utilization, loss, and nitrogen transformation processes under the application of chemical (urea) and organic (compost) fertilizers. 【Result】The results showed that earthworms significantly increased the fresh weight of plants and the amount of nitrogen uptake by plants by 12.14% and 15.24% under chemical fertilizers and 18.38% and 37.28% under organic fertilizers, respectively. Earthworms significantly increased the cumulative soil N?O emissions and the cumulative soil ammonia volatilization only under the application of chemical fertilizers. There was no significant difference in nitrogen leaching loss between the treatment with and without earthworms. Overall, earthworms increased the nitrogen loss by 6.31 and 1.69 mg·pot?1 under the application of chemical and organic fertilizers, respectively. Also, earthworms significantly increased the ratio of the total nitrogen utilization by plants to the total nitrogen loss under the application of organic fertilizers, but no significant difference was found under the application of chemical fertilizers. The soil nitrogen primary transformation rate model showed that earthworms affected more nitrogen transformation processes under the application of organic fertilizers than under the application of chemical fertilizers, significantly increasing the total primary nitrogen mineralization rate of the soil. 【Conclusion】Regardless of the type of fertilizer applied, earthworms played a dual role in promoting plant nitrogen utilization and increasing nitrogen loss. However, considering the ratio of nitrogen utilization to loss, the application of organic fertilizers provided a more conducive environment for achieving the beneficial effects of earthworms in the soil nitrogen cycle.

• Effects of Biological Nitrification Inhibitor Application on Nitrification Rate and Nitrous Oxide Emission in Upland Soils Amended with Organic Fertilizer

  guo qirui, zhang yinghua, chen meiqi, liu zihan, jing hang, wang jing, Ahmed S. Elrys, cai zucong, chengyi

  DOI: 10.11766/trxb202505210232

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  【Objective】Application of biological nitrification inhibitors (BNIs) is an effective strategy to suppress nitrification rates and mitigate nitrous oxide (N?O) emissions in agricultural soils. However, how the addition of BNIs affects soil nitrification rate and N?O emission under organic fertilizer application remains unclear. 【Method】The microcosm aerobic incubation experiment was conducted using upland red and black soils, with two levels of organic fertilizer (chicken manure: N 0 and 100 mg·kg?1 soil) and three levels of BNIs addition (1,9-decanediol: 0, 1,000, and 2,000 mg·kg?1 soil). During the incubation, concentrations of inorganic nitrogen (N) and N?O emissions were measured, and quantitative PCR was employed to analyze microbial gene abundances related to N transformation. 【Result】The addition of 1,9-decanediol significantly decreased the net nitrification rate in both soils regardless of organic fertilizer input (P<0.05), exhibiting a dose-dependent suppression effect. Specifically, with organic fertilizer input, high concentrations of 1,9-decanediol decreased the net nitrification rate in black soil by 79% and even shifted the net nitrification rate in red soil from positive to negative. In contrast to nitrification, the addition of 1,9-decanediol either low or high concentrations significantly elevated N?O emissions in both soils, irrespective of organic fertilizer input (P<0.05). Also, a dose-dependent stimulation of N?O emissions occurred only in black soil. In red soil with and without organic fertilizer input, 1,9-decanediol significantly reduced the abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) amoA genes (P<0.05), with greater suppression at higher doses. In contrast, the suppressive effect in black soil was significantly weaker than in red soil. Regardless of organic fertilizer application, only high dosage of 1,9-decanediol significantly reduced the abundance of key denitrifying genes in red soil. In addition, partial least squares regression analysis indicated that under organic fertilizer plus BNIs treatment, net N mineralization rate and AOA/AOB amoA abundances were identified as primary determinants of nitrification rates, while net nitrification and mineralization rates were key drivers of N?O emissions. Net nitrification rate was significantly negatively correlated with N?O emissions (P<0.05), suggesting that denitrification rather than nitrification is the major pathway of N?O production. 【Conclusion】Combined application of organic fertilizer with biological nitrification inhibitor significantly reduced nitrification rates in red and black soils, but significantly enhanced N?O emissions. Therefore, rational selection of BNIs types and application rates is critical to avoid paradoxically stimulating N?O emissions while suppressing nitrification in upland agricultural soils.

• Effects of Fertiliser Adjustment on the Physicochemical Properties, Bacterial Community Composition and Ion Transport in Saline-Alkali Corn Fields

  LIU Weifan, LIU Hao, WAN Menghu, MA Fenglan, LI Yueqi, LI Qingyun, WU Na, LIU Jili

  DOI: 10.11766/trxb202507080335

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  【Objective】This study aimed to investigate the synergistic effects of different water and fertilizer treatments on the physicochemical properties, bacterial community structure, and ion transport function of saline-alkali maize fields, thereby providing a theoretical basis for their targeted improvement. 【Method】A field experiment was conducted in saline-alkaline land in Pingluo County, Ningxia. A split-plot design was used with two irrigation levels as main plots: conventional irrigation (w1, 6 000 m3hm-2) and water-saving irrigation (w2, 4 800 m3hm-2)， and four fertilization modes as sub-plots: f1 (nitrogen fertilizer alone), f2 (nitrogen with controlled-release fertilizer), f3 (nitrogen with organic fertilizer), and f4 (controlled-release fertilizer with organic fertilizer). Soil physicochemical properties were measured. Bacterial community structure was analyzed by 16S rRNA high-throughput sequencing, and the abundance of ion transporter genes was predicted using PICRUSt2 software. 【Result】Water-saving irrigation w2 exhibits no significant difference in its impact on soil physicochemical properties compared to conventional irrigation w1. Compared with w2f1 treatment, the w2f3 treatment significantly increased the contents of soil organic matter (SOM), total nitrogen, alkaline hydrolyzable nitrogen, available phosphorus, available potassium, and Ca2+ (P<0.05), while significantly decreasing pH, electrical conductivity, and Na+ content (P<0.05). The water-fertilizer interaction had highly significant effects on the contents of sodium, magnesium, potassium, and calcium ions (P<0.01). Microbial analysis showed that the w2f4 treatment significantly increased the Simpson diversity index and Pielou evenness index (P<0.05). At the phylum level, w2f3 and w2f4 significantly increased the relative abundance of Proteobacteria and Actinobacteria, while decreasing the relative abundance of Acidobacteria (P<0.05). At the genus level, Kaistobacter and Lysobacter were the dominant genera, and their abundance was significantly increased by the w2f3 treatment (P<0.05). Linear discriminant analysis effect size analysis identified 32 biomarker species across five phyla, with w2f3 significantly enriching Proteobacteria and Bacteroidota. Prediction of ion transporter genes indicated that the w2f3 treatment simultaneously activated the magnesium transporter gene CorA and the Na+/H+ antiporter gene nhaA. The ecological dominance of Proteobacteria was positively regulated by KefB and CorA. Mantel test confirmed that SOM and pH were the core environmental factors driving the evolution of the microbial community structure.【Conclusion】Under water-saving irrigation, the combined application of nitrogen fertilisers with organic fertilisers (w2f3) achieves systematic restoration of ecological functions in saline-alkali soils by synergistically enhancing soil fertility, optimising bacterial community structures, and activating ion homeostasis networks. This provides both theoretical and technical underpinnings for the efficient remediation of saline-alkali land.

• Gross Nitrogen Transformation Rates and Their Regulation in Soils of Three Typical Ecosystems in China

  HAO Tianxiang, YANG Meng

  DOI: 10.11766/trxb202507290364

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  【Objective】Soil gross nitrogen (N) transformation processes are fundamental and critical components of terrestrial N cycling. However, the mechanisms controlling gross N transformation rates and their controlling factors across soils with contrasting properties and land uses remain underexplored.【Method】Seven typical soils from three major ecosystems in China were selected: forest (Changsha, Linzhi, Chongqing), grassland (Duolun, Bayanbulak), and upland (Shangzhuang, Quzhou). A short-term incubation experiment was conducted using the?1?N isotope dilution technique combined with a numerical N tracing model. Ten key gross N transformation processes were quantified. 【Result】 Mineralization, immobilization, and autotrophic nitrification were identified as the dominant gross N transformation pathways. No significant differences in gross transformation rates were found among land use types. The means (±S.D.) of gross mineralization rates were 1.40±1.31, 2.07±1.46, and 1.83±0.01 mg·kg?1·d?1 for forest, grassland, and upland soils; corresponding to gross immobilization rates of 4.24±3.04, 6.93±3.79, and 5.54±2.00 mg·kg?1·d?1, and gross nitrification rates of 1.47±1.30, 3.75±1.86, and 5.26±2.52 mg·kg?1·d?1, respectively. Significant differences were observed between individual soils in most gross N transformation rates, indicating spatial heterogeneity in soil N supply and retention capacity. Correlation analysis showed that gross mineralization rates were positively correlated with soil organic carbon and negatively correlated with bulk density, whereas gross nitrification rates were positively correlated with soil salinity. 【Conclusion】These results demonstrate that soil properties and environmental factors jointly regulate the gross N transformation process. Under the context of global change, a multi-scale and multi-factor integrative framework, explicitly accounting for land use type, soil characteristics, and environmental conditions, is essential for improving the accuracy of ecosystem N dynamics modeling and predicting nitrogen loss risks.

• Quantifying Pedoturbation with Luminescence Dating Techniques: Principles and Progress

  ZHANG Aimin, LONG Hao, YANG Fei, ZHANG Jingran, PENG Jun, ZHANG Ganlin

  DOI: 10.11766/trxb202508180402

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  Pedoturbation is a ubiquitous surface dynamic process that profoundly influences soil development, nutrient and contaminant transport, soil erosion, and geomorphic evolution. Traditional investigation methods primarily rely on field observations, morphological analysis, or spatial distribution characteristics of short-lived radionuclides, which, while providing valuable information, are often labor-intensive, predominantly qualitative, and limited to short-term quantitative studies. Optically stimulated luminescence (OSL) dating, a well-established Quaternary dating method used to determine the last sunlight exposure of mineral grains, has recently demonstrated unique advantages in quantifying pedoturbation through technological advancements, particularly by single-grain OSL dating techniques. This review examines the fundamental principles of OSL dating, elaborates its methodological framework for pedoturbation quantification, and systematically synthesizes its recent applications in analyzing soil formation processes, reconstructing bioturbation history, and investigating soil erosion-landform evolution relationships. Finally, the review discusses the technique’s strengths and limitations, aiming to demonstrate its potential for addressing pedological questions and promoting interdisciplinary innovation between Quaternary geochronology and soil science.

• Effects of Precipitation Change on Soil Microbial Biomass and Their Stoichiometric Ratios in an Alpine Meadow

  PU Zhongyu, HUANG Yuchen, TIAN Shasha, WANG Changting, LIU Dan, LIU Yang

  DOI: 10.11766/trxb202504070161

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  【Objective】The increase in global CO2 concentration and climate warming has accelerated changes in the global water cycle and led to changes in global precipitation patterns. The Qinghai-Tibetan Plateau (QTP) is highly sensitive to global climate change, and its precipitation patterns have also shifted in response to the global precipitation pattern. Soil microorganisms constitute an important part of the underground ecosystem and play key roles in the soil carbon and nutrient cycle. An in-depth understanding of the response of soil microorganisms to precipitation changes is vital for analyzing the internal mechanism of the impact of global climate change on ecosystem carbon and nutrient cycles. However, it is still unclear how precipitation changes affect soil microbial biomass carbon (MBC), nitrogen (MBN), phosphorus (MBP), and their stoichiometric ratios in the alpine grassland ecosystem of the QTP. Therefore, the current study aims to investigate the response mechanisms of soil microbial biomass and their stoichiometric ratios to precipitation changes in an alpine meadow of the QTP. 【Method】A field manipulation experiment simulating precipitation variations was conducted in an alpine meadow of Hongyuan County, Sichuan Province. Five precipitation gradient treatments were established: a 90% decrease in precipitation (0.1P), a 50% decrease in precipitation (0.5P), a 30% decrease in precipitation (0.7P), a control (1P), and a 50% increase in precipitation (1.5P). Rhizosphere soil was collected in each precipitation gradient treatment. Soil MBC, MBN, and MBP content were determined by the chloroform fumigation method. Soil microbial biomass stoichiometric ratios were calculated by the soil MBC, MBN, and MBP content. At the same time, soil physicochemical properties, including soil water content (SWC), soil pH, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), dissolved organic carbon (DOC), ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), and available phosphorus (AP) were also determined. 【Result】The results showed that: (1) Soil MBC and MBN contents were increased with the increase of precipitation; however, MBP was not changed along the precipitation gradient. Compared with the control (1P), soil MBC and MBN content were significantly reduced in the 0.1P treatment; (2) Soil MBC∶MBN and MBC∶MBP showed an increasing trend with the increase of precipitation. The 0.1P treatment significantly reduced the MBC∶MBP ratio when compared with control; (3) Pearson correlation analysis showed that soil MBC, MBN, and MBP content were significantly positively correlated with SWC, and the MBC and MBN content were also significantly positively correlated with NO3−-N and negatively correlated with DOC. The MBC∶MBP and MBN∶MBP were significantly positively correlated with soil C∶N; (4) Multiple linear regression analysis showed that DOC had a significant negative effect on MBC and MBN, while TP and soil N∶P had significant positive effects on MBC and MBN. SWC showed a significant positive effect on MBN and MBP, while the soil C∶N showed a significant negative effect on MBP. Soil DOC and SWC had significant negative effects on MBC∶MBN, and soil C∶N had significant positive effects on MBC∶MBP and MBN∶MBP. 【Conclusion】Our study demonstrates that soil moisture and soil nutrients drive the dynamic response of soil microbial biomass to precipitation changes in the alpine grassland ecosystem of the Qinghai-Tibetan Plateau. By understanding the response mechanism of soil microbial biomass to precipitation changes, we can better predict and respond to the potential impacts of climate change on alpine ecosystems, and develop more effective ecological protection and management strategies to maintain the balance and sustainable development of alpine ecosystems. Therefore, this study provides a microbiological theoretical basis for the management of alpine ecosystems in the context of climate change.

• Effects of Straw Incorporation Combined with Decomposition Agent on Soil Erosion Resistance in Medium-low Yield Purple Soil Sloping Farmland

  WANG Dingbin, CHEN Xiaoyan, LIAO Congyun, CHEN Libo, ZHANG Shenghui, ZHANG Qiujie, ZHU Pingzong

  DOI: 10.11766/trxb202506180290

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  【Objective】 Straw return is vital for improving soil structure, controlling erosion, and mitigating degradation. Nevertheless, the low straw decomposition efficiency under natural conditions greatly limits its widespread application. As a critical measure to promote straw decomposition, investigating the impacts of straw returning combined with decomposition agents on soil erosion resistance of medium-low yield sloping farmland, as well as the underlying mechanisms, holds significant importance for applying soil and water loss control measures that integrate the resource utilization of agricultural waste.【Methods】 A field in-situ monitoring experiment was conducted under the condition of full straw return. With no decomposition agent application as the control, four straw decomposing agents were co-applied with straw at rate of 1, 2, 3, and 4 kg·hm-2 and designed based on the viable bacterial count of the decomposer. The differences in soil erosion resistance and their dominant influencing factors under varying decomposer application rates were clarified.【Results】 The application of straw decomposition agent significantly promoted straw decomposition efficiency and improved soil structure. The straw decomposition amount and efficiency increased significantly with the increase in the application rate of the decomposition agent. Also, application of decompositing agent significantly reduced soil silt and clay contents, while significantly increasing soil sand content, saturated water content, field capacity, and organic matter content. Moreover, the soil erosion resistance was significantly improved with the application of straw decomposition agent. Compared to the control, the comprehensive soil resistance index (CSRI) increased by 43.24% ~ 360.77%. In addition, the results of PLS-SEM showed that the increase of CSRI was mainly governed by the direct binding and consolidation of residual straw (path coefficient 0.43) and the indirect effect of straw decomposition on the increase in soil organic matter content (path coefficient 0.40).【Conclusion】 Straw return combined with straw decomposition agents significantly increased soil erosion resistance of medium-low yield purple sloping farmland. Moreover, the direct effects of residual straw in enhancing soil erosion resistance slightly outweigh its indirect effects in increasing soil organic matter content via decomposition. However, a significant increase in CSRI was only detected when the application rate exceeded 3 kg·hm-2. This indicates that effective enhancement of erosion resistance requires a threshold application rate exceeding 3 kg·hm-2 for decompositing agents. These findings provide scientific guidance for the sustainable utilization of medium- low-yield purple soil sloping farmland and the green and high-quality development of the Yangtze River Economic Belt.

• Effect of Tillage Practices and Straw Management on Soil Pore Structure Characteristics in Fluvo-aquic Soil

  XIA Hao, WANG Guangshui, XIE Kun, QIAN Yongqi, JIANG Fahui, PENG Xinhua, YAO Shuihong, ZHANG Zhongbin, ZHANG Yueling, BI Lidong

  DOI: 10.11766/trxb202506300317

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  Abstract:

  【Objective】The plough layer of fluvo-aquic soil is shallow, while the subsoil is hard and compacted, exhibiting significant structural obstacles. Tillage and straw return are key measures for improving soil structure; however, the mechanism through which the combination of these agricultural practices affects soil structure remains elusive. 【Method】Undisturbed soil columns (20 cm height × 10 cm diameter) were collected from a fluvo-aquic soil experimental site at the Shangqiu Station of the national field Agro-ecosystem experimental network. The samples represented plots under rotary tillage (RT), deep ploughing (DP), and biennial deep ploughing (BDP), with and without straw returning. X-ray computed tomography (XCT) scanning, ImageJ software, and machine learning techniques were employed to perform three-dimensional reconstruction and visualization of the soil pore structure. The effects of different tillage methods and straw treatments on macroporosity, pore size distribution, pore morphology, network characteristics, saturated hydraulic conductivity, and air permeability were quantitatively analyzed. 【Result】Without straw return, deep ploughing and biennial deep ploughing increased macroporosity by 31.5% and 5.7%, respectively, compared to rotary tillage. With straw return, deep ploughing significantly increased macroporosity by 92.9% and 68.4% compared to rotary tillage and biennial deep ploughing, respectively (P < 0.05). Furthermore, the hydraulic radius increased significantly by 53.8% and 42.9%, respectively. Compactness increased significantly by 1.5 and 2.9 times, and global connectivity increased significantly by 12 times. Both saturated hydraulic conductivity and air conductivity were significantly enhanced (P < 0.05). 【Conclusion】 Deep ploughing increased the hydraulic radius of soil pores, improved connectivity, and enhanced pore network complexity, thereby constructing a relatively favorable soil pore morphology and network structure. This enhanced hydraulic and air conductivity, significantly reducing the structural obstacles in fluvo-aquic soil.

• Effect of Phenolic Acid Accumulation and Microbial Community Response in Strawberry Continuous Cropping Soil

  YANG Tongyi, ZHANG Li, WANG Xiujie, DONG Xiaona, JIA Qianqian

  DOI: 10.11766/trxb202509290480

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  Abstract:

  【Objective】Continuous cropping obstacles (CCOs) represent a critical constraint on the sustainable development of the strawberry industry, with core mechanisms involving soil phenolic acid accumulation, microbial community imbalance, and functional degradation. Although existing studies have demonstrated close correlations between phenolic acid autotoxic substances and microbial community changes, the dynamic evolution patterns and causal relationships of phenolic acid-microbiome interactions at the field scale remain unclear. Thus, this study aims to reveal the dynamic changes of phenolic acids, enzyme activity responses, and microbial community structure evolution in strawberry soil under long-term continuous cropping conditions. Also, the results will clarify the driving mechanisms of phenolic acid-microbiome interactions in CCO formation, and provide theoretical basis for developing precise regulation strategies. 【Methods】Greenhouse strawberry continuous cropping soils (0, 2, 5, 15, and 18 years) were selected as research objects to measure soil physicochemical properties, enzyme activities (urease, catalase, acid phosphatase, and sucrase), and phenolic acid contents (p-hydroxybenzoic acid, ferulic acid, and p-coumaric acid). Illumina MiSeq high-throughput sequencing technology was employed to analyze bacterial and fungal community structures, and redundancy analysis (RDA) was innovatively combined with structural equation model to construct causal networks of phenolic acid-microbiome-soil function interactions. 【Results】The results revealed that long-term continuous cropping resulted in significant soil acidification (pH decreased from 7.35 to 6.20), with continuous accumulation of phenolic acids reaching 247.3 mg·kg-1 at 18 years. Soil enzyme activities exhibited “increase-then-decrease” nonlinear dynamics, peaking at 5 years of continuous cropping (urease activity reached 1 527 U·g-1h-1), followed by a significant decline at 15 and 18 years. In addition, microbial community analysis revealed that continuous cropping led to a 23.6% reduction in bacterial Shannon diversity, a 43.3% decrease in the bacteria/fungi ratio, and an increase in the relative abundance of pathogenic fungi (e.g., Fusarium). Redundancy analysis first confirmed that p-coumaric acid (p-CA) was the dominant factor explaining bacterial community variation (18.9%), while ferulic acid (FA) was the key factor explaining fungal community variation (21.2%). Structural equation model further revealed that phenolic acids affected microbial communities through dual pathways of direct inhibition (path coefficient = -0.85) and indirect regulation (via soil acidification), with phenolic acids serving as the direct dominant factor inhibiting bacterial communities, while fungal community structure was primarily directly regulated by soil acidification. 【Conclusion】This study elucidated the formation mechanism of CCOs through the “phenolic acid accumulation-soil acidification-microbial imbalance” cascade, revealing the specific effects of phenolic acid as key factors at the field scale. These findings provide a theoretical foundation for developing green prevention and control strategies for CCOs based on microbiome regulation, offering technical support for the sustainable development of the strawberry industry.

• Spatial mapping of effective soil thickness and its surface matrix constraint mechanism in the black soil area of eastern Mongolia

  LI Xinye, SHI Pu, LIU Hang, YANG Yong

  DOI: 10.11766/trxb202502150061

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  Abstract:

  Effective soil layer thickness is a decisive indicator for evaluating soil health and productivity, and accurate depiction of the spatial distribution pattern of effective soil layer thickness and its response mechanism to land use change and surface matrix type is of great significance for the sustainable protection of soil resources. In this paper, we selected the black soil area in the eastern part of Inner Mongolia as the study area, and based on the surface matrix survey data and soil-landscape modeling, we carried out the digital mapping and spatial pattern analysis of effective soil layer thickness in this area, identified the main controlling factors of spatial variability of effective soil layer thickness through SHAP analysis, and ascertained the differential distribution pattern of effective soil layer thickness under different land use types and surface matrix zoning. The results showed that the regression model of effective soil thickness based on Cubist had good performance (R2=0.5,RMSE=43.8), and the generated spatial distribution map could accurately reveal its spatial pattern. SHAP analysis revealed that topographic and climatic factors were the main controlling factors determining the spatial variability of the effective soil thickness, which was specifically reflected in the fact that the high elevation areas within the same watershed were affected by the erosion, and the soil layer was thinner; while the monthly average soil thickness was lower than the monthly average soil thickness, and the monthly average soil thickness was lower than the monthly average soil thickness, which was lower than the monthly average soil thickness. The effect of mean monthly temperature extremes on the effective soil layer thickness was positive. Both surface substrate zoning and land use types have important constraints on the spatial characteristics of the effective soil layer thickness, with the overall soil layer thickness in the residual slope deposit area being greater than that in the slope floodplain and slope deposit areas, and the soil layer thickness in cropland being significantly lower than that in woodland and grassland due to soil disturbance by high-intensity cultivation. The mean values of effective soil layer thickness in different surface substrate zones were in the order of residual slope deposits>slope flood deposits>slope deposits. This paper provides a methodological reference for the spatial modeling and characterization of effective soil layer thickness, and the results of the study can provide a data basis for identifying the background conditions of regional natural resources and their response mechanisms to human interactions.

• Microbial Assimilating Straw-derived Carbon in Response to Nitrogen and Phosphorus Supply in Paddy Soils: From Microbial Necromass Formation and Accumulation Perspective

  YANG Dongqiao, Lu Mengya, WANG Zhiquan, DING Xueli

  DOI: 10.11766/trxb202508030379

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  Abstract:

  【Objective】Crop straw input and nutrient supply may influence microorganism-mediated formation and transformation of soil organic carbon (SOC). However, the mechanisms by which straw and nutrient supply influence SOC transformation remain unclear. The objective of this study was to explore how and to what extent of straw-derived carbon (C) can be assimilated by microbes into necromass following crop straw amendment combined with nitrogen and phosphorus nutrients supply. 【Method】Using a 13C-labelled rice straw, the 300-day incubation experiment study examined the pattern of microbial assimilating straw-derived C in necromass (indicated by 13C-amino sugar dynamics) and its accumulation efficiency (CAE) as affected by nutrient supply levels. 【Result】The results showed that straw C could be transferred into microbial necromass rapidly as evidenced by the production of 13C-labelled individual and total amino sugars. There were higher amounts of 13C-amino sugars and CAE during the early stage of straw incubation (before 30 days), but a strong decline of total 13C-amino sugars, especially bacterial necromass (decreased by 18%-28% across treatments) was observed during the middle and later stages. The effect of nutrient supply on microbial assimilation of straw C processes was highly time-dependent, that is, no significant effect in the early stage and significant inhibition in the later stage. Specifically, nutrient supply did not have pronounced effects on straw C incorporation into amino sugars but significantly decreased 13C-amino sugars and CAE towards the end of incubation, suggesting an accelerated turnover of newly-formed amino sugars in treatments of straw combined with nitrogen and phosphorus supply. This might be related to potential changes of microbial strategies regarding nutrient acquisition and C allocation, highlighting the complex relationship between extraneous C and nutrient availability. Noteworthy, the total amino sugars (including 13C-labelled and unlabeled) were higher in nutrient supply treatments despite lower amounts of 13C-amino sugars, suggesting that crop straw addition with nutrient supply stimulated microbial transformation of native SOC components into necromass via microbial C pump mechanisms. 【Conclusion】This study highlights that straw input could stimulate microbial-derived C production and accumulation by accelerating microbial anabolisms via microbial C pump. The nutrient supply exerted an overall negative effect on the straw-derived microbial necromass accumulation in the long term, but stimulated native SOC-derived necromass contribution. It is suggested that the microbial necromass accumulation from newly added (fresh organic matter) and old soil carbon (inherent SOC) needs to be further investigated when evaluating the impacts of straw input on SOC formation and transformation. These findings advance the understanding of the mechanisms of microbial control over SOC formation and sequestration following extraneous organic matter input under varying nutrient conditions.

• Mechanism of a Cadmium-Lead Tolerant Phosphorus-Solubilizing Bacterium, Bacillus sp. PSB32, in Metal Removal and Plant Growth Promotion in Contaminated Systems

  FU Liyuan, LIU Meijing, LI Yang, HE Jianhua, LI Xiaoyi, LIANG Xinran, HE Yongmei, WU Longhua, ZHAN Fangdong

  DOI: 10.11766/trxb202508030376

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  Abstract:

  【Objective】Phosphorus-solubilizing bacteria (PSB) are ubiquitous in heavy metal-contaminated soils; however, their impacts on soil heavy metals and crop growth remain inadequately understood. 【Method】This study investigated the mechanisms and efficacy of Bacillus sp. PSB32, a Cd- and Pb-tolerant PSB strain isolated from the maize rhizosphere in the Yunnan Plateau, in removing aqueous Cd and Pb and influencing maize (Zea mays L.) growth in contaminated soils.【Result】Under Cd and Pb stress, strain PSB32 primarily removed Cd via intracellular accumulation(43.7%) and surface precipitation(43.2%), with biosorption playing a secondary role (13.0%). In contrast, Pb removal was dominated by surface adsorption (53.2%), followed by surface precipitation (28.8%) and intracellular accumulation (18.0%). Scanning electron microscopy (SEM) revealed the formation of granular precipitates on the bacterial cell surface, which were identified by X-ray diffraction (XRD) as Cd?(PO?)?, Pb?(PO?)?Cl (Pyromorphite), and Pb?(PO?)?OH. Fourier transform infrared (FTIR) spectroscopy confirmed the involvement of functional groups (e.g., -COOH, -OH, -NH?) and anionic groups (e.g., PO?3?, SO?2?) in the surface complexation of Cd and Pb. In the pot experiments, the amendment of PSB32 across the three differentially contaminated soils (contaminated farmland, tailings, and slag) led to a consistent increase of 5.90%-9.43% in the residual fraction of Cd, alongside a decrease of 7.20%-18.8% in the reducible fraction of Pb. Concurrently, the soil available phosphorus content was enhanced by 3.00%-18.7%, which contributed to a substantial promotion of maize biomass, ranging from 25.7% to 82.2%. Notably, PSB32 also increased the Cd content in maize shoots by 61.9% and 32.9% in the farmland and tailings soils, respectively, and significantly enhanced the accumulation of Cd and Pb in the roots by 365% and 35.3% in the slag soil.【Conclusion】In conclusion, Bacillus sp. PSB32 demonstrates a dual ecological function: effectively removing aqueous Cd and Pb through multiple mechanisms, and enhancing plant tolerance in contaminated soils by altering metal speciation and improving phosphorus nutrition. This strain presents a promising microbial resource for the bioremediation of heavy metal-contaminated soils.

• Community Structure of Aerobic Methanotrophs and Environmental Drivers in Coastal Wetlands

  lixiaoyong, wanghuan, zhengyue, wuyicheng

  DOI: 10.11766/trxb202503280141

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  Abstract:

  【Objective】 This study investigated the community structure of aerobic methanotrophs in coastal wetlands of southeastern China and the key environmental factors shaping their distribution. 【Method】Sediment samples were collected from four coastal wetlands (Shanghai, Fuzhou, Xiamen, and Dongguan). Methane oxidation rates were determined, physicochemical properties were analyzed, and 16S rRNA amplicon sequencing was performed to resolve community composition. Redundancy analysis (RDA) was applied to assess the influence of environmental factors such as temperature, precipitation, and salinity on community distribution. 【Result】The results showed significant differences in methane oxidation rates among wetlands, with the highest rate observed in Fuzhou (0.11 mmol·L-1·d-1) and the lowest in Dongguan (0.058 mmol·L-1·d-1). Community composition also varied substantially: Methylomicrobium dominated in Shanghai and Xiamen, while Methylobacter and Methylocystis were more abundant in Fuzhou and Dongguan. RDA indicated that temperature, water content, and salinity were the major drivers of community structure, with Methylobacter abundance positively correlated with temperature, and Methylocystis abundance negatively correlated with salinity. These findings demonstrate that the community structure and metabolic activity of aerobic methanotrophs in coastal wetlands are regulated by multiple environmental factors, and regional differences are primarily shaped by the adaptive responses of functional taxa to local conditions. 【Conclusion】This study highlights the spatial heterogeneity and environmental drivers of methanotroph communities in coastal wetlands and provides theoretical insights into wetland carbon cycling processes.

• Research Progress on Soil Particulate versus Mineral-Associated Organic Carbon dynamics Mediated by Microorganisms

  LIU Lei, ZHANG Yunlong, ZHANG Junling, WANG Ling, SUN Shiyou

  DOI: 10.11766/trxb202505260240

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  Abstract:

  The turnover and stabilization of soil organic carbon (SOC) play a crucial role in the terrestrial carbon cycle, contributing approximately 25% to natural climate solutions. Particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) are pivotal in the soil carbon dynamics. Soil microorganisms are the primary drivers of the carbon cycle, by decomposing plant residues to form POC via the “ex vivo modification” pathway and accumulating microbial residual carbon via “in vivo turnover” pathway, which then combines with soil minerals to form MAOC. However, the role of microorganisms in POC and MAOC formation is constrained by multiple factors, including nutrient management practices, soil properties, and climatic conditions, which limit the microbial regulation of carbon sequestration in agricultural soils. This article systematically introduced the framework of POC and MAOC. The contributions of growth anabolism (living and residual microorganisms) and non-growth anabolism (enzymes and extracellular polymers) to POC and MAOC were described. This study elucidated the regulatory mechanisms governing POC and MAOC through microbial community structure and physiological functions, whilst analyzing the influencing factors. On this basis, the study systematically considered the mechanisms and approaches by which microorganisms regulate and increase SOC, providing an important basis for constructing a theory of SOC increase based on physical-biological synergistic regulation.

• Green Intelligent Fertilizers: Innovative Approaches to Intelligent Regulation and Industrialization Pathways

  ZHANG Fusuo, CHENG Lingyun, HUANG Chengdong, ZHANG Lin, WANG Jianchao, LYU Yang, LU Zhenya, WEI Changzhou, MA Wenqi, Ma Hang, SHEN Jianbo

  DOI: 10.11766/trxb202508230411

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  Abstract:

  As global agriculture evolves alongside the increasing demand for environmental protection, green intelligent fertilizers have emerged as a novel approach to enhancing crop productivity and resource use efficiency. This paper reviews the core concepts and development status of green intelligent fertilizers, exploring the principles of intelligent regulation within plant-microbe-environment interactions and the design and application strategies based on the rhizobiont theory. Green intelligent fertilizers operate by maximizing the biological potential of crops and microorganisms to regulate the integrated plant-microbe-soil system, thereby promoting plant growth and minimizing environmental impact. Looking ahead, breakthroughs in material innovation, process optimization, and intelligent fertilizer formulation will enable intelligent fertilizers to drive agricultural green transformation, providing critical support for global food security and environmental sustainability.

• The Impact of anoxic Microsites on Soil Respiration and Their Distribution Characteristics in Soil Aggregates

  zhang xu sheng, wang xia, zhao yun fei, yuan meng han, wang fei, xia jie yi, li liu jun

  DOI: 10.11766/trxb202501050008

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  Abstract:

  Anoxic microsites are potential significant contributors to the inhibition of soil organic carbon loss. Soil aggregates, as potential suitable sites for the development of anoxic microsites, are closely related to the accumulation of soil organic carbon. However, few studies have investigated the impact of anoxic microsites on organic carbon within soil aggregates. This study collected dryland soils from four types of vegetation restoration and employed soil incubation and gas chromatography to measure and calculate the extent of anoxic protection. Anaerobic conditions were used to obtain soil samples from the internal and external layers of macroaggregates through the dry dissection method, and their anoxic microsite abundance and organic matter composition were compared. The results indicate that the extent of anoxic protection was 33.5% and 36% of natural shrubland and natural grassland, respectively. Planted forest exhibited a lower protection value at 15.9%, while farmland exhibited the most negligible anoxic protection at ?8.9%. And the internal layer of macroaggregates generally exhibits a high concentration of Fe2+, consequently, this region is characterized by a greater prevalence of hypoxic microenvironments. Organic matter, such as aromatics, lipids, and lignin, protected by anoxic microsites, is relatively abundant in the inner layer of aggregates. Soil respiration rate was significantly negatively correlated with the extent of anoxic protection. The aforementioned results reveal the formation mechanism, stability, and protective role of anoxic microsites within the inner layers of soil aggregates towards organic matter. The extent of anoxic protection is contingent upon a stable soil environment. These microsites selectively conserve the reducing organic matter within macroaggregates, significantly reducing the loss of soil organic carbon. This finding contributes a nuanced understanding of soil carbon cycling and carbon sequestration processes.

• Soil Health Evaluation of Farmland in Arid Areas Based on Minimum Data Set

  JING Yili, HUANG Bin, SU Xinyue, WU Lei, LI Jianhua, XU Minggang

  DOI: 10.11766/trxb202509010431

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  Abstract:

  【Objective】 Soil health assessment is a critical technical approach for achieving sustainable farmland management. However, existing evaluation systems often suffer from limitations such as indicator redundancy and high operational costs, which hinder their widespread application. This study aims to construct a cost-effective and efficient minimum data set (MDS) for soil health evaluation in the semi-arid farmland regions of the Loess Plateau, and to scientifically validate its reliability and applicability under local ecological conditions. 【Method】A total of 100 soil samples were collected from dryland farmlands in Wuzhai County, Shanxi Province, a representative area of the Loess Plateau. A comprehensive set of 23 soil indicators covering physicochemical and biological properties was analyzed. The MDS was established through an integrated statistical procedure that combined the principal component analysis (PCA), norm value calculation, and Pearson correlation analysis to identify the most representative and non-redundant indicators. The soil health index (SHI) was subsequently calculated using both linear and nonlinear scoring functions based on the MDS and the total data set (TDS). The performance of the MDS was evaluated by comparing SHI values derived from both data sets and further validated through correlation analysis with crop yield data. 【Result】The MDS was successfully established and included six key indicators: soil bulk density, total nitrogen, urease, cellobiohydrolase, bacterial Shannon index, and fungal Shannon index. These indicators accounted for 82.47% of the total variance explained by the TDS. Notably, biological indicators constituted two-thirds of the MDS, underscoring the vital role of microbial processes in soil health within arid regions. The SHI values calculated using the MDS showed a strong and significant positive correlation with those from the TDS under both nonlinear and linear scoring functions (P < 0.001), confirming the MDS’s capability to effectively represent the full data set. Validation with crop yield data further demonstrated that the nonlinear scoring function applied to the MDS provided a better fit (r = 0.70) than the linear function (r = 0.64), indicating its superior suitability for soil health assessment in the regions. The average SHI across the studied area was 0.49, reflecting a moderate overall soil health status. Spatially, soil health exhibited a pattern of lower values in the north and higher values in the south, largely influenced by the high erodibility of loess soils and more pronounced aridity in the northern part. 【Conclusion】This study developed a simplified yet robust MDS for soil health evaluation in semi-arid farmland systems of the Loess Plateau, effectively balancing comprehensiveness and feasibility. The results highlight the essential role of microbial diversity and functional indicators, such as enzyme activities and bacterial/fungal diversity, in evaluating soil health under dryland conditions. The spatial variation in soil health calls for region-specific management strategies, particularly in northern areas where soil erosion and moisture limitation are more severe. It is recommended that future research place greater emphasis on incorporating microbial functional parameters into soil health assessment frameworks. Moreover, integrating emerging technologies such as soil sensing and molecular tools could further enhance the efficiency and predictive power of soil health monitoring in arid and semi-arid agricultural landscapes.

• Distribution of Photosynthetic Carbon in Corn-soil System and Its Effect on Maize Biomass under Biological Fertilization

  GONG Yong-qi, FAN Cong-cong, YIN Chang, ZHU Guo-fan, ZHAO Li-xia, SHEN Ren-fang, WANG Xiao-yue, JIANG Yu-ji

  DOI: 10.11766/trxb202503060105

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  Abstract:

  【Objective】To investigate the effects of different biological fertilization practices on photosynthetic carbon (C) allocation and maize biomass, a field experiment was conducted at the Red Soil Ecological Experimental Station of the Chinese Academy of Sciences. 【Method】Four treatments were selected from a long-term biological fertilization trial: ① Chemical fertilizer + Organic manure (FO), ② Chemical fertilizer + Organic manure + Microbial inoculant (FOP), ③ Chemical fertilizer + Organic manure + Nematode inoculation (FON), and ④ Chemical fertilizer + Organic manure + Microbial inoculant + Nematode inoculation (FOPN). After soil samples were collected from the four treatments, a pot experiment using 13CO? pulse labeling was performed to study the allocation of photosynthetically fixed carbon within the maize-soil system. 【Result】The 13C pulse labeling results showed that, compared with the FO treatment, the FOPN treatment significantly increased the total amount of photosynthetic carbon in both aboveground and belowground parts, with a more pronounced increase in the aboveground portion. This led to a reduced belowground-to-aboveground allocation ratio of photosynthetic carbon. Moreover, the trends of maize biomass in aboveground and belowground parts under different treatments were consistent with the trends in carbon allocation. All biofertilization treatments significantly increased total and available soil nutrients, the total abundance of nematodes, and altered nematode community composition, with the most pronounced effects observed under the FOPN treatment. Random forest analysis and structural equation modeling jointly revealed that biofertilization enhances nutrient availability and increases aboveground photosynthetic carbon allocation by elevating nematode abundance and shifting community composition, ultimately promoting maize aboveground biomass.【Conclusion】 This study clarifies the mechanism by which nematode predation influences maize productivity and provides important theoretical guidance for biological fertilization technologies in red soil ecosystems.

• Plant–soil feedback driven mechanisms and regulation strategies for soil health

  Wang Guangzhou, Shen Jianbo, Zhang Junling, Zhang Fusuo

  DOI: 10.11766/trxb202506290314

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  Abstract:

  A healthy soil is the foundation for ensuring food security and serves as a core pillar for achieving agricultural green development. However, current intensive agricultural systems are primarily focused on maximizing crop yields, relying heavily on high-yielding crop varieties and external inputs such as synthetic fertilizers and pesticides. This overreliance often overlooks the impact of crops and field management practices on soil health, leading to various forms of soil degradation that negatively affect crop productivity and food quality. Drawing on the ecological concept of plant-soil feedback (PSF), this paper proposes a new systematic research paradigm that places soil health as the key to the co-improvement of farmland quality and crop productivity. Future sustainable agriculture urgently requires the development of system-based strategies and solutions grounded in PSF theory, integrating aboveground crop management with belowground soil processes in a tightly coupled manner. By elucidating the reciprocal interactions among different components of the soil ecosystem, we can develop soil health management technologies based on positive plant-soil feedback, thereby enhancing the synergy between productivity and other soil multifunctionalities. Specifically, at the individual plant level, modern molecular breeding and functional genomics can be leveraged to modify root architecture, root exudate composition, and signal transduction properties in a targeted way. This enables the precise recruitment of beneficial microbes and suppression of pathogens, triggering cascade amplification effects that reinforce positive feedback loops and mitigate negative ones. At the field management level, integrated strategies such as crop-microbiome holobiont breeding, optimized nutrient management, conservation tillage, and diversified cropping systems can promote beneficial interactions between crops and soils. These approaches reduce dependence on external inputs, improve internal system efficiency, and ultimately achieve the co-enhancement of crop yield and soil health.

• Differential Responses of Net Nitrogen Transformations in Rhizosphere Soil with Different Root Diameters to Nitrogen Deposition

  Lu Lu, Zhou Jiake, Wang Jing, Jing Hang, Cheng Yi

  DOI: 10.11766/trxb202503200125

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  Abstract:

  【Objective】Under the influence of root, rhizosphere soil has rich nutrients and active microbial biochemical activities, and its nitrogen (N) cycling process is significantly faster than that of non-rhizosphere soil. However, whether rhizospheric N transformation characteristics differ among root diameters, and whether their responses to N deposition are significant remain unclear. 【Method】This study focused on non-rhizosphere and rhizosphere soil with different root diameters of Pinus tabuliformis on the Loess Plateau of China (very fine root, 0-0.5 mm; medium fine root, ＞0.5-1.0 mm; coarse fine root, ＞1.0-2.0 mm). Additionally, long-term experimental plots were established with four simulated N deposition levels (N 0, 3, 6, 9 g·m-2·a-1). An indoor incubation experiment was carried out to determine changes in soil net N mineralization and nitrification rates of non-rhizosphere soil and rhizosphere soil with different root diameters, as well as their responses to N deposition. 【Result】The results showed that: 1) The net N transformation rates in rhizosphere soil varied significantly among different root diameters (P<0.05), and the highest rates were observed in rhizosphere soil of very fine root (2.16 mg·kg-1·d-1 for mean net N mineralization rate and 6.67 mg·kg-1·d-1 for mean net nitrification rate). 2) With the increase of N addition, net N mineralization and net nitrification rates decreased first and then increased, peaking at N 6 g·m-2·a-1 or 9 g·m-2·a-1 treatment. In contrast, the net N transformation rates of non-rhizosphere soil were significantly inhibited by N addition (P<0.05). Moreover, net N transformation rate of rhizosphere soil of very fine root was more sensitive to N addition than that of coarse root and non-rhizosphere soil. 3) Correlation analysis and structural equation model showed that low N addition inhibited net N transformation rates through its significant association with soil ammonium content, whereas high N addition enhanced rates via significant linkage to soil carbon-nitrogen ratio. 【Conclusion】N deposition significantly altered the N transformation process of rhizosphere soil, with distinct variations observed among different root diameters. Therefore, strengthening the study of N transformation process in plant rhizosphere soil is helpful to refine the rhizosphere effect and the assessment of forest soil N cycle.

• Study on the Process of Nitrite-Dependent Anaerobic Methane Oxidation in Rhizosphere and Bulk Soils of Paddy Fields

  dailei, wangyanping, baiyanan, shenlidong

  DOI: 10.11766/trxb202503250136

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  Abstract:

  【Objective】Paddy fields are significant anthropogenic sources of methane emissions, and anaerobic oxidation of methane (AOM) is an important pathway for mitigating methane emissions from paddy fields. The application of nitrogen fertilizers in paddy fields makes nitrite a primary electron acceptor for AOM. However, existing studies have focused on nitrite-dependent AOM in bulk soils of paddy fields, leaving the activity and functional microbial community characteristics of nitrite-dependent AOM in rhizosphere soils poorly understood. 【Method】Through indoor slurry incubation experiments combined with 13CH4 stable isotope tracing, quantitative PCR, and high-throughput sequencing, this study systematically investigated the nitrite-dependent AOM activity, NC10 bacterial gene abundance, and community structure in rhizosphere soils and bulk soils at different depths (0-10, 10-20 and 20-30 cm) under different fertilization treatments (CF: chemical fertilizer; OF: organic fertilizer combined with chemical fertilizer; SF: straw return combined with chemical fertilizer). 【Result】The results showed that the nitrite-dependent AOM activity in rhizosphere soils ranged from 1.03 to 2.42 nmol·g-1·d-1, which was significantly higher than that in 0-10 cm, 10-20 cm, and 20-30 cm bulk soils, respectively. The pH, soil organic carbon (SOC), and nitrite contents were identified as the main environmental factors influencing nitrite-dependent AOM activity. The NC10 bacterial gene abundance in 0-10 cm bulk soils ranged from 7.44×106 to 2.39×107 copies·g-1, which was significantly higher than that in rhizosphere soils, 10-20 cm, and 20-30 cm bulk soils, respectively. Correlation analysis revealed that SOC was the primary factor affecting NC10 bacterial abundance. Additionally, high-throughput sequencing revealed significant differences in NC10 bacterial community structure between rhizosphere and bulk soils. PCoA analysis indicated that soil water content, pH, and nitrate content were the main environmental factors influencing NC10 bacterial community structure.【Conclusion】These findings demonstrate significant differences in nitrite-dependent AOM activity, NC10 bacterial abundance and community structure between rhizosphere and bulk soils under different fertilization treatments. The findings demonstrate that the rhizosphere serves as an active hotspot for nitrite-driven AOM, providing a deeper understanding of the AOM process and offering theoretical basis for mitigating methane emission from paddy fields.

• Study on the Community Characteristics and Ecological Functions of Periphyton

  ZHANG Zhike, SHI Qing, ZHAO Bin, WEI Yuquan, ZHANG Hao, CAI Linying, SONG Yinan, CHEN Weisheng

  DOI: 10.11766/trxb202502170064

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  Abstract:

  Periphyton (PHT), widely distributed in aquatic ecosystems, function as critical multi-interface carriers across water-sediment-atmosphere boundaries, playing vital ecological roles in energy flow, element cycling, and pollutant remediation. This work reviews recent advancements in the fields of PHT research, both in domestic and international contexts, emphasizing on the analysis of community structures and the corresponding characteristics exhibited under varying environmental conditions. The ecological functions of PHT within aquatic ecosystems are explored, along with the identification of key environmental factors like environmental conditions and media that influence its growth and ecological functions. PHT plays a crucial role in nutrient cycling within aquatic ecosystems. As primary producers, they offer essential nutrients to the ecosystem and serve as effective bioindicators of water quality, with the ability to bioaccumulate heavy metals. Key environmental factors such as temperature, light availability, and pH regulate the growth of PHT, with dominant species in the community shifting in response to changing environmental conditions. Furthermore, anthropogenic activities, nutrient loading, and soil conditions significantly influence the composition, structure, and functional dynamics of PHT communities. Additionally, this work evaluates the potential of the application of PHT-based research to environmental management, sustainable agricultural practices, as well as ecological amendment, with an emphasis on innovative eco-engineering solutions. According to these findings, present study recommends that future work should undertake more in-depth and systematic investigations into the roles of PHT in the degradation and treatment of emerging contaminants, the integration with multidisciplinary approaches and advanced technologies, as well as their applications in other fields. This review aims to provide a theoretical framework and scientific guidance for interdisciplinary research and industrial development on identifying PHT community structures, enhancing ecological functions, and advancing sustainable ecological restoration practices.

• Distribution Characteristics of Typical Antibiotic-Resistant Bacteria and Antibiotic Resistance Genes in Different Land Types in Jinji River Basin

  Li Yeshan, Feng Shuo, Zhang Zhuoyi, Zhu Changxiong, Zhang Yanrong, Li Hongna

  DOI: 10.11766/trxb202502130059

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  【Objective】 The application of antibiotics has significantly advanced animal husbandry and agriculture. However， the resulting contamination by antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) poses a severe threat to the ecological environment and human health. This study aims to systematically investigate the effects of different land use types within the same region on the distribution of ARB and ARGs in soil. 【Method】 This study collected 210 soil samples from six typical land use types (vegetable fields, wheat fields, flower gardens, orchards, nurseries and livestock farms) in the Jinji River basin of Beijing. The abundance of total cultivable bacteria, chlortetracycline-resistant bacteria, sulfamethoxazole-resistant bacteria, and representative ARGs in the soil was measured. Additionally, the structural characteristics of representative soil microbial communities were analyzed using high-throughput sequencing technology. 【Result】 The results indicate that the resistance contamination in Zhang Town and Longwantun Town of the Jinji River basin was the most severe. The abundance of ARB, ARGs, and intI1 in vegetable field soil was significantly higher than that in other land use types (P<0.05). Bacteroidetes, Firmicutes, Saccharibacteria, and Deinococcus-Thermus were the dominant bacterial phyla in the soil. Also, Lysobacter and Devosia were identified as the main host bacteria for ARGs, and they showed significant positive correlations with sul1, sul2, tetG, tetX, and intI1 (P<0.05). 【Conclusion】 Based on our results, the resistance level of vegetable field soil in the Jinji River sub-basin was significantly higher than that of other land use types. Thus, it is essential to focus on the optimized application of organic fertilizers to reduce the potential risks of soil microbial resistance and ecological health.

• Isolation and Characterization of Poly(butylene adipate-co-terephthalate) Microplastic Film-Degrading Bacteria from Soil Co-Composting Environments

  ZHOU Qian, DAI Guoli, PAN Chennan, JIANG Jiamiao, WEI Ji''an, ZHANG Jun, ZHANG Ming, ZHANG Daoyong, PAN Xiangliang

  DOI: 10.11766/trxb202507050330

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  【Objective】Poly(butylene adipate-co-terephthalate) (PBAT) serves as a crucial alternative to conventional plastic mulch films. However, the presence of aromatic chains renders PBAT more recalcitrant to biodegradation compared to other biodegradable plastics (e.g., polylactic acid). Moreover, there are limited microbial resources exhibiting efficient PBAT degradation capabilities.【Method】This study employed a soil-compost enrichment approach to screen high-efficiency PBAT-degrading microbial strains. Microbial consortia were enriched at 60 ℃ under thermophilic composting conditions using PBAT as the sole carbon source, yielding six candidate strains (designated B1-B6). Degradation efficacy was comprehensively evaluated through mass loss, surface morphology analysis, and water contact angle measurements.【Result】Strain B3 demonstrated superior PBAT degradation efficiency, achieving a 17.85%±11.22% mass loss within 7 days, exceeding currently reported values for PBAT-degrading microorganisms. Atomic force microscopy (AFM) analysis revealed significant surface modification across all treatment groups, with B3-exposed PBAT exhibiting the most pronounced surface roughness (Ra = 44.84±26.48 nm). Concurrent physicochemical characterization showed a 15.6° reduction in water contact angle, collectively indicating substantial polymer matrix alteration. Taxonomic identification through 16S rRNA gene sequencing classified strain B3 as?Parageobacillus toebii.?In addition, characterization of the degradation performance of the mixed microbial consortium (designated as MIX) showed that MIX achieved a PBAT degradation rate of 12.48%±1.11%. Although the impact on surface roughness of PBAT was relatively minor, MIX induced the most significant changes in water contact angle, indicating a pronounced degradation effect. High-throughput 16S rRNA sequencing analysis revealed that, at the species level, the dominant strain within the MIX consortium was Parageobacillus toebii, accounting for 98.50% of the population. Other minor constituents included Aeribacillus pallidus (1.45%), unclassified_g_Lactobacillus (0.01%), unclassified_c_Bacilli (0.02%), unclassified_k_norank_d_Bacteria (0.01%), and unclassified_g_Clostridium_sensu_stricto_1 (<0.01%). These findings suggest that the PBAT degradation capability of the MIX consortium is primarily attributed to Parageobacillus toebii. Through whole genome sequencing and Kyoto Encyclopedia of Genes and Genomes (KEGG) gene function annotation, it was identified that strain B3 possesses genes encoding enzymes relevant to PBAT degradation, including carboxylesterase, arylesterase, long-chain acyl-CoA synthetase, aldehyde dehydrogenase, alcohol dehydrogenase, and catechol 2,3-dioxygenase. Based on the above results, the potential degradation pathway of PBAT microplastics by the degrading microbes could be inferred as follows: (1) Initial hydrolysis: PBAT ester bonds are first cleaved by carboxylesterases, releasing intermediate products such as terephthalic acid and adipic acid. (2) Aliphatic chain metabolism: Adipic acid is activated into its CoA derivative by long-chain fatty acid-CoA ligase and subsequently undergoes β-oxidation catalyzed by acyl-CoA dehydrogenase to form acetyl-CoA. Short-chain aldehyde/alcohol byproducts generated during aliphatic chain metabolism are further degraded by aldehyde dehydrogenase and alcohol dehydrogenase. (3) Aromatic ring degradation and ring-cleavage: Terephthalic acid undergoes hydroxylation to form catechol, which is then cleaved by dioxygenases, producing intermediates that enter the tricarboxylic acid cycle.【Conclusion】This study successfully isolated Parageobacillus toebii B3 as a high-performance PBAT degrader through multi-parametric characterization (mass loss, surface topography, and hydrophilicity changes). The findings provide both theoretical foundations and practical microbial resources for controlling biodegradable microplastic pollution.

• Responses of Soil Bacterial and Fungal Community Characteristics to Organic Materials Application in Urban Green Soils

  Niu Yuhui, Wang Qingfeng, Ma Xiang, He Xiaoli, Liang Jing

  DOI: 10.11766/trxb202412230502

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  【Objective】Adding organic waste materials into soils significantly affects microbial characteristics, however, the responses of bacterial and fungal diversity, community compositions and their interactions to the addition of different types of organic materials in urban green soils remain poorly understood.【Method】Using mesh bag method, six types of organic materials including green waste (GW), green waste compost (GWC), biogas residue (BR), biogas residue compost (BRC), peat (PT) and biochar (BC) were selected to investigate the effects of organic materials addition on soil properties, microbial communities and co-occurrence network in urban green soils through a 16-month in situ experiment.【Result】The addition of organic materials greatly increased soil electrical conductivity, soil organic carbon, and soil total nitrogen content by 12.7%-49.0%, 34.1%-87.0%, and 4.2%-14.7%, respectively. Soil bacterial alpha (?) diversity did not change among all the treatments, while soil fungal ? diversity was obviously increased after organic materials addition, which was mainly regulated by soil electrical conductivity. The dominant fungi were Ascomycota in urban green soils. Fungal communities in GW and GWC treatments obviously differed from other treatments, which was significantly influenced by soil pH and microbial biomass carbon. In contrast, Proteobacteria, Acidobacteria, Chloroflexi and Fimicutes were abundant in urban green soils. Bacterial communities in BR and BRC treatments were distinctly separated from other treatments, which was primarily driven by the aromaticity index of organic materials. Further analysis of occurrence-network revealed six main ecological clusters. The relative abundances of microbe in each module were different among all the treatments and were significantly correlated with soil nutrients and aromaticity index of organic material. Specifically, the highest relative abundance of bacteria community in module 2, 3 and 4 was observed in BR and BRC treatments, which was positively correlated with dissolved organic carbon, microbial biomass carbon, and soil total nitrogen, indicating that addition of biogas residue and biogas residue compost might enhance soil nutrient availability and subsequently facilitate microbial activity.【Conclusion】This study concludes that adding different types of organic materials can regulate urban green soil microbial community composition and interaction patterns by influencing soil physicochemical properties, thereby altering soil carbon cycling. Organic materials with low aromaticity index, which are more easily decomposed by microorganisms, may accelerate soil carbon cycling, whereas organic materials with high aromaticity index may favor carbon retention in soils. These findings hold significant implications for accurately assessing the resource utilization of urban organic wastes and the improvement of microbial diversity and ecological function in green space soils.

• Microbial Multi-kingdom Interaction Mechanism Underlying the Control of Tomato Bacterial Wilt by Reductive Soil Disinfestatio

  XU Shunan, XIE Yi, LU Zhiyu, LI Ruimin, YAN Yuanyuan, REN Yi, ZHOU Xing, CAI Zucong, HUANG Xinqi

  DOI: 10.11766/trxb202506070264

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  【Objective】The interrelationships within soil microbial communities play a crucial role in maintaining plant health. As an efficient ecological regulation measure for controlling crop soil-borne diseases, the impacts of reductive soil disinfestation (RSD) on the interrelationships of soil microbial communities and its contribution to plant disease control efficacy remain unclear. 【Method】Based on two field experiments, this study systematically investigated the effects of RSD on the intra-kingdom and cross-kingdom interactions within soil bacterial, fungal, and protist communities, as well as the associations between community interactions and tomato growth. 【Result】The results showed that compared with the control, the incidence of tomato bacterial wilt significantly decreased by 90.2% after RSD treatment, while the plant height of surviving plants and tomato yield increased by 13.5% and 57.4%, respectively. RSD treatment significantly reduced the diversity indices of soil bacterial and fungal communities, and significantly altered the community structures of bacteria, fungi, and protists. The microbial groups enriched by RSD treatment included the bacterial phyla Proteobacteria and Acidobacteria, the fungal phyla Ascomycota and Mortierellomycota, and the protist groups Rhizaria and Archaeplastida. Following RSD treatment, the total cohesion within soil bacterial communities, protist communities, and cross-kingdom communities significantly increased. Correlation analysis revealed that compared with community diversity and compositional structure, the total cohesion of bacterial communities, bacteria-fungi communities, and bacteria-fungi-protist communities exhibited stronger and more stable relationships with plant disease incidence, shoot length, and yield, and was significantly negatively correlated with plant disease incidence, and significantly positively correlated with yield and shoot length.【Conclusion】This study highlights the critical role of bacterial and cross-kingdom community interactions in determining plant growth and provides new insights into the disease-suppressive mechanisms of RSD treatment.

• Ecological Intensification Enhance Soil Multifunctionality: A Review

  Xue Wenfeng, Cheng Saisai, Hu Feng, Liu Manqiang

  DOI: 10.11766/trxb202505040204

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  With the exacerbation of global food demand and climate change, there is an urgent need for agricultural systems to deliver multiple ecosystem functions and services. However, conventional agriculture, with its emphasis on yield maximization, has often exacerbated ecological issues such as biodiversity loss, soil degradation, and environmental pollution. Ecological intensification, grounded in nature-based solutions, aims to harmonize agricultural production with ecosystem functioning while enhancing soil multifunctionality at minimal environmental cost, thereby driving the transition of agricultural systems toward more sustainable production models. This review synthesizes the mechanisms through which ecological intensification enhances soil multifunctionality and elucidates the regulatory pathways of key management practices, including conservation tillage, diversified cropping, organic amendments, and the inoculation of beneficial organisms. Furthermore, we identified the major challenges, including the absence of a comprehensive evaluation framework for soil multifunctionality, limited understanding of trade-offs and synergies among functions, and insufficient insights into the mechanisms underlying the synergistic effects of multiple practices, and proposed targeted solutions to address these gaps. Finally, this review outlines future research priorities, emphasizing the need to establish dynamic, multi-scale research frameworks of soil multifunctionality that incorporate spatial and temporal dimensions; to deepen mechanistic understanding through theoretical and methodological innovation; and to promote regionally adaptive, context-specific management strategies through the integration of multiple ecological practices. By bridging scientific research and practical application, ecological intensification offers significant potential to simultaneously enhance agricultural productivity and ecosystem services, thereby supporting the long-term sustainability of agricultural systems.

• Cultivated Land Soil Security Evaluation Based on the Earth

  fengzhe, wangyixin, kanglong, peiwei, liangmeng, chen''anqi, wukening

  DOI: 10.11766/trxb202503250139

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  【Objective】 Ensuring the security of soils in the Northeast Black Soil Region, a critical commodity grain production base in China, is essential for safeguarding the national food supply and promoting sustainable resource utilization. However, existing evaluation systems lack a comprehensive integration of multi-sphere interaction mechanisms within the Earth’s critical zone, making it difficult to quantify the synergistic effects of natural substrates and human activities. Thus, this study aims to address this gap by developing a systematic decision-making tool for the sustainable management of cultivated land resources in the Northeast Black Soil Region. 【Method】This study focused on Suihua City, a typical black soil region, and constructed a four-dimensional evaluation system of "Condition (C1)-Capability (C2)-Capital (C3)-Connectivity (C4)" guided by the Earth""s critical zone theory. Seventeen indicators (such as black soil layer thickness, cation exchange capacity, soil organic matter content, etc.) were selected from aspects including soil physical, chemical, and biological properties to characterize the cultivated land soil security pattern of Suihua City. Also, the influencing mechanism of Earth""s critical zone elements on soil security was evaluated by combining with the Random Forest model. 【Result】The results showed that: (1) The C1 state scores exhibited a spatial variation with higher values in the northeast and lower values in the southwest; C2 scores were generally high; C3 capital scores showed an opposite spatial pattern to C1, with lower values in the northeast and higher values in the southwest; and C4 scores did not display a clear spatial pattern. (2) The comprehensive soil security scores ranged from 54.3 to 88.4 (average of 77.7), with 84.9% of cultivated land classified as moderately secure or higher. Higher security regions (56.5%) were concentrated in Beilin District, Anda City, and Hailun City, while critical and insecure regions (15.1%) were mainly distributed in Qing’an County and Mingshui County. (3) The average means square error increase (%IncMSE) for the 17 indicators was 1.3%, with black soil layer thickness and soil organic carbon content having %IncMSE values of 10.7% and 3.7%, respectively, significantly higher than other indicators. 【Conclusion】The results of the study demonstrate that the four-dimensional evaluation framework rooted in the Earth""s critical zone theory effectively quantifies the interplay between natural substrates and anthropogenic activities. This approach elucidates the response mechanisms of soil security within the multi-layered structure of the critical zone, offering a systematic decision-making tool for sustainable management of cultivated land resources in black soil regions. These findings provide actionable insights for balancing agricultural productivity with ecological sustainability in ecologically fragile agroecosystems.

• Spatial Differentiation Characteristics and Driving Factors of the Silica Neoformation Accumulation Layer in Northeast Black Soil Region: A Case Study of Liaoning Province

  LIU Siwei, SUN Zhongxiu†, GUO Long, DUAN Siyi, WANG Qiubing

  DOI: 10.11766/trxb202503210129

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  【Objective】This study aims to systematically investigate the spatial distribution and driving factors of silica neoformation accumulation layers in the Northeast Black Soil Region, which significantly affect soil physical properties, impede plant root penetration and water transport, and exacerbate slope erosion. 【Method】Taking Liaoning Province as a representative region, a total of 333 soil profile samples were integrated, and advanced machine learning techniques were used to quantitatively analyze the spatial distribution and characteristics of silica neoformation accumulation layers.【Result】The results indicate that silica neoformation accumulation layers were predominantly distributed across Shenyang, Tieling, Fushun, Benxi, Dandong, and Chaoyang, encompassing a total area of approximately 4,261 km2 with a model prediction accuracy of 0.42. Notably, the layers exhibited deep accumulation in the central terrace and hilly regions, whereas they were relatively shallower in the eastern mountainous areas. Specifically, the was an abundance of silica neoformation peaks in the central region (6.66% to 27.35%), with higher densities observed in the central and western regions (132.70–611.94 g·dm-3). The depth of occurrence was greater in the central and northern regions (21.06–74.06 cm), whereas the thickness was thinner in the eastern region (31.78–97.71 cm). Furthermore, the distribution of silica neoformation accumulation layers was significantly influenced by annual mean ground temperature, relative humidity, and precipitation. In the eastern part of Shenyang, frequent groundwater activities and favorable climatic conditions contributed to the formation of profound silica neoformation accumulation layers. Conversely, in mountainous areas such as Fushun, limited groundwater influence, higher terrain, affected by biological enrichment processes and precipitation patterns, resulted in limited silicon leaching. Furthermore, the depths of leaching and deposition were shallow, and the silica neoformation accumulation layer remains superficial. 【Conclusion】This study provides an important solid scientific basis for understanding the spatial distribution and influencing factors of silica neoformation accumulation layers. It also offers practical guidance for developing effective soil improvement strategies, highlighting the importance of addressing the issues related to enhancing soil health and sustainability in the Northeast China Black Soil Region.

• Microbial Mechanisms Underlying the Effects of Elevated Atmospheric CO₂ Concentrations on Nitrogen Fixation Potential in Paddy Soils

  WU Yanlin, HUANG Wei, HU Zhenghua

  DOI: 10.11766/trxb202412250509

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  【Objective】?Biological nitrogen fixation?, which converts inert nitrogen into plant-available nitrogen, is a critical process for maintaining the soil nitrogen cycle and supporting the productivity of agroecosystems. However, the effect of atmospheric CO2 on biological nitrogen fixation in paddy fields remains poorly understood. Thus, this study aims to elucidate the microbial-driven mechanism of biological nitrogen fixation in paddy soils affected by elevated atmospheric CO2. The findings of this study will provide a scientific basis for the optimization of nitrogen cycling in paddy fields and sustainable nitrogen management in agriculture under climate change scenarios.【Method】In this study, we investigated the microbial-driven mechanism of biological nitrogen fixation in paddy fields by elevated atmospheric CO2 concentration. Two treatments, CK (ambient CO2 concentration) and EC (elevated ambient CO2 concentration by 200 μmol·mol?1) were set up by using an open-top chamber (OTC)-based platform for the automated control of CO2 concentration. Soil physicochemical properties, nitrogen fixation potential (NFP), and the abundance and community composition of nitrogen-fixing bacteria (nifH gene) of paddy soils were analyzed by microcosmic cultivation, real-time quantitative PCR, and high-throughput sequencing.【Result】The results showed that across the whole rice plant growth period and compared with CK, EC treatment significantly increased the microbial biomass nitrogen (MBN) content by 3.3% and significantly decreased the NH4+?N content by 11.6%. Also, the NFP and nifH gene abundance were significantly increased by EC treatment. At the maturity stage, the community structure of the nifH gene in the EC treatment changed significantly compared with CK. In addition, the TN content was positively correlated with NFP, which was regulated by soil MBN content, SOC content, and nifH gene abundance.【Conclusion】This study reveals that elevated atmospheric CO2 concentration increased soil MBN content and nifH gene abundance, enhanced NFP, and increased the nitrogen content of paddy soils.

• Polarization‐Induced Covalent Bonding between H+ and Surface O Atoms Promotes Clay Mineral Dissolution

  TANG Yuting, XIAO Shuang, DING Wuquan, LI Hang, LIU Xinmin

  DOI: 10.11766/trxb202501090018

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  【Objective】Dissolution reactions of clay minerals are one of the essential processes contributing to natural soil acidification and mineral weathering. However, the surface reaction mechanism of mineral dissolution remains unclear. 【Method】The strong electric field generated by the surface charges of minerals induces a new type of covalent bonding between the oxygen (O) atoms on the mineral surface and the hydrogen (H+) ions, a phenomenon known as polarization-induced covalent bonding (PICB). In this study, we selected montmorillonite (MMT), illite (ILI), and kaolinite (KLI) to explore the interfacial reaction mechanisms promoting the dissolution of clay minerals by PICB using mineral dissolution analysis and hydrothermal experiments. 【Result】The dissolution density of mineral elements increases with decreasing pH, and the initial stage of mineral dissolution aligns with three processes of chemical weathering: desalination, desilicification, and ferrallitization. The PICB significantly enhanced the H+ adsorption energy density (γH(0)), and the absolute value of γH(0) increased with the decrease of pH, indicating an interaction between H+ and the mineral. Also, the surface was stronger under low pH conditions, and a consistent critical pH of 3.0 was observed based on both the theoretical analyses of γH(0) and the dissolution density of mineral elements as a function of pH. At a pH < 3.0, the PICB was significantly enhanced, resulting in a notably weakened Si-O bonding energy and a substantial increase in the dissolution efficiency of silicate minerals. Although the dissolution behaviors of various minerals exhibited significant variations in response to pH, they can be described as a function of γH(0), indicating that γH(0) has an important influence on the structure of clay minerals. Moreover, the enhancement of γH(0) resulted in a higher content of SiO2 in the hydrothermal reaction products of MMT, accompanied by a subsequent reduction in the residual products represented by Al2O3. 【Conclusion】This study quantified the impact of H+-mineral bonding on the chemical weathering of minerals and revealed that the PICB between H+ and surface O atoms of minerals enhanced the γH(0) of H+ on the mineral surface and weakened the Si-O bond energy, thus significantly affecting the dissolution reactions of clay minerals. The results of this study provide theoretical insights for proposing targeted modulation techniques aimed at enhancing the structural stability of minerals.

• Sustainable Utilization of Cadmium-Contaminated Soil: Safe Utilization Strategies Based on Mechanisms of Plant Cadmium Accumulation

  HUANG Jiu, HU die, GAO Yongqiang, CHEN Changzhao, JIANG Mengmeng, WANG Haoyu, ZHONG Chongwei, ZHENG Lu, SHEN Rengfang, ZHU Xiaofang

  DOI: 10.11766/trxb202502260089

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  Objectives: Cadmium contamination poses a significant threat to agricultural production and human health due to its persistence, toxicity, and potential to accumulate in crops and the food chain. However, there is a need for a comprehensive review that provides scientific guidelines for understanding Cd soil-solution chemistry, decreasing Cd levels in the food chain, and bridging the gap between laboratory research and field applications. Methodology: This study conducted an in-depth literature analysis of both laboratory and field research to provide a comprehensive analysis of the soil chemistry of cadmium, which is crucial for understanding its bioavailability and mobility. Results: The chemical behavior of Cd in soil is influenced by various factors, such as soil pH, organic matter content, and redox conditions. These factors determine the speciation of Cd, which in turn affects its uptake by plants and its potential to enter the food chain. The phytotoxic effects of Cd are manifold, impacting plant growth, physiological functions, and metabolic processes. Cd can suppress plant growth by inhibiting root and shoot development, reducing chlorophyll content, and disrupting photosynthesis. It also induces oxidative stress by increasing the production of reactive oxygen species (ROS), which can damage cellular components such as lipids, proteins, and DNA. The review also sheds light on the molecular mechanisms underlying plant responses to Cd stress. Two major molecular systems are highlighted: metal transporter families and regulatory transcription factor families. Metal transporters, including Nramp, HMA, ZIP, ABC, and YSL, play essential roles in Cd uptake from the soil, translocation from roots to shoots, and detoxification within plant cells. These transporters facilitate the movement of Cd through cellular membranes and into subcellular compartments, such as vacuoles, where it can be sequestered to reduce its toxicity. On the other hand, transcription factors like WRKY, MYB, bHLH, and NAC regulate the expression of genes involved in Cd tolerance and detoxification. They activate defense mechanisms that help plants mitigate Cd-induced oxidative damage and maintain cellular homeostasis. Based on the understanding of these molecular mechanisms, the review proposes innovative strategies for the sustainable utilization of Cd-contaminated soils. These strategies integrate molecular design approaches, such as engineering transporters to limit Cd uptake and enhance its sequestration, with phytoremediation techniques that utilize metal-tolerant plant species. By providing scientific guidelines for reducing Cd levels in agricultural products and enhancing food safety protocols, this study bridges the gap between laboratory research and field applications. It offers valuable insights for developing environmentally sustainable agricultural practices in regions affected by Cd pollution, thereby contributing to global food security and environmental protection. The proposed approaches not only aim to decrease Cd accumulation in crops but also seek to improve the overall health and productivity of plants grown in contaminated soils, ensuring safer food supplies for the growing global population. Furthermore, the review emphasizes the importance of these strategies in mitigating the adverse effects of Cd contamination on soil fertility and ecosystem health. By reducing Cd levels in soil and crops, these strategies can help maintain soil fertility, protect biodiversity, and promote the overall health of ecosystems. Conclusion: The integration of different approaches can lead to the development of more resilient agricultural systems that can withstand the challenges posed by Cd contamination and other environmental stresses. This comprehensive review thus provides a foundation for future research and practical applications aimed at addressing the complex issue of Cd pollution in agricultural environments.

• Change characteristic of Soil Organic Carbon and Its Fractions during the Natural Restoration of Cultivated Black Soil

  wuyanan, ZOU Wenxiu, WANG Shouyu, LU Xinchun, Han Xiaozeng

  DOI: 10.11766/trxb202503140117

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  【Objective】The restoration of cultivated land to natural grassland can increase soil organic carbon (SOC) content. This study aimed to investigate the changes in black soil organic carbon during vegetation restoration.【Method】Based on a 19-year long-term field experiment, the temporal dynamics of SOC and its fractions were examined during the restoration of cultivated black soil to natural grassland vegetation (GL), with comparisons made to continuous cultivated land (CL) and bare land (BL) without vegetation cover.【Result】The results showed that: (1) Compared to the initial soil, the SOC content in the topsoil (0-20 cm) increased by 26.19% in the GL treatment, with an annual growth rate of 1.38% (0.41 g·kg-1·a-1). In contrast, the SOC content decreased by 7.99% in the BL treatment, while no significant change was observed in the CL treatment; (2) Across the entire 0-100 cm soil profile, GL not only significantly increased the SOC content in the topsoil (0-20 cm), but also increased the SOC content in the subsoil layers (20-60 cm). The increments in the 0-20, 20-40 and 40-60 cm layers were 26.19%, 12.08% and 8.70%, respectively. However, no significant changes in SOC content were observed below 20 cm in the CL and BL treatments; (3) Compared to the initial soil, the GL treatment increased the carbon contents of free light fraction (fLFC), occluded light fraction (oLFC) and heavy fraction (HFC) by 199.45%, 112.83% and 12.00%, respectively. Additionally, GL increased the proportions of fLFC and oLFC while reducing the proportion of HFC in the SOC; (4) For humus fractions, the GL treatment increased the contents of fulvic acid (FA), humic acid (HA) and humin (HM) by 74.82%, 29.69% and 11.46%, respectively, and decreased the HA/FA ratio, indicating a reduction in the humification degree of soil organic matter.【Conclusion】In conclusion, long-term restoration of cultivated land can effectively increase the organic carbon content of black soil and promote the accumulation of labile SOC fractions.

• The Impact of Cover Crops on Organic Carbon and Microbial Community in Biopore Sheaths of Shajiang Black Soil

  Xiewanyu, Liushuai, Guozichun, Gaolei, Chenyan, Shenxintao, Zhangzhongbin, Pengxinhua

  DOI: 10.11766/trxb202412300513

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  【Objective】Cover crops are very important for regulating soil structure and enhancing soil organic carbon. Cover crops can improve soil pore structure by creating biopores through root penetration and subsequent decomposition. However, the effects of different cover crops on organic carbon accumulation and microbial communities in biopore sheaths remain unclear. 【Method】A field experiment was conducted in a typical Shajiang black soil, including four winter cover crop treatments (fallow, alfalfa, rapeseed, and a mixture of radish + hairy vetch) in rotation with summer maize. Soil organic carbon (SOC) and total nitrogen (TN) contents in the biopore sheaths of the 20–40 cm soil layer under different treatments were determined, while bacterial and fungal community structures were analyzed via high-throughput sequencing. 【Result】The results showed that, compared with bulk soil, SOC content in the biopore sheaths increased significantly by 33.4% under the alfalfa treatment, while TN content increased significantly by 24.6% and 18.5% under the alfalfa and radish + hairy vetch treatments, respectively. However, no significant differences in SOC and TN contents of the biopore sheath were observed among different cover crops. The microbial community structure varies significantly with the interaction between cover crop species and soil habitats. The bacterial α-diversity indices and niche breadth indices in biopore sheaths were significantly higher than those in bulk soil, particularly in the radish + hairy vetch treatment, whereas no significant differences were observed in fungal communities between the two soil compartments. Furthermore, microbial communities within biopore sheaths exhibited a shift toward copiotrophic taxa compared with bulk soil. The relative abundance of Pseudomonas and Bacillus was higher in alfalfa-derived biopore sheaths than in other treatments. Correlation analysis indicated that the relative abundance of core microbial taxa involved in carbon decomposition and transformation was significantly positively correlated with SOC content. 【Conclusion】In summary, SOC and TN contents in the biopore sheaths under the alfalfa treatment significantly increased. SOC content may regulate microbial community structures within biopore sheaths by influencing bacterial α-diversity indices, niche breadth indices, and the relative abundance of core microbial taxa.

• Effects of Improvement Measures on Aggregate Stability and Humus Composition of Soda Saline Meadow Soil

  lisiyan, liangxiaoyan, wangchen, wangyuqing, xiewei, yangdi, zhangmingcong

  DOI: 10.11766/trxb202501060011

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  Abstract:

  【Objective】This study was aimed to investigate the regulation mechanisms of different improvement measures on soil structure and humus characteristics of soda saline-alkali land.【Method】A field comparative experiment was conducted to study the effects of conventional (CK), biochar (T1), organic fertilizer (T2), and structural modifier (T3) on aggregate stability, humus composition, and soybean yield in soda saline meadow soil.【Result】The results showed that compared with CK, T1, T2 and T3 treatments significantly promoted the transformation of microaggregates to macroaggregates. The effect of T3 treatment was the most significant, and the mass fraction of >2 mm aggregates increased by 12.66% (P<0.05), which was significantly higher than that of T1 and T2. T3 treatment significantly improved nutrient availability by reducing soil pH by 3.02% and simultaneously increasing available phosphorus (67.84%) and alkali-hydrolyzable nitrogen (7.98%) content. The average weight diameter and geometric mean diameter of soil increased by 7.99% and 2.39%, respectively, and the organic carbon content of microaggregates (0.053-0.25 mm) increased by 24.58%-31.14%, which was significantly higher than other treatments. In terms of humus components, the contents of humic acid, fulvic acid, and humin in each particle size of T3 treatment increased by 19.95%-29.62%, 3.64%-6.48%, and 7.33%-36.92%, respectively, which were better than those of T1 and T2 treatments. T3 treatment significantly increased the complexity of humus, and the ratio of E4/E6 significantly increased by 84.84%. The PLS-PM structural equation model revealed that soil organic carbon (path coefficient 0.96) significantly affected aggregate stability by regulating total humic acid (1.13) and humin (1.29). Yield analysis showed that T3 treatment achieved a soybean yield of 2653.97 kg·hm-2 by increasing plant height (61.32%) and pod number per plant (11.96%), with an increase of 42.67%.【Conclusion】The results showed that the compound modifier (T3) complicated the molecular structure of large-grained aggregates by reconstructing the molecular structure of humus, promoted the increase of cementing materials, increased the content of organic carbon, significantly increased the mass fraction of aggregates with >2 mm particle size and the stability of soil aggregates, and effectively improved the soil structure of the plough layer of soda-saline meadow soil. This provides a theoretical basis for the improvement of soda saline-alkali land and the synergistic improvement of production capacity.

• Effects of Biological Fertilization on the Phosphorus Solubilizing Bacterial Community and Maize Productivity in Upland Red Soil

  Peng Ziyi, Zheng Jie, Zhu Guofan, Shi Guangping, Wang Xiaoyue, Ding Yanghuiqin, Zhou Shungui, Jiang Yu-ji

  DOI: 10.11766/trxb202412310518

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  Abstract:

  【Objective】Phosphorus solubilizing bacterial communities in the rhizosphere are critical functional components in soil phosphorus cycling. Their abundance, community composition, and diversity determine the activity of soil alkaline phosphomonoesterase (ALP) and phosphorus availability. Thus, this study aimed to explore the impact of different bio-fertilization regimes on phosphorus-solubilizing bacterial communities in red soil and maize productivity. 【Method】Based on a long-term (11-year) bio-fertilization experiment at the Yingtan Red Soil Ecological Experiment Station of the Chinese Academy of Sciences, four treatments were selected: chemical fertilizer + organic fertilizer (FO), FO + phosphate-solubilizing bacteria (FOP), FO + nematodes (FON), and FO + phosphate-solubilizing bacteria + nematodes (FOPN). Quantitative real-time PCR (qPCR) and high-throughput sequencing technologies were employed to elucidate the mechanisms through which biological amendments affect rhizosphere phosphorus solubilizing bacterial communities, ALP activity, and maize productivity. 【Results】(1) Compared with the FO treatment, bio-fertilization treatments (FOP, FON, FOPN) significantly improved soil fertility and maize yield, with the combined inoculation treatment (FOPN) showing the most pronounced effects. Soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), and maize yield increased by 8.08%, 24.2%, 30.5%, 20.2%, and 39.7%, respectively. (2) Bio-fertilization significantly increased the abundance of rhizosphere phosphorus solubilizing bacteria, showing notable interactive effects, while the Shannon index remained consistently lower than that in the FO treatment. The abundance of phosphorus-solubilizing bacteria exhibited significant positive correlations with TN and AN. (3) AN, phosphorus solubilizing bacterial abundance and ALP activity were identified as the key drivers of maize yield. Structural equation modeling revealed that AN not only directly promoted maize yield but also indirectly enhanced yield by increasing phosphorus-solubilizing bacterial abundance and ALP activity. 【Conclusion】Bio-fertilization significantly increased phosphorus solubilizing bacterial abundance, suggesting that microbial population dynamics may regulate phosphorus uptake in maize. These amendments enhanced upland red soil fertility by indirectly promoting phosphorus solubilizing bacterial abundance and ALP activity, thereby facilitating organic phosphorus mineralization and maize growth.

• The spatiotemporal variation characteristics of soil enzyme activity in alpine meadow after adding yak dung

  SUBINUER·wubuli, YIN Xiaoyue, FENG Jingying, SUONAN Jiangcai, WANG Changting[†]

  DOI: 10.11766/trxb202501160033

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  Abstract:

  Yak dung is an important factor affecting the nutrient cycling of soil in alpine grassland ecosystems, and changes in soil enzyme activity can effectively measure the soil nutrient cycling processes. To explore the temporal and spatial variations in soil enzyme activity under the addition of yak dung in alpine meadows, a fluorescence analysis method using 96-well microplate enzyme assays was employed. Key enzymes involved in soil carbon and nitrogen transformation processes in the alpine meadow soils of the eastern Tibetan Plateau：β-glucosidase (BG), peroxidase (PER), phenol oxidase (PPO), β-N-acetylglucosaminidase (NAG), and protease (LAP)—were studied to analyze the potential impacts of yak dung decomposition over different periods in warm and cold seasons. Also, the effect of the yak dung on the determined properties was considered at varying distances from the dung pile (under the dung (D0), 10 cm away (D10), and 20 cm away (D20)). The results indicate that (1) The decomposition of yak dung in both warm and cold seasons significantly increased the activities of BG, PER, PPO, NAG, and LAP, with the highest enzyme activity observed under D0. As the decomposition time progressed from warm to cold seasons and the distance from the dung increased, soil enzyme activity gradually decreased; (2) The decomposition of yak dung in both seasons significantly enhanced the total soil nutrients (total carbon, total nitrogen, total phosphorus) and available nutrients (ammonium nitrogen, nitrate nitrogen, available phosphorus), soil moisture, and pH, although the impacts of decomposition time on these soil environmental factors varied between seasons. The correlation between soil physicochemical properties and enzyme activity in the cold season was significantly stronger than in the warm season, with the C/N ratio in the cold season having the most pronounced effect on enzyme activity. The addition of exogenous nutrients led to the redistribution of nutrients and organic matter, with changes in enzyme activity exhibiting spatial and temporal gradient distribution characteristics, which were significantly correlated with the distance from the dung (radiating outward) and soil depth (extending downward).

• Vertical Differentiation Characteristics and Main Controlling Factors of Acid Buffering Capacity in the Strongly Acidic Red Soil Regoliths

  CUI Zixiao, WU Huayong, SONG Xiaodong, YANG Shunhua, ZHANG Ganlin

  DOI: 10.11766/trxb202503090107

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  Abstract:

  【Objective】This study aimed to investigate the vertical variation characteristics and controlling factors of acid buffering capacity (pHBC) of strongly acidic red soil regoliths.【Method】The strongly acidic red soil regoliths with pH values less than 5.0 were selected as the study objects, which are developed from Quaternary red clay (including an upper uniform red clay layer and a lower reticulate red clay layer) underlain by sandstone bedrock located at a small agricultural watershed in Yujiang District, Yingtan City, Jiangxi Province. Approximately 8-meter-deep soil-rock core samples were collected from two upland boreholes using drilling, which were classified into four layers, including a uniform red clay layer, reticulate red clay layer, weathered sandstone layer, and sandstone bedrock layer. Regolith pHBC and other related physicochemical properties were measured. Multiple linear regression and random forest modeling as well as acid-base equilibrium theory analysis were used to quantify the relative contributions of regolith organic matter, mechanical compositions, mineral compositions, iron and aluminum oxides, exchangeable base cations, exchangeable acidity, and pH to pHBC variations across different layers.【Result】The red soil regoliths exhibited layer-specific acid buffering characteristics. The regolith pHBC were 2.53 ± 0.41 cmol·kg-1·pH unit-1, 1.93 ± 0.59 cmol·kg-1·pH unit-1, and 1.39 ± 0.22 cmol·kg-1·pH unit-1 in the uniform red clay layer, the reticulate red clay layer, and the weathered sandstone layer, respectively. The regolith pHBC increased with depth in the uniform red clay layer, decreased with depth in the reticulate red clay layer and the weathered sandstone layer, and increased from the weathered sandstone layer to the sandstone bedrock layer. Interestingly, the exchangeable base cations of the Quaternary red clay layer at a strongly acidic state were exhausted and played a limited role in the changes of pHBC. Moreover, the pHBC depended on the protonation process of crystalline iron oxide and organic matter in the uniform red clay layer, the dissolution of amorphous and crystalline aluminum oxides and the protonation of amorphous and crystalline iron oxides in the reticulate red clay layer, and on feldspar dissolution and exchange of exchangeable calcium and magnesium ions in the weathered sandstone layer. Also, the dissolution of carbonates plays a key role in the pHBC in the sandstone bedrock layer.【Conclusion】The acid buffering mechanism in the strongly acidic red soil regoliths primarily centers around the protonation and dissolution processes of iron and aluminum oxides. These research findings provide support for the acidification assessment and improvement of the red soil ecosystems.

• Elemental Geochemical Characteristics and Chemical Weathering Intensity of Soils in the Shergyla Mountain, Qinghai-Tibet Plateau

  ZHANG Chu, YANG Jinling, YANG Fei, YE Mingliang, GU Jun, CHEN Yamin, ZHANG Ganlin

  DOI: 10.11766/trxb202503130113

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  Abstract:

  【Objective】This study aimed to unravel the weathering intensity and elemental geochemical characteristics of soils in the southern mountainous regions of the Tibetan Plateau. 【Method】 Shergyla Mountain in Linzhi City was selected as the study area. Fifteen typical soil profiles were sampled across different landscapes and altitudes, and the geochemical characteristics of soil elements were analyzed, with weathering intensity estimated for different soil horizons. 【Result】The results indicate that the soils of Shergyla Mountain, influenced by the alpine climate, are weakly developed, with the soil types dominated by Gelic Cambosols. For the studied soils, primary minerals were predominant in soil minerals while secondary minerals were present in low abundance. The Chemical Index of Alteration (CIA) ranged from 47 to 62, suggesting that most soils were in a state of weak weathering. The low temperatures at high altitudes restricted chemical weathering of soil minerals, resulting in insignificant impacts of precipitation, temperature, altitude, slope, and parent material on soil chemical weathering. The weathering intensity indicators (CIA, weathering leaching coefficient ba, Weathering Index of Parker WIP) across soil profiles exhibited different distribution patterns from the surface layer downwards, primarily influenced by transportation and deposition processes driven by external forces such as wind, gravity, and runoff. Nevertheless, the results indicate that chemical weathering had a relatively small impact on soil formation. 【Conclusion】The alpine environment controls overall soil development thus weakening the difference between other soil forming factors. The findings of this study provide theoretical support for the evolution of pedogenesis and soil classification on the Tibetan Plateau and offer pedological insights into the rational utilization of land resources.

• Progress of soil temperature prediction equation

  Zhang Jianbin, Gao Zhi Qiu, Tong Bing, Wang Linlin

  DOI: 10.11766/trxb202210220581

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  Abstract:

  Soil temperature (especially surface temperature) is a key physical quantity in the interaction between land and atmosphere, and plays a very important role in the earth system. Soil temperature prediction technology has always been the core scientific problem in land surface model, numerical weather prediction and climate prediction. This paper systematically reviews the research progress of soil temperature prediction equation, from the classical heat conduction equation to the heat conduction convection equation that takes into account the physical process of vertical movement of soil moisture, from the single sine wave approximation to the Fourier series approximation of the daily change of surface temperature, from the assumption that the diurnal change of convection parameters is constant to the consideration of its diurnal change, and emphatically summarizes the creation, improvement and solution of the soil heat conduction convection equation. Finally, this paper reviews the application of heat conduction convection equation in the study of surface energy balance, vertical movement of soil moisture, water flux, earthquake and frozen soil heat transfer. At the same time, it is pointed out that the influences of soil water phases and plant roots on the heat conduction-convection equation is warranted for the future research of soil temperature prediction equation.