Insights and Perspectives

• Plant-Soil Feedback Driven Mechanisms and Regulation Strategies for Soil Health

  WANG Guangzhou, SHEN Jianbo, ZHANG Junling, ZHANG Fusuo

  2026,63(5):1385-1397, 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.

Reviews and Comments

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

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

  2026,63(5):1398-1408, 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.

• 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

  2026,63(5):1409-1423, DOI: 10.11766/trxb202509010430

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  Abstract:

  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.

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

  CHEN Xiaowei, LI Xueying, YANG Xiaofan

  2026,63(5):1424-1448, DOI: 10.11766/trxb202505120216

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  Abstract:

  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.

Research Articles

• Assessment of Soil Resilience in China

  WU Kening, CHEN Xingyu, CHEN Anqi, FENG Zhe

  2026,63(5):1449-1461, DOI: 10.11766/trxb202507010320

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  Abstract:

  【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.

• Digital Mapping of Soil Argillic Horizon Thickness in Northeast China

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

  2026,63(5):1462-1475, DOI: 10.11766/trxb202507040326

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  Abstract:

  【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.

• Spatial Mapping of Effective Soil Thickness and Its Surface Substrate Constraint Mechanism in the Black Soil Area of Eastern Inner Mongolia

  LI Xinye, SHI Pu, LIU Hang, YANG Yong

  2026,63(5):1476-1489, DOI: 10.11766/trxb202502150061

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  Abstract:

  【Objective】 Effective soil thickness is a decisive indicator for evaluating soil health and productivity, it is therefore of great significance to accurately depict the spatial distribution pattern of effective soil thickness and its response mechanism to land use change and surface substrate type for the sustainable protection of soil resources. 【Method】 In this study, leveraging on the surface substrate survey data and soil-landscape modeling, we carried out predictive modelling and mapping of effective soil thickness in the black soil area of eastern Inner Mongolia. Based on the modelling results, the spatial variability of effective soil thickness was analyzed among land use types and surface substrate zoning. SHAP analysis was employed to identify the main controlling factors underlying the spatial distribution pattern of effective soil thickness. 【Result】 The results show that the Cubist-based regression model had a good performance(R²=0.5, RMSE=43.8) for effective soil thickness prediction, 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 effective soil thickness, which was specifically reflected in the fact that highly eroded areas with high elevation had thinner soils, while monthly average temperature extremes had a positive effect. 【Conclusion】 Both surface substrate zoning and land use types exerted important constraints on the spatial characteristics of the effective soil layer thickness, with the overall soil layer thickness in the floodplain and sloping deposit areas being greater than that in the residual slope deposit area. Forestlands, which were mostly distributed in mountainous areas or regions with steep slopes, had the thinnest effective soil layer. This study provides a methodological reference for the spatial modeling and characterization of effective soil thickness, and the results can provide a data basis for identifying the background conditions of regional natural resources and their response mechanisms to human interactions.

• 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

  2026,63(5):1490-1503, DOI: 10.11766/trxb202506250309

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  Abstract:

  【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.

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

  YANG Jicun, GUO Bing, HAN Baomin

  2026,63(5):1504-1514, 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.

• 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

  2026,63(5):1515-1528, DOI: 10.11766/trxb202503090107

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  【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^-1in 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.

• 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

  2026,63(5):1529-1541, 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 Guangshuai, XIE Kun, QIAN Yongqi, JIANG Fahui, PENG Xinhua, YAO Shuihong, ZHANG Zhongbin, ZHANG Yueling, BI Lidong

  2026,63(5):1542-1556, DOI: 10.11766/trxb202506300317

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  【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.

• 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

  2026,63(5):1557-1567, DOI: 10.11766/trxb202506090267

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  Abstract:

  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.

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

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

  2026,63(5):1568-1582, DOI: 10.11766/trxb202507080335

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  Abstract:

  【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 m³·hm^-2) and water-saving irrigation (w2, 4 800 m³·hm^-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 fertilizers (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.

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

  XIE Wanyu, LIU Shuai, GUO Zichun, GAO Lei, CHEN Yan, SHEN Xintao, ZHANG Zhongbin, PENG Xinhua

  2026,63(5):1583-1595, 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.

• 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

  2026,63(5):1596-1609, 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 pallidu s(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.

• 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

  2026,63(5):1610-1621, 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.

• 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, LIANG Xinran, HE Yongmei, WU Longhua, ZHAN Fangdong

  2026,63(5):1622-1634, DOI: 10.11766/trxb202508030376

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  【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 Cd₃(PO₄)₂, Pb₅(PO₄)₃Cl (Pyromorphite), and Pb₅(PO₄)₃OH. Fourier transform infrared(FTIR)spectroscopy confirmed the involvement of functional groups (e.g., -COOH, -OH, -NH₂) and anionic groups (e.g., PO₄^3-, SO₄^2-) 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.

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

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

  2026,63(5):1635-1646, DOI: 10.11766/trxb202509190459

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  Abstract:

  【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.

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

  HAO Tianxiang, YANG Meng

  2026,63(5):1647-1658, 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 ¹⁵N 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.

• The Effect of Elevated Ozone Concentrations on the Methane Production Process in Paddy Soil

  WANG Mingke, MA Jinfeng, ZHANG Yijia, DU Yiming, WANG Yanbo, ZHENG Haifeng, SHANG Bo, JI Yang, FENG Zhaozhong

  2026,63(5):1659-1670, DOI: 10.11766/trxb202601160036

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  【Objective】 Elevated near-surface ozone(O₃)concentrations have been shown to reduce methane(CH₄)emissions from rice paddies. However, the underlying mechanisms regulating soil CH₄ production remain poorly understood. Thus, this study aimed to decipher the mechanisms regulating soil CH₄ production at different rice growth stages and identify the main controlling factors. 【Method】 In this study, a widely cultivated rice cultivar(Nanjing 9108)in the Yangtze River Delta was used to investigate the effects of elevated O₃ on methane production processes. An open-top chamber(OTC)system was employed to simulate elevated ozone conditions, including ambient air (NF) and ambient air supplemented with O₃(NF40 + 40 nmol·mol^-1 O₃). Rhizosphere soils were collected at the typical growth stages of rice(the filling stage and the maturity stage) and subjected to microcosm incubation experiments. Root morphological traits, soil carbon components, microbial abundance, and methanogenic archaeal community composition were simultaneously analyzed to elucidate the regulatory mechanisms of O₃ on CH₄ production. 【Results】 The results showed that elevated O₃ reduced specific root length (SRL) and specific root area (SRA) during the filling stage of rice, while enhancing soil organic carbon stability during the maturity stage of rice. This simultaneously altered the community composition of methanogens, characterized by an increase in the relative abundance of hydrogenotrophic methanogens and a decrease in the relative abundance of acetoclastic methanogens. O₃ elevation reduced CH₄ production rates in paddy soils by 38.1%-46.8%, with decreased acetoclastic methanogenesis rates by 66.6%-68.1%. Conversely, CH₄ production rates via hydrogenotrophic methanogenesis increased by 6.1%-24.7%. 【Conclusion】 This study provides a process-based understanding of how elevated O₃ regulates methane production in rice soils through coupled changes in plant root traits, soil carbon stabilization, and methanogenic community structure, offering critical insights for predicting CH₄ emissions from agricultural ecosystems under future O₃ pollution scenarios.

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

  WU Yanlin, HUANG Wei, WANG Yuanyuan, HU Zhenghua, DING Xueli

  2026,63(5):1671-1681, 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, the microbial-driven mechanism of biological nitrogen fixation in paddy fields were investigated 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.

• 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

  2026,63(5):1682-1694, 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.

• 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 Yuji

  2026,63(5):1695-1705, DOI: 10.11766/trxb202412310518

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  【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 + phosphorus solubilizing bacteria (FOP), FO + nematodes (FON), and FO + phosphorus 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 8.1%, 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.

• 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

  2026,63(5):1706-1720, DOI: 10.11766/trxb202507260360

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  Abstract:

  【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.

• 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

  2026,63(5):1721-1736, DOI: 10.11766/trxb202507300365

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  Abstract:

  【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 micro-environment, 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.

• 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

  2026,63(5):1737-1751, DOI: 10.11766/trxb202412230502

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  【Objective】 Although adding organic waste materials into soils significantly affects microbial characteristics, the responses of soil bacterial and fungal diversity, community composition and their interactions to different organic material amendments in urban green soils remain poorly understood. 【Method】 Using the 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 (α) diversity did not change among all the treatments, while soil fungal α 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 significantly differed from other treatments, which was significantly influenced by soil pH and microbial biomass carbon. In contrast, Proteobacteria, Acidobacteria, Chloroflexi and Firmicutes 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 co-occurrence network revealed six main ecological clusters. The relative abundances of microbes in each module were different among all the treatments and were significantly correlated with soil nutrients and aromaticity index of organic materials. Specifically, the highest relative abundance of bacterial 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.

• 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

  2026,63(5):1752-1767, 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 Landslide Deposition on Soil Formation and Evolution in Mountainous Regions of Southwest China

  SUN Yueqi, YANG Jinling, ZHANG Haozhe, YANG Geyu, YUAN Dagang, LÜ Linyi, ZHANG Ganlin

  DOI: 10.11766/trxb202605250264

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  【Objective】Mountain landslides alter pre-existing surface landscapes through intense material transport and deposition, severely disrupting long-developed soil horizons and thereby affecting post-disaster ecological recovery. However, the specific mechanisms involved in this process of horizon disruption remain poorly explored. Thus, this study aimed to reveal the effects of landslide material transport and deposition on soil genesis, profile development, and nutrient recovery. 【Method】Two typical landslide sites in mountainous Southwest China, with recovery periods of 8 years and approximately 30 years, were selected along with their respective natural control sites. Soil profile morphology and genetic horizons were described in the field, and soil samples were collected from each genetic horizon to determine selected physicochemical properties and nutrient contents. 【Result】The results showed that landslide material transport and deposition increased soil thickness in deposition zones and led to increased gravel content, a coarser particle-size distribution, and reorganization of soil horizons. In the deposition zone of the large landslide after 8 years of recovery, a weakly developed incipient horizon occurred below the surface horizon, and the soil was identified as belonging to Cambosols, whereas the natural control belongs to Primosols. The contents of soil organic carbon, total nitrogen, available phosphorus, and available potassium were all lower than those in the natural control, indicating that the early-stage deposition zone is still nutrient-poor. In the deposition zone of the small landslide after approximately 30 years of recovery, soil thickness was also greater than that of the natural control, and a buried horizon with relatively high contents of organic matter and several nutrients occurs in the middle part of the profile. Surface soil organic carbon, total nitrogen, and available phosphorus recovered to 57.7%, 52.5%, and 35.7% of the corresponding values in the natural control, respectively, whereas available potassium reached 13.6% of the control value and remained a prominent limiting nutrient during recovery. 【Conclusion】Soil recovery in landslide deposition zones is jointly influenced by deposited material composition, soil horizon reorganization, surface organic matter accumulation, and limited nutrient availability. Natural recovery is a prolonged process and may have long-term implications for ecosystem restoration. Restoration measures should be implemented in stages according to the time since the landslide and the dominant limiting factors. These results provide a reference for soil recovery and ecological reconstruction of mountain landslide-affected sites.

• Effects of Gene-Edited Rice on the Composition and Potential Functions of the Rhizosphere Bacterial Community

  ZOU Lingli, FAN Yixuan, LIANG Ziteng, WANG Luyao, GE Lei, WANG Min, SUN Yu, LI Peng

  DOI: 10.11766/trxb202511290571

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  【Objective】Clustered interspaced short palindromic repeats/CRISPR-associated proteins (CRISPR/Cas)-mediated gene editing technology has been widely applied in molecular plant breeding. However, the effects of genotypic variation induced by this technology on the structure and potential functions of soil bacterial communities constitute a central issue in environmental safety assessment. 【Method】The herbicide-resistant gene-edited rice SF24HI708, carrying mutations in the Acetyl-CoA carboxylase (ACCase) gene and its parental cultivar Huanghuazhan (HHZ) were used as model plant materials. High-throughput sequencing of 16S rRNA genes was employed to characterize the structure and functional metabolic pathways of rhizosphere bacterial community at the tillering and heading stages. 【Result】Neither genotype nor growth stage significantly affected the α-diversity indices of rhizosphere bacterial communities, including the abundance-based coverage estimator (ACE), Chao 1, Shannon and Simpson indices. However, both factors significantly altered community composition. In both rice lines, the assembly patterns of rhizosphere bacterial communities at the tillering and heading stages was predominantly governed by stochastic processes, with drift and other processes each contributing ≥68%. Co-occurrence network analysis further revealed that the rhizosphere bacterial community associated with the gene-edited rice exhibited higher stability than that of the parental cultivar. Kyoto Encyclopedia of Genes and Genomes(KEGG) functional analysis showed that, compared with the parental cultivar, the sphingolipid signaling pathway was significantly upregulated in the gene-edited rice at the tillering stage. At the heading stage, metabolic pathways involved in the synthesis and degradation of lipids and polysaccharides were significantly downregulated, whereas key pathways related to energy metabolism and substance transport were significantly upregulated.【Conclusion】Although gene-edited rice changed the composition and potential functional pathways of the rhizosphere bacterial community, it did not lead to decreased alpha diversity indexs or weakened community stability, indicating that its cultivation had no adverse effects on rhizosphere microecology.

• Effects of Nitrogen and Phosphorus Addition on Soil Organic Nitrogen Mineralization in Different Soil Layers of Subtropical Moso Bamboo Forests

  CHEN Luoxuan, PAN Yizu, LI Yongfu, WU Jiasen, LIU Juan

  DOI: 10.11766/trxb202512030574

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  【Objective】Anthropogenic nitrogen (N) deposition is a key issue in global-change research. As the two most critical nutrients for plant growth, nitrogen and phosphorus (P) regulate ecosystem functioning; however, elevated N deposition intensifies N-P imbalance in P-limited subtropical forest soils, strongly altering soil N cycling.【Method】A three-year experiment was conducted in a subtropical moso bamboo (Phyllostachys edulis) plantation to evaluate the effects of control (CK, 0 kg·hm-2· a-1), nitrogen addition (N, 120 kg·hm-2·a-1 (in terms of N, the same below) ), phosphorus addition (P, 120 kg·hm-2·a-1(in terms of P, the same below)), and combined N and P addition (NP, 120 kg·hm-2·a-1 + 120 kg·hm-2·a-1) on soil organic N mineralization across 0-20, 20-40 and 40-60 cm soil depths.【Result】The results showed that: (1) The activities of soil enzymes responsible for C and N transformations were found to be generally reduced under N and NP treatments but increased under P treatment. A significant effect of soil depth was identified, revealing a pronounced decreasing trend in enzymatic activities with greater depth; (2) Overall, N treatment and NP treatment significantly reduced microbial biomass C and N (MBC, MBN) and dissolved organic C and N (DOC, DON) in the 20-40 cm and 40-60 cm soil layers, except for the P treatment reducing DOC and MBC in the 20-40 cm soil layer. Also, P treatment had a trend of increasing MBC, MBN, DOC, and DON in all soil layers. Soil depth significantly affected the content of soil active C and N, with both gradually decreasing as soil depth increased. (3) N and NP additions exerted an inhibitory effect on organic N mineralization, whereas P addition showed a stimulatory trend. However, CK, N, P, and NP treatment differences were not statistically significant. Soil depth strongly affected mineralization rates: net N mineralization in the 0-20 cm layer was significantly higher than in the 20-40 cm and 40-60 cm layers. No significant difference was detected between the 20-40 and 40-60 cm layers. (4) Structural equation modeling (SEM) revealed that nitrogen addition and soil layer effects indirectly inhibit organic N mineralization by reducing β-glucosidase (BG) and DON; P addition indirectly promotes organic N mineralization by increasing DON.【Conclusion】In summary, in the N-rich and P-limited soil of a subtropical Phyllostachys edulis (moso bamboo) forest, short-term (three-year) N addition alone (N treatment) and combined N and P addition (NP treatment) exhibit an inhibitory trend on soil organic N mineralization, whereas P addition alone (P treatment) shows a promoting trend. Considering the vertical mobility of inorganic N in subtropical forest soils, further attention should be paid to the long-term effects of N and P additions on soil N mineralization across different soil layers. By elucidating the characteristics and underlying mechanisms of soil organic N mineralization in response to N and P additions and soil depth in a moso bamboo forest, this study provides data support for understanding soil N transformation under N deposition.

• Comparison of Soil Particle Size Distribution in the Black Soil Region of Northeast China Measured by Laser Diffraction Method and the Sieve-Pipette Method

  LENG Zihe, ZHAGN Tianyu

  DOI: 10.11766/trxb202509270475

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  【Objective】The Laser Diffraction Method(LDM) has been increasingly adopted for determining Soil Particle Size Distribution(PSD) due to its rapid measurement speed, high degree of automation, and minimal labor requirement. These advantages make LDM particularly attractive for large-scale soil surveys, laboratory routine analysis, and studies requiring high-resolution particle-size information. Nevertheless, substantial discrepancies persist between PSD measured by LDM and that obtained from the traditional Sieve-Pipette Method(SPM), which remains the reference method in most national and international soil texture classification systems. These inconsistencies arise mainly from differences in measurement principles, contrasting assumptions regarding particle shape and density, the optical models used in LDM instruments, and the absence of unified sample pretreatment protocols. As a result, the direct use of LDM-derived PSD for soil texture classification often yields biased or inconsistent outcomes. Therefore, this study aims to: 1) comprehensively compare PSD measured by LDM and SPM for major soil types in the Black Soil Region(BSR) of Northeast China; and 2) develop and evaluate calibration models based on regression analysis and Lin’s Concordance Correlation Coefficient(CCC) to convert LDM results into an SPM-compatible reference framework. 【Method】Soil samples representing 36 dominant soil series across the BSR, including black soil, chernozem, chestnut Soil, and aeolian Sandy Soil, were collected in the field. After air-drying, the samples were gently ground using a mortar and passed through a 2 mm sieve. PSD for each sample was determined using both LDM and SPM following their respective protocols. Differences in clay, silt, and sand fractions were quantified to characterize systematic deviations. Two calibration strategies were developed: one based on regression analysis, which establishes quantitative relationships between LDM and SPM values using linear regression models; and the other based on Lin’s CCC, which adjusts particle-size cutoff thresholds in LDM to maximize consistency with SPM and identify optimized boundary values for clay, silt, and sand. Model performance was evaluated based on reductions in mean absolute differences and improvements in soil texture classification accuracy using the USDA textural classification system. 【Result】1) Pronounced discrepancies were observed between LDM and SPM. Relative to SPM, LDM consistently underestimated clay content and substantially overestimated silt content across all soil types, whereas deviations in sand content varied depending on sample-specific characteristics. The mean absolute differences for clay, silt, and sand were -30.1%, 34.5%, and -4.4% respectively. 2) Following regression-based correction, the mean absolute differences decreased to 0.9%, 0.5%, and -1.4%, and the accuracy of soil texture classification improved markedly to 36.1%. 3) Lin’s CCC-based calibration further reduced the mean absolute differences to 1.3%, -3.4%, and 2.1%, yielding a classification accuracy of 38.9%. Although both calibration approaches substantially improved agreement between LDM and SPM, the regression-based method was more computationally efficient to apply in routine laboratory workflows. 【Conclusion】Uncorrected LDM-derived PSD is unsuitable for direct soil texture classification in the BSR. However, applying appropriate calibration models, whether regression-based or Lin’s CCC-based, effectively harmonizes LDM data with SPM reference values, significantly enhancing its reliability and practical utility. These findings offer a methodological foundation for integrating LDM into soil survey, monitoring, and classification programs, and provide valuable guidance for improving the comparability of PSD data obtained using different analytical techniques.

• Study on the Anaerobic Degradation of DDT Enhanced by Nano-Fe3O4 Coupled with Na2S2O4 in Soil

  LIU Cuiying, WANG Zhiyu, YANG Dongsheng

  DOI: 10.11766/trxb202601200041

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  【Objective】2,2-Bis(4-chlorophenyl)-1,1,1-trichloroethane (DDT), a typical persistent organic pollutant, remains widely accumulated in soil due to its high stability, posing severe threats to the ecological security of soil. Magnetite can enhance the efficiency of extracellular electron transfer of microorganisms, and dithionite, as a reducing agent, may drive the chemical reductive dechlorination of DDT. Thus, this study aims to elucidate the effect and its mechanism of the interaction of nano-magnetite (Fe3O4) and Na2S2O4 on the anaerobic degradation of DDT in paddy soil. 【Method】A slurry anaerobic incubation experiment using hydragric Acrisols was designed by setting up the following eight treatments: (1) Unsterilized DDT-contaminated soil (CK), (2) Unsterilized DDT-contaminated soil+nano-Fe3O4 (Fe3O4), (3) Unsterilized DDT-contaminated soil+Na2S2O4 (Na2S2O4), (4) Unsterilized DDT-contaminated soil+nano-Fe3O4+Na2S2O4 (Fe3O4+Na2S2O4), (5) Sterilized DDT-contaminated soil (S-CK), (6) Sterilized DDT-contaminated soil+nano-Fe3O4 (S-Fe3O4), (7) Sterilized DDT-contaminated soil+Na2S2O4 (S-Na2S2O4), (8) Sterilized DDT-contaminated soil+nano-Fe3O4+Na2S2O4 (S-Fe3O4+Na2S2O4). During the anaerobic incubation period, dynamic changes of pH, Eh, adsorbed Fe(II), and dissolved Fe(II) in slurries were regularly monitored, and their correlation with DDT degradation dynamics was quantitatively analyzed to reveal the driving factors of reductive dechlorination.?【Result】Results showed that the anaerobic degradation rates of DDT for different treatments were Fe3O4+Na2S2O4 > S-Fe3O4+Na2S2O4 > Na2S2O4 > S-Na2S2O4 > Fe3O4 > CK > S-Fe3O4 ≈ S-CK. After 42 d of anaerobic incubation, the extractable residues of DDT decreased by 77.0%, 68.4%, 66.2%, 60.8%, 56.1%, 52.6%, 30.2%, and 29.4%, respectively, for the treatments of Fe3O4+Na2S2O4, S-Fe3O4+Na2S2O4, Na2S2O4, S-Na2S2O4, Fe3O4, CK, S-Fe3O4, and S-CK. The dominant degradation product of DDT was 1, 1-dichloro-2, 2-bis(4-chlorophenyl)-ethane (DDD), with a small amount of 1, 1-dichloro-2, 2-bis(4-chlorophenyl)ethylene (DDE) and 1-chloro-2, 2-bis(4-chlorophenyl)ethylene (DDMU). Soil microorganisms, nano-Fe3O4, and Na2S2O4 all significantly enhanced the anaerobic degradation of DDT, and the order of their effects was Na2S2O4 > soil microorganisms > nano-Fe3O4, but there was no significant interaction among the three factors. A highly significant negative correlation was observed between DDT residues and the contents of adsorbed Fe(II) in the reaction systems, indicating that adsorbed Fe(II) was the key factor driving the anaerobic degradation of DDT. 【Conclusion】In conclusion, the combined application of nano-Fe3O4 and Na2S2O4 under flooded anaerobic conditions can effectively accelerate the reductive dechlorination of DDT in soil, which is a feasible remediation strategy for soils contaminated with polychlorinated organic compounds.

• Limiting Factors for Revegetation and Bacterial Community Structure Responses in Reclaimed Topsoil of Coal Gangue Dumps

  JI Chuning, BIAN Zhengfu, HU Zhenqi, SHEN Renfang, CHEN Baodong

  DOI: 10.11766/trxb202604210201

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  【Objective】Coal gangue dumps are commonly reclaimed through topsoil covering and artificial planting, yet stable vegetation remains difficult to establish in some reclaimed areas. Identifying the associated constraints is essential for facilitating ecological restoration. 【Method】Four coal gangue dumps reclaimed in 1990, 2005, 2012, and 2018 in Yangquan, Shanxi Province, were investigated. Well-vegetated and revegetation-limited sites within each dump were sampled in pairs. Topsoil physicochemical properties, structural stability, enzyme activities, bacterial abundance, and community composition were analyzed. Response ratios, grouped Mantel tests, and partial least squares path modeling (PLS-PM) were used to identify stable indicators and potential pathways of vegetation limitation. 【Result】Sulfur accumulation and insufficient water and nutrient supply were the most prominent characteristics of vegetation-limited topsoil. In the revegetation-limited sites of the four reclamation years, total sulfur contents were 2.40, 3.63, 5.08, and 7.65 g?kg?1, and sulfate sulfur contents were 337.2, 528.8, 863.7, and 1 947 mg?kg?1, respectively. Bulk density in well-vegetated sites was significantly lower than that in revegetation-limited sites across all four reclamation years, indicating higher structural stability. Enzyme activities and bacterial alpha diversity showed unstable response directions, whereas 16S rRNA gene copy numbers were significantly higher in well-vegetated sites than in revegetation-limited sites across all four reclamation years, indicating that bacterial abundance showed a stable response to revegetation-status differentiation. Micrococcaceae was the dominant taxon in all sites. Principal coordinates analysis (PCoA) and permutational multivariate analysis of variance (PERMANOVA) showed significant differentiation in bacterial community structure. Bacterial Bray-Curtis dissimilarity was most strongly correlated with sulfur-salinity constraints. Sulfur-salinity constraints had significant negative effects on water supply, nutrient supply, structural stability, and bacterial response. The PLS-PM further revealed correlations among topsoil limiting factors. 【Conclusion】Sulfur-salinity accumulation, structural compaction, insufficient water and nutrient supply, and reduced bacterial abundance jointly formed the topsoil barrier to revegetation establishment. Total sulfur, sulfate sulfur, bulk density, and 16S rRNA gene copy number can serve as priority diagnostic indicators. These findings provide a scientific basis for topsoil quality diagnosis and ecological restoration of coal gangue dumps.

• Mechanisms of Gaseous Nitrogen Emissions from Denitrification in Agricultural Soils as Affected by Organic Material Quality

  YU Heng, WEI Zhijun, MA Xiaofang, ZHANG Yumeng, YAN Xiaoyuan, SHAN Jun

  DOI: 10.11766/trxb202512020572

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  【Objective】Denitrification in agricultural soils is jointly regulated by the quantity and quality of organic carbon materials. This study aimed to reveal how organic materials of different quality affect denitrification-derived gaseous nitrogen (N) emissions and the N2O/(N2O+N2) product ratio in typical agricultural soils, and to elucidate the underlying mechanisms. 【Method】Paddy soil from a rice–wheat rotation field and greenhouse vegetable soil in the Taihu Lake region were collected as test soils, to which six types of exogenous organic carbon with contrasting C/N ratios were applied. The treatments include wheat (WS), rice (RS) and maize straw (MS) and their corresponding biochars (WSB, RSB, and MSB). In parallel, the respective straw- and biochar-derived leachates (LWS, LRS, LMS, LWSB, LRSB, and LMSB) were added, and a Robot automatic gas analysis system, qPCR and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were employed to quantify gaseous N emissions and the N2O/(N2O+N2) product ratio, denitrification functional genes, and the molecular composition of dissolved organic matter (DOM) in the leachates.【Result】The results showed that, in paddy soil, both straw and biochar increased the abundances of nirS and nirK, leading to significantly higher cumulative N2O emissions and N2O/(N2O+N2) ratios. Their leachates similarly enhanced N2O production, with LMS showing the greatest increase of 242.4%. Straw and its leachates exhibited substantially higher (nirS+nirK)/nosZ ratios than biochar and its leachates, corresponding to higher N2O/(N2O+N2) ratios. In vegetable soil, straw and biochar also increased N2O emissions, and this effect was further pronounced when their leachates were applied. The LWS treatment showed the greatest cumulative N2O emission (268.57 mg kg?1) and an N2O/(N2O+N2) ratio of 0.87, attributable to high background NO3?-N, which suppressed nosZ abundance and N2O reduction. FT-ICR MS revealed that straw-leached dissolved organic matter (DOM) was dominated by recalcitrant lignin-like and condensed aromatic compounds, which accounted for 88.43%, 86.90% and 85.03% of the DOM molecular abundance in LWS, LRS and LMS, respectively. The increase in relative abundance of condensed aromatics and the aromaticity index (AImod) significantly (P < 0.05) increased both N2O emissions and the N2O/(N2O+N2) ratio. In contrast, biochar-leached DOM contained more labile lipid-like and protein/amino sugar-like compounds, and the relative abundance of protein/amino sugar molecules was positively associated with cumulative N2 emission (P < 0.05). 【Conclusion】In summary, the qualitative properties of organic carbon inputs are a key determinant of denitrification rates and the partitioning of gaseous N products in agricultural soils. Therefore, optimizing organic material inputs to regulate the chemical composition of soil organic carbon, together with coordinated control of pH and NO3?-N levels, is critical for achieving high NO3?-N removal efficiency while minimizing the N2O/(N2O+N2) ratio. This, in turn, promotes the conversion of denitrification end-products toward N2, thereby facilitating reactive N mitigation and sustainable N cycling in agroecosystems.

• Soil Genesis and Its Spatial and Temporal Variations in the Warm Temperate Zone, taking Pizhou County of Jiangsu Province, Southeast China, as an Example

  NIE Dalin, LI Jiaqi, CAI Tianle, LIU Tingxiao, PENG Chen, HU Xuefeng

  DOI: 10.11766/trxb202604060165

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  【Objective】This study aimed to the pedogenesis and spatial distribution of major soil types in the Warm Temperate Zone of China.【Method】Comprehensively considering factors such as topography, parent material, and land use pattern, 65 soil profiles were established and identified in Pizhou City, Jiangsu Province, Southeast China, of which, 11 typical soil profiles were selected and studied in depth. 【Result】 The results indicated that the main soil groups in Pizhou were Fluvisols, which were majorly distributed in the plain and accounted for approximately 68% of the total arable land, along with other soil groups with regional characteristics such as Cinnamon Soils, Brown Soils and Calcified Black Soils. Soil types exhibited a regular spatial distribution with topographic change, forming a soil subgroup spectrum of “Calcic (or neutral) Skeleton Soils, Podzolized Brown Soils, Eluviated Cinnamon Soils, Aquatic Cinnamon Soils, Calcified Black Soils, Brown Fluvisols, Yellow Fluvisols, and Saline Fluvisols”. Within the plains or hills, the spectra of soil families or species were also presented in accordance with micro-topographic undulation. 【Conclusion】In the low mountains and hills of Pizhou, as the tectonic movement is stable, the rocks have been exposed and weathered for a long time, which may have experienced warm and humid climates during the Pleistocene, forming red clay or red paleosol that served as the parent material for Cinnamon Soils and Brown Soils. The characteristics of clay accumulation, iron-manganese cementation and podzolization of the Brown Soils in Pizhou are inherited from the red paleosol. In contrast, the Fluvisols develop from modern river sediments and are of very young pedogenic age. The origin of the parent materials should be regarded as the starting point of soil genesis to facilitate a better understanding of the formation processes of various soils.

• Digital Characterization of the Spatial Distribution of the Albic Horizon in the Northeast Black Soil Region

  LV Shouxi, SUN Zhongxiu†, JIANG Yingying, DUAN Siyi, LIU Feng, WANG Qiubing

  DOI: 10.11766/trxb202606140304

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  【Objective】 This study aims to clarify the spatial distribution, characteristics, and multi-factor driving mechanisms of the albic horizon—a critical soil constraint layer in the Northeast Black Soil Region, which serves as China’s premier grain production base. The albic horizon, characterized by high bulk density, elevated hardness, and shallow burial depth, severely restricts plant root penetration and hydrological processes, hindering sustainable agricultural development in this strategically important region. 【Method】Taking the Northeast Black Soil Region as the research area, a soil profile dataset was constructed by integrating measured data from 5 field-investigated standard profiles and systematically compiled records from 776 historical survey profiles. Combined with 21 environmental covariates spanning 7 categories (including climate, topography, hydrology, and soil properties), a random forest (RF) machine learning model was applied to quantitatively analyze the spatial distribution and characteristics of the albic horizon.【Result】The results showed that the albic horizon was mainly distributed in the Sanjiang Plain (covering Jiamusi, Shuangyashan, and Jixi), the northern foothills of the Changbai Mountains (including Mudanjiang, Hegang, and Harbin), and the central low mountain-hilly terrain of Jilin (encompassing Liaoyuan, Tonghua, and Yanbian), with a total predicted area of approximately 29,100 km2 (model Kappa coefficient=0.87, indicating excellent predictive accuracy). In terms of characteristics, the burial depth exhibited a distinct "deep northeast, shallow southwest" spatial gradient: deeper zones concentrated in the Sanjiang Plain interior and central Jilin hilly regions, while shallower zones occurred in the southern Wanda Mountain foothills and western Changbai Mountain foothills, with burial depths ranging from 13.44–38.29 cm. Thickness showed a "thicker central, thinner peripheral" pattern: thick layers mainly located in the eastern Songnen Plain and western Zhangguangcai Mountain foothills, while thinner layers? distributed along the southern Xiao Hinggan Mountain foothills and northern Liaoning Horqin Sandy Land margins, with thickness spanning 12.98–33.36 cm. Multivariate analysis identified key environmental drivers: climate-topography interactions primarily regulated burial depth, hydrology-geomorphology-biology synergies shaped thickness spatial patterns, and soil property-climate-topography interactions dominated albic horizon occurrence and distribution.【Conclusion】This study establishes a robust digital characterization framework for the albic horizon and accurately delineates its spatial distribution patterns alongside multi-factor driving mechanisms. The findings provide a scientific foundation for developing differentiated black soil conservation and restoration strategies, which hold profound implications for sustainable black soil resource utilization and regional food security assurance.

• Root Water Source and Hydrological Niche Segregation of Artificially Restored Plants in the Mu Us Sandy Land

  WANG Ziwei, HUANG Laiming, WANG Linzhi, PEI Yanwu, SHAO Ming’an

  DOI: 10.11766/trxb202508270420

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  【Objective】Understanding the water use patterns and dynamic changes of sand-fixing plants is crucial for scientifically guiding the sustainable development of artificial vegetation and the efficient use of water resources in desert ecosystems in arid and semi-arid regions. However, in water-limited desert ecosystems, there is still a lack of in-depth understanding of the seasonal variation in water sources of different sand-fixing plants. This study was designed to examine the root water source and hydrological niche segregation of artificially restored plants in the Mu Us Sandy Land, aiming to provide scientific bases for the rational configuration of artificial vegetation and sustainable use of water resources in desert ecosystems.【Method】This study focused on three typical sand-fixing plants in the Gechougou catchment in the northeastern margin of the Mu Us Sandy Land, northwest China, including Pinus sylvestris var. mongolica (P. sylvestris), Salix psammophila (S. psammophila), and Amygdalus pcdunculata Pall (A. pedunculata). The plant xylem water and their potential water sources (rainwater and soil water at different depths) were collected monthly during three consecutive growing seasons (May—October) of 2019—2021. δ²H and δ¹⁸O of xylem water were measured by Isotope Ratio Mass Spectrometry (IRMS; MAT253, Thermo Fisher Scientific, Germany) to mitigate interference from trace organic compounds. δ²H and δ¹⁸O of rainwater and extracted soil water were measured by Laser-Based Liquid Water Isotope Analyzer (LWIA; Picarro L2130i, USA). The vertical distribution of fine root (<2 mm) biomass and soil water content in each species stand were also determined. The MixSIAR model was used to quantitatively analyze the seasonal changes in plant water sources, and the proportional similarity index (PSI) was employed to quantify the degree of hydrological niche separation and overlap. 【Result】 Results indicated that the water use patterns of P. sylvestris, S. psammophila, and A. pedunculata exhibited significant seasonal variations. During the dry season, P. sylvestris and S. psammophila primarily absorbed water from the 120～300 cm soil layer (63.43±8.42% and 56.12±1.23%, respectively), while A. pedunculata mainly obtained water from 40～200 cm soil layer (54.00±4.16%). In the rainy season, all three species mainly absorbed water from the 0～120 cm soil layer (57.18±5.84%, 60.78±15.00%, and 60.43±6.80%, respectively). Compared with the dry season, P. sylvestris, S. psammophila, and A. pedunculata significantly increased their absorption of water from the 0–40 cm soil layer during the rainy season (P<0.05). The changes in water use patterns of different sand-fixing plants were closely related to their root vertical distribution and the seasonal variation of soil water availability. P. sylvestris and A. pedunculata exhibited relatively low hydrological niche overlap (PSI<0.75), suggesting minimal competition for the same water sources, making them suitable for interplanting. In contrast, P. sylvestris and S. psammophila showed very similar water use strategies throughout the growing season, displaying significant water competition. 【Conclusion】The findings of this study highlight the importance of considering species-specific water use patterns when planning vegetation restoration efforts. Specifically, our results support the idea of strategically interplanting species with complementary hydrological niches to enhance vegetation resilience, improve water use efficiency, and promote sustainable ecosystem restoration in arid and semi-arid desert regions.

• Rapid Identification of Gley Horizon in Paddy Soil and Its Spatial Continuous Variation Using GPR Technology

  ZHANG Daoyu, ZHAO Mingsong, LUO Fangzhou, JIA Zhihui, JIAN Le, WU Huayong, CHEN Songchao, WANG Fumin, XIONG Changsheng, HU Wenyou, ZHAO Yongcun

  DOI: 10.11766/trxb202509230466

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  Accurate identification and characterization of the spatial distribution of the soil gley horizon are essential for improving soil tillage capacity and arable land quality. However, at larger spatial scales, conventional methods for gley horizon investigation—such as soil profiling and auger drilling—are constrained by low efficiency, high labor and time costs, and poor spatial continuity. Ground-penetrating radar (GPR), with its non-destructive, continuous, and large-area detection capabilities, has therefore demonstrated considerable potential for identifying soil gley horizons. Nevertheless, rapid and accurate identification of gley horizons using GPR remains challenging due to the pronounced spatial heterogeneity of soil structures and the complexity of GPR signal processing. In this study, typical gleyed paddy soils in Chengmai County, Hainan Province, China, were selected as the research object. GPR surveys using two antenna frequencies were conducted to detect the location and thickness of gley horizons in paddy soils exhibiting both surface-gley and bottom-gley characteristics. By comparing wavelet transform and variational mode decomposition (VMD) for GPR signal processing, it was found that VMD provides a stronger capability for revealing soil structural features. VMD was therefore applied to identify the vertical distribution of gley horizons, and the accuracy of gley horizon detection using the two GPR frequencies was systematically evaluated.The results indicate that, compared with wavelet transform, VMD exhibits stronger spectral amplitude intensity in the depth range of 7–36 cm, demonstrating a superior ability to characterize soil structure. In fields CM02 and CM04, the errors in gley horizon thickness detected using the 1 GHz antenna (1.5 cm and 2.0 cm, respectively) were smaller than those obtained using the 700 MHz antenna (2.4 cm and 4.0 cm, respectively), indicating higher identification accuracy at the higher frequency. The spatial distributions of gley horizons differed markedly between fields with typical surface-gley and bottom-gley features, while the coefficient of variation for gley horizon thickness across all experimental fields remained below 3%. For gley horizon depth estimation, the coefficient of determination (R²) was 0.83 at 700 MHz, with absolute errors mainly ranging from 2 to 9 cm, whereas the R² increased to 0.90 at 1 GHz, with absolute errors primarily concentrated between 3 and 5 cm. Overall, this study demonstrates that GPR combined with VMD provides an efficient and accurate approach for the rapid identification of gley horizons in paddy soils, offering strong technical support for diagnosing soil constraints and improving cultivated land quality.

• Can Precipitation Penetrate Thick Loess Profiles to Recharge Groundwater? — Mechanism Conflicts and Evidence Evaluation

  WANG Li, LÜ Xiangrong, JI Zhenxia, SHAO Ming''an

  DOI: 10.11766/trxb202604030164

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  The Loess Plateau hosts the thickest aeolian loess deposits in the world, forming an exceptionally deep vadose zone. Under this unique geological setting, whether precipitation can penetrate thick loess profiles to recharge groundwater has long been a central scientific question in hydrogeology. Based on a systematic review of the regional hydrogeological background, this study synthesizes and evaluates two contrasting perspectives and their supporting evidence. One perspective suggests that, under the combined influence of piston flow and preferential flow, precipitation can migrate downward either gradually or rapidly through preferential pathways, thereby contributing to long-term or event-based groundwater recharge. The opposing view, drawing on evidence from dried soil layers, soil water deficits, loess–paleosol stratification, and the water-blocking effect of unsaturated fractures, argues that infiltration depth is limited, with most precipitation participating only in shallow soil water cycling and failing to penetrate the thick vadose zone; deep groundwater may instead largely consist of “paleo-groundwater” formed under past climatic conditions. Further analysis indicates that discrepancies between these views primarily arise from differences in research scale, observational methods, and geomorphic settings. Small-scale or event-based studies tend to capture rapid processes such as preferential flow, whereas regional-scale and long-term observations more often reflect slow or restricted infiltration. In addition, pronounced hydrological differences among geomorphic units (tablelands, slopes, and gullies) lead to strong spatial heterogeneity in groundwater recharge. Integrating available evidence, this study concludes that groundwater recharge in thick loess regions is not governed by a single mechanism but is instead a complex and heterogeneous process. The capacity of precipitation to directly penetrate the deep vadose zone via diffuse infiltration and form regional groundwater recharge is likely limited. Future research should emphasize long-term monitoring of deep vadose zones, the integrated use of multiple tracers, and multi-scale analyses to better constrain the coupling between precipitation infiltration and groundwater recharge.

• Chronology and Development Patterns of Alpine Meadow Soils in the Three-Rivers Headwater Region, Qinghai–Tibetan Plateau

  XIANBa Ji, E Chongyi, SUN Manping, ZHANG Jing, ZHANG Shuaiqi, ZHANG Zhaokang

  DOI: 10.11766/trxb202505110213

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  【Objective】The chronology and development history of Alpine Meadow Soils in the Three-Rivers Headwater Region remain poorly constraint, limiting understanding of their pedogenic mechanisms on the Qinghai–Tibetan Plateau. Thus, this study aimed to determine the formation ages, parent material sources, and dominant climatic controls of the Alpine Meadow soils, in order to elucidate their developmental patterns. 【Method】In this study, 21 alpine meadow soil profiles from the Three-River Headwaters Region were selected. Optically stimulated luminescence (OSL) dating was applied to both the turf layer and the parent material layer, combined with grain-size analysis to investigate soil formation processes. 【Result】The results show that the formation ages of the turf layer are generally within 1 ka. The parent material was mainly formed since the last deglaciation, with a few samples dating back to interstadials of the last glacial period. Grain-size distributions of the parent materials commonly exhibited a trimodal pattern, with a dominant peak at 40–60 μm (silt fraction). The grain-size frequency curves were similar to those of typical loess, indicating that aeolian dust is an important source of parent material for alpine meadow soil development. During the period from the last deglaciation to the Holocene, climate played a dominant role in controlling both aeolian dust input and pedogenic intensity. The concentration of parent material ages in the late Holocene suggests enhanced dust availability under relatively cold and dry climatic conditions, which provided essential materials for soil formation. 【Conclusion】These findings indicate that alpine meadow soils in the Three-River Headwaters Region follow a development pattern characterized as a “mixed parent material-aeolian accretion model.”

• Soil calcium carbonate leaching process of millennial soil chronosequence in coastal regions

  CAI Yajing, ZHAO Chengyi, JIAO Caixia, ZENG Rong, XU Mingxing, CHENG Sheng, LIU Gengyuan, GU Jiajing, ZHANG Yaqi, ZHANG Wenjie, Inamov Aziz

  DOI: 10.11766/trxb202601280067

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  Abstract:【Objective】 Soil inorganic carbon (SIC) plays a crucial role in soil ecosystem functions and carbon cycling processes. While the dynamics of soil organic carbon have been extensively studied, the long-term evolution of SIC in coastal regions remains poorly understood.【Method】 This study focused on soil calcium carbonate in coastal regions. By establishing a millennial soil chronosequence, we determined the calcium carbonate stock at different soil depths and soil ages to investigate the evolution of soil inorganic carbon in coastal areas. 【Result】 SIC stock was higher within the 20~100 cm soil layer and lower in the surface soil layer (0~20 cm). A significant positive linear relationship was observed between SIC stock in the 0~50 cm layer and that in the entire 1 m soil profile (R2 = 0.904, P < 0.01), indicating that SIC stock in the 0~50 cm layer can be used to approximate the total SIC storage in the 1 m profile in the study area. This provides a reference for SIC stock assessments in similar coastal reclaimed areas. The SIC stock showed a negative correlation with soil age, meaning it decreased significantly as soil age increased. Also, the rate of SIC leaching decreased significantly with both increasing soil age and greater soil depth. 【Conclusion】 This study provides novel insights for estimating regional inorganic carbon storage and elucidating the leaching dynamics of inorganic carbon during pedogenesis, offering a scientific basis for refining carbon cycle models, predicting terrestrial carbon sink potential, and formulating evidence-based management strategies.

• Effects of microplastic aging on the distribution and stability of carbon and nitrogen in soil aggregates of vegetable fields in South China

  ZHOU Pengyu, Chen Zonghai, Hu Jiashuai, Lu Ying, Li Bo

  DOI: 10.11766/trxb202511250563

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  【Objective】The accumulation of microplastics in terrestrial ecosystems has garnered increasing concern, as their aging in agricultural soils over time can subsequently affect soil quality. Although intensive vegetable soils face high microplastic accumulation risk and contain abundant aggregates, the effects of naturally aged microplastics on soil aggregate stability and the distribution characteristics of soil organic carbon (SOC) and total nitrogen (TN) remain unclear.【Method】This study conducted a two-year pot experiment simulating vegetable cultivation, including a control with fresh microplastics (CK) and two polyethylene (PE) addition treatments (0.1% and 2%). Soil samples were collected after 2 (2MA), 12 (12MA), and 24 months (24MA) of PE aging to determine the contents of aggregate fractions (>2 mm, 2~0.25 mm, 0.25~0.053 mm, <0.053 mm), aggregate stability indices (R＞?.??、MWD、GMD、FD), as well as SOC and TN contents in each fraction, aiming to identify key factors influencing aggregate stability under microplastic aging.【Result】The results showed that compared to CK, the high-concentration (2%) PE treatment at 12MA significantly increased the contents of >2 mm and 2~0.25 mm aggregates by 122.29% and 43.88%, respectively, while significantly reducing the content of 0.25~0.053 mm aggregates by 66.67%. It also significantly increased SOC and TN contents in the 0.25~0.053 mm fraction by 66.16% and 10.45% (P < 0.05), respectively. The aggregate stability indices R＞?.??, MWD, and GMD also peaked at this stage, reaching 81.19%, 1.22 mm, and 0.93 mm, respectively. By 24MA, the 2% PE treatment significantly increased the content of <0.053 mm aggregates by 305.18% compared to CK (P < 0.05), and the fractal dimension (FD) reached a peak value of 2.75. In addition, compared to CK, the low-concentration (0.1%) PE treatment at 12MA significantly increased the contents of >2 mm and 2~0.25 mm aggregates by 27.71% and 26.56%, respectively, while significantly reducing the content of 0.25~0.053 mm aggregates by 47.54% and TN content in the <0.053 mm fraction by 13.03% (P < 0.05). At 24MA, this treatment significantly increased the content of <0.053 mm aggregates by 156.03% while reducing TN content in the >2 mm fraction by 10.39% (P < 0.05). Random Forest analysis indicated that TN content in the <0.053 mm fraction contributed more than 13% to various aggregate stability indices, representing the primary driving factor influencing the stability of vegetable soil aggregates under microplastic aging.【Conclusion】This study demonstrates that the impact of PE microplastic aging on aggregate size distribution and structural stability in vegetable soils exhibits a dynamic effect: structural stability peaked at 12MA, but prolonged aging led to the breakdown of larger aggregates and a subsequent reduction in structural stability. These findings provide a theoretical basis for evaluating the effects of microplastic aging on agricultural soil structure stability and carbon-nitrogen coupling characteristics.

• Effects of Biodegradable Microplastics and Nitrogen Fertilizer on Soil Microbial Community Composition and Ecosystem Functionality

  SHI Yue, ZHAO Qian, YAN Wei, Pan Fuxia

  DOI: 10.11766/trxb202512270617

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  【Objective】Plastic film mulching and nitrogen fertilization are widely adopted in agriculture; yet the interactive effects of biodegradable microplastics and nitrogen on soil microbial composition and ecological functions in farmland soils remain unclear. 【Methods】Four treatments were established: control (CK), urea addition (N), urea combined with polylactic acid microplastics (NPL), and urea combined with polybutylene adipate terephthalate microplastics (NPB). Soil physicochemical properties and microbial characteristics were analyzed to evaluate the combined effects of biodegradable microplastics and nitrogen fertilizer on carbon and nitrogen transformation processes as well as soil ecological functions. 【Results】The NPL and NPB treatments increased soil dissolved organic carbon content (DOC) and mitigated the pH decline induced by urea. Variations in physicochemical properties among treatments drove shifts in bacterial community structure, with NPL and NPB exhibiting similar influences on microbial community composition. Urea and microplastic amendments selectively enriched taxa involved in nitrogen transformation (phylum Nitrospirota) and organic matter decomposition (genera Arthrobacter and Rhodanobacter). Moreover, NPL and NPB treatments altered the abundance of genes associated with carbon and nitrogen metabolism. Key functional genes related to denitrification (nirS, nosZ), carbon fixation (rbcL), and methanogenesis (mcr) were upregulated. In contrast, genes associated with nitrification (amoA, amoB, amoC, hao) and methane oxidation (pmoA, mmoX) were significantly suppressed. The soil multifunctionality index (SMI) was lower in the N, NPL, and NPB treatments compared to CK. Enzyme activities and the abundance of carbon- and nitrogen-cycling genes exerted positive direct effects on SMI, while changes in soil nutrients availability drove shifts in SMI indirectly by regulating enzyme activities and the abundance of functional genes involved in carbon and nitrogen cycling.【Conclusion】The coexistence of biodegradable microplastics and urea alters soil physicochemical properties and reshapes microbial community composition, thereby influencing soil ecological functions.

• Environmental Magnetic Characteristics and Source Apportionment of Heavy Metal Contaminated Soils Surrounding Coal Mines in Arid Regions

  LIN Zhanwei, QIAO Qingqing, LI Gangqiang, WANG Dong, CHEN Yudong, GAO Zhongyin

  DOI: 10.11766/trxb202512220609

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  【Objective】Soil heavy metal contamination in mining areas has become an important environmental concern, particularly in arid regions where fragile ecosystems and intensive anthropogenic activities accelerate pollutant accumulation. While environmental magnetism has emerged as a cost-effective proxy for monitoring heavy metals, conventional statistical methods, such as simple correlation analysis, often fail to decipher the complex driving directions and causal mechanisms between magnetic parameters and pollutants. This is especially severe in areas with heterogeneous emission sources. Therefore, this study aimed to characterize the spatial distribution of heavy metals (Zn, Pb, As, Ni, Cr, and Fe) and to elucidate their causal linkages with magnetic mineralogical proxies.【Method】This study focuses on the Qiquanhu coal-mining area in the Turpan Basin, Xinjiang, China. A total of 330 soil samples were collected from 165 sites at two depths (0–10 cm and 10–20 cm) across the study area. Magnetic susceptibility (χ), saturation isothermal remanent magnetization (SIRM), and anhysteretic remanent magnetization (ARM) were measured, alongside the calculation of grain-size- dependent ratios (χARM/χ and χARM/SIRM). The concentrations of six heavy metals were determined using inductively coupled plasma mass spectrometry (ICP–MS). To quantitatively apportion pollution sources, the absolute principal component scores–multiple linear regression (APCS–MLR) receptor model was employed. The geographical convergent cross mapping (GCCM) method was utilized to identify the bidirectional causal relationships and driving strengths between magnetic parameters and heavy metal concentrations based, overcoming the limitations of traditional linear correlation.【Result】The results demonstrated that heavy metal enrichment in the study area was characterized by distinct multi-source superposition. The concentrations of Pb, Zn, and Fe were significantly higher in proximity to industrial facilities, showing a strong coupling with magnetic concentration-dependent parameters (χ, SIRM, and χARM). This suggested that high-temperature smelting activities released coarse-grained magnetic spherules that co-precipitated with these metals. In contrast, As and Ni were primarily associated with fine-grained magnetic particles generated during coal mining and transportation, exhibiting a sensitive response to χARM/χ and χARM/SIRM. However, Cr enrichment showed localized heterogeneity, primarily linked to the accumulation of mining solid waste. The APCS–MLR model identified three primary pollution factors accounting for 86.2% of the total variance, representing industrial smelting, coal-related activities, and lithogenic/waste sources, respectively. GCCM analysis further confirmed that magnetic concentration parameters exerted a strong causal drive on Pb and Zn, while grain-size-sensitive ratios served as robust causal indicators for As and Ni, effectively reducing the risk of misinterpretation inherent in simple correlation.【Conclusion】This study confirms that environmental magnetic parameters can effectively fingerprint the source-specific distribution of heavy metals in arid coal-mining soils. The integration of environmental magnetism, APCS–MLR source apportionment, and GCCM causal analysis provides an advanced diagnostic framework for pollution identification. These findings offer critical scientific evidence for targeted environmental management, risk mitigation, and the development of magnetic-based monitoring protocols in complex polymetallic contaminated regions.

• Synergistic Regulation and Contribution of Different Amendment Materials to Cation Exchange Capacity of Yellow Soil

  YIN Qilu, SHAN Wenlong, LI Rui, NIU Jiahui, DING Wuquan, LIU Xinmin

  DOI: 10.11766/trxb202512310626

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  【Objective】Yellow soils are an important agricultural resource in China. However, the productivity of the yellow soil has been significantly altered by both climate change and anthropogenic activities. Thus, to improve the understanding of the response mechanisms of yellow soil to these changes, this study systematically evaluates the effects of mineral and electrolyte materials combined with organic matter on soil cation exchange capacity (CEC) under different pH conditions.【Methods】A soil incubation experiment was conducted using yellow soil with 14 treatment groups: (1) CK (no amendment); (2) D (dolomite, 6 gkg-1); (3) B1 (sodium-based bentonite, 2 gkg-1); (4) DB1 (dolomite 6 gkg-1 + sodium-based bentonite 2 gkg-1); (5) DB2 (dolomite 6 gkg-1 + sodium-based bentonite 4 gkg-1); (6) DB3 (dolomite 6 gkg-1 + sodium-based bentonite 6 gkg-1); (7) DB3C (dolomite 6 gkg-1 + sodium-based bentonite 6 gkg-1 + carboxymethyl cellulose 1 gkg-1); (8) DB3CH (dolomite 6 gkg-1 + sodium-based bentonite 6 gkg-1 + carboxymethyl cellulose 1 gkg-1 + potassium humate 2 gkg-1); (9) K (potassium nitrate, 0.5 gkg-1); (10) Ca1 (calcium phosphate，0.33 gkg-1); (11) KCa1 (potassium nitrate 0.5 gkg-1 + calcium phosphate 0.33 gkg-1); (12) KCa2 (potassium nitrate 0.5 gkg-1 + calcium phosphate 0.66 gkg-1); (13) KCa3 (potassium nitrate 0.5 gkg-1 + calcium phosphate 1 gkg-1); (14) KCa3H (potassium nitrate 0.5 gkg-1 + calcium phosphate 1 gkg-1 + potassium humate 2 gkg-1). The CEC under actual soil pH and varying pH conditions was determined using the ion-selective electrode method. 【Result】The results indicated that (1) the amendment materials affected CEC by increasing soil pH. For instance, at the 75th day of incubation, the soil pH increased by 0.38-1.27 pH units, with an enhancement range of 6.35%-21.24%; the CEC increased by 4.59-13.55 cmolkg-1, with an enhancement range of 35.56%-105.00%. (2) Different types of ameliorants exerted a significant synergistic effect on increasing the pH and CEC of yellow soils. For example, at pH 7.0, the CEC of the soil treated with mineral + organic matter (DB3CH) was 49.57% and 35.01% higher than that of the soil treated with single minerals (D and B1), respectively, after 75 days of incubation; while the CEC of the soil treated with electrolyte + organic matter (KCa3H) was 19.27% and 10.37% higher than that of the soil treated with single electrolytes (K and Ca1), respectively. (3) Soil particles were more sensitive to pH changes in the low pH range. The CEC of most treatments showed a substantial increase in the pH intervals of 4.0-7.0, whereas the CEC increment slowed down in the high pH range. (4) The direct contribution of amended materials to the CEC of yellow soil is dominant (72.98%-90.60%), while the indirect contribution through increasing pH is relatively low (9.40%-27.02%). 【Conclusion】Organic materials directly provide negative charges through the dissociation of functional groups; inorganic electrolyte materials optimize the adsorption environment by supplying base cations; while mineral materials increase the CEC via their high permanent charge, large specific surface area, and pH-elevating effect. The findings of this study can provide a theoretical basis and practical experience for the amelioration of acidic soils and the improvement of soil fertility. Future research could further combine long-term field in-situ experiments to verify the synergistic contributions of different ameliorative measures to sustainability and ecological effects under actual environmental conditions. This can promote the directional improvement of cultivated yellow soil quality and the green development of agriculture.

• Precipitation and Parent Material Co-regulate the Spatial Differentiation of Soil Calcium Carbonate in Northern China

  miaoziyi, yangfei, wenhuiying, songxiaodong, zhangganlin

  DOI: 10.11766/trxb202602020077

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  【Objective】Soil inorganic carbon is a vital component of the terrestrial carbon pool in arid and semi-arid regions, and its accumulation and differentiation mechanisms profoundly influence regional carbon cycling processes. Climate is the dominant factor controlling soil carbonate accumulation, but the distribution of soil carbonates is also often affected by non-climatic factors such as parent material. 【Method】To elucidate how precipitation and parent material synergistically regulate the spatial variation of soil calcium carbonate (CaCO3) at a regional scale, this study systematically analyzed the CaCO3 content, depth of the enriched layer, and their main controlling factors in 13 typical soil profiles along the precipitation gradient from the Northeast China Plain to the Inner Mongolia Plateau. ?【Result】The results showed that precipitation governed the macro-scale vertical differentiation of CaCO3, with the depth of the enriched layer exhibiting a significant positive correlation with mean annual precipitation (R2 = 0.43, P < 0.05). The total accumulation of CaCO3 was controlled by the calcium source abundance of the parent material and showed no significant correlation with precipitation. Particle size analysis further revealed that, in profiles with homogeneous parent material, the deposition depth of CaCO3 responded very sensitively to precipitation (R2 = 0.97, P < 0.05). However, in profiles with discontinuous parent material or abrupt textural changes, water movement was obstructed by physical interfaces, creating a “perching” or “retention” effect, which caused the depositional layer to deviate significantly from the value predicted by precipitation alone. ?【Conclusion】This study proposes a synergistic regulatory mechanism for the soil calcification process: precipitation regulates the deposition depth, parent material determines the calcium source supply, and soil texture modulates solute transport. This mechanism reveals the multi-factor interaction processes controlling soil carbonates in arid and semi-arid regions.

• The Significant Regulatory Role of the Polarization Effects in the Adsorption of Heavy Metals on Soil/Mineral Surfaces

  XI Shuning, LIU Xinmin, QU Jiawen, TANG Yuting, LI Hang

  DOI: 10.11766/trxb202511200556

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  【Objective】The adsorption of heavy metals in soils/minerals is one of the key processes for heavy metal pollution remediation. Owing to an insufficient in-depth understanding of the unique properties of soils/minerals, the interfacial reaction mechanism of heavy metal adsorption remains unclear. Therefore, this study aimed to investigate the regulatory effects of polarization on heavy metal adsorption at the soil/mineral interface, and quantitatively clarify the contribution of each interaction force to the total adsorption energy.【Method】Based on orbital hybridization theory, combined with surface property evaluation, heavy metal ion adsorption experiments, and Fourier-transform infrared (FTIR) spectroscopy, it was systematically investigated the regulatory effects of polarization on heavy metal adsorption at the soil/mineral interface, and quantitatively clarified the contribution of each interaction force to the total adsorption energy. 【Result】The results showed that: (1) Both the specific surface area and surface charge quantity followed the order: permanent-charged montmorillonite > permanent-charge-dominated purple soil > variable-charged yellow soil. However, the surface negative charge density and negative electric field strength generally followed the sequence of purple soil > yellow soil > montmorillonite. (2) The surface charge density and electric field strength of soils/minerals increased with increasing pH, and exhibited a significant ion specificity. The adsorption capacity followed Pb2+ > Zn2+ > Cu2+ > Cd2+ on the montmorillonite surfaces, and Pb2+ > Cu2+ > Cd2+ > Zn2+ on purple soil surfaces at low concentrations. As the equilibrium concentration increased, the adsorption rate of Cu2+ gradually became lower than that of Cd2+ and Zn2+, following Pb2+ > Cu2+ > Cd2+ > Zn2+ on yellow soil surfaces. (3) The polarization effects enhanced the heavy metal adsorption ability, and the adsorption capacity of heavy metal cations followed montmorillonite > purple soil > yellow soil. (4) The adsorption energy was negatively correlated with ionic strength but positively correlated with pH. The components of adsorption energy followed the order: Coulomb energy > Covalent energy > Polarization energy, indicating that the covalent and polarization forces, dependent on the polarization effects, were still weaker than the Coulomb force. (5) The polarization effects of heavy metals played a crucial regulatory role in their adsorption. Moreover, the adsorption intensity could be regulated by the polarization effect through the surface electric field, which depended on pH and surface charge density (the ratio of surface charge quantity to specific surface area). 【Conclusion】This study revealed the quantum mechanism of heavy metal adsorption on soils/minerals from the perspective of micro-interfacial behavior, laying a theoretical foundation for the development of soil heavy metal passivation/activation regulation technologies.

• Effect of Dry-Wet Cycles on Gravel Weathering and Topsoil Nutrient Supplement in Gravel-Mulched Farmland

  HUANG Yahao, AN Wenju, LI Wangcheng, ZHANG Yifan, HE Lei

  DOI: 10.11766/trxb202601090020

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  【Objective】The mulched sand field system in arid and semi-arid regions of Northwest China has long been used for crop cultivation, where a surface gravel layer plays a critical role in moisture conservation and soil protection. However, over continuous cultivation periods exceeding 30 years, the degradation of these sand fields has become increasingly evident, yet the weathering behavior of the gravel cover under water-rock interaction and its potential contribution to soil nutrient replenishment remain poorly understood.【Method】To address this knowledge gap, this study selected a degraded sand field that had been under continuous cultivation for more than 30 years and was currently in a fallow phase. Gravel samples within the major particle size ranges present in the field were collected and analyzed to investigate their physical and chemical weathering responses to repeated dry-wet cycles. Furthermore, the study sought to reveal the regulatory mechanisms by which element leaching from the weathered gravel influences the nutrient status of the underlying plough layer soil.【Result】The results of this investigation are summarized as follows. (1) The gravel used for mulching in the studied sand field is predominantly composed of silicate minerals, which possess a certain intrinsic weathering potential and a notable capacity for nutrient release. Under the influence of dry-wet cycling, the slightly alkaline water environment in the field imposed only a limited chemical weathering effect on the gravel, whereas physical weathering played a dominant role. The water-rock interaction significantly accelerated gravel mass loss and enhanced the gravel’s water absorption efficiency, with all observed differences being statistically significant (P < 0.05). Among the different particle size fractions examined, the fine-grained gravel with a size range of 5 to 10 mm exhibited the most sensitive response to the imposed dry-wet cycles. This fraction achieved the highest mass loss rate, recorded at 2.09%, and the highest water absorption rate, reaching 1.70%. Compared with the control group (no dry-wet cycles or water-rock interaction), these values represent substantial increases of 242.11% and 23.10%, respectively. (2) No significant transformation or conversion among secondary minerals was detected throughout the experimental period. However, chlorite showed the most pronounced loss in the fine-grained gravel fraction, decreasing by 10% due to the combined effects of thermal stress induced by temperature fluctuations and the leaching action of infiltrating water. Accompanying the loss of pore-filling, magnesium-rich chlorite, various elements in the plough layer soil exhibited different degrees of enrichment. The sequence of element release from the gravel into the soil, ranked from highest to lowest relative release intensity, was ranked by ability as follows: Mg > Ca > Fe > Mn > K > Zn. (3) Correlation analyses and principal component analysis (PCA) further confirmed that the physical weathering characteristics of the gravel, including mass loss and water absorption rate, were significantly correlated with the content of rock-forming elements in the soil (P < 0.05). This finding demonstrates that water-rock interaction under dry-wet cycles has a pronounced influence on gravel fragmentation and also significantly modulates the elemental composition of the soil.【Conclusion】In conclusion, the dry-wet cycling process serves as an effective accelerator for the weathering of mulching gravel in degraded sand fields. The elemental leaching accompanying gravel fragmentation plays an important role in supplementing soil nutrients in the plough layer. Notably, the fine-grained gravel fraction exhibits the strongest nutrient release capacity among all tested particle sizes. These results suggest that the surface gravel layer in degraded sand fields possesses a certain potential for resource utilization in terms of nutrient supply. This study provides a new and valuable perspective for improving the soil environment of mulched sand fields, mitigating the ongoing degradation of such fields, and facilitating their future reclamation.

• Biochar Mitigates the Kinetic Release of Aluminum from Soil Driven by Exogenous Acid

  WANG Qing, ZHANG Ka, SHI Renyong†, LAI Hongwei, JIANG Jun, LI Jiuyu, CUI Xiumin, XU Renkou

  DOI: 10.11766/trxb202511250564

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  【Objective】The release of solid aluminum (Al) in soil, induced by exogenous acid, is the primary factor limiting crop growth in acidic soils. Biochar has been demonstrated to reduce the concentration of active Al in soil under equivalent acid input. However, the dynamic mechanisms by which it mitigates Al release remain unclear. 【Method】A stirred-flow dynamic acidification experiment was conducted to comparatively analyze the kinetic processes of solid-phase Al release in soils amended with biochar and Ca(OH)2. 【Results】The results showed that the release of Al from all treatments exhibited a two-stage pattern during acidification: accelerated release followed by decelerated release. These stages can be accurately fitted using piecewise functions combining first-order and pseudo-first-order kinetics (R2 > 0.999). The fitting results suggested that the two stages were controlled by proton diffusion and diffusion of potentially active Al, respectively. At the end of the reaction, the cumulative release of Al from biochar-amended soil was 8.98%-17.23% lower than that from Ca(OH)2-amended soil. In the initial stage, biochar competed for H+ involved in Al release via protonation of surface organic functional groups, and simultaneously reduced the H? diffusion rate constant. This resulted in biochar slowing down the rate of Al release from soil in the initial stage. Peanut straw biochar mainly inhibited Al release at this stage, with a better effect than rice straw biochar. In the later reaction stage, both biochars reduced the soil Al diffusion rate constant by 14.81%–51.06%. Meanwhile, rice straw biochar decreased the content of soil potentially active Al pool by 17.84% and thus reduced the release rate of soil Al during the later stage. Consequently, rice straw biochar was more effective than peanut straw biochar in mitigating soil Al release throughout the acidification process. 【Conclusion】 Biochar can enhance the kinetic stability of soil solid-phase Al release during acidification by improving soil pH buffering capacity, reducing the potentially active Al pool, and optimizing soil pore structure. These findings provide a theoretical basis and technical support for the long-term prevention of Al toxicity in acidic soils.

• Applicability of Mobile Cosmic-Ray Neutron Sensing for Mesoscale Soil Moisture Monitoring in Desert Photovoltaic Power Stations

  WANG Haixian, ZHANG Yongyong, XIAO Jianhua, CHEN Tao, MA Shijun, KANG Wenrong, WU Shaoxiong

  DOI: 10.11766/trxb202508130391

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  【Objective】This study aimed to evaluate the applicability of cosmic-ray neutron sensing (CRNS) for mesoscale soil moisture monitoring in desert photovoltaic (PV) power stations. 【Method】Three desert PV stations and adjacent control areas in Zhangye, Gansu Province, China, were investigated by integrating Monte Carlo N-Particle Transport (MCNPX) simulations with mobile CRNS field observations. Soil moisture was inverted using the N0 parameter method, and spatial representativeness was quantified through neutron weighting functions. 【Result】(1) PV panels exerted negligible interference on near-surface neutron flux. MCNPX simulations revealed a 1.27% relative difference in total neutron flux and a 0.12% difference in the fast neutron range (0.5～1000 eV) between panel-present and panel-absent scenarios. Moreover, mobile CRNS field measurements showed no statistically significant difference (P>0.05) in neutron intensity under panel-present and panel-absent conditions. (2) CRNS-inverted values exhibited strong agreement with oven-dried measurements (R2 = 0.73, RMSE = 0.01 g·g-1), confirming the accuracy of mobile CRNS for soil moisture retrieval in desert PV environments. (3) The effective vertical detection depth and horizontal footprint radius of CRNS were estimated to range from approximately 21～49 cm and 123～151 m, respectively. The mean detection depth within the PV areas (32 cm) was slightly lower than that in the control areas (39 cm). 【Conclusion】Mobile CRNS provides a technically feasible solution for non-invasive, mesoscale soil moisture monitoring in desert PV power stations, offering an innovative approach for hydrological assessment in arid-region solar energy installations.

• Environmental Factors Influencing Soil Particle Composition and Their Spatial Distribution Characteristics in the Tarim River Basin

  HU Yang, ZHOU Lei, JI Hongjie, LONG Huaiyu, LIAO Chaozi, XU Aiguo, XU Mengze

  DOI: 10.11766/trxb202508280421

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  【Objective】Soil particle composition directly influences soil texture, fertility, ecological functions, and agricultural productivity. Therefore, investigating the environmental factors affecting soil particle composition and its spatial distribution characteristics in the Tarim River Basin is of great significance for soil resource management and ecological environment construction in arid regions.【Method】This study analyzed soil particle composition data from 383 soil layers within 107 typical soil profiles (0~100 cm) in the Tarim River Basin. The Kruskal-Wallis test was used to determine inter-group differences, Spearman’s correlation analysis was employed to examine relationships between climatic factors and soil particle composition, and the random forest algorithm was applied to analyze the influence of environmental factors on the spatial distribution. Model accuracy and variable importance were assessed using R² (coefficient of determination), RMSE (root mean square error), ME (mean error), and %IncMSE (percentage increase in mean squared error) to predict the spatial distribution characteristics.【Result】The results showed that: (1) The soil particle composition within the 1-meter soil profile was dominated by sand and silt particles, with contents of 44.23%, 45.26%, and 10.51% for sand, silt, and clay, respectively. A highly significant negative correlation was found between sand content and both silt and clay contents, while a highly significant positive correlation existed between silt and clay. This suggests weakened pedogenesis in the Tarim River Basin, characterized by relatively strong physical weathering and relatively weak chemical weathering. (2) Environmental variables, including landform, soil type, sunshine duration day(≥3 hours), active accumulated temperature(≥10℃), elevation, and annual evaporation, significantly influenced the spatial distribution of soil particle composition. Variable importance analysis from the random forest model indicated that landform had the greatest influence, contributing over 20% to the model explanation across all soil layers, followed by soil type, which consistently exceeded 10%. (3) In terms of vertical profile distribution, sand content was higher in the 0~25 cm and 25~50 cm layers within the Tarim Basin (central Taklimakan Desert) but lower in the surrounding annular piedmont zone. In the 50~75 cm and 75~100 cm layers, sand content decreased in the central desert area, while the West Kunlun Mountains maintained high sand content throughout all layers. The silt and clay contents in the 0~25 cm and 25~50 cm layers were lower in the desert area than in the surrounding annular piedmont zone, with the opposite pattern observed in the 50~75 cm and 75~100 cm layers. (4) On a macro scale, the spatial distribution characteristics of soil particle composition are controlled by the annular geomorphological pattern of “a basin flanked by two mountain ranges”. This geomorphological pattern influenced the spatial distribution of environmental factors such as soil parent material, soil type, and climate, which consequently governs the spatial distribution of soil particle composition.【Conclusion】 This study provides a scientific basis for the precise management and sustainable utilization of soil resources in the Tarim River Basin, offering support for ensuring the sustainable development of oasis agriculture and ecological environment construction.

• Impact of Moisture-Driven Variations in δ13C and δ15N Signals on the Accuracy of Organic Carbon Source Apportionment

  CHEN Junji, NIE Xiaodong, WANG Shilan, SUN Ziqing, HUANG Zheng, LI Zhongwu

  DOI: 10.11766/trxb202509300481

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  【Objective】Stable carbon and nitrogen isotopes (δ13C and δ15N) have been widely applied due to their excellent source specificity and relative conservatism. They are particularly valuable in studies such as land-use identification and quantification of soil erosion effects. However, in the context of global climate change, the mechanisms underlying water-driven fractionation of stable carbon and nitrogen isotopes in soils remain unclear, which limits the accuracy of organic carbon source apportionment. Thus, this study aimed to investigate the mechanisms by which moisture conditions influence stable carbon and nitrogen isotope signals in soil and to analyze how the non-conservative behavior of stable carbon and nitrogen isotopes under different moisture conditions affects the accuracy of organic carbon source apportionment. 【Method】In this study, we designed soil incubation experiments under four typical moisture scenarios (drying, wetting, flooding, and drying-wetting cycles). We systematically investigated the patterns of stable carbon and nitrogen isotope signals driven by moisture and their implications for organic carbon source identification. In addition, we supplemented our analysis with Bayesian mixing models (MixSIAR model) and random forest models.【Result】The results showed that when using δ13C for tracing, the contribution bias for each source was generally below 10 %. Its significant conservatism makes it an excellent tracer for carbon source identification. In contrast, the δ15N signal is sensitive to moisture. Under extreme moisture conditions such as flooding and alternating wetting and drying, δ15N showed strong fractionation effects. Using δ15N alone for source identification results in substantial errors, with source contribution biases ranging from 0.067% to 24.77%. The combined application of δ13C and δ15N achieved higher apportionment accuracy under most moisture scenarios. However, it was still affected by the fractionation of δ15N under extreme moisture fluctuations.【Conclusion】The robustness of δ13C highlights its potential as a core indicator for analyzing organic carbon sources, while correction methods should be incorporated for δ15N to enhance result reliability. This study not only deepens the understanding of the processes and mechanisms of δ13C and δ15N signal fractionation in the context of climate change but also breaks through the inherent black box theory in traditional source apportionment methods for organic carbon sources at a mechanistic level. It also provides scientific support for optimizing organic carbon source apportionment methods under climate change.

• Characterization and High-Throughput Cultivation of Rhizosphere Bacteria from Wild Plants in Soda Saline-Alkali Soils of Northeast China

  FU Bingxu, CAI Yuanfeng, TENG Zhaojun, XIA Weiwei, JIA Zhongjun

  DOI: 10.11766/trxb202511130541

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  【Objective】Rhizosphere bacteria play a key role in plant stress resistance and nutrient acquisition. However, the community structure and culturable potential of rhizosphere bacteria in soda saline-alkaline soils remain poorly understood. 【Methods】In this study, rhizosphere soil samples of seven common wild grass species (including Suaeda glauca, Phragmites australis, and Setaria viridis) were collected from four typical soda saline-alkaline areas in the Songnen Plain: Da"an, Zhaoyuan, Zhenlai, and Tongyu. The bacterial community structure was analyzed by high-throughput sequencing of the 16S rRNA gene, and high-throughput cultivation using 1/10 TSB medium was conducted to assess the cultivation preferences of different taxa.【Results】Results showed that: rhizosphere bacterial abundance ranged from 1.79×109 to 1.24×1010 gene copies/g d.w.s, and significant differences in diversity were observed among plant species: Taraxacum mongolicum exhibited high abundance and high diversity; Artemisia capillaris had low abundance but high diversity; Plantago asiatica and Phragmites australis showed both low abundance and low diversity. Principal component analysis indicated that while the rhizosphere bacterial communities of different wild plant did not differ significantly, sampling location significantly influenced the rhizosphere bacterial community structure. The dominant bacterial taxa were generally consistent across plant species. At the phylum level, Proteobacteria was the most abundant (26.3%), followed by Actinobacteria (17.2%) and Acidobacteria (11.3%). The dominant genera included Arthrobacter, Microvirga, Bacillus, Ramlibacter, Skermanella, Rubrobacter, Sphingomonas, and Nocardioides. High-throughput cultivation yielded 117 pure bacterial ASVs, belonging to 52 genera and 4 phyla. The isolation efficiency averaged 3.1 genera and 7.1 pure strains per 100 positive wells. Frequently isolated taxa included the phyla Proteobacteria, Firmicutes, and Actinobacteria, and the genera Pseudomonas, Lysinibacillus, Rhodococcus, and Limnobacter. Notably, five of the top eight most relatively abundant genera in the rhizosphere were successfully cultured.【Conclusion】In conclusion, at a broad geographic scale in the Songnen Plain soda saline-alkaline region, sampling location rather than plant species was the primary factor driving rhizosphere bacterial variation. Although different bacterial groups exhibited distinct cultivation preferences, high-throughput cultivation proved to be an effective method for capturing most dominant taxa, demonstrating its utility for mining rhizobacterial resources in saline-alkaline soils.

• Long-term Combined vetiver hedgerows (Vetiveria Zizanioide) and Straw Mulching Improves Soil Pore Structure and Air Permeability In Red Soil Sloping Cropland

  ZHOU Qitao, DING Tianyu, GUO Zichun, LI Jiaqi, HUANG Shangshu, WU Yan, CHENG Yanhong, ZHANG Shuaipu, GAO Lei, GAN Lei, PENG Xinhua

  DOI: 10.11766/trxb202603020108

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  【Objective】In red soil sloping cropland, prolonged erosion and tillage disturbance often degrade the pore structure in the plow layer, restricting infiltration and aeration processes and ultimately reducing crop productivity. This study evaluated how four soil and water conservation practices—peanuts grown in high order (CK), vetiver hedges (vetiveria zizanioides) (H), straw mulching (M), and their combined application (HM)—affect plow-layer pore structure, and quantified the relationships between pore structure characteristics and saturated hydraulic conductivity (Ks) and air permeability (Ka). 【Method】A 15-year field experiment was conducted on red soil sloping cropland. Intact soil cores from the plow layer were scanned using high-resolution X-ray computed tomography (CT) to characterize pore structure under CK, H, M, and HM. Soil saturated hydraulic conductivity (Ks) and air permeability (Ka) were measured the same cores to assess water and gas transport and to relate functional properties to CT-derived pore metrics.【Result】Compared to CK, HM significantly increased macropore porosity (>60 μm), the largest connected macropore porosity, hydraulic radius, porosity of pores >150 μm, mean pore diameter, and global connectivity by 79.0%, 113%, 30.2%, 112%, 51.2%, and 54.4%, respectively (P < 0.05). HM also significantly increased biopore porosity and maximum biopore diameter by 129% and 80.0%, respectively (P < 0.05). Straw mulching alone (M) significantly increased Ks by 5.46% (P < 0.05), whereas H and HM treatments significantly increased Ka by 8.15% and 9.02%, respectively (P < 0.05). Ka was positively correlated with macropore porosity, the largest connected macropore porosity, hydraulic radius, porosity of pores >300 μm, and critical pore radius (P < 0.05). Among biopore parameters, Ka was positively correlated with biopore porosity and biopore length density (P < 0.05). 【Conclusion】Long-term integration of vetiver hedgerows (vetiveria zizanioide) with straw mulching substantially improved plow-layer pore structure and enhanced soil air permeability in red soil sloping cropland, providing practical evidence to support optimized soil and water conservation and plow-layer structural improvement in this region.

• Structural and Interfacial Mechanisms of Soil Organic Carbon Stabilization Under Wildfire Disturbance

  WEI Jing, MENG Xinru, TU Chen, LIANG Yan, DENG Shaopo, WHITE C. Jason, LUO Yongming

  DOI: 10.11766/trxb202604270214

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  Wildfire is an important natural disturbance affecting terrestrial ecosystem carbon cycling under global change, and the increasing frequency and intensity of wildfire events are continuously reshaping the migration, transformation, and stabilization of post-fire soil organic carbon. This review focuses on the structural and interfacial mechanisms of soil organic carbon stabilization following wildfire disturbance and systematically synthesizes the roles of soil structural change, mineral interfacial reactions, and microbial processes in regulating post-fire carbon pool dynamics. Wildfire first causes rapid losses of surface soil organic carbon through high-temperature combustion and pyrolysis, while also inducing aggregate breakdown, pore structure reorganization, enhanced soil water repellency, and intensified runoff and erosion. These changes alter the exposure of organic carbon, its vertical migration within soil profiles, and its lateral redistribution from hillslopes to depositional zones. At the same time, thermally induced dehydroxylation of clay minerals, crystallization of iron and aluminum oxides, and the formation of pyrogenic mineral phases can reshape mineral surface reactivity and interfacial binding conditions. These effects do not simply increase or decrease mineral protection, but depend on fire severity, mineral composition, heating duration, and soil background conditions, thereby influencing the pathways and efficiency by which pyrogenic dissolved organic matter, pyrogenic carbon, plant-derived organic matter, and microbial necromass enter mineral protection systems. At the biological level, post-fire microbial communities undergo a successional shift from rapid reassembly to metabolic strategy transition. In the early stage, microbial activity promotes rapid turnover of labile carbon, whereas in later stages, enzymatic oxidation, metabolite release, necromass accumulation, and microbe–mineral electron transfer can drive the transformation of organic carbon from labile or mobile forms toward mineral-associated and physically protected states. Overall, the evolution of post-fire soil carbon pools is not governed by any single process but results from the combined effects of structural disturbance, erosion–deposition redistribution, mineral interfacial reconstruction, and microbial transformation. A systematic synthesis of these processes and their coupling relationships is important for improving mechanistic understanding of soil carbon stabilization under wildfire disturbance and for supporting post-fire carbon sink assessment and ecosystem management.

• Effects of Different Fertilization Practices on the Structure and Function of Microbial Communities in Tobacco-Growing Soil

  liusina, dongjianxin, xialonglong, xiaoxin, suwenyan, zhangguangyu, congping

  DOI: 10.11766/trxb202601070014

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  This study aimed to investigate the differential responses of rhizosphere and bulk soil microbial diversity to long-term fertilization and to identify the key nutrient drivers. 【Method】 Rhizosphere and bulk soils were collected from tobacco plants under five treatments in a long-term field experiment established in 2010. The samples were collected from plots with no fertilization (CK), inorganic fertilizer alone (NPK), organic fertilizer alone (OM), combined inorganic and organic fertilization (NPKO), and inorganic fertilizer plus green manure incorporation (NPKG). Using high-throughput sequencing, soil physicochemical analyses, and functional prediction, we evaluated the effects of different fertilization treatments on the composition, diversity, and potential functions of bacterial and fungal communities in rhizosphere and bulk soils. 【Result】 The results showed that long-term fertilization significantly altered bacterial community structure in both rhizosphere and bulk soil, whereas fungal community structure responded significantly only in bulk soil. Proteobacteria, Actinobacteriota, Acidobacteriota, Ascomycota, and Basidiomycota were the dominant phyla shared by both habitats. Fertilization generally promoted the enrichment of Sphingomonas. Meanwhile, compared with CK, the relative abundance of Fusarium under NPKG increased significantly by 117.20%, whereas NPKO increased the abundance of Humicola in the rhizosphere and reduced Fusarium to the lowest level among all treatments, representing a 42.86% decrease relative to CK. Also, fertilization significantly increased soil carbon (32.32%–159.76%) and nitrogen (17.68%–229.80%) fractions. Soil pH, total nitrogen, total organic carbon, and dissolved organic carbon were the key factors driving rhizosphere bacterial succession (P < 0.05), whereas bulk soil fungal communities were mainly driven by alkali-hydrolyzable nitrogen. Fertilization enhanced the potential functions of bulk soil bacteria related to carbon and nitrogen metabolism and transmembrane transport. In addition, NPKO not only strengthened the potential of fungi to decompose complex organic substrates, but also reduced the predicted abundance of functions associated with potential rhizosphere pathogens.【Conclusion】 Bacterial and fungal communities showed clear habitat-specific responses to long-term fertilization, with their succession driven primarily by multiple nutrient factors in the rhizosphere soil and by alkaline hydrolyzable nitrogen in bulk soil. Additionally, combined organic–inorganic fertilization was more effective in coordinating nutrient turnover and maintaining rhizosphere microecological health.

• Simulation Study on Soil Moisture under Different Soil-Rock Structure in Karst Areas

  LI Yanqiu, PENG Tao, ZHOU Li, GUI Yuxiang, XU Shaoqiang, CAO Le, ZHAI Jiang, WANG Shijie

  DOI: 10.11766/trxb202512190602

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  Abstract:

  【Objective】The highly heterogeneous soil-rock structure in the karst area of Southwest China affects the soil hydrological process. Clarifying its controlling effect and driving factors on soil moisture is of great significance for understanding the regional hydrological cycle and improving the ecological governance of rock desertification. 【Method】Taking two typical lithologies (limestone and dolomite) as the research objects, this study designed 12 simulated soil tanks with different soil-rock structure. Based on soil moisture data (at 10, 20, 40, 70, and 100 cm soil depths) and meteorological monitoring data (precipitation, temperature, and humidity) from the hydrological year spanning March 2023 to February 2024, this study employs statistical analysis and fitting methods to investigate the characteristics of soil moisture variation across different soil-rock structures. It further examines how soil moisture content differences are influenced by both soil-rock structure characteristics and meteorological factors.【Result】The results showed that the fluctuation of soil moisture in different karst soil-rock structure decreased with the increase of soil depth; the soil moisture (11.07~43.21%) and coefficient of variation of each limestone soil-rock structure in the rainy period were higher than those in the dry period, the soil moisture in the 40~70 cm soil layer was the lowest while the storage in the 100 cm layer was relatively high, and the soil water storage was jointly controlled by the soil-rock ratio (negative correlation) and the thickness of the surface soil layer (positive correlation), with the fitting formula Z=-24.48X+0.88Y+100.47 (R2=0.9328) ; the soil moisture of dolomite was concentrated and lower than that of limestone, the average value in the rainy period (18.36~28.70%) was slightly higher than that in the dry period (15.10~25.53%), the coefficient of variation in the dry period was higher, and the soil water storage increased exponentially with the increase of soil thickness, with the fitting formula Z=13.85e(X/12.70)-13.26 (R2=0.9958) ; the soil water storage of limestone was significantly correlated with precipitation and relative humidity, while dolomite was only significantly correlated with relative humidity.【Conclusion】This study reveals the regulatory mechanism of lithology difference-dominated soil-rock structure on the variation characteristics and storage of karst soil moisture, clarifies that soil-rock fabric is a key factor in karst soil hydrology research, and provides data support and theoretical reference for regional eco-hydrological research and rock desertification governance.

• Determining Soil Thickness Using Ground-Penetrating Radar in the Pisha Sandstone Area, China

  HU Jian, ZHANG Zhiao, CAO Tao, LIU Xinyue, ZHEN Qing

  DOI: 10.11766/trxb202604210203

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  【Objective】The thickness of the loess layer overlying the Pisha sandstone area is crucial for regional ecological restoration; however, efficient detection methods are still lacking. Although ground-penetrating radar (GPR), owing to its rapid and non-destructive advantages, has been successfully applied in areas underlain by residual parent material, its suitability for detecting the soil–rock interface in regions covered by transported parent material (loess) has not yet been systematically validated. This study therefore aimed to evaluate the applicability of GPR for loess thickness determination in the Pisha sandstone area and to assess the performance of the Topp model in estimating the dielectric permittivity of loess in this region. 【Method】GPR was employed to measure loess thickness on three typical vegetation slopes (shrubland, arbor land, and grassland) in the Pisha sandstone area. The dielectric permittivity of loess was calibrated in situ through field excavation and pre-buried iron pipes. The measured permittivity values were compared with predictions from the Topp model to assess the model’s performance in this region, and the GPR-derived loess thicknesses were compared with actual excavation depths to evaluate the measurement accuracy of GPR. 【Result】The results showed that the measured relative dielectric permittivities of loess were 13.33, 19.57, and 13.92 for shrubland, arbor land, and grassland, respectively. The Topp model predicted loess dielectric permittivity with an accuracy ranging from 92.51% to 97.23%, showing no significant difference from the measured values. Also, the accuracy of GPR in determining loess thickness ranged from 87.16% to 97.78%, and the measured depths did not differ significantly from the actual burial depths. On all three slopes, loess thickness exhibited a clear increasing trend from the upper to the lower slope positions. The grassland had the largest average thickness (36.16 cm), while the arbor land had the smallest (19.06 cm). 【Conclusion】This study provides an efficient and accurate method for soil thickness investigation in the Pisha sandstone area and offers fundamental data support for soil and water conservation and hydrological process research in this region.

• Molecular Characteristics of Organic Matter in Red Paddy Soil Under Long-Term Different Fertilisation Treatments

  LIU Qing, LIU Ming, LI Zhongpei, QIU Cunpu, LI Xin, WU Meng

  DOI: 10.11766/trxb202602020076

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  Abstract:

  【Objective】The molecular composition of soil organic matter (SOM) is central to understanding carbon cycling in agroecosystems. However, how the SOM molecular composition evolves under long-term different fertilization regimes remains poorly understood. This study aimed to elucidate the regulatory mechanisms of long-term fertilization on SOM molecular composition in red soil paddy fields.【Method】Based on a long-term field experiment, four treatments were selected: no fertilizer (CK), organic matter recycling (C), chemical NPK fertilizers (NPK), and chemical NPK fertilizers plus organic matter recycling (NPKC). Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was employed to analyze the molecular composition of SOM.【Result】(1) All fertilization treatments significantly increased soil organic carbon (SOC) and total nitrogen (TN) contents, while the NPK treatment specifically enhanced dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) contents. (2) CHO-type compounds dominated the SOM composition, accounting for 64.0% of all identified molecular formulas. (3) Compared with CK, fertilization, especially NPKC, significantly increased the relative abundance of lipid-like compounds, whereas CK enriched more plant-derived lignin-like compounds. (4) Different fertilization treatments altered the molecular classes of SOM. Specifically, the molecular composition of lipids, tannins, lignins, and carbohydrates differed significantly among fertilization treatments, whereas the responses of condensed aromatics and unsaturated hydrocarbons to fertilization were not significant.【Conclusion】This study demonstrates that long-term fertilization reshapes the molecular composition of SOM in red soil paddy fields primarily by regulating key components, including carbohydrates, tannins, lipids. This and lignins, provides direct molecular evidence for fertilization-induced alterations in soil organic matter composition.

• Quantitative Inversion of Hematite in Tongling Red Earth Based on Diffuse Reflectance Spectroscopy and Its Environmental Significance

  ZHANG Futian, YANG Lihui, ZHU Min, LIU Xinyu, ZHAO Shuo

  DOI: 10.11766/trxb202602270101

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  Red earth sediments, widely distributed in southern China, are important archives of Quaternary environmental evolution in the mid-low latitudes. Hematite (Hm) within these sediments is a key indicator of dry and hot paleoclimates. However, traditional chemical methods fall short for rapid and precise quantification in complex soil matrices. Diffuse reflectance spectroscopy (DRS) combined with multiple linear regression (MLR) was used to quantify Hm content under complex mineral backgrounds. Applied to the Tongling red earth profile in the lower Yangtze River, this approach reconstructed the Hm content record since the Middle Pleistocene. The results show a good correspondence between the reconstructed hematite Hm content and the redness index (a*), validating the reliability of a* as a Hm proxy from an absolute data perspective. Moreover, this quantitative result provides evidence for deciphering the magnetic depletion mechanism in vermiculated red earth and demonstrates the utility of DRS in paleoenvironmental studies of southern Chinese red earth. Thus, DRS-based quantitative inversion is an effective tool for analyzing complex multi-source sediments and improves the ability to identify multi-stage pedogenic overprinting in southern red earth.

• Effects of Salt Stress on the Functional Genes Related to Organic Phosphorus Mineralization in the Rhizosphere Microbiome of Puccinellia distans

  XU Shanshan, LI Qing, LI Bo, LI Yanjie, ZHANG Ran, YANG Liang, LU Yingshuai, XU Yudan, ZHAO Xiang, CHEN Xiaopeng

  DOI: 10.11766/trxb202602040081

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  【Objective】??Soil salinization imposes combined stresses of high salinity and phosphorus (P) deficiency, thereby severely constraining plant growth. Puccinellia distans is a salt-tolerant halophyte; however, the response mechanisms of its rhizosphere microbiome to salt stress, particularly concerning organic P mineralization functional genes, remain poorly understood. This study aimed to clarify the response patterns of organic P mineralization functional genes in the rhizosphere of P. distans and to identify the underlying mechanisms. It is hypothesized that salt stress affects these microbial functional genes indirectly by altering soil physicochemical properties and root traits, which subsequently reshape root exudation patterns. 【Method】A controlled pot experiment was conducted using P. distans under five NaCl-induced salt stress gradients: control (0 g·kg-1), light (2 g·kg-1), moderate (4 g·kg-1), severe (6 g·kg-1), and extreme (8 g·kg-1). After 30 days of continuous salt stress, rhizosphere and bulk soil samples were collected. Metagenomic sequencing was employed to determine the relative abundances of key genes involved in organic P mineralization, including phnM, 3-Phytase, phnI, phnL, phoA, phoD, phnH, and phnW. Analysis of variance (ANOVA), Pearson correlation, random forest models, and partial least squares structural equation modeling (PLS-SEM) were used to identify the major drivers and causal pathways underlying changes in these genes under salt stress.【Result】??Salt stress significantly altered the relative abundances of phnM, 3-Phytase, phnI, phnL, and phoA genes in the rhizosphere, whereas only phoA and phnW responded significantly in bulk soil; phoD and phnH were not significantly affected. In the rhizosphere, 3-Phytase, phnI, phnL, and phoA exhibited a unimodal pattern, initially increasing and then decreasing with increasing salt stress. Under severe stress, the abundances of phnM, phnI, phnL, and phoA increased by 24.7%, 34.5%, 52.9%, and 34.7%, respectively; while 3-Phytase increased by 8.0% and 7.2% under moderate and severe stress. In bulk soil, phoA increased by 26.0% and 17.5% under severe and extreme stress, while phnW decreased by 13.3% under extreme stress. Correlation analysis showed that in the rhizosphere, soil electrical conductivity (EC) and salinity were positively correlated with several genes, whereas root traits were generally negatively correlated with them. Among root exudates, quinones were positively correlated with phoA, 3-Phytase, phnL, and phnM, whereas terpenoids and stilbenes showed negative correlations. PLS-SEM further indicated that salt stress enhanced soil EC (path coefficient = 0.882, P<0.001), which inhibited root exudation (terpenoids, stilbenes, quinones; path coefficient = -0.79, P<0.001), subsequently influencing the abundances of rhizosphere organic P mineralization genes (path coefficient = -0.49, P<0.05) (R2=0.72). In bulk soil, salt stress primarily affected phoA by altering soil properties and inhibiting exudates (R2=0.82).【Conclusion】??Salt stress differentially impacts the relative abundances of organic P mineralization genes in the rhizosphere and bulk soil of P. distans, with the rhizosphere exhibiting a more pronounced adaptive response. By altering electrical conductivity and simplifying root architecture, salt stress further reshapes root exudation patterns, which in turn regulates the relative abundances of rhizosphere microbial organic P mineralization genes, thereby contributing to plant P acquisition strategy. These findings provide molecular insights into the salt tolerance mechanisms of P. distans and offer a theoretical basis for the sustainable use of saline-alkali soils.

• Advances and Perspectives on the Role of Microbial Extracellular Polymeric Substances (EPS) in Soil Organic Carbon Stabilization

  YI Yuwei, WU Yichao, ZHANG Ming, DAI Ke, GAO Chunhui, QU Chenchen, HUANG Qiaoyun, CAI Peng

  DOI: 10.11766/trxb202511230558

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  Extracellular polymeric substances (EPS), as a key component of soil organic carbon (SOC) sequestration, have long been overlooked. Although the prevalent theories emphasize microbial cell residues as the dominant contributor to SOC formation, emerging evidence indicates that EPS is widely present in soils and is produced at rates comparable to or even higher than cellular biomass, representing a major pathway of microbially derived carbon input into soils. This review systematically synthesizes current knowledge, with a focus on the distinctive role of EPS in soil carbon stabilization. We summarized four key mechanisms through which EPS promote soil organic carbon stability: the formation of mineral-associated organic matter, participation in geopolymerization reactions, driving the formation of soil aggregates, and regulating pore structure. This reveals the pathway for achieving carbon sequestration through both direct and indirect effects. Following our findings, we outline future research priorities, emphasizing the need to develop reliable extraction and quantification methods, incorporate EPS dynamics into SOC models, and elucidate the environmental and microbial factors regulating EPS production and degradation. Addressing these gaps will significantly advance our understanding of microbial roles in the global carbon cycle and inform strategies for enhancing soil carbon sequestration.

• Research Progress on the Acidification of Shajiang Black Soil: Current Status, Driving Factors, and Remediation Strategies

  HAN Tianfu, GUO Zichun, ZHAO Yanfeng, CHEN Jie, ZHANG Huimin, LIU Kailou, WANG Huiying, ZHANG Shuiqing

  DOI: 10.11766/trxb202511160547

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  Abstract:

  Shajiang black soil is a major cultivated soil type distributed in the Huang–Huai–Hai region of China. It is characterized by a heavy clay texture, compact structure, low organic matter content, and poor nutrient availability. In recent years, the acidification of Shajiang black soil has become increasingly prominent due to multiple factors, including long-term intensive fertilization, acid deposition, and nutrient removal by crops. This issue has emerged as one of the key constraints on sustainable agricultural development in the region. Soil acidification not only weakens the buffering capacity and nutrient-supplying capacity of Shajiang black soil but also leads to soil structural degradation, microbial community imbalance, and reductions in crop yield. This review synthesizes current research progress on the acidification of Shajiang black soil, with a focus on its status and characteristics, major driving factors, and underlying mechanisms, as well as commonly applied amelioration and management strategies. Furthermore, it analyzes contemporary research hotspots and future development directions, and proposes a classification-based prevention and mitigation framework centered on optimizing tillage systems, improving nutrient resource management, selecting appropriate soil amendments, and enhancing biological synergistic interactions. This framework can provide scientific guidance for the graded amelioration and fertility restoration of acidified Shajiang black soil.

• Rapid Identification and Spatial Prediction of the Black Soil Layer Thickness Based on GPR and VMD Integrated Methods

  JIA Zhihui, LUO Fangzhou, YU Dongsheng, HU Wenyou, ZHANG Daoyu, JIANG jun, GAO Zhang, XU Yingde, RAO Wenbo, KUANG Enjun, ZHANG Jiuming

  DOI: 10.11766/trxb202511250565

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  Abstract:

  【Objective】The thinning of the black soil layer is one of the primary issues in black soil degradation, and accurate identification of its thickness and spatial variations holds significant importance for the protection and sustainable utilization of black soils. This study aimed to integrate ground penetrating radar (GPR) and variational mode decomposition (VMD) technologies to develop methods for in-situ identification and spatial prediction of black soil layer thickness.【Method】Three typical slope surfaces with thick, medium, and thin black soil layers in Nenjiang, Heilongjiang Province, were selected as the study sites. The 700 MHz GPR was used to detect the black soil layer thickness along the slope surfaces and validated the GPR identification accuracy using data from soil drilling and profile surveys. The VMD technology was applied to decompose the GPR signals, selected key modal components through spectrum analysis, and combined this with envelope analysis to precisely identify the black soil layer thickness. Furthermore, the sparse sampling (lateral ratio of 50:1 and longitudinal ratio of 100:1) and natural neighborhood interpolation was applied to predict the spatial distribution of black soil layer thickness at the slope scale.【Result】The GPR-VMD method effectively separated noise from the signals, resulting in root mean square errors for black soil layer thickness detection at the profile scale ranging from 2.03 to 6.86 cm. The average root mean square errors for the thick, medium, and thin black soil layers were 6.26, 4.30, and 3.73 cm, respectively. Overall, across all validation points, the overall detection root mean square error was approximately 6.08 cm, the overall prediction error was controlled within 9.7%, and the overall coefficient of determination (R2) reached 0.94. At the slope scale, the spatial predictions of black soil layer thickness showed significant correlations with measured data (R2 > 0.87), enabling efficient, non-destructive, and continuous detection of black soil layer thickness. The generated spatial distribution maps revealed associations between black soil layer thickness and factors such as slope position and terrain, illustrating gradient changes and spatial differentiation patterns induced by erosion processes.【Conclusion】The integration of GPR and VMD methods achieves efficient, non-destructive, and high-precision in-situ identification and spatial prediction of black soil layer thickness in typical black soil regions of Northeast China. This study provides important methodological and technical support for revealing the spatial-temporal variations and underlying mechanisms influencing black soil layer thickness.

• The Effect of Food Waste Composting on Soil Salinity in Subtropical Vegetable Fields

  WANG Jiantong, CHEN Jiayi, MOHAMMAD Jawad Alami, HUANG Wei, CUI Shenghui, GAO Bing

  DOI: 10.11766/trxb202512110590

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  Abstract:

  【Objective】The composting and return of food waste to the soil are of great significance to the sustainable development of urban food systems. However, it is still unclear how the salt in this composted food remains affects the soil in the long run. Thus, this study aimed to investigate the risk of soil salinization caused by salt (NaCl) carried by food waste composted using different methods. 【Method】A four-season field observation experiment was conducted in vegetable plots. A total of five treatments were established: nitrogen-free control (CK), conventional chemical fertilizer (CF), conventional chicken manure + chemical fertilizer (MF), food waste aerobic compost + chemical fertilizer (FWAF), food waste digestate + chemical fertilizer (FWDF). Vegetable yield, soil electrical conductivity (EC) at a depth of 0-20 cm, sodium (Na+) and chloride (Cl-) concentrations, soil sodium adsorption ratio (SAR), plant uptake of Na+ and Cl-, and the annual input-output balance of soil Na+ and Cl- were measured. 【Result】The results showed: (1) Under conditions of 20% nitrogen reduction, both methods of food waste composting increased vegetable yields compared with CF and MF treatments, with the FWDF treatment showing a significant increase. (2) Compared with the CF and MF treatments, food waste composting had no significant effect on soil electrical conductivity (EC), and none of the treated soils reached the level of salinization. (3) The SAR values for the FWAF and FWDF treatments were significantly lower than those for the CF treatment, but there was no significant difference compared with the MF treatment. Also, the SAR values for all treatments were below the risk threshold (<13). (4) In the top 0-20 cm soil layer, the Na+ content in the FWAF treatment was 25.5% higher than in the CF treatment, but there was no significant difference compared with the MF treatment. However, the Cl- content in the FWAF and FWDF treatments was significantly higher than in the CF treatment, but there was no significant difference compared with the MF treatment. (5) The Na+ and Cl- balance indicated that shallow irrigation water in the study area was the primary source of soil Na+ and Cl-, accounting for 51%-73% and 63%-85% of total Na+ and Cl- inputs, respectively, which was significantly higher than the contribution from aerobic food waste compost (Na+ 29%, Cl- 14%) and anaerobic food waste digestate (Na+ 11%, Cl- 2%). 【Conclusion】In coastal regions, the NaCl introduced into the soil through the application of compost from aerobic kitchen waste and anaerobic digester sludge is not a major factor in soil salinization. In the south-eastern coastal and southern regions of China, where rainfall causes intense leaching, the risk of residual Na+ and Cl- in soil resulting from the composting of both types of food waste remains at a manageable level compared to the use of traditional organic fertilizer (chicken manure). These regions are therefore priority areas for the application of food waste compost to farmland.

• Changes in Aliphatic Acids and Their Driving Factors in the Black Soils under Continuous Cultivation in Northeast China

  CHEN Haihao, LI Ye, CHEN Zengming, DING Weixin

  DOI: 10.11766/trxb202601110026

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  【Objective】Aliphatic acids are widely regarded as one of the most recalcitrant and stable components of soil organic matter, and their abundance and molecular composition provide molecular-level indicators for assessing the extent of soil organic matter decomposition and accumulation. Therefore, elucidating the dynamics and controlling factors of the relatively labile free aliphatic acid fraction in soils is therefore critical for advancing mechanistic understanding of soil organic matter degradation under long-term agricultural cultivation, particularly in the black soils. Thus, this study aimed to characterize changes in the content and composition of free aliphatic acids along a century-long cultivation chronosequence and to identify the key environmental drivers regulating their dynamics. 【Method】Soil samples were collected from a 5?100 year dryland cultivation chronosequence in the Sanjiang Plain, Northeast China. Changes in the concentrations and molecular characteristics of free aliphatic acids during soil organic matter depletion were quantified. Random forest models were applied to assess the relative importance of soil physicochemical properties in regulating short-chain and long-chain aliphatic acids. 【Result】The results show that long-term cultivation markedly reduced soil free aliphatic acid contents, with a 58.4% decline from 5 to 100 years after reclamation, substantially exceeding the decrease in SOC (47.6%). This indicates that free aliphatic acids are more sensitive to cultivation disturbance than bulk soil organic matter. Prolonged cultivation induced pronounced shifts in molecular composition, characterized by a 43.9% reduction in the relative contribution of short-chain aliphatic acids to SOC and a concurrent 30.2% increase in long-chain aliphatic acids, resulting in a significant increase in average chain length (ACL). After 100 years of cultivation, unsaturated aliphatic acids in black soils declined by 80.2%, accompanied by a significant decrease of 17.7% in the carbon preference index (CPI), indicating intensified decomposition losses of plant-derived aliphatic acids. Collectively, these molecular-level changes demonstrate a progressive enhancement of soil organic matter decomposition under conventional straw removal management in the Mollisols. Correlation analysis and random forest modeling further demonstrated that the rapid depletion of short-chain aliphatic acids was mainly driven by reduced availability of labile carbon substrates and enhanced microbial decomposition, whereas long-chain aliphatic acids were preferentially preserved due to their higher chemical recalcitrance and association with clay minerals. 【Conclusion】Enhancing external organic matter inputs, such as through straw return, may help replenish labile carbon pools and mitigate the progressive loss of stable soil organic matter fractions. Overall, this study provides new molecular-level insights into cultivation-induced soil organic matter degradation and offers a scientific basis for the sustainable management and conservation of black soils.

• Mechanisms of Zn Migration and Translocation in a Soil-Rice System Revealed by Isotope Fractionation

  Lin Yufeng, Cao Kaiwen, Yin Guangcai, Pan Dandan, Su Pengji, zhong Songxiong

  DOI: 10.11766/trxb202601120028

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  Abstract:

  【Objective】Fluctuation in water levels has a significant influence on the bioavailability of zinc (Zn) and its ecotoxicological impact. However, the effects of water regimes on Zn isotope fractionation and gene expression, and the subsequent role of water management modulation on Zn uptake and transport in rice remains timidly explored. Thus, this study elucidates the mechanisms controlling Zn mobilization and translocation in a soil-rice system at the jointing stage under two contrasting water management regimes (flooding and drainage).【Method】A controlled pot experiment was conducted to investigate Zn isotope fractionation in soil pools, pore water, and rice organs. Zn stable isotopes were measured across bulk soil, HCl- and CaCl2-extractable fractions, iron plaques on root surfaces, and pore water. Rice plants were sampled for roots, stems, leaves, and shoots, and gene expression analyses of key Zn transporters were performed using quantitative real-time PCR. The genes included OsZIP3, OsZIP4, OsZIP5, OsZIP7a, OsZIP8, OsZIP9, OsHMA2, OsHMA3, OsNAS3, OsNAAT1, OsTOM2, and OsYSL15. Isotope fractionation values (Δ66Zn) were calculated between different soil and plant pools, and water management effects were assessed.【Result】 Zn isotope fractionation in soil exhibited similar patterns under both water regimes. Relative to bulk soil, HCl-extractable and CaCl2-extractable Zn and root-surface iron plaques were enriched in heavier Zn isotopes, whereas pore water was enriched in lighter Zn isotopes. The mean fractionation values were Δ66ZnHCl?soil = 0.40‰ ± 0.05‰, Δ66ZnCaCl2?soil = 0.45‰ ± 0.03‰, and Δ66Znpore water?soil = ?0.095‰ ± 0.035‰. Zn uptake by rice plants displayed water-regime-dependent isotope fractionation. Specifically, under flooding, Δ66Znrice?pore water = 0.16‰ ± 0.09‰, whereas under drainage, Δ66Znrice?pore water = 0.06‰ ± 0.08‰. In contrast, Zn translocation from roots to shoots (Δ66Znshoot?root = 0.32‰ to 0.36‰) and from stems to leaves (Δ66Znleaf?stem = ?0.11‰ to ?0.09‰) was largely unaffected by water regime, suggesting that translocation fractionation is less sensitive to water management. At the molecular level, flooding significantly upregulated root expression of OsZIP5 and OsZIP9, responsible for Zn uptake, and OsNAAT1, OsTOM2, and OsYSL15, which mediate the synthesis and secretion of deoxymugineic acid (DMA) and uptake of Zn-DMA complexes. Flooding also increased OsHMA3 expression in roots, facilitating vacuolar sequestration of Zn, while concurrently suppressing OsHMA2 expression, which mediates root-to-shoot transport of Zn2+. Meanwhile, the expression of root-to-shoot transporters OsZIP3, OsZIP4, OsZIP7a, and OsZIP8, as well as OsNAS3 involved in nicotianamine synthesis, was modulated to maintain Zn homeostasis and promote xylem loading. These coordinated gene expression patterns indicate that flooding enhances root absorption of Zn(II)-DMA and heavier Zn2+ through specific ZIP transporters and facilitates the translocation of both Zn(II)-nicotianamine (NA) complexes and Zn2+ to shoots via OsYSL15 and other dedicated transporters.【Conclusion】The integration of Zn stable isotope fractionation with gene expression data reveals that water management strongly influences Zn uptake and transport mechanisms in rice. Flooding promotes the preferential uptake of heavier Zn isotopes via DMA chelation and ZIP-mediated pathways, enhances vacuolar Zn sequestration, and coordinates efficient root-to-shoot translocation, whereas drainage reduces isotopic fractionation during uptake but maintains root-to-shoot transport. This study provides mechanistic insights into the water-regime-dependent regulation of Zn absorption and translocation, highlighting the role of specific transporters and chelators in controlling Zn isotope fractionation and its movement through the soil-rice system. These findings offer a foundational understanding for optimizing Zn nutrition in rice under different water management strategies and can inform agronomic interventions aimed at improving micronutrient use efficiency.

• Impacts and underlying mechanisms of climate change factors on CH₄ Emissions from Coastal Wetlands

  YU Xuchen, PENG Sili, LIU Deyan, HAN Guangxuan, DING Weixin, YUAN Junji

  DOI: 10.11766/trxb202601270063

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  Abstract:

  【Objective】Coastal wetlands serve as crucial "blue carbon" sinks for mitigating climate change, while they also represent significant sources of marine methane (CH₄) emissions. However, the impacts of multiple climate change factors on CH₄ emissions from coastal wetlands has not been systematically evaluated. 【Method】This study integrated 241 observational datasets from 41 peer-reviewed papers published between 1995 and 2025, and comprehensively analyzed the effects of elevated atmospheric CO₂ concentration (eCO₂), warming and sea level rise(SLR) on the CH₄ emissions from coastal wetlands.【Result】The results indicated that eCO₂ increased CH₄ emissions by an average of 33.26%, but had no significant effect on wetlands dominated by C4 plants. Furthermore, prolonged eCO? exposure was found to attenuate its stimulatory effect on CH? emissions. Warming increased CH₄ emissions by 58.15% on average. The promoting effect was stronger with greater warming magnitudes, and active warming had a more pronounced effect than passive warming. Nitrogen addition significantly weakened the stimulatory effect of warming on CH₄ emissions. SLR exerted the most pronounced stimulatory effect on CH? emissions, with an increase of 112.85%, which was significantly negatively correlated with salinity. Additionally, the interactive effect of warming and SLR significantly enhanced CH? emissions, with a response magnitude markedly higher than that under warming alone.【Conclusion】Overall, eCO₂, warming, and SLR as individual drivers significantly enhanced CH₄ emissions from coastal wetlands, but the magnitude of their effects was regulated by both biotic and abiotic factors, and interactions among climate drivers were highly complex. Therefore, future studies should prioritize multifactorial simulation experiments to elucidate how multiple climate change drivers and their interactions synergistically regulate CH? emissions through biotic and abiotic pathways, thereby improving predictions of greenhouse gas feedbacks from coastal wetlands under ongoing climate change.

• Inversion of Electrical Conductivity of Soil Profile Extracts Using Electrical Resistivity Tomography in the Hetao Irrigation District

  LIU Xuelian, WU Huayong, WANG Huihui, LU Ying, YANG Fei, ZHAO Yuguo, ZHANG Ganlin

  DOI: 10.11766/trxb202603020107

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  Abstract:

  【Objective】This study aimed to provide a scientific basis for rapid monitoring and regionalized classification-based reclamation of salinized soils by constructing an inversion model for electrical conductivity (EC1:5) of soil profile extracts in salinized areas of Northwest China.【Method】Typical saline-alkali farmland in the Hetao Irrigation District was selected as the study area. Electrical resistivity tomography (ERT) was used to obtain soil resistivity profiles with lengths of 35.5~71 m and depths of 0–6 m. Meanwhile, nine boreholes (3~5 m deep) were sampled by layers to measure soil EC1:5, water content, and bulk density. Based on pedogenetic theory, soil resistivity, depth, water content, and bulk density were selected as input variables. Random forest (RF), support vector machine (SVM), extreme gradient boosting (XGBoost), and linear regression (LR) algorithms were applied to perform EC1:5 inversion at a field scale.【Result】The results indicate that soil resistivity and depth were the dominant variables controlling EC1:5 inversion, while water content and bulk density had relatively minor contributions. Among the models, the RF model achieved the best performance, with an independent validation R² of 0.65 and a root mean square error (RMSE) of 56.51 μS·cm⁻¹, effectively matching the vertical variation characteristics of electrical conductivity measured in the nine boreholes. The inverted soil EC1:5 exhibited significant spatial heterogeneity on the two-dimensional profile, ranging from 170.58 to 441.01 μS·cm⁻¹, with a mean value of 275.48 ± 58.81 μS·cm⁻¹, which is opposite to the variation characteristics of soil resistivity.【Conclusion】The ERT-based inversion method for soil profile EC1:5 demonstrated good applicability and can effectively compensate for the limited vertical resolution of electromagnetic induction (EMI) techniques. It provides reliable technology for the rapid acquisition of high-resolution salinity information in soil profiles.

• Vertical Differentiation Characteristics and Main Controlling Factors of Soil Acid Buffering Capacity in the Red Soil Critical Zone Derived from Different Lithologies

  LI Yaqiong, WU Huayong, †, LI Jifu, SONG Xiaodong, YANG Shunhua, WANG Zhao, ZHANG Ganlin

  DOI: 10.11766/trxb202512080586

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  Abstract:

  【Objective】This study aimed to analyze the characteristics and influencing factors of soil acid buffering capacity (pHBC) in the critical zone of forested red soils derived from different lithologies, to provide a theoretical basis for controlling red soil acidification and maintaining the stability of forest ecosystems in southern China. 【Method】The selected soils within the forested red soil critical zone are derived from phyllite, red sandstone, and granite. Soil samples were collected at depths of 4.5-6.0 m and were systematically analyzed for pHBC, pH, mechanical composition, mineral composition, as well as the contents of organic matter, iron and aluminum oxides, exchangeable acidity, and exchangeable base cations. Based on soil acid buffering theory, linear regression and random forest modeling were employed to analyze the vertical variation of soil pHBC and its main influencing factors. 【Result】Soil pHBC showed distinct vertical differentiation: it decreased with increasing depth within a certain range, and increased after reaching an inflection point. Within the pH range of 4.4-5.6, the vertical variation of pHBC was primarily governed by soil pH, clay content, and organic matter content, showing a monotonic increase with decreasing pH and increasing clay and organic matter. Under the overall dominance of pH, the pHBC of phyllite-derived soils showed significant positive linear correlations with the contents of organic matter, clay, kaolinite, and crystalline iron oxides. In the red sandstone-derived soils, pHBC correlated positively with the contents of clay, silt, kaolinite, and amorphous aluminum oxides. For granite-derived soils, pHBC was positively correlated with the contents of organic matter, clay, silt, hydromica, amorphous aluminum oxides, crystalline aluminum oxides, exchangeable K+, and exchangeable Na+. 【Conclusion】Soils within the studied red soil critical zone are highly weathered, featuring high exchangeable acidity and aluminum saturation but low total exchangeable base cation content that varied little with depth. Within the 4.5–6.0 m depth range, base cation exchange contributed minimally to pHBC. The primary buffering mechanisms were proton adsorption onto solid surfaces (organic matter, clay, silt, iron and aluminum oxides, kaolinite) and the dissolution of aluminum oxides. Secondary silicate clay minerals, along with minor amounts of primary minerals such as anorthite, albite, and microcline, also provided a measurable acid buffering effect via mineral dissolution reactions.

• Soil Methane Emission Effects and Microbial Mechanisms of Rice Field Soils with Different Rice Straw Application Rates over 13 Consecutive Years

  LI Yuying, HUANG Qiong, JIN Keda, ZHANG Guangbin, MA Jing, XU Hua

  DOI: 10.11766/trxb202511100537

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  Abstract:

  【Objective】This study was designed to investigate the long-term effects of straw returning on methane (CH4) emissions in rice paddies and their microbial driving mechanisms to provide a theoretical basis for optimizing long-term straw returning management and synergistically achieving “carbon sequestration and emission reduction”.【Method】Based on a continuous 13-year (2006-2018) field experiment with rice-wheat rotation, four straw returning gradients were established: S0 (control at 0?t·hm-2), S1 (1.6?t·hm-2), S2 (3.2?t·hm-2), and S3 (4.8?t·hm-2). The changes in CH4 emissions during the rice season (2017-2018) and related soil environmental factors were observed.【Result】The results showed a significant positive correlation between straw returning amount and cumulative CH4 emissions, with the cumulative emissions in S1, S2, and S3 treatments increasing by 166%-219%, 420%-527%, and 660%-785% compared to S0, respectively. The microbial mechanism lies in the fact that straw input enhances soil organic carbon and dissolved organic carbon content while reducing soil redox potential, creating a strongly anaerobic environment. This significantly increases the abundance of methanogenic functional genes (mcrA) (with average increases of 2.5, 3.8, and 3.6 times compared to S0 for S1, S2, and S3, respectively) and enriches the Methanosarcinaceae family, which metabolizes multiple substrates, leading to a substantial increase in CH4 production potential (S3 increased by 246% compared to S0). Although the abundance and oxidation potential of methanotrophic functional genes (pmoA) also increased, the growth was far lower than the production potential, resulting in a metabolic imbalance of “more production than oxidation”, further exacerbating net CH4 emissions. Although S3 could enhance soil carbon sequestration rates, it had the highest mitigation benefit offset rate (12.93). In contrast, under conditions where there was no significant difference in mitigation benefit offset rates, S1 achieved the lowest CH4 emission coefficient (5.05%), while S2 achieved the highest carbon sequestration rate (2.27?t?CO2-eq t·hm-2·a-1), indicating that moderate straw returning optimally synergizes carbon sequestration and emission reduction. 【Conclusion】The results of this study reveal that moderate straw returning is a key measure to reconcile the contradiction between “carbon sequestration” and “emission reduction” in rice paddies.

• Research Status and Hotspots of Soil and Plant Diversity Based on Bibliometric Analysis

  DING Yu, ZHANG Ning, LI Jing, SUN Yunjuan, JIANG Jianchun

  DOI: 10.11766/trxb202512050582

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  Abstract:

  【Objective】This study aimed to understand the research status and future development trend of soil and plant diversity-related fields.【Method】The research status, hotspots, and frontier trends in soil and plant diversity using bibliometrics and CiteSpace visualization software, based on the core database of Web of Science (WOS) and the China National Knowledge Infrastructure (CNKI) database, were systematically analyzed.【Result】The results showed that the total number of publications in both Chinese and English within the field of soil and plant diversity continued to rise from 2000 to 2024, showing an explosive growth around 2016. The total number of articles published in the CNKI database was 17.72% of those in the WOS database. Also, the number of publications in the field of soil and plant diversity in China and the United States accounted for 34.85% and 24.35% of the total number of papers, respectively. Chinese Academy of Sciences, University of California System, and Centre National de la Recherche Scientifique were the main publishing institutions and hubs. Keywords of Chinese literature mainly focused on diversity, plant community, soil nutrients, and environmental factors, with the research frontiers including functional traits, altitude gradient, redundancy analysis, Pinus massoniana, and β-diversity. The keywords of English literature mainly revolved around plant diversity, biodiversity, species richness, vegetation, and community, with the research frontiers encompassing ecosystem multifunctionality, nitrogen addition, phylogenetic diversity, etc. This paper summarizes the dilemmas of dimension imbalance, scale limitation and path dependence in the current research, and puts forward some suggestions, such as constructing multi-trophic interaction network, promoting the two-way interaction between local empirical and global models, from correlation to causal mechanism analysis and constructing biodiversity-oriented ecological management technology.【Conclusion】Future research should focus on promoting the bidirectional internationalization of achievements with Chinese ecological characteristics and the localization of international frontier methods， thereby realizing the mutual development of regional practice and global theory.

• 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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  Abstract:

  【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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  Abstract:

  【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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  Abstract:

  【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.

• 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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  Abstract:

  【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.

• 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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  Abstract:

  【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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  Abstract:

  【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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  Abstract:

  【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.

• 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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  Abstract:

  【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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  Abstract:

  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 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.

• 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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  【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.

• 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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  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.

• 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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  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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  【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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  【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.

• 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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  【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.

• 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.

• 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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  Abstract:

  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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  Abstract:

  【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.

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

  lixiaoyong, wanghuan, zhengyue, wuyicheng

  DOI: 10.11766/trxb202503280141

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  【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.

• 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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  【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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  【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.

• 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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  【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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  【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.

• 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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  Abstract:

  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.

• 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.

• 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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  【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.

• Prediction of Soil Thickness in Hilly and Mountainous Regions Based on the Integration of Machine Learning and Geostatistics

  WANG Bin, ZHANG Tian, RAO Luman, CI En

  DOI: 10.11766/trxb202512200605

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  Abstract:

  【Objective】The hilly region of western Chongqing is a transitional zone characterized by fragmented terrain and substantial elevation gradients, where soil thickness exhibits pronounced spatial variability driven by complex geomorphic processes. Soil thickness is a key indicator of soil resource status and plays a critical role in hydrological processes, ecosystem productivity, and geological hazard assessment. Traditional models used for soil thickness prediction often lack generalizability in hilly regions due to pronounced spatial heterogeneity, while pure machine learning approaches tend to overlook inherent spatial autocorrelation, potentially introducing local prediction biases. Therefore, accurate spatial prediction is essential for understanding soil resource distribution and supporting sustainable land management. 【Method】Based on 117 soil profiles (2020–2025) and 38 environmental covariates spanning topography, climate, remote sensing, parent material, and human activities, three benchmark models were compared: multiple linear regression (MLR), random forest (RF), and extreme gradient boosting (XGBoost) against a hybrid model, random forest residual Kriging (RFRK). A multi-stage variable selection procedure incorporating variance inflation factor, boruta algorithm, and recursive feature elimination addressed multicollinearity and overfitting. Climate variables (1 km) were resampled to 12.5 m via bilinear interpolation. After excluding five outliers (3σ/5σ criteria), 112 valid samples were partitioned into training (80%) and validation (20%) sets. Model performance was assessed using mean absolute error (MAE), root mean square error (RMSE), coefficient of determination (R2), and Lin’s concordance correlation coefficient (LCCC). For RFRK, variogram analysis characterized residual spatial structure, with model hyperparameters optimized through grid search. 【Result】(1) The screening strategy reduced 38 covariates to seven core variables, ranked by importance: total catchment area (TCA) > channel network baseline (CNBL) > soil enhancement index 2 (SER2) > channel network distance (CND) > soil enhancement index 1 (SER1) > aspect (ASP) > slope (SLP). This subset (five topographic, two remote sensing) underscores terrain-driven material redistribution as the primary control on soil thickness. (2) RFRK achieved the highest accuracy (R2 = 0.68, LCCC = 0.79, MAE = 14.59 cm, RMSE = 19.86 cm), significantly outperforming all benchmarks. Relative to the best benchmark (RF), RFRK improved R2 by 9.7%, reduced MAE by 12.3%, and reduced RMSE by 6.2%. MLR performed the poorest (R2 = 0.37), whereas XGBoost was intermediate (R2 = 0.56). (3) Variogram analysis revealed strong residual spatial autocorrelation (nugget/sill = 0.0017; range = 179.08 m), justifying kriging for local bias correction. The predicted map showed “thick northeast/southwest, thin central,” with thick layers (>80 cm) in valleys and gentle slopes, and thin layers (0–40 cm) on steep ridges and areas with intense anthropogenic disturbance. 【Conclusion】The RFRK hybrid model, integrating machine learning for nonlinear responses with geostatistical modeling of residual autocorrelation, characterizes soil thickness patterns in complex terrains more accurately than pure machine learning or linear models. This study validates the VIF-Boruta-RFE screening strategy and confirms RFRK’s superiority in capturing both deterministic environmental controls and stochastic spatial structures. The findings provide robust technical support for soil resource assessment and management and offer a generalizable methodological reference for digital soil mapping in comparable hilly and mountainous landscapes worldwide.