Insights and Perspectives

• Mechanisms of Organic Carbon Sequestration and Stabilization Mediated by the Soil “Mineral Carbon Pump(MnCP)”

  XIAO Keqing, LI Xinnan, XING Wen, FENG Mengxi, ZHANG Ming, ZHAO Yao, ZHU Yongguan

  2025,62(3):595-609, DOI: 10.11766/trxb202404250169

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  Abstract:

  Soil organic carbon (SOC) is the largest carbon pool in terrestrial ecosystems and plays a key role in preventing soil degradation, conserving soil health, and addressing global climate change. Soil minerals are important component of the soil solid phase, and their interaction with soil organic carbon directly affects soil interfacial activity, physicochemical properties, and fertility status. The concept of mineral carbon pump (MnCP) emphasizes the crucial role of soil minerals in driving the active organic carbon sequestration, and elaborates on the function of minerals in the process of soil organic carbon stabilization. This review takes the mineral-mediated soil carbon sequestration process as the main line, systematically sorts out the concept of MnCP, introduces in detail the five MnCP-mediated carbon sequestration mechanisms, influencing factors, and related characterization techniques. Key scientific issues that need further exploration within the MnCP framework are proposed in the end.

Reviews and Comments

• Research Progress of Combined Effects Between High Temperatures and Hydrophobic Organic Compounds on Soil Fauna

  XIAO Naichuan, DAI Wencai, WANG Zifang, YOU Lelin, ZHAO Huan, ZHANG Yarong, GAO Ming

  2025,62(3):610-624, DOI: 10.11766/trxb202404290178

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  Soil fauna constitutes a vital component of soil ecosystems and plays a crucial role in ecosystem functioning. The high temperature caused by global warming will cause damage to soil fauna and affect their ecological functions. In addition, chemical pollutants released by human activities can also have toxic effects on soil fauna. Hydrophobic organic compounds (HOCs) are a kind of widely prevalent class of pollutants in soil. The combined effects of high temperatures and HOCs can impact soil fauna, and the tests for HOC risk assessment are typically conducted at optimal temperatures for the test species, resulting in inaccurate outcomes due to the disregard of temperature effects. Currently, there is a lack of in-depth understanding of the combined effects and mechanisms of high temperatures and HOCs on soil fauna. Therefore, we systematically reviewed the studies on the combined effects of different high-temperature scenarios and HOCs on soil fauna, and the significance of these studies in environmental risk assessment. Our discussion highlights that future research should focus on the combined effects of HOCs and high temperatures in real-world scenarios, particularly at the molecular level, and enhance the development and application of ecotoxicological models. This will improve our understanding of HOCs in the natural world and refine existing methods of environmental risk assessment to better address the challenges ecosystems face under climate change.

• Developments and Prospects of Research on Size Exclusion Effects in the Transport of Colloids in Porous Media

  WANG Changxi, SHEN Chongyang, LIAO Renkuan

  2025,62(3):625-639, DOI: 10.11766/trxb202406180241

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  Abstract:

  Colloids are among the most active components in agricultural soils and their large specific surface area and surface charge make them highly susceptible to pollutant adsorption. During the water cycle in the saturated-unsaturated zone, colloids can carry contaminants through porous media via size exclusion effects, leading to accelerated diffusion and significant impacts on groundwater quality. This paper reviews the size exclusion mechanisms of colloid transport in porous media, systematically analyses the key factors influencing the size exclusion effects of colloid transport, and summarizes the mathematical models used to describe the size exclusion effect of colloid transport. Finally, it explores high-precision tracer methods for characterizing colloid transport behavior and discusses strategies for constructing mathematical models to depict size exclusion effects in colloid transport. This study holds significant implications for deepening the understanding of environmental effects associated with colloid transport in the saturated-unsaturated zone water cycle and guiding the prevention and control of groundwater pollution in farmlands.

Research Articles

• Impacts of Simulated Erosion and Fertilization on Soil Quality and Corn Yield in Northeastern Black Soil Region

  WANG Zhiqiang, LI Yangyang, ZHANG Xiaoping

  2025,62(3):640-652, DOI: 10.11766/trxb202401220038

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  【Objective】 Soil erosion is a major factor causing soil degradation and crop productivity reduction in the northeast black soil region. However, the in situ systematic and quantitative assessment of the effects of erosion on soil quality and crop productivity remains unclear. 【Method】 A long-term field experiment on erosion-productivity relation was set up at Heshan Farm, Heilongjiang Province in 2005 based on comprehensive effects of erosion and tillage on soil profile. The experiment was a two-factor completely randomized block design with simulated erosion depth (8 levels of 0, 10, 20, 30, 40, 50, 60, and 70 cm)and fertilization (no fertilization and fertilization), totaling 16 treatments with 3 replications per treatment. In 2022, a series of soil physicochemical properties [bulk density (BD), soil water content (SWC), clay content, pH, soil organic C(SOC), alkali-hydrolyzed N(AN), Olsen-P(AP) and available K(AK)] and biological properties [microbial biomass C and N(MBC, MBN), catalase, urease, β-glucosidase, cellulase activity] in 0-20 cm soil layer and corn yield were measured after 18 years of the setup. 【Result】 1) Soil clay content, SOC, AN, AP, MBC and cellulase activities decreased significantly with the increase of simulated erosion depth, while soil BD and AK increased significantly. Also, fertilization significantly decreased soil BD, pH, AK, and catalase activity, but increased clay content, SOC, AN, AP, and the activities of urease, β-glucosidase, and cellulase. Interestingly, fertilization weakened the correlation between soil urease activity, BD and other physicochemical properties. 2) Simulated erosion resulted in significant reductions in soil quality and corn yield, the decrease mainly occurred before the erosion depth of 40 cm. Soil quality index decreased by 28.1% for the unfertilized treatment and 26.7% for the fertilized treatment, and yield loss was 45.8% for the unfertilized treatment and 11.7% for the fertilized treatment at 40 cm of erosion depth. Additionally, fertilization increased the soil quality index by 7.0% and corn yield by 3.0 fold. 3) The main factors affecting soil quality under simulated erosion were cellulase activity, MBC and AN for the unfertilized treatment, and cellulase activity, MBC, AP for the fertilized treatment. Also, the main factors affecting corn yield under long-term simulated erosion were AN for the unfertilized treatment and AP for the fertilized treatment. 【Conclusion】 These results quantified the degree of soil erosion on soil quality and productivity and clarified the major factors affecting soil quality and productivity in black soil, and can serve as reference for the restoration of degraded black soil.

• Prediction of Soil Carbon-to-Nitrogen Ratio Based on Visible-Near Infrared and Mid-Infrared Spectroscopy

  KONG Xiangqi, GAO Weichang, PAN Wenjie, CAI Kai, YANG Jing, LI Decheng, ZHENG Gaunghui, ZENG Rong

  2025,62(3):653-664, DOI: 10.11766/trxb202404120152

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  【Objective】 The soil carbon-to-nitrogen ratio (C/N) reflects not only soil quality but also the nutrient balance of soil carbon and nitrogen elements. Thus, rapid and accurate determination of this ratio and the grade is crucial for guiding real-time scientific fertilization and improvement of soil quality. 【Method】 This study used visible-near infrared (VNIR) and mid-infrared (MIR) spectroscopic data, along with total organic carbon (TOC), total nitrogen (TN), and C/N data from 501 typical tobacco-corn rotation farmland topsoil samples(0～20 cm) in Guizhou Province for characterization. After processing the spectra with Savitzky-Golay (SG) smoothing and standard normalization, three modeling methods were applied: partial least squares regression (PLSR), random forest (RF), and Cubist. Models for predicting soil C/N were constructed using both direct prediction of C/N and indirect prediction (first predicting TOC and TN, then calculating C/N), and the precision of C/N value and grade predictions was analyzed. 【Result】 The results revealed that: (1) For C/N value prediction, the optimal prediction strategy was direct prediction using MIR-PLSR, which had a prediction precision(relative standard error, RPD) of 1.20; (2) C/N grade could be accurately predicted, with the optimal strategy being direct prediction using the MIR-PLSR model, achieving a grade determination accuracy of 0.71; (3) The main reasons for the low prediction accuracy of C/N values are twofold. First, the uniform stringent fertilization measures in the tobacco fields have reduced the spatial variation in the carbon and nitrogen content of the plow layer soil, thereby also reducing the spatial variation of C/N(the coefficient of variation is 17.15%, indicating moderate variation). Second, the correlation between C/N and both VNIR and MIR spectra was relatively low. 【Conclusion】 Therefore, the MIR-PLSR model can be used for direct prediction of C/N grades.

• Assessing the Impacts of Extreme High Temperatures and Long-term Warming on Paddy Soil Organic Carbon Based on the DNDC Model-A Case Study in Zhangzhou of Fujian Province

  LI Jing, CHEN Weiming, SUN Jiarui, XIE Xilin, ZHANG Hua, SHEN Jinquan, LIAO Wenqiang, XING Shihe, ZHANG Liming

  2025,62(3):665-676, DOI: 10.11766/trxb202402070064

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  【Objective】 Soil organic carbon(SOC) is an essential indicator of soil health. It not only provides a carbon source for plant growth and maintains the physical structure of soil, but also releases carbon into the atmosphere in the form of greenhouse gases, such as carbon dioxide. Therefore, it plays a critical role in the global carbon balance. Currently, the world is experiencing climate change characterized predominantly by warming and increasing frequency and intensity of extreme weather events. However, the impacts of the changing climate, including long-term warming and extreme weather events on SOC are not entirely the same. Distinguishing and quantifying the effects of extremely high temperatures (EH) and long-term warming(LW) on SOC is the key to formulating adaptive strategies. 【Method】 In this study, we focused on paddy soils in Zhangzhou of Fujian Province, a typical subtropical region of China. Based on a 1: 50, 000 detailed soil database, we employed the biogeochemical process model (DeNitrification-DeComposition, DNDC) to simulate SOC dynamics under four climate scenarios: de-trended climate base state (CTRL), extreme high temperatures (EXP_EH), long-term warming (EXP_LW), and measured temperatures (EXP_obs). 【Result】 The results revealed that the total amount of carbon sequestered by paddy fields in Zhangzhou from 1980 to 2016 under the four different climate scenarios (CTRL, EXP_EH, EXP_LW, and EXP_obs) was 1, 032.17, 952.15, 1, 045.98 and 966.03 Gg, with the corresponding average annual sequestration rates of 93.98, 86.70, 95.24, and 87.96 kg·hm^-2, respectively. The long-term warming led to a net increase of 13.81 Gg of SOC in paddy fields across Zhangzhou, while extremely high temperatures resulted in a net decrease of 80.02 Gg. The combined effect of these two factors was -66.14 Gg in SOC, indicating that long-term warming promoted the sequestration of organic carbon in paddy soils, while extremely high temperatures reduced the soil carbon sink capacity, with extremely high temperatures exerting a dominant negative effect. Also, the variations in annual carbon sequestration rates between different climate scenarios indicated that extremely high temperatures throughout the years from 1980 to 2016 had a negative effect on carbon sequestration in the paddy soils of Zhangzhou, but the long-term warming effect on SOC turned from positive to negative around the year of 2000. This may be related to the diminishing effect of warming on plant growth over time. At the county level, climate change had the greatest impact on the carbon sequestration of Nanjing County. Additionally, the extremely high temperatures and long-term warming caused -26.23% and 7.27% impacts on its carbon sequestration rate, respectively. Furthermore, among different terrain and topographical areas, the carbon sequestration rate of hilly and mountainous areas was significantly affected by extremely high temperatures and long-term warming, with -8.84% and 1.98% changes, respectively. 【Conclusion】 In conclusion, while the paddy soils in Zhangzhou still maintain a strong carbon sequestration capacity in the context of climate change, the increasing extreme high-temperature events in the future may potentially contribute to greater carbon losses to some extent.

• Characteristics of Spatial Distribution of Soil Organic Carbon in Anhui Province Based on Soil Profile Occurrence Layer and Environmental Variables

  GAO Wenjing, XIA Bing, LU Yuanyuan, YING Rongrong, HU Pengjie, LI Yixu, CHEN Hongfeng, QIAN Jiazhong

  2025,62(3):677-691, DOI: 10.11766/trxb202402040063

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  【Objective】 Soil organic carbon (SOC) plays an important role in the global carbon cycle, and extremely small changes in SOC could cause dramatic changes in atmospheric CO₂ concentration. Accurately grasping the spatial distribution characteristics of SOC and its main controlling factors is an important requirement for improving soil carbon sequestration potential and coping with climate change. Therefore, this study aimed to analyze the spatial distribution of SOC in the topsoil layer (A genetic horizon), subsoil layer (B genetic horizon), and parent material layer(Parent material)in Anhui Province from the perspective of the soil profile occurrence layer and explore the factors controlling the changes of SOC in different profile occurrence layers. 【Method】 In this study, a total of 451 sites were distributed in the study area using the systematic distribution method combined with the judgmental distribution method. The basic soil parameters, such as SOC content, pH, soil texture, and bulk density, were obtained from 451 sites through wild sampling and indoor experiments. Meanwhile, the related environmental variables, such as climatic factors, topographic factors, and normalized difference vegetation index, were also collected. Also, we used geostatistical methods to obtain the best half-variance function model and spatial distribution characteristics of SOC content at different soil profile levels, as well as correlation analysis and random forest regression analysis to explore the influencing factors of spatial differences in SOC content. 【Result】 The results showed that the average organic carbon content of the soil profile in Anhui Province was 8.47 g·kg^-1 and there was a phenomenon of surface aggregation of SOC, whose occurrence in the layer was as follows: A genetic horizon: 15.86 g·kg^-1＞ B genetic horizon: 5.80 g·kg^-1＞ Parent material: 3.74 g·kg^-1 and all of them had moderate spatial variability. The spatial distribution map of SOC showed that the spatial distribution of organic carbon content in each occurrence layer was generally increasing from north to south. We also found that there were some differences in the driving factors of SOC content in different profiles of the occurrence layer. In the A genetic horizon, soil texture, and bulk density were the most important factors affecting SOC content; as the depth of the soil layer increased, the influence of topographic factors and soil texture gradually strengthened on the accumulation of SOC content in the B genetic horizon. For the Parent material, the influence of soil texture, topographic factors, and bulk density were all more influential on the SOC content. 【Conclusion】 Soil texture is the main factor driving the spatial distribution characteristics of SOC in Anhui Province, but the effects of topographic factors and bulk density should also be fully considered in the subsequent development of SOC control measures, to provide theoretical support for improving soil quality and coping with climate change.

• The Decomposition Characteristic of Crop Straws and Their Released Dissolved Organic Matter Properties

  YIN Yingjie, SHANG Jianying

  2025,62(3):692-704, DOI: 10.11766/trxb202311130472

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  【Objective】 It is an essential prerequisite to understanding the environmental behavior of straw carbon in farmland soil to understand the decomposition characteristics of crop straw and the properties of dissolved organic matter (DOM) released. However, the information on straw decomposition characteristics obtained from relevant studies needs to be more comprehensive and requires further investigation. 【Method】 In this study, the straws of corn, wheat, soybean, and rape were laboratory incubated for 69 days. The two-dimensional correlation-Fourier transform infrared spectroscopy (2D-COS-FTIR), ultraviolet-visible spectroscopy (UV-Vis), three-dimensional excitation-emission-matrix spectra (3D-EEM), and parallel factor analysis (PARAFAC) were employed to monitor the changes in the components of straw during decomposition (0-69 days), as well as the humification characteristics of their released DOM. 【Result】 The results showed a double increase in corn, wheat, and corn straws during their decomposition period, and all four straws reached maturity at 65-69 d. At the end of decomposition, the mass loss rates of the four straws were 56.8 %(rape), 51.1 %(corn), 48.5 %(soybean), and 44.0 %(wheat), respectively. Although the decomposition order of different substances differed in the four straws, the decomposing intensity of functional groups on the surface of the corn, wheat, and rape straw exhibited the same order (C=O > O-H > -CH₂ > -COO^-) but the soybean straw showed a different order. The dissolved organic carbon (DOC) content released by the corn, wheat, soybean, and rape straws gradually decreased and was stable at 69 days of decomposition, of which the DOC content was 23.6, 12.2, 17.2, and 10.7 mg·g^-1 biomass, respectively. During the decomposition, the SUVA₂₅₄ value and aromaticity of DOM released from decomposed corn and soybean straws gradually increased, and the E₂/E₃ value gradually decreased. In contrast, those in wheat and rape straws showed a fluctuating trend. At the end of the decomposition, the aromaticity of DOM released from decomposed corn, wheat, soybean, and rape straw was 20.58, 10.55, 17.45, and 8.32, as well as the E₂/E₃ value being 3.27, 4.29, 3.16, and 5.77. In addition, the aromaticity of maize and soybean straw DOM was higher than that of wheat and rape straw, and the E₂/E₃ value showed the opposite trend. The 3D-EEM results showed that though the DOM composition in the four crop straws varied, a similar conversion was observed from protein-like substances (I + II) to humic-like and fulvic-like substances (III + V). Four fluorescence components in the straw DOM identified by the parallel factor analysis model showed similar results. Finally, the humic-like substances (C2 and C4) comprised 35.0%-41.9%, and the fulvic-like substances (C1) accounted for 19.9%-42.9%. In contrast, the protein-like substances(C3) only accounted for 10.0%-29.4%. 【Conclusion】 Our study revealed that the decomposition of straw and the content of its released DOM were influenced by the type of crop, while the substance degradation strength and transformation pattern remained consistent.

• Study on Gross Nitrogen Transformation Rates of Soils Under Different Land Use Types in Caohai Nature Reserve

  LANG Man, NIE Hao, ZHU Sixi, LI Ping

  2025,62(3):705-715, DOI: 10.11766/trxb202403110102

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  【Objective】 To understand the effects of land use type change on soil N cycle and eco-environment, this study aimed to elucidate the gross N transformation rates in soils under different land use types. 【Method】 A laboratory incubation experiment was conducted using a ¹⁵N labeled technique and the numerical FLUAZ model to study the difference of gross N transformation rates among soils under different land use types such as wetland, dryland, vegetable land, and forest land in the Caohai nature reserve located in the Yunnan-Guizhou Plateau. 【Result】 The results showed that land use type significantly affected gross N transformation rates in the soils. Wetland soil had the highest rates of gross N mineralization (11.95 mg·kg^-1·d^-1) and immobilization (6.13 mg·kg^-1·d^-1) while the forest soil had the lowest gross N mineralization rate (2.39 mg·kg^-1·d^-1), but the gross N immobilization rate (2.09 mg·kg^-1·d^-1) was comparable to that of dryland soil and vegetable soil (2.29 and 1.52 mg·kg^-1·d^-1, respectively). The gross nitrification rate of forest soil (0.77 mg·kg^-1·d^-1) was significantly lower than that of wetland soil, dryland soil, and vegetable soil(2.68, 6.33 and 5.39 mg·kg^-1·d^-1, respectively). The ratios of gross nitrification to NH₄⁺ immobilization and gross N mineralization to the immobilization of dryland soil and vegetable soil were both >1, whereas the ratio of gross nitrification to NH₄⁺ immobilization rate was <1 in wetland soil and forest soil, and the ratio of gross N mineralization to the immobilization rate was close to 1 in forest soil. The gross N mineralization rate was significantly positively correlated with soil organic carbon (SOC), total nitrogen (TN), C/N ratio, and soil pH, and significantly negatively correlated with silt content. Also, the gross N immobilization rate and ammonium immobilization rate were significantly positively correlated with SOC, TN, water-soluble organic C(SOC_w), and soil pH, and significantly negatively correlated with silt content. The gross nitrification rate was significantly negatively correlated with SOC_w and clay content and significantly positively correlated with sand content. 【Conclusion】 The results indicate that in comparison with the wetland soil, dryland soil, and vegetable soil, the mineralization and immobilization processes in forest soil were more tightly coupled, thereby decreasing the occurrence of nitrification and subsequent NO₃^- loss to the environment. The results of this study can provide a scientific basis for the rational layout of land use and the evaluation of the environmental effects of ecological restoration projects within the Caohai Nature Reserve.

• Effect and Mechanism of Food Waste Compost on the Stability of Paddy Soil Aggregates

  AO Hui, CHEN Chong, ZHOU Hu

  2025,62(3):716-728, DOI: 10.11766/trxb202402240077

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  【Objective】 Food waste composting is one of the potential directions of food waste resource utilization. Food waste compost is rich in organic matter and salt, and its impact on soil aggregates is still unclear. Exploring the influence of food waste compost application on the stability of paddy soil aggregates and its mechanism can provide references for agricultural utilization of food waste compost. 【Method】 Six treatments were set up in this study: No fertilizer (CK), Chemical fertilizer (F), Food waste fresh compost (FC), Food waste aged compost (AC), Chicken manure organic fertilizer (CM), Pig manure organic fertilizer(PM), The effects of these treatments and the influence of food waste compost on the stability of soil aggregates and soil surface electrochemical parameters were investigated. Correlation analysis and redundancy analysis (RDA) were used to investigate the main factors affecting the stability of aggregates. 【Result】 The results showed that: (1) Food waste compost enhanced the water stability of paddy soil aggregates, and reduced the slaking and differential swelling effects. Also, the MWD_Yoder, MWD_LB-fast,and MWD_LB-slow of AC were 21.4%, 107.8%, and 49.3% higher than CK, respectively. (2) The electrochemical properties of the soil surface were the main factors affecting the stability of aggregates and the surface charge density of the four organic fertilizers increased by 29.0%-45.2%. (3) Organic matter has a significant correlation with surface charge density, specific surface area, and surface charge number, and the correlation coefficients are 0.67, 0.53, and -0.63, respectively. Furthermore, exchangeable calcium showed a significant positive correlation with organic matter and the correlation coefficient was 0.90. 【Conclusion】 Food waste compost can enhance the surface charge density of soil by increasing soil organic matter, thus increasing the cementation between exchangeable calcium and soil particles and enhancing the stability of soil aggregates.

• Dynamics and Influencing Factors of Transpiration of Pinus sylvestris in the Sandy Region of Yulin in Northern Shaanxi Province

  WANG Xuanzhen, DUAN Yizhong, HUANG Laiming, PEI Yanwu, WANG Ziwei

  2025,62(3):729-739, DOI: 10.11766/trxb202403120106

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  Pinus sylvestris var. mongholica is one of the major vegetation restoration trees in the northern sand-prevention belt of China, which plays a vital role in the sheltering of wind and sand fixation, regulating regional microclimate, and maintaining ecosystem stability. 【Objective】 This study seeks to clarify the dynamics and controlling factors of transpiration in P. sylvestris plantations in water-limited sandy regions and provide a scientific basis for the reasonable construction and sustainable management of artificial plants. 【Method】 This study used the thermal dissipation probes, soil moisture sensor, automatic weather station, and groundwater level monitor to continuously observe the sap flow density, soil moisture content, meteorological parameters, and groundwater level in the sandy region of Yulin City, northern Shaanxi Province. With this design, we aimed to reveal the characteristics and controlling factors of transpiration water consumption of P. sylvestris. 【Result】 Results showed that: (1) The sap flow density of P. sylvestris increased initially and then decreased during the monitored period (May 2021 to October 2021). On a sunny day, the sap flow density displayed an unimodal curve and had a relatively high peak value; however, on cloudy and rainy days, the sap flow density varied irregularly and had relatively low peak values. (2) The sap flow density was most sensitive to the changes in wind speed and air temperature, followed by groundwater level fluctuation. (3) The average daily transpiration rate of P. sylvestris was 0.67 mm·d^-1, and the total transpiration water consumption in the growing season was 147 mm. 【Discussion】 The seasonal variations of meteorological parameters (vapour pressure deficiency, wind speed, air temperture, photosynthetically active radiation) and groundwater level and the associated changes in soil water content were the main factors controlling the dynamics of transpiration water consumption of P. sylvestris. The study results can provide theoretical guidance for high efficient use of water resources and sustainable management of sand-fixing plants in the sandy region.

• Effect of Shewanella putrefaciens CN32 and Geobacter sulfurreducens PCA Co-culture on Mercury Transformation Mediated by Dissolved Organic Matter

  SONG En, WANG Yuncheng, JIANG Yangzhao, ZHAO Haoyu, HU Dafu, HU Yujie, BIAN Yongrong, YANG Xinglun, YE Mao, JIANG Xin

  2025,62(3):740-751, DOI: 10.11766/trxb202402030060

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  【Objective】 A variety of dissolved organic matter (DOM) and microorganisms affect mercury transformation under anaerobic conditions by mediating biogeochemical cycles. However, it is still unclear how specific organic matter would affect mercury transformation under this condition. 【Method】 Using batch experiments, the effect of DOM and the co-culture of microorganisms on mercury transformation were investigated. Under simulated the anaerobic environment, three kinds of DOM(cysteine and glutathione containing sulfhydryl and fulvic acid) and two kinds of bacteria (Shewanella putrefaciens CN32 and Geobacter sulfurreducens PCA) were selected to create a reduction environment and methylated mercury, respectively. Batch experiments were carried out to investigate the effect of DOM and the co-culture of microorganisms on mercury transformation. 【Result】 The results showed that the unit cell adsorption/uptake capacity of G. sulfurreducens PCA for Hg(Ⅱ) was 69.0% of that of S. putrefaciens CN32. Cysteine and glutathione did not alter the proportion of intracellular mercury in G. sulfurreducens PCA, but the proportion of intracellular mercury in S. putrefaciens CN32 was decreased. In the culture of G. sulfurreducens PCA, cysteine promoted mercury reduction and methylation, glutathione promoted mercury reduction, and fulvic acid inhibited mercury reduction and methylation. In the co-culture system of S. putrefaciens CN32 and G. sulfurreducens PCA, the mercury methylation ratio was as high as 18.7%±3.1% after the addition of cysteine complexed mercury, which was mainly attributed to the enhancement of Hg methylation of G. sulfurreducens PCA by microbial co-culture. 【Conclusion】 The results of this study elucidate the mechanism of DOM and co-culture of microorganisms on mercury species transformation in anaerobic condition, and provide a theoretical basis for the remediation of mercury pollution in flooded paddy field wetland.

• Mechanisms of Mn-modified Biochar to Mediate Inorganic Arsenic Speciation in the Soil-Solution System

  HUANG Qin, TONG Fei, WANG Bo, DU Xiaofei, FAN Guangping, LIU Lizhu, ZHANG Mingchao, QIU Yige, GAO Yan

  2025,62(3):752-765, DOI: 10.11766/trxb202401030007

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  【Objective】 The reductive release of arsenic (As) from paddy soils can be enhanced under waterlogged conditions. This study aimed to investigate the mechanisms of Mn-modified biochar (MBC), with high oxidation and adsorption capacity, on inhibiting As release in the waterlogged paddy soil microcosms and to reveal the potential pathways of mediating As transformation and speciation in soil solution and soil. 【Method】 This study determined changes in the basic properties of soil solution, soil, and biochar through mixed or separate incubation of biochar and flooded soil. 【Result】 The results showed that, compared with the control and unmodified biochar, MBC significantly promoted the oxidation of As (III) to As(V) in the soil solution, keeping a low concentration of As(III) (0.02-0.88 mg·L^-1) throughout the incubation period. The Mn released from MBC into the soil solution was readily precipitated with As(V). Also, the MBC containing rich pore structure and oxygen-containing functional groups would promote its adsorption for more inorganic arsenic (iAs). MBC showed greater affinity for Fe (3.12 mg·g^-1 of Fe was adsorbed on MBC after 28 d), leading to a significant decrease of Fe concentrations in the soil solution (P < 0.05) and enhanced the adsorption of iAs on the solid-phase. The reduction of Mn-oxides on MBC increased the pH (0.08-0.22 pH units) of the soil solution, which further promoted the precipitation of Fe on the solid phase thereby strengthening its adsorption for iAs. As a result, the concentration of iAs extracted from the MBC was 12 times higher than that of the unmodified biochar after incubation of 28 d. The high oxidative properties of MBC inhibited the reductive dissolution of Fe minerals, thereby significantly reducing the soil-available Fe and As concentrations (P < 0.05). This led to the transformation of soil available As to iron-manganese bound and residual fraction As. As a result, the soil available As was stabilized under a lower range of concentrations. 【Conclusion】 Generally, the addition of MBC to waterlogged paddy soil can inhibit the release of iAs from the solid phase and promote the transformation of mobile iAs into more stable forms in the soil, resulting in a significant reduction in arsenic mobility and toxicity in waterlogged paddy soil.

• Amelioration of Acidic Purple Soil with Calcareous Purple Mudstones

  CHEN Jingjing, GUO Xinyi, LI Zhongyi, YU Junfeng, WU Wenchun, ZHOU Jia

  2025,62(3):766-778, DOI: 10.11766/trxb202403170116

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  【Objective】 Extensive regions of purple soil are afflicted by acidification, whereas calcareous purple mudstones, distinguished by their alkaline pH, abundant mineral composition, and low heavy metal content, are theoretically well-suited to ameliorating acidic purple soil in their vicinity. 【Method】 An 80-day laboratory incubation experiment was conducted to evaluate the effectiveness of calcareous purple mudstones in ameliorating acidic purple soil. The geological ages of the two parent rocks were the Jurassic Shaximiao Formation (J₂s) and the Jurassic Suining Formation (J₃sn). 【Result】 The findings revealed that both purple mudstones effectively neutralized soil acidity, enhanced soil potassium content and, increased potassium bioavailability, and reduced the bioavailability of heavy metals. These mudstones offer a promising solution for improving acidic purple soil, thereby promoting soil health and fertility. Compared to J₂s mudstone, J₃sn mudstone exhibited a superior overall improvement effect on acidic purple soil due to its richer calcium content. (1) When J₂s mudstone was added to acidic purple soil at rates of 2%, 5%, and 10%, the soil pH increased gradually from 4.73 to 4.93, 5.30, and 6.27, respectively. Concurrently, the soil exchangeable acidity decreased from 2.84 cmol·kg^-1 to 2.79, 1.40, and 0.70 cmol·kg^-1, respectively. Differently, when J₃sn mudstone was added at the same rates, the pH of the acidic purple soil increased significantly to 7.20, 7.87, and 8.00, achieving neutral to alkaline levels. Notably, no exchangeable H⁺ or Al³⁺ was detected in the soil after the addition of J₃sn mudstone. Additionally, the addition of both mudstones resulted in an increase in soil exchangeable Ca²⁺, effective cation exchange capacity, and base saturation. (2) Overall, the addition of both J₂s and J₃sn mudstones to acidic purple soil resulted in a gradual increase in the contents of rapidly available potassium (K), slowly available K, and total K. Specifically, after an 80-day incubation period, the proportion of soil available K to total K increased from 1.58% to 1.76%, 1.88%, and 2.08% with the addition of 2%, 5%, and 10% J₂s mudstone, respectively. In comparison, the addition of J₃sn mudstone at the same rates led to a more significant increase in the proportion of available K to total K, reaching 1.91%, 2.01%, and 2.24%, respectively. (3) The addition of purple mudstones did not significantly increase the content of total heavy metals (Cu, Zn, Ni, Pb, Cd) in soil, but it significantly decreased the available heavy metal content in proportion to the total content. This reduction was more pronounced with the addition of J₃sn mudstone compared to J₂s mudstone, indicating its superior passivation effects on heavy metals in acidic purple soil. 【Conclusion】 Given the widespread availability, cost-effectiveness, ease of crushing, and convenience of application of calcareous purple rocks in regions where purple parent rocks are naturally exposed, they offer a practical solution for improving acidic purple soil. It is recommended that, under field conditions, 15～45 tons per ha of J₃sn mudstone or 75～120 tons per ha of J₂s mudstone should be applied to ameliorate acidic purple soil. By leveraging these mudstones, farmers and land managers can efficiently ameliorate acidic purple soil, thereby promoting soil health, crop yield, and overall ecosystem resilience.

• Role of a Highly-Efficient Plant Growth-Promoting Bacterium in Decreasing Cd Uptake of Wheat Plant in Cd-contaminated Weakly Alkaline Arable Soils

  FENG Hai, ZHANG Qiangbing, WANG Qi, WU Hongsheng, CHENG Cheng

  2025,62(3):779-790, DOI: 10.11766/trxb202402170070

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  【Objective】 The safe utilization of farmland with mild to moderate cadmium (Cd) pollution is of great significance for the safety of agricultural products and human health. However, the effects of plant growth-promoting bacteria with the ability to immobilize Cd and regulate Cd-uptake by wheat plant from weakly alkaline farmland soil remains unexploited. 【Method】 Triticum aestivum L. Yangmai-13 was used as the tested plant, and weakly alkaline heavy metal polluted farmland soil was used as the test soil. Pot experiments were conducted to study the dynamic effects of Pseudomonas taiwanensis WRS8 on wheat growth, Cd content in rhizosphere soil and different parts of wheat, as well as rhizospheric and root endophytic bacterial communities during the jointing, booting, and maturity stages. 【Result】 The results showed that compared to the control group without inoculation, rhizosphere inoculation with strain WRS8 led to a significant increase in the aboveground biomass, root biomass, and grain weight of Yangmai 13 by 34% - 64%, 60% - 102%, and 10% - 14%, respectively. It decreased the Cd content in shoots, roots, grains, and rhizosphere soil by 55% - 60%, 5% - 8%, 78% - 82%, and 32% - 49%. Moreover, inoculation with strain WRS8 significantly increased the pH value of the rhizosphere soil during the booting and maturity stages. In terms of rhizospheric and root endophytic bacterial communities, inoculation with strain WRS8 only resulted in a significant reduction in the alpha diversity index of endophytic bacterial communities during the booting stage; The principal co-ordinates analysis clustering results showed that both the treatment with live and inactivated bacteria significantly changed the bacterial community structure in the rhizosphere soil and roots, and the bacterial community structure also changed significantly with the extension of the growth period. Inoculating strain WRS8 reduced the relative abundances of Chloroflexi and Proteobacteria in the rhizosphere soil, while increasing the relative abundance of Arthrobacter and Bacillus. Also, strain WRS8 inoculation reduced the relative abundances of Actinobacteria and Chloroflexi phyla of root endophytic bacterial communities, while increasing the relative abundance of Pseudomonas during the jointing and booting stages. 【Conclusion】 In summary, strain WRS8 not only significantly reduced the absorption of Cd by Yangmai 13 from weakly alkaline farmland soil, but also effectively improves wheat biomass and yield, suggesting its potential to achieve safe utilization of weakly alkaline heavy metal polluted farmland.

• Lettuce Foliar Uptake of Heavy Metals Directly from the Deposition of Atmospheric Particulate Matter Emitted from Coal Combustion

  LIU Xin, TONG Xin, CHEN Zhihuai, ZHANG Tingting, GUO Haohua, LUO Xiaosan

  2025,62(3):791-800, DOI: 10.11766/trxb202401290047

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  【Objective】 The combustion of fossil fuels such as coal emits a large amount of particulate matter and heavy metals into the atmosphere, which are then significant sources of input into the agricultural environment by dry and wet deposition. These pollutants will directly influence crop growth and heavy metal accumulation, and indirectly threaten human health through the food chain. Atmospheric particulate matter rich in heavy metals can enter the plant through two pathways: deposition into the soil followed by root absorption or direct foliar uptake of dry deposition on the crop leaf surface. However, the respective proportions and specific mechanisms of these pathways remain elusive. 【Method】 An open-side(covered with fine particulate matter filter membranes) transparent chamber was designed for vegetable pot experiments, simulating the actual dry deposition flux of atmospheric particulate matter in diverse coal-burning regions. This quantitative study systematically compared the effects of fly ash from two representative coal-fired power plants in southern and northern China on lettuce (Lactuca sativa L.) growth and the leaf accumulation of typical heavy metals through deposition into soil and leaf surface, respectively. 【Result】 The results indicated that atmospheric deposition is a significant source of Cd, Pb, Cr, and As in crops. The heavy metal contents in lettuce leaves increased with the fly ash deposition. The proportion of deposited Cd accumulated by the edible above-ground parts of lettuce through the foliar uptake is 40.9%-84.2% and the proportion of Pb can be 62.3%-85.6%. This indicates that direct foliar uptake is the main pathway for lettuce leaf accumulation of Cd and Pb in atmospheric particulate matter, especially for metals with high content (Pb) or bioavailability (Cd) in particulates, and if the amount of particle deposition does not exceed the foliar uptake capacity. However, when the atmospheric deposition flux is high or the bioavailability is low, heavy metals such as As in particulate matter are mainly accumulated by leaves through the traditional pathway of soil-root migration, absorption, and transport. Because of the higher contents of most heavy metals and stronger bioavailability in the soil-lettuce system, the southern fly ash induced higher accumulation of heavy metals by the leaf, and stronger toxic effects translated to lower photosynthetic activity and less biomass. 【Conclusion】 Consequently, comprehensive pollution control measures such as source prevention and reduction of heavy metal deposition input from the emissions of atmospheric particulate matter like coal combustion, as well as suppression of leaf dust retention, are of great environmental and health significance for ensuring crop growth and the quality and safety of leafy vegetables in coal burning areas.

• Peanut/maize Intercropping Promotes Peanut Soil Organic Carbon Sequestration by Increasing Soil Microbial Activity

  LI Shiwen, LU Jumeng, HUANG Geng, SHEN Yi, SUN Bo, ZHANG Qin, CHEN Yan

  2025,62(3):801-810, DOI: 10.11766/trxb202312260540

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  【Objective】 Intercropping is an effective strategy for increasing soil carbon (C) sequestration by utilizing farmland biodiversity. The aim of this study was to investigate the contribution of peanut rhizosphere microbes adjacent to maize to soil organic C (SOC) sequestration in an intercropping system. 【Method】 Based on the long-term peanut/maize intercropping experimental platform of Jiangsu Academy of Agricultural Sciences, two rows of peanuts and two rows of maize were planted in strips. Ecological test plate (BIOLOG) and gas chromatography were used to analyze the C metabolic ability of maize to adjacent peanuts rhizosphere microbes and the accumulation of microbial necromass C. 【Result】 The results showed that compared with peanuts planted far away from maize, peanuts planted adjacent to the maize decreased rhizosphere polyphenol oxidase activity by 19.0%, soil respiration rate by 18.2%, average color change rate (AWCD) by 22%, rhizosphere microbial metabolism of phenolic acids and amino acids by 149.4% and 16.1%, respectively. The total amino sugar ( TAS ) content of peanut rhizosphere soil adjacent to maize was 6.45% higher than that of peanut planted far away from maize, and the content of bacterial necromass C and fungal necromass C was increased, which eventually led to a 12.9% increase in SOC. 【Conclusion】 Our study suggests that adjacent maize does not change the soil respiration rate of the peanut rhizosphere, but reduces the activity of SOC decompositiong enzymes in the peanut rhizosphere and enhances the ability of rhizosphere microbes to metabolize a wider range of organic carbon components, thereby increasing SOC by accumulating bacterial and fungal necromass C.

• Stoichiometric Characteristics of Nutrient-Microbial Biomass-Extracellular Enzyme Activity in Different Salt-affected Soils

  CHEN Yuqi, XU Lingying, WANG Zhiwang, WANG Xiangping, YAO Rongjiang, ZHAO Xu

  2025,62(3):811-824, DOI: 10.11766/trxb202403220128

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  【Objective】 Soil salinization restricts the improvement of nutrient utilization efficiency and productivity enhancement. Studying the dynamics of soil nutrient changes and microbial feedback under saline stress can provide a scientific basis for nutrient management in salt-affected soils. 【Method】 Soils with salinity ranging from <3 g·kg^-1(S₁), 3～10 g·kg^-1(S₂), and >10 g·kg^-1(S₃) of typical soil salinization areas in China were collected. By analyzing the differences in carbon, nitrogen, and phosphorus contents, microbial biomass, extracellular enzyme activity and their ecological stoichiometric ratios, this study aimed to clarify the changing trend of soil nutrients and microbial metabolism limitation characteristics under different salinity barriers. 【Result】 The results of the study showed that: (1) Organic carbon, total nitrogen, total phosphorus, alkaline dissolved nitrogen, and available phosphorus contents of the salt-affected soils all decreased. According to the nutrient grading standards of the Second National Soil Census, the organic carbon, total nitrogen, and alkaline dissolved nitrogen of S₃ all dropped to the fifth level (deficiency), while soil phosphorus and potassium pools were all relatively sufficient. (2) The ratio of extracellular carbon-acquiring enzyme activity to extracellular nitrogen-acquiring enzyme activity (Enzyme C/N), the ratio of extracellular carbon-acquiring enzyme activity to extracellular phosphorus-acquiring enzyme activity (Enzyme C/P) and the ratio of extracellular nitrogen-acquiring enzyme activity to extracellular phosphorus-acquiring enzyme activity (Enzyme N/P) of different salt-affected soils all deviated from 1: 1 to different degrees. Also, the results of vector characteristics of extracellular enzyme stoichiometry showed that microbial carbon limitation and microbial nitrogen limitation in S₃ were significantly higher than those in S₁ and S₂. This phenomenon indicates that increased salinization caused soil elements and microbial metabolic activity to gravitate towards carbon and nitrogen resource limitation. (3) The salt content (TS), Na⁺, K⁺, exchangeable sodium percentage (ESP), Cl^-and annual average evaporation-precipitation ratio(MAV/MAP)were the key constraints on changes in the carbon, nitrogen, and phosphorus stoichiometric ratios of soil nutrients, microbial biomass, and extracellular enzyme activities in salt-affected soils. The results of the random forest model showed that Cl^-, TS, and MAV/MAP were the main drivers of microbial relative carbon limitation. TS, ESP, sodium adsorption ratio(SAR), Cl^-, Na⁺ and MAV/MAP were the main drivers of microbial relative nitrogen limitation. 【Conclusion】 In summary, salinity barriers are more likely to lead to carbon and nitrogen limitation in arable soils than the relative abundance of phosphorus and potassium nutrient pools, and the degree of limitation increases with the strengthening of salinity barriers. Therefore, there is an urgent need to put forward methods of organic regulation and efficient carbon and nitrogen management for salt-affected arable soils.

• Effects of Different Carbon-nitrogen Ratios of Substrate Addition on the Priming Effect of Purple Soil and Its Regulation Mechanism

  HUANG Chuanxiong, YAO Zhiyuan, WANG Tao, HUANG Qishun

  2025,62(3):825-835, DOI: 10.11766/trxb202311240495

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  【Objective】 Exogenous substrate quality (carbon to nitrogen ratio, C/N) can mediate priming effect (PE). However, the effects and regulation mechanism of priming effect under different C/N ratios of substrate addition is still unclear. 【Method】 The effects and regulation mechanism of purple soil which was fertilized by crop straw with synthetic fertilizers were explored through an indoor incubation experiment using glucose and ammonium sulfate. 【Result】 Positive priming effect during the incubation period was significantly reduced by 87.4% and 93.7% when the material C/N was 10 (CN10) compared to the treatments with a C/N of 50 (CN50) and 100(CN100). CN100 and CN50 treatments significantly increased soil soluble organic carbon (DOC) and microbial carbon (MBC) content but significantly decreased total soluble nitrogen(TDN)content compared to CN10. After 14 and 43 days of incubation, CN100 treatment significantly elevated the activities of cellobiohydrolase (CBH), β-N-acetylglucosaminoglycosidase (NAG), and leucine aminopeptidase (LAP) compared to CN10. Positive PE in the first two weeks was significantly positively correlated with MBC, CBH, NAG, and LAP, and negatively correlated with TDN, (βG+CBH)/(NAG+LAP)(βG, β-glucosidase), and at the end of the incubation, the positive PE was significantly positively correlated with MBC, βG, CBH, NAG, LAP, and (βG+CBH)/(NAG+LAP) and remained negatively correlated with TDN. 【Conclusion】 Lower C/N substrate addition significantly reduced the positive PE in purple soils and contributed to efficient soil carbon sequestration; Microorganisms responded to changes in the relative effectiveness of nutrients in the soil environment mainly by adjusting the activities of key enzymes, which in turn regulated the PE. This study can provide a theoretical basis for regional development of fertilizer application programs for efficient carbon sequestration, as well as an in-depth understanding of carbon dynamics in agroecosystems and their microbial-driven mechanisms.

• Effects of Biochar on Red Soil Nematode Community Characteristics Under Chemical Fertilizer Reduction

  CHENG Liuzhu, ZHU Baijing, CHENG Yanhong, WAN Bingbing, LIU Ting, TAO Yiheng, CHEN Xiaoyun, HU Feng, LIU Manqiang

  2025,62(3):836-846, DOI: 10.11766/trxb202311120469

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  【Objective】 The approach of reducing chemical fertilizer usage while increasing the application of organic amendment is a common strategy for maintaining optimal crop yields and preserving soil ecological functions. Biochar, as a carbon-rich, alkaline, and porous byproduct produced from biomass pyrolysis, has great potential in soil biodiversity restoration and soil health improvement in acidic red soil areas. 【Method】 This study conducted a 2×3 full factorial interactive design experiment in red soil cultivated with sweet potato-rapeseed in subtropical arid areas. The experiment involved the application of organic amendment (control without organic material application, straw, and biochar) and two fertilizer application rates (full dose of NPK fertilizer and reduced dose of 60% NPK fertilizer), totaling six treatments. The aim was to investigate the impact of biochar application on nematode communities in upland red soils and to understand the underlying mechanisms after five years of application. 【Result】 The results indicated that under full chemical fertilizer application, the use of biochar significantly increased the abundance of bacterivores and the ratio of microbivores to herbivores, reduced the root-to-shoot ratio of sweet potatoes and soil soluble organic carbon, and increased soil mineral nitrogen. Under reduced chemical fertilizer application, compared to the control and straw application, biochar significantly increased the abundance of total nematode, bacterivorous, herbivorous, and omnivorous predators. Simultaneously, it increased the sweet potato root biomass, root-to-shoot ratio, and soil pH but significantly decreased soil mineral nitrogen. By analyzing the relationship between soil nematode communities and plant growth as well as soil properties, it was evident that the application of biochar in combination with reduced chemical fertilizer led to a reduction in soil nutrient availability, thus nutrient limitation prompted plants to allocate more photosynthetic products below ground, resulting in increased crop root biomass and the abundance of herbivores. 【Conclusion】 This study suggests that under the background of reducing chemical fertilizer and increasing the application of organic amendment in China, soil fertilization practices combining biochar application with reduced chemical fertilizer should take into comprehensive consideration the potential adverse effects of nutrient deficiency on crop growth.

• Effects of Organic Fertilization on the Phosphorus Solubilizing Bacteria Community and Maize Productivity in Dryland Red Soil

  YANG Yeyuping, ZHENG Jie, JIN Lele, PENG Ziyi, WANG Xiaoyue, XU Qinsong, JIANG Yuji

  2025,62(3):847-856, DOI: 10.11766/trxb202311170480

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  【Objective】 Phosphorus solubilizing bacteria (PSB) is an important functional group of the soil microbial community. The changes in the abundance, composition, and diversity of the PSB community in the rhizosphere can affect soil alkaline phosphomonoesterase (ALP) activity and phosphorus (P) cycle dynamics. Here, we explored the mechanism of the abundance, composition, and diversity of the PSB community in regulating maize productivity under different organic fertilization treatments. 【Method】 In this study, we conducted a long-term field experiment with different organic fertilization treatments at the Yingtan National Agroecosystem Field Experiment Station of the Chinese Academy of Sciences in Jiangxi. The field experiment included four treatments: no manure (M0), low manure (M1), high manure (M2), and high manure with lime addition (M3). Illumina sequencing was used to investigate the abundance, composition, and diversity of the PSB community in the rhizosphere. 【Result】 Different organic fertilization treatments(M1, M2, and M3) significantly increased pH, soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), available phosphorus (AP), abundance of PSB, ALP activity, and maize productivity compared to M0 treatment, with the highest values observed under M3 treatment. Organic fertilizer treatments affected the PSB community composition and diversity in the rhizosphere. Bradyrhizobium, Mesorhizobium, and Pseudomonas were the dominant genera in the PSB community under M2 and M3 treatments. Compared with the M0 treatment, the PSB community diversity was significantly increased under the M1 treatment. The abundance and dominant genera of the rhizosphere PSB community were mainly affected by AP. Correlation analysis and structural equation modeling revealed that AP and TP indirectly affected maize productivity by increasing the abundance and changing the relative abundance of dominant genera of PSB. 【Conclusion】 Taken together, this study elucidates the promotion mechanisms of the rhizosphere PSB community on the mineralization of soil organic phosphorus and maize productivity. Our findings provide a scientific basis for establishing better organic fertilization practices and enhancing the fertility and health of red soils.

• Effects of Chinese Milk Vetch Incorporation on the Gene Abundance of Ammonia-oxidizing Microorganisms in Red Paddy Soil

  SUN Luyuan, LIU Jia, FENG Mengmeng, LIU Han, MA Tingting, CHEN Xiaofen, LIN Yongxin

  2025,62(3):857-869, DOI: 10.11766/trxb202401110021

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  Abstract:

  【Objective】 Nitrification, an important component of nitrogen cycling, has the potential to influence soil nitrogen availability. As a result, it will lead to ecological and environmental issues such as eutrophication, and greenhouse gas (nitrous oxide) emissions. The objective of this study was to explore the effect of Chinese milk vetch incorporation on the gene abundance of ammonia-oxidizing microorganisms in red paddy soil under a rice-Chinese milk vetch planting system. 【Method】 In a field experiment, five fertilization treatments were applied, including Chinese milk vetch incorporation (G), 100% chemical fertilizer (C), Chinese milk vetch incorporation + 100% chemical fertilizer (GC), and Chinese milk vetch incorporation + 20% chemical fertilizer reduction (GCT20), with a no fertilization treatment serving as the control (CK). Real-time quantitative PCR was used to determine the abundance of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and comammox Nitrospira Clade A and Clade B in each treatment. 【Result】 The results showed that Chinese milk vetch incorporation increased soil organic carbon and total nitrogen content compared with CK, while the 100% chemical fertilizer treatment showed no significant effect. There was no significant difference in AOA and Clade B abundance among all the treatments, indicating a weak response to nitrogen inputs from both chemical fertilizers and green manure. However, both the sole application of chemical fertilizer and its combination with Chinese milk vetch incorporation significantly increased the abundance of AOB and Clade A. Additionally, Chinese milk vetch incorporation alone had no significant effect on AOB and Clade A, suggesting their sensitivity to chemical fertilizer, but resistance to green manure nitrogen input. Furthermore, gene abundance of all ammonia-oxidizing microorganisms showed a similar trend across growth stages, with higher abundance observed during the mature stage followed by the booting stage and then the tillering stage. This suggests that growth stage and oxygen concentration are key factors influencing the growth of these microorganisms in paddy soils. 【Conclusion】 Growth stage is a key factor affecting the abundance of ammonia-oxidizing microorganisms in paddy soils. Additionally, Chinese milk vetch incorporation had a weaker promotion effect on AOB and Clade A abundance compared to chemical fertilizer, potentially contributing to nitrogen retention and stability in paddy soils.

• Effects of Experimental Warming on Soil Microorganisms: A Meta-Analysis

  ZHAO Wenyu, MIAO Run, CHENG Cheng, WANG Qi

  2025,62(3):870-880, DOI: 10.11766/trxb202402180071

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  【Objective】 Microbial community plays an important role in soil ecological activities. It can regulate soil nutrient supply by changing the structure and function of the soil ecosystem. At present, the response of soil microbial community to warming and the main influencing factors are not well understood. 【Method】 This study collected 1 020 sets of data from 206 published domestic and foreign research literature and synthesized them to evaluate the effects of experimental warming on soil microbial community (microbial biomass, community diversity, and soil enzyme activity) using meta-analysis. The different responses of soil microbial communities to different magnitudes, durations and methods of warming, as well as planting habits and ecosystem types were evaluated and discussed. Also, the relationship between the response of soil microbial communities to warming treatment and environmental factors (annual mean precipitation, annual mean temperature, and mean altitude) was explored. 【Result】 It was found that experimental warming decreased the soil microbial community diversity by 6.7%, increased the activities of soil antioxidant enzymes, enzymes related to carbon (C), and nitrogen (N) conversion by 7.5%, 10.8%, and 19.7%, respectively. A high magnitude of warming (≥4℃)significantly reduced soil microbial biomass and increased the activities of soil antioxidant enzymes and enzymes related to C conversion. Low- temperature increase (≤2℃) had more significant effects on soil microbial community diversity and soil enzymes related to N and phosphorus (P) conversion. Also, long-term warming (>2 years) had significant effects on soil microbial biomass, community diversity, antioxidant enzymes and enzymes related to C conversion. The responses of enzymes related to N and P conversion to medium-term warming (0.5 to 2 years) were more significant and the response of soil microorganisms to experimental warming was different among different ecosystems. Further analysis revealed that the response of enzyme activities related to P conversion to warming was positively correlated with annual mean temperature and annual precipitation. The response of soil microbial community diversity was negatively correlated with mean annual temperature, annual precipitation and mean altitude. 【Conclusion】 In summary, the experimental warming significantly reduced the diversity of soil microbial communities while increasing soil enzyme activity. The warming amplitude, warming duration, and ecosystem type all affect the effects of experimental warming on soil microbes.

• Differences in Rare Bacterial Community Compositions at High Elevation Regions and Their Influencing Factors in Farmland and Forest Soils

  XIAO Xiwen, HU Ang, WU Hao, WANG Jianjun

  2025,62(3):881-892, DOI: 10.11766/trxb202402030059

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  Abstract:

  【Objective】 Microbial communities contain a lot of rare species and play important roles in soil ecosystem functioning. However, the elevational patterns of rare microbes in soils and their effects by land-use types remain elusive for mountain ecosystems. 【Method】 In this study, soil samples were collected from farmland and forest along an elevational gradient ranging from 1 880 to 3 010 m in Laojun Mountain, Yunnan Province, China. The bacterial communities were analyzed based on high-throughput sequencing of the 16S rRNA gene. Rare species were defined based on their relative abundance and the rarity of bacterial communities was determined. The elevational patterns of rare bacterial communities and their underlying factors for the two land-use types were further explored. 【Result】 It was found that the bacterial rarity was 0.266±0.71 and 0.209±0.064 in the farmland and forest, respectively. The rarity in the farmland was significantly higher by 21.56% than in the forest and showed a significantly decreasing elevational trend. The main drivers of bacterial rarity were pH and electrical conductivity in both land-use types. The alpha diversity, such as the Chao1 index, Shannon index, and Evenness index of rare bacterial communities were significantly higher in farmland soil than in forest soil, with increases of 19.99%, 4.43%, and 0.64%, respectively. In addition, the Chao1 diversity index of rare bacteria of both land-use types, showed a significantly decreasing elevational pattern of 31.39% and 34.40%, respectively. Also, the Shannon index of rare bacteria of farmland soil showed a significant decrease of 4.93% with elevation. Compared to the forest, the rare bacterial communities in farmland had significantly higher alpha diversity and lower beta diversity, the latter of which indicates biotic homogenization. In addition, for forest soil, the relative abundance of Actinobacteria showed a significant U-shaped elevational pattern, and the relative abundance of Bacteroidota and Chloroflexi showed significant increasing and decreasing elevational patterns, respectively. However, there was no significant elevational pattern of all the dominant phyla in farmland soil. Overall, the community compositions of rare bacteria were significantly influenced by the land-use type, elevation changes, and their joint effects, where the land-use type showed the greatest effect. Rare bacterial communities in farmland and forest soils were mainly influenced by physicochemical properties such as pH, moisture, electrical conductivity, and total nitrogen, with pH having the strongest effect. Compared to farmland, the rare bacterial communities of forest showed significant relationships with more physicochemical properties and higher correlations, and thus had greater sensitivity to environmental changes. 【Conclusion】 In summary, the rare bacterial communities of both farmland and forest soils showed a significantly decreasing elevational distribution pattern in Laojun Mountain, which was mainly driven by environmental factors such as pH. The findings of this study reveal the important roles of land-use type and elevation on soil rare bacterial communities on mountainsides. These results will help to foster a deep understanding of the formation and maintenance mechanisms of soil rare bacterial communities under land-use changes and provide scientific guidance for the sustainable development of mountain ecosystem land resources.

• Effects of Short-term and Long-term Nitrogen and Phosphorus Additions on Microbial Necromass Accumulation Coefficients in Meadow Soils of the Qinghai-Tibet Plateau

  LI Yifan, SHI Biwan, YANG Zhiying, GAO Wenjing, MA Tian, ZHU Jianxiao, HE Jinsheng

  2025,62(3):893-904, DOI: 10.11766/trxb202401090018

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  【Objective】 Microbes and their necromass play a key role in the accumulation and long-term sequestration of soil organic carbon (SOC). Moreover, continuous increases in nitrogen (N) and phosphorus (P) inputs can significantly affect microbe-mediated SOC accumulation processes. The microbial necromass accumulation coefficient (NAC), which quantifies the accumulation of microbial necromass per unit of microbial biomass, plays a key role in assessing the efficiency of microbial necromass accumulation. However, the influence of short-term and long-term additions of N and P on this coefficient within meadow ecosystems remains unclear. This study focused on investigating the differential responses of NAC to (1) short-term and long-term N and P additions and (2) additions of N and P across different soil layers. 【Method】 To explore the response of NAC to N and P additions, this study analyzed soil samples from the meadow on the Qinghai-Tibet Plateau subjected to 1 year (short-term)and 10 years (long-term)of N and P additions. It was measured the soil microbial necromass carbon (MNC) and the soil microbial biomass carbon (MBC), and calculated the value of NAC. Additionally, considering other environmental factors including soil physical and chemical properties, microbial extracellular enzyme activities, and plant biomass, the main influencing factors of NAC were identified. 【Result】 The results showed that after short-term N and P additions, the NAC values in the 0-10 cm and 20-30 cm soil layers were 31.33±2.97 (mean±SE) and 38.12±3.90, respectively, and N and P additions had no significant effect on NAC (P>0.05). After long-term additions of N and P, the NAC values in the 0-10 cm and 20-30 cm soil layers were 14.46±1.12 and 17.49±3.22, respectively; and the additions of N and P significantly reduced the NAC in the 20-30 cm layer (P<0.05). The results of the Random Forest indicated that pH was the most important factor affecting NAC, and the correlation analysis revealed a significant positive relationship between soil pH and NAC. Moreover, the long-term N addition, P addition and simultaneous addition of N and P significantly reduced the pH of the 20-30 cm soil layer. These findings suggest that the decrease in soil pH due to long-term N and P supplementation is the main cause of the reduction in NAC. The lowered soil pH may lead to the dissolution of minerals, thereby reducing the mineral protection of MNC, making it more susceptible to decomposition, ultimately decreasing the NAC of microorganisms. 【Conclusion】 In summary, changes in pH resulting from long-term nutrient additions dominated the changes in NAC. In the context of ongoing increases in N and P deposition, it is advisable to closely monitor changes in soil pH and implement timely measures to maintain the stability of SOC. This study explores the differential responses of NAC to N and P additions and their influencing factors, providing data support for understanding microbial-mediated carbon accumulation under the context of increasing N and P deposition.

• Spatial Distribution Pattern of Soil Microbiota Stoichiometry and the Influencing Factors in the Northwest Sichuan Alpine Meadow

  CHEN Danyang, WANG Changting, DING Luming, LIAO Xiaoqin, QIAO Fusheng, SUONAN Jiangcai

  2025,62(3):905-916, DOI: 10.11766/trxb202401290049

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  Abstract:

  【Objective】 As indicators reflecting soil fertility and biological activity, the soil microbial community plays key roles in global biogeochemical cycles by participating in litter decomposition and nutrient mineralization. The soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial biomass phosphorus (MBP) are labile and available nutrients for plants, and important for maintaining ecosystem functions. However, there is still a lack of information on the spatial distribution of the soil microbial biomass and the potential key drivers affecting it in the alpine meadows of Northwest Sichuan Province. Therefore, the current study aims to investigate the spatial heterogeneity of soil microbial biomass in the alpine meadows of Northwest Sichuan and its influencing factors based on the Second Comprehensive Scientific Expedition to the Qinghai-Tibet Plateau project. 【Method】 The typical alpine meadows in Northwestern Sichuan were investigated in this study to determine soil MBC, MBN and MBP by chloroform fumigation method. Soil pH, water content, total carbon, total nitrogen and total phosphorous were also measured. 【Result】 The results showed that (1) The content of MBC and MBN showed a decreasing trend from South to North alpine meadow in the Northwest Sichuan Province. Conversely, the MBP content showed an increasing trend from South to North while the MBC: MBN ratio showed a decreasing trend from Northeast to Southwest. Nevertheless, the MBC: MBP ratio was more complex and showed an overall decreasing trend from South to North while the MBN: MBP ratio showed an increasing trend from West to East.; (2) Random forest modeling results showed that mean annual temperature (MAT), mean annual precipitation (MAP), soil pH, and soil moisture (SMC) were important factors that positively affected soil microbial biomass and its stoichiometric ratio. The structural equation modeling (SEM) results further showed that soil pH and soil bulk density (BD) had direct negative effects on the changes of soil microbial carbon, nitrogen and phosphorous biomass whereas the stoichiometric ratio and soil total carbon (TC) had direct positive effects on them. MAT and MAP indirectly and negatively affected soil MBC, MBN, MBP, and the stoichiometric ratio, which was mainly attributed to the effects of MAT and MAP on soil physicochemical properties. Specifically, MAT and MAP increased both MBC and MBP mainly by lowering soil pH, and MAT also directly decreased TC, which increases MBN as well as decreased MBP; (3) Generally, the soil nutrients are limited in the alpine meadows of Northwest Sichuan Province, and showed the following trend: carbon > nitrogen > phosphorus. 【Conclusion】 Soil pH, BD, and TC had direct effects on the alteration of soil microbial biomass and its stoichiometric ratios in the alpine meadows of Northwest Sichuan Province, while MAT and MAP indirectly affected the soil microbial biomass and its stoichiometric ratios. In addition, the latitude and longitude showed effects on the spatial distribution pattern of nutrient limitation in the study area.

• The Impact of Brown Algae Substances on Soil Carbon Components, Enzyme Activity, and Greenhouse Gases Emissions

  LÜ Haonan, YANG Wentian, ZHOU Xiaojia, LU Fangke, WU Qingyun, ZHAN Liangjin, SHAN Fuye, DONG Qinde, YANG Yuechao, SHEN Tianlin

  DOI: 10.11766/trxb202410280412

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  Abstract:

  【Objective】 Continuous advancements have been achieved in optimizing the formulation, application strategies, and overall applicability of seaweed-derived fertilizers. However, a mechanistic understanding of how their key functional components modulate soil processes remains incomplete. This study investigated the impact of brown algae substances, central functional constituents of seaweed fertilizers, on soil properties, carbon fractions, carbon turnover-related enzymes, and associated greenhouse gas emissions. 【Method】 In this study, a soil incubation experiment was conducted with five treatments: control (CK), brown seaweed powder treatment (Sea), sodium alginate treatment with a viscosity of 66 mPa?s (Alg66), sodium alginate treatment with a viscosity of 360 mPa?s (Alg360), and fucoidan treatment (Fuc). The soil was incubated at 25 ℃ for 112 days and sampled periodically to determine the soil properties, carbon composition, enzyme activity, and greenhouse gas emissions. On the 56th and 112th day of incubation, the effects of adding different brown algae substances on soil β-glucosidase (BG), cellobiohydrolase (CBH), β-xylosidase (BX), and N-acetyl-β-glucosaminidase (NAG) and particulate organic carbon (POC), mineral-associated organic carbon (MOC), dissolved organic carbon (DOC), and easily oxidizable organic carbon (EOC) were determined. Nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) emissions were monitored during the first 50 days of incubation. 【Result】 The results showed that the addition of different brown algae substances had varying effects on the soil properties. Compared to CK, the addition of brown seaweed substances significantly increased soil organic carbon and total nitrogen content. The most significant effects on organic carbon and total nitrogen were Fuc treatment and Sea treatment, respectively. The Sea treatment enhanced soil available phosphorus and potassium content by 19.83% and 260.23%, respectively. Conversely, the brown algae polysaccharide treatments (Alg66, Alg360, Fuc) decreased soil available phosphorus by 17.67%, 2.74%, and 20.15% and soil available potassium by 11.41%, 3.85%, and 6.36%, respectively. Also, the Fuc treatment significantly improved the activated carbon component content, particularly the dissolved organic carbon, which was significantly different from other treatments at the end of the incubation period, and 6.34 times that of CK. The Fuc treatment also increased the enzyme activities of soil BG, CBH, BX, and NAG. Compared to the CK, the addition of brown algal substances increased CO? emissions, while the addition of Alg66 and Alg360 reduced N2O emissions. There was no significant difference in the effect of all treatments on CH4 emission. Therefore, new fertilizers that combine soil improvement and greenhouse gas reduction functions can be developed by optimizing the component ratios of brown algae substances. 【Conclusion】 Brown algae substances can enhance soil carbon and nitrogen nutrients whereas fucoidan can significantly enhance soil enzyme activity and active carbon components and sodium alginate can reduce N2O emissions. These results show that brown algae substances have a certain potential for green enhancement, with different components exerting varying effects on soil properties, thus, showing potential for the development of brown algae substances for the production of new fertilizers.

• A Programming Idea for Solving One-dimensional Unsaturated Infiltration Equation by Finite Element Method

  ZHANG Qingqing, LI Xiang, WANG Zhognfu

  DOI: 10.11766/trxb202412010459

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  Abstract:

  Some Key Research Fields of Chinese Soil Physics in the New Era: Progresses and Perspectives pointed out that one of the reasons for the lack of original research on soil physics in China is that Chinese scholars engaged in soil physics research lack a strong mathematical foundation. This makes it difficult to achieve breakthroughs in the numerical simulation of soil physical processes. The key equation for numerical simulation of soil physical processes is the Richards equation. Although there are many papers on solving the Richards equation using the finite element method, most are highly theoretical and lack practicality, posing significant challenges for researchers with limited mathematical and physical backgrounds in understanding and programming implementation. Therefore, this paper aims to present a programming framework incorporating detailed derivation steps for solving the one-dimensional Richards equation using the finite element method. The weak form of the Richards equation was derived by establishing the weighted residual equation. Subsequently, the weak form equation was transformed into a nonlinear algebraic equation by employing Jacobian transformation and Gaussian numerical integration. Finally, the nonlinear algebraic equation was solved using the Newton-Raphson method with boundary condition substitution. The corresponding code developed based on this programming framework demonstrated simulation results validated by experimental data from soil infiltration tests. The programming framework and code provided in this paper enable researchers with limited mathematical and physical backgrounds to efficiently implement numerical simulation of the one-dimensional Richards equation using the finite element method. This effort aims to facilitate potential breakthroughs in numerical modeling of soil physical processes in China, thereby contributing positively to future advancements in this field.

• Effects of Vegetation Restoration on Soil Nematode Communities in Dry-Hot Valley under Different Altitude Gradients

  ZENG Xiaoling, JIANG Chuan, CHEN Yuanyang, FENG Defeng, CHEN Shujie, YANG Yana, JIN Yanqiang, LIU Chenggang

  DOI: 10.11766/trxb202407020268

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  Abstract:

  【Objective】Vegetation restoration is one of the most effective approaches to improve the ecological environment of the dry-hot valley of the Jinsha River, Yunnan province. Exploring the changes in composition and structure of soil nematode communities under artificial and natural vegetation restoration can provide a theoretical basis for the reasonable management of the forest ecosystem in this region. 【Method】 In dry-hot valley of the Jinsha River, Leucaena leucocephala plantation and natural shrub-grass with Phyllanthus emblica and mixed Terminalia franchetii + Pistacia weinmannifolia were selected at low (1,150 – 1,200 m), middle (1,350 – 1,400 m) and, high (1,550 – 1,600 m) altitudes. The effects of the vegetation restoration approach under different altitudes on the functional structure of nematode communities were analyzed by using ecological indices, c-p life history, and nutritional structure indices. 【Result】 1) A total of 17 genera of bacterivores were captured, accounting for 37.3% of the total number, and omnivores-predators belonging to 21 genera, accounted for 53.2%. Also, Aporcelaimus, Acrobeles, and Microdorylaimus were the dominant genera. 2) Nematode trophic taxa were dominated by omnivores-predators and bacterivores, while plant-parasites and fungivores had relatively low proportions. However, the taxa were biased towards K-strategies. 3) The responses of nematode abundance, trophic taxa, and life history strategies to vegetation restoration varied across different altitudes. As the altitude increased, the diversity and stability of the nematode community under T. franchetii + P. weinmannifolia mixed shrub-grass increased gradually, while that under P. emblica shrub-grass showed the opposite trend. However, the L. leucocephala plantation showed the lowest "V" pattern with the middle altitude. Meanwhile, L. leucocephala plantation at the low altitude increased the metabolic footprints of bacterivores and omnivores-predators, implying that the food web was relatively complex and stable. 4) Soil nitrate nitrogen, available phosphorus, and moisture were the main driving factors of nematode community changes in artificial and natural vegetation restoration. 【Conclusion】 We recommend taking L. leucocephala as the main plantation at the low altitude area in the process of vegetation restoration and actively protect the pure and mixed natural shrub-grass at the middle and high altitudes to promote the ecological restoration of degraded soil in the dry-hot valley of the Jinsha River.

• Response of Soil Denudation Process to Vegetation Coverage of Dumping Site under Extreme Rainstorm Conditions

  XIONG Shuzhen, LÜ Gang, LI Yexin, WANG Jingxing, LI Kunhen

  DOI: 10.11766/trxb202409270378

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  【Objective】 Under the influence of extreme rainstorms, the slope of a dump site (a typical artificial re-plastic landform) is prone to geological disasters such as landslides and debris flow. This has resulted in soil erosion and vegetation restoration difficulties in the nearby mining areas. Therefore, to understand this phenomenon, this study focuses on the soil of an open-pit coal mine as the research object. 【Method】 The soil erosion process on the slope of the dump site was studied using an artificial simulated rainfall test. Runoff and sediment samples were collected when the slope of the dump site began to produce runoff after rainfall. Data on the flow velocity, flow width, flow depth, runoff, sediment content, etc., were collected once every 3 min. The runoff and sediment samples were collected and the volume was measured with a graduated measuring cup. Then, the cups were allowed to stand, and when the upper liquid was static and precipitated, the liquid was removed, and the erosion was measured by drying method (105 ℃). Furthermore, Reynolds number, runoff shear force, runoff power, and soil erosion rate were calculated from the collected data. Based on the data analysis of different rainfall intensities (50, 75, 100 mm∙h -1) and vegetation coverage (0%, 40%, and 70%), the change characteristics of slope denudation rate with water flow generation time and the quantitative relationship between soil denudation rate and hydrodynamic parameters were explored.【Result】 (1) The soil erosion rate increased with the increase of rainfall intensity, and decreased with the increase of vegetation coverage. The contribution rates of the two factors to the soil erosion rate were 50% and 36%, respectively. (2) Under the three rainfall intensifies, the total sediment yield of 70% vegetation coverage decreased significantly by 18%~27% and 84%~87% compared with 0% (P < 0.05), respectively. Compared with 50 mm∙h -1, the total sediment yield of 100 mm∙h -1 was significantly increased by 1940~2530 mL and 66.92~386.14 g, re-spectively (P < 0.05). (3) At 0%, 40%, and 70% vegetation coverage, soil denudation rate showed a significant power function relationship with Reynolds number, runoff shear force, and runoff power (P < 0.01) while the hydrodynamic parameters showed a significant linear positive correlation (P < 0.01). In terms of goodness of fit, the vegetation coverage of different hydraulic parameters was 70% > 40% > 0%. The fitting effect between soil denudation rate and runoff power was the most significant, and the determining coefficient R2 was 0.894, followed by runoff shear force. 【Conclusion】 Rainfall intensity is the main factor affecting soil erosion rate and with an increase in rainfall intensity, the rate of soil erosion also increases. The increase in vegetation cover led to a decrease in soil erosion rate. Under 70% vegetation coverage, the regression relationship between runoff power and soil erosion rate was most significant, and this parameter was the best hydraulic index to describe runoff erosion of the mine dump slope.

• Status and Influencing Factors of Soil Fertilities in the Major Regions of Peanut Production in China

  SUO Yanyan, LI Liang, LI Qian, SI Xianzong, XU Fengdan, CHENG Peijun, YAN Meng, WU Shiwen†

  DOI: 10.11766/trxb202411050424

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  Abstract:

  【Objective】Clarifying the soil nutrient status of peanut production regions in China is crucial for guiding the scientific fertilization practices in peanut cultivation and promoting high yield and high nutrient use efficiency. 【Method】In 2022, 1 020 soil samples were collected from major peanut production regions in China, and the soil organic matter (SOM), total nitrogen (TN), available N (AN), available phosphorus (AP), available potassium (AK) and pH status were evaluated. The variation characteristics of soil nutrients in peanut planting soils were also analyzed by different ridge planting methods, yield levels, soil types and soil textures. 【Result】The results showed that the average SOM, TN and AN contents in the peanut-producing regions were 15.15 g?kg-1, 1.01 g?kg-1 and 104.49 mg?kg-1, respectively. Also, 78.62%, 60.49% and 43.72% of the sampling points for SOM, TN and AN were deficient, mainly concentrated in the Northeast, Northwest, and Huang-Huai-Hai peanut production regions, such as Liaoning, Hebei, Henan, and Xinjiang provinces. The average soil AP content was 39.76 mg?kg-1, with only 13.14% of the sample points in the P deficiency level, mainly distributed in the south and the Yangtze River basin, in areas such as Sichuan and Yunnan provinces. The average soil AK content was 126.71 mg?kg-1 and 38.62% of the sample points were deficient in K and mainly distributed in Hebei and Guangdong province in the Huang-Huai-Hai and southern peanut production regions. In addition, the soil nutrient status was affected by the tillage practices, planting modes, and yield levels, with the soil AN and AP contents in ridge cropping significantly increased by 6.04% and 31.72% compared with those of flat cropping. The result also revealed that SOM, AN, AP, and TN contents in summer peanut were significantly increased by 24.33%, 67.37%, 25.85%, and 14.87% (respectively) compared with those of spring peanut and intercropped peanuts with wheat. The soil pH, AN, and AP contents of high-yield plots were respectively increased by 5.48%, 6.33%, and 26.24% compared with those of low-yield plots. There were also differences in soil nutrient characteristics among different soil types. For instance the SOM content (16.08 g?kg-1) of all soil types was generally low, with the lowest in the wind-sand soil (11.5 g?kg-1) while the soil AN content of the wind-sand soil (79.2 mg?kg-1), brown soil (75.33 mg?kg-1), grey calcareous soil (84.29 mg?kg-1), and tidal soil (84.88 mg?kg-1) was deficient. The AP content (39.43 mg?kg-1) of all soil types was relatively abundant and highest in the lime concretion black soil (70.31 mg?kg-1) whereas AK content was deficient in the latosols (78.78 mg?kg-1). 【Conclusion】There are significant differences in soil nutrients in different peanut-producing regions in China. The deficiencies of SOM, TN, and AN mainly occurred in wind-sand soil, tidal soil and brown soil in the northeast, northwest China, and Huang-Huai-Hai peanut production regions. Also deficiencies in AK mainly occurred in the peanut areas of southern brick-red soil. It was recommend strict control of the input of P fertilizer and increase the application of N and K fertilizers in soils with N and K deficiencies in peanut production regions of China.

• Response of Soil Metabolites, Microorganisms, and Lycium barbarum Yield Under Cover Crop Cultivation

  CHEN Haonan, MA Yaran, GAO Yamiao, NAN Xiongxiong, ZHU Lizhen, YANG Liu, WANG Fang

  DOI: 10.11766/trxb202410220409

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  Abstract:

  【Objective】The global wolfberry (Lycium barbarum L.) industry is undergoing a paradigm shift from traditional Ningxia-dominated production to multipolar cultivation systems across Northwest China. In this transitional context, developing sustainable soil management strategies becomes imperative for maintaining agricultural productivity and ecosystem resilience. While cover crop intercropping has emerged as an advanced agroecological practice demonstrating dual benefits in fruit quality enhancement and environmental stewardship, conventional field management approaches; particularly long-term monoculture and chemical fertilizer overapplication, continue to compromise both yield and phytochemical quality of wolfberry. This study systematically investigates the rhizosphere engineering effects of wolfberry/forage radish (Raphanus sativus L.) intercropping coupled with organic fertilization, focusing on its mechanistic impacts on soil microbiome restructuring and metabolic reprogramming.【Method】This study investigated the effects of wolfberry (Lycium barbarum L.) /radish (Raphanus sativus L.) intercropping with manure on edaphic microbial communities and metabolite profiles through a split-plot field experiment(2019-2021)in arid northwestern China. It also considered the effects of cover crop planting patterns on soil microbial community structure, metabolite composition, and yield of wolfberry orchards. Three organic fertilization regimes (0, 6 660 kg?hm-2, and 13 320 kg?hm-2) were applied under two planting systems: monoculture (M) and intercropping (I). Using Illumina high-throughput sequencing technology, quantitative PCR methods, and liquid chromatography-tandem mass spectrometry (LC-MS), microbial information and metabolites were measured. The correlation between soil physicochemical properties, microbial diversity, key metabolite components, crop yield and its differential metabolites, microbial diversity index, and environmental factors under different planting modes was analyzed.【Result】Compared with the traditional wolfberry monoculture, intercropping significantly enhanced soil multifunctionality, increasing surface soil electrical conductivity (EC) by 29.66%, organic carbon (SOC) by 47.80%, total nitrogen (TN) by 39.09%, available nitrogen(AN)by 46.23%, available potassium (AK) by 36.64%, and microbial biomass nitrogen (MBN) by 22.56%compared with monoculture (P<0.05). Additionally, intercropping enhanced soil microbial diversity, with the bacterial Shannon index increasing by 4%and the Simpson index decreasing by 43.04%. Metabolomic analysis identified 867 metabolites, including 84 differentially abundant compounds such as lipids, organic acids, phenylpropanoids, and carbohydrates. Among these, two key metabolites were positively correlated with yield enhancement. Consequently, wolfberry yield increased significantly by 6.36%.【Conclusion】These findings indicated that cover crop intercropping improved soil microecological conditions, induced specific metabolite shifts, and effectively enhanced wolfberry productivity, demonstrating its applicability in sustainable wolfberry cultivation systems.

• The Mechanism of γ-MnO2-mediated Abiotic Nitrogen Mineralization in Peptone and Its Influencing Factors

  HONG Jun, XIA Xiange, CHEN Yunfeng, LIU Bo, DUAN Xiaoli, ZHANG Minmin, NIE Xinxing, YANG Li

  DOI: 10.11766/trxb202412050475

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  【Objective】Existing literature has predominantly concentrated on the influence of microbial activity on soil organic nitrogen mineralization. However, the role of abiotic processes, particularly the non-biological mineralization of organic nitrogen facilitated by typical manganese oxides, has received little attention. 【Method】This study employed nsutite (γ-MnO2) as the experimental mineral and soybean-derived peptone as a representative of soil organic nitrogen to investigate the effect of abiotic nitrogen mineralization mediated by γ-MnO? under a near-neutral environment and elucidated the reaction mechanism. Three experimental systems were designed: a peptone system (0.25 g?L–1), a γ-MnO2 system (1.0 g?L–1), and a mixed system comprising both peptone (0.25 g?L–1) and γ-MnO2 (0.25~2.0 g?L–1). 【Result】The results indicated that under pH 7.0 and in an air atmosphere, γ-MnO2 could facilitate the mineralization of peptone nitrogen, producing inorganic nitrogen. The mineralization rate of peptone (0.25 g?L–1) initially increased and then tended to stabilize with increasing initial γ-MnO? concentrations (0.0-2.0 g?L–1). In this process, Mn(IV) and Mn(III) present in γ-MnO?, along with reactive oxygen species (ROS) generated on the mineral surface, served as the principal oxidizing agents facilitating the mineralization of peptone into inorganic nitrogen. 【Conclusion】This study is anticipated to advance the understanding of organic nitrogen mineralization mechanisms in farmland soils and to enhance the comprehension of nitrogen cycling processes within agricultural ecosystems.

• Spatiotemporal Distribution Characteristics of Soil Nitrification Rate and Influencing Factors in the Fen River Riparian Zone

  diyani, zhangyike, zhangzewen, wangchunling

  DOI: 10.11766/trxb202406110229

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  Abstract:

  【Objective】The water-land ecotone is the last barrier to effectively intercept runoff nitrogen pollutants from entering the water body. Nitrification is a key process of soil nitrogen cycle, and studying the temporal and spatial distribution characteristics and influencing factors of soil nitrification rate in riparian water-land ecotone is helpful to understand soil denitrification in riparian water-land ecotone.【Method】In this study, the spatiotemporal distribution characteristics of soil nitrification rate and physicochemical properties in the riparian water-land ecotone of the Taiyuan section of the Fen River were studied by taking soil samples at different distances, depths and in seasons. By measuring and analyzing the nitrification rate and physicochemical indexes, the main driving factors affecting the soil nitrification rate in the riparian water-land ecotone were explored through Spearman correlation analysis, RDA ranking analysis, and structural equation model. 【Result】The results showed that: (1) The soil moisture content, organic matter, total nitrogen, ammonium nitrogen, and nitrate nitrogen in the water-land ecotone decreased as distance from the shore increased while the bulk density increased. Soil moisture content, electrical conductivity, organic matter, total nitrogen, ammonium nitrogen, and nitrate decreased with the increase in soil depth. Also, in summer, the average values of soil moisture content, bulk density, organic matter, total nitrogen, and nitrate were lower than those in autumn, while ammonium nitrogen was higher than that in autumn. (2) The soil nitrification rate increased first and then decreased with the increase in distance from the shore, and the nitrification rate of surface soil (20.43 mg·kg-1·d-1) was higher than that of the lower layer (8.97 mg·kg-1·d-1). In addition, the average soil nitrification rate in summer and autumn was 15.12 mg·kg-1·d-1 and 14.28 mg·kg-1·d-1, respectively. (3) Soil total nitrogen was the main influencing factor affecting the soil nitrification rate in summer in the water-land ecotone.【Conclusion】 In summary, the results of this study show that in the case of serious nitrogen pollution in river water, it is necessary to fully protect the water-land ecotone within 1 m of the waterbody, which will help improve the ability of riparian soil to intercept runoff nitrogen pollution, thereby protecting river water bodies. Thus, this study provides a scientific basis for the ecological construction, protection, and management of riparian ecotone.

• Effects of Different Management Measures on Paddy Productivity and Phosphorus Balance in the Taihu Lake Lake Basin

  Chen Guanglei, Yue Ke, Yuan Jiahui, Zhu Yiyong, Kai Lei

  DOI: 10.11766/trxb202408030317

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  Abstract:

  【Objective】This study aimed to evaluate the impact of various phosphorus (P) fertilizer application rates and irrigation methods on rice yield, P uptake, P loss, and P balance in the Taihu Lake Basin. The goal was to optimize nutrient management and mitigate non-point source pollution by assessing the effects of different P levels and water management practices on rice paddies. 【Method】The research applied a two-year field experiment with three P application rates (P2O5 0, 45, and 90 kg·hm-2) and three irrigation strategies: continuous flooding, mild dryness, and severe dryness. Soil and rice samples were collected at harvest. Soil P fractions were analyzed using sequential extraction, and rice yield and P uptake were measured from grain and straw. Runoff and leachate samples were obtained to assess P loss. 【Result】Compared to the control treatment (no phosphate fertilizer), applying P fertilizer increased rice yield by 2.20% to 11.5%. The P2O5 90 kg·hm-2 treatment reduced P agronomic and P use efficiencies by an average of 34.9% and 29.4%, respectively, compared to the application of P2O5 45 kg·hm-2. P application significantly increased the soil Olsen-P and available P fractions (the sum of Resin-P, NaHCO3-Pi, and NaOH-Pi) by 19.1%~62.4% and 36.5%~101%, respectively, while also enhancing P loss from paddy fields by 79.1% to 292%, compared to the control. In addition, the mild and severe dryness strategies significantly reduced P loss, with average decreases of 27.0% and 35.6%, respectively, particularly in runoff, where reductions were 31.5% and 41.3%, compared to flooding. The P2O5 90 kg·hm-2 treatment maintained a P balance for the rice season, while the application of P2O5 45 kg·hm-2 was sufficient to meet rice demands due to the high availability of soil P and Olsen-P higher than 20 mg·kg-1. Structural equation modeling indicated that Olsen-P and NaOH-Pi were the main influencing factors for rice yield, while Resin-P was the main influencing factor of P loss. 【Conclusion】Moderate P fertilization at P2O5 45 kg·hm-2 effectively increased rice yield with minimal P loss. Mild dryness irrigation and appropriate P application based on crop P requirements and soil P levels are vital for maximizing crop yields while minimizing P loss. The findings provide a scientific basis for nutrient management in paddy fields and the control of non-point source pollution in the Taihu Lake Basin.

• The Influence of Straw Treatment Methods on Straw Mineralization and Priming Effects in Soil

  YANG Xin, ZHU Jun, REN Tao, LI Xiaokun, LU Jianwei

  DOI: 10.11766/trxb202406290265

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  【Objective】 The application of crop straw to soil is a popular strategy for managing cropland soil. However, the effects of pre-treatment of crop straw on its decomposition and priming effect in soil have received little attention. 【Method】 In this study, the structure, mineralization, and priming effect of pyrolyzed, biodegraded, and raw corn straw in the soil were investigated through an incubation experiment combined with the natural abundance approach. 【Result】 The results showed that the cumulative mineralization of straw materials in soil within 60 days followed the order biodegraded straw (1,945 mg kg-1), raw straw (1,576 mg kg-1), pyrolyzed straw (27 mg kg-1). The priming effect of pyrolyzed and raw straw on the mineralization of native soil organic matter was persistently negative and positive, respectively. Also, the priming effect of biodegraded straw changed from positive in the initial stage of incubation to negative in the latter period of incubation. Both raw and biodegraded straw significantly increased the abundance of fungi and the activities of β-glucosidase and cellulase in soil (P < 0.05), however, pyrolyzed straw did not significantly affect the fungal abundance and the activities of β-glucosidase and cellulase. High-throughput sequencing revealed that biodegraded straw significantly increased the relative abundance of Actinobacteria while raw straw significantly increased the relative abundance of Firmicutes (P < 0.05). 【Conclusion】 Because of low mineralization and negative priming effect, pyrolyzed straw showed higher potential than biodegraded and raw straw in the sequestration of soil organic carbon.

• Changes of Community Diversity and Assembly Processes of Culturable Potassium-Solubilizing Bacteria in Soil under Different Enrichment Strategies

  Zeng Tao, Ba Mengya, Xia Weiwei, Zhang Yaohong, Cai Yuanfeng, Chen Xiao Fen, Jia Zhongjun

  DOI: 10.11766/trxb202406230255

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  Abstract:

  【Objective】Potassium-solubilizing bacteria (KSB) are considered key plant growth-promoting bacteria for the sustainable development of ecological agriculture due to their unique advantage of potassium solubilization. To fully explore the resources of potassium-solubilizing bacteria in the environment, the changes in the characteristics of soil potassium-solubilizing bacterial communities were investigated in this study under various enrichment strategies. 【Methods】By using a potassium-solubilizing bacteria enrichment medium (KM),with a bacterial enrichment medium (BM) as a control, the study employed liquid (L) and solid (S) culture methods to continuously enrich and culture potassium-solubilizing bacteria in the test soil samples through three consecutive passages (1st, 2nd, and 3rd). The culturable microbial enrichments from each passage were collected, and high-throughput sequencing technology was used to analyze the 16S rRNA genes in the soil background and the enrichments. This analysis aimed to evaluate the proportion of culturable bacteria or potassium-solubilizing bacteria in the soil background bacterial community, as well as the community composition and diversity patterns under different enrichment strategies. 【Results】The results indicated that the bacterial diversity enriched by both media BM and KM was significantly lower than that in the background soil and the bacterial diversity in KM enrichments was significantly higher than that in BM enrichments. A total of 17 phyla, 38 classes, 91 orders, 145 families, and 267 genera of bacteria were detected in both L-KM and S-KM enrichments, with the most significant proportion at the phylum level accounting for approximately 29.31% of the soil background bacteria. The number of bacterial taxa enriched with L-KM medium was higher than S-KM at all levels. At the phylum level, the dominant phyla in L-KM were Firmicutes and Proteobacteria while in S-KM, the dominant phyla were Actinobacteriota and Proteobacteria. At the genus level, groups with distinct physiological and metabolic characteristics were enriched through three consecutive passages. Among them, the dominant genera in L-KM were Aminobacter, Chelatococcus, Cupriavidus, Hydrogenophilus, Microvirga, Paenibacillus, and Phenylobacterium. The only genus in S-KM that overlapped with L-KM was Cupriavidus, while other dominant genera included Burkholderia, Luteibacter, Massilia, Pseudomonas, and Ralstonia. Compared with known potassium-solubilizing bacteria databases, only 50 known genera were enriched in the KM medium, while unknown potassium-solubilizing bacteria accounted for over 81%. Using null model inversions to analyze the bacterial community assembly process during continuous passaging enrichment under different media, it was found that deterministic processes dominated the changes in community structure from the soil suspension inoculation to the first-generation media, while stochastic processes, mainly genetic drift, governed the intergenerational bacterial community succession. 【Conclusion】These results indicate that the composition and form of the medium are the main factors influencing the culturable potassium-solubilizing bacterial community, but continuous passaging enrichment does not lead to homogenization and simplification of the community structure. A relatively large number of both known and unknown potassium-solubilizing bacterial genera can be obtained under different enrichment strategies and used to enrich the existing resource bank of potassium-solubilizing bacteria. This can provide valuable insights for further development and utilization of these bacteria.

• The Relationship Between Microbial Necromass Carbon and Soil Aggregate Stability on a Global Scale

  Kuang Yanyun, Hu Han, Li Sen, Liang Yuting

  DOI: 10.11766/trxb202409030355

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  【Objective】 The soil organic carbon (SOC) pool is the largest carbon reservoir in terrestrial ecosystems, playing an essential role in mitigating climate change and maintaining soil fertility. Among the various components of SOC, microbial necromass carbon (MNC) constitutes a significant proportion, contributing approximately 30-80% to the total SOC, and playing a crucial role in stabilizing soil carbon stocks. Accumulation and stabilization of MNC in soil are closely linked to the formation and stability of soil aggregates, which provide physical protection against microbial decomposition. Despite the known connection between MNC and soil aggregation, no comprehensive studies have systematically explored the relationship between MNC and soil aggregate stability. This study aims to further explore the global association between MNC and soil aggregate stability.【Method】 To assess the relationship between MNC and soil aggregate stability, we compiled global observational datasets on soil amino sugars (biomarkers of MNC) and soil aggregates. Using machine learning techniques, we predicted the global distribution of MNC and analyzed its correlation with the stability of soil aggregates. The PLS-PM was employed to further investigate the pathways through which soil aggregate stability influences MNC sequestration, takin into account factors such as soil physical properties, nutrient availability. 【Result】 The results revealed that MWD is a key predictor of MNC, with a significant positive correlation between MNC and MWD on a global scale (P < 0.05). Further correlation analysis of global prediction data confirmed this relationship and showed that it is consistent across different ecosystems. The Partial Least Squares Path Model (PLS-PM) analysis revealed that soil aggregates protect MNC directly by forming physical barriers and indirectly by regulating soil physical properties and nutrient availability, which in turn influence MNC accumulation and stabilization. In particular, soil nutrients had the most significant positive impact on MNC (path coefficient = 0.67, P < 0.05). The process through which MWD influences MNC shows significant differences across different ecosystems, specifically in terms of the direction and strength of the pathways. For example, in agricultural ecosystems, the indirect effects through soil physical properties and nutrients are more pronounced, while in forest ecosystems, the direct effect is stronger. 【Conclusion】The findings of this study underscore the significant role of soil aggregates in stabilizing MNC, and highlight the potential of soil aggregation as a key factor in enhancing soil carbon storage. Also, the positive correlation between MNC and aggregate stability suggests that strategies aimed at improving soil structure; eg., practices that enhance aggregation and optimize nutrient management, can effectively contribute to greater carbon sequestration. By fostering more stable soil aggregates, we can improve MNC sequestration, mitigate climate change, and sustain soil fertility. Furthermore, these findings can inform the development of predictive models for MNC sequestration and the integration of soil aggregate stability as a critical indicator for assessing the carbon sequestration potential of soils.

• Differences in Mineral-Associated Organic Carbon and Particle Organic Carbon Mineralization in Typical Grassland Soils

  YUAN Chenyang, YANG Renmin, FU Zihuan, CHEN Shiping, YAN Zhifeng

  DOI: 10.11766/trxb202410060383

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  【Objective】The mineralization process of soil organic carbon (SOC) and its components is complex. For example, particulate organic matter (POM) and mineral-associated organic matter (MAOM) are two components with different physicochemical properties and turnover rates. However, few studies have paid attention to the differences in the response of these different components to climatic factors. Thus, this study aimed to investigate the differences in the mineralization of POM and MAOM under different temperatures and moisture conditions and provide a basis for the estimation and prediction of CO2 emission fluxes in the context of global climate change. 【Method】The soil of Xilingol grassland in Inner Mongolia was collected to obtain POM and MAOM using a physical grading method and controlling the same mass of each fraction. Bulk soil was incubated under optimum conditions for 180 days, and POM and MAOM were incubated at different temperature and moisture conditions for 60 days to investigate the differences in mineralization of the two fractions and their response to temperature and moisture. 【Result】After 180 days of incubation experiments under optimal conditions, the cumulative CO2 emission from the grassland soil reached 2688 mg kg-1. MAOC in the grassland soil was relatively large, which accounted for 60% to 75% of TOC. Under different temperature conditions, the mineralization rates of both POM and MAOM increased with increasing temperature, while the two fractions responded differently to soil moisture content. There was a positive but insignificant correlation between the CO2 emission rate of MAOM and soil moisture, while there was no significant correlation between the CO2 emission rate of POM and soil moisture. It was also found that MAOM was much larger than POM in terms of cumulative CO2 emissions per unit of soil mass, while POM was much larger than MAOM in terms of cumulative CO2 emissions per unit of organic carbon. 【Conclusion】The mineralization of grassland soils MAOM and POM showed significant differences in response to temperature and moisture, suggesting that the mechanisms controlling the mineralization of these two carbon pools are different. The cumulative CO2 emission per unit of organic carbon in POM was much larger than that in MAOM, suggesting that the carbon in POM is more easily mineralized under the same conditions. Thus, distinguishing between POM and MAOM helps to better understand SOC turnover and provides a scientific basis for improving the SOC mineralization model.

• Global Spatial Distribution and Driving Factors of Soil Microbial Necromass Carbon Stability

  ZHENG Hongfeng, ZHAO Yuan, HU Han, LI Sen, ZHANG Li, LIANG Yuting

  DOI: 10.11766/trxb202410150397

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  【Objective】Microbial necromass carbon plays a significant role in the global carbon cycle and is a key contributor to soil organic carbon. Its importance stems from its stability, which is crucial for carbon protection and long-term carbon storage in soils. Within microbial necromass carbon, fungal necromass carbon (FNC) and bacterial necromass carbon (BNC) are two main components, and research has shown that FNC is more stable than BNC. Therefore, a higher proportion of FNC relative to BNC, expressed as the FNC/BNC ratio, is often considered indicative of greater microbial necromass carbon stability. However, despite the recognition of this relationship, the global distribution patterns of microbial necromass carbon stability and the factors influencing these patterns remain unclear due to a lack of large-scale observational data. Addressing this gap is essential for advancing our understanding of the mechanisms behind soil carbon cycling and protection.【Method】To address these uncertainties, this study employs a combination of meta-analysis and machine learning techniques to analyze microbial necromass carbon stability on a global scale. Meta-analysis allows for the synthesis of findings from multiple studies to produce more robust conclusions, while machine learning enables the identification of complex patterns in large datasets. Together, these methods offer a powerful approach to uncovering the spatial distribution of microbial necromass carbon stability and its driving factors. The study specifically examines the relationship between FNC/BNC ratios and various environmental variables, including soil nutrient levels (such as soil organic carbon, total nitrogen, and total phosphorus) and climatic factors (such as annual mean temperature and evaporation). By analyzing data from different ecosystems and climatic zones, the study aims to clarify the global patterns of microbial necromass carbon stability and the key factors influencing it.【Result】The results showed that the global average stability of microbial necromass carbon was 3.09. Among different ecosystems, forests had the highest average value (3.94), while deserts had the lowest (1.09). In terms of climate zones, the highest average value was found in the polar regions (4.14), and the lowest in arid climate zones (1.69). In different aridity index regions, the stability of microbial necromass carbon was lowest in extremely arid areas (0.75) and highest in semi-humid regions (3.77). Also, microbial necromass carbon stability exhibits distinct characteristics across different regions.【Conclusion】Overall, microbial necromass carbon stability tends to be lower under conditions of higher annual mean temperature or greater annual evaporation, indicating a negative correlation between climatic conditions and microbial necromass carbon stability. Soil organic carbon, total nitrogen, and microbial biomass nitrogen were identified as key regulators of microbial necromass carbon stability, with positive correlations to its stability. Moreover, annual mean temperature and evaporation indirectly affected microbial necromass carbon stability by influencing the levels of soil organic carbon, total nitrogen, and total phosphorus. The study highlighted the global spatial distribution of microbial necromass carbon stability and the major driving factors behind it. These findings provide valuable theoretical support for developing soil management strategies that focus on protecting and enhancing organic carbon based on the stability of necromass. Such strategies can help maintain and improve soil health, carbon sequestration, and ecosystem functioning in the face of changing environmental conditions.

• The influence of mycorrhizal types on the soil microbial biomass carbon and its distribution

  MA Zhenyi, SUN Yichun, SHI Zhaoyong, GAO Jiakai, WEI Wenjing

  DOI: 10.11766/trxb202406120230

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  【Objective】Soil microbial biomass carbon (SMBC) is an important indicator of microbial activity, and the type of mycorrhizal has a potential impact on SMBC content. The objective is to explore the impact of different mycorrhizal types on soil microbial biomass carbon and clarity their functions under global climate changes. 【Method】Based on the SMBC database established by predecessors, the SMBC content and its distribution of plants of different mycorrhizal types were explored by dividing different soil layers (0-100 cm, 0-40 cm, 40-100 cm) and determining the mycorrhizal types of plants in the database. 【Result】The results showed significant differences in SMBC between different layers of Arbuscular mycorrhiza (AM) and Ectomycorrhiza (ECM) plants, among which ECM plant soil SMBC was significantly higher than that of AM plant. There were also differences in the response of SMBC to soil parameters (soil depth, soil total nitrogen) and climate parameters (average annual temperature, average annual rainfall). At soil depth of 0-40 cm, the effects of factors (48.9%, 47.99%) on SMBC were significantly higher than that of climate factors under both AM and ECM plants (8.45%, 2.25%). Also, at soil depth of 40-100 cm, the SMBC of the ECM plant was more affected by climate factors (53.94%) than soil factors (25.32%), while the AM plant was affected differently, with the soil factor (45.17%) showing a more significant effect than climate factors (25.32%). 【Conclusion】Under the influence of different types of mycorrhiza, SMBC was significantly positively correlated with soil organic carbon and total nitrogen (P<0.01), among which ECM was more affected by soil organic carbon and total nitrogen. The analysis of variance decomposition found that with the increase in soil depth, AM plant SMBC in deep soil was mainly affected by soil factors, while ECM plant SMBC was mainly affected by climate factors. In summary, the SMBC content of the ECM plant was significantly higher than that of the AM plant, and the response to organic carbon and soil total nitrogen was also higher than that of the AM plant.

• Effects of Different Organic Materials on the Stability of Saline-alkali Soil Colloid

  SUN Yuliang, LI Qirui, Li Wei, Wang Xiang, SHANG Jianying

  DOI: 10.11766/trxb202408300349

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  【Objective】Soil colloid stability plays an important role in soil nutrient retention, structure formation and crop growth. The application of organic materials is an effective method for improving saline-alkali soil, but their effects on soil colloid stability in these conditions remain unclear.【Method】In this study, we investigated the effects of biochar (BC), cattle manure (CM), and maize straw (MS) on soil colloid stability at different salinity-alkalinity levels (non-saline-alkali, mild saline-alkali and moderate saline-alkali) through soil incubation and sedimentation experiments in the laboratory.【Result】(1) The addition of organic materials significantly reduced the diameter of saline-alkali soil colloidal particles, making it similar to the diameter of non-saline-alkali soil colloid. In mild saline-alkali soil, the effect of MS treatment was most effective, and the colloidal particles size decreased from 785.7 nm to 360.2 nm. In moderate saline-alkali soil, the effect of CM treatment was most effective, decreasing the colloidal particles size from 675.8 nm to 393.6 nm. (2) The stability of soil colloid is related to the degree of soil salinity. Compared with non-saline-alkali soil and mild saline-alkali soil, moderate saline-alkali soil colloid exhibited significantly high stability, likely due to elevated high pH and high alkalinity. (3) Organic materials had minimal effect on the colloid stability of non-saline-alkali soil and mild saline-alkali soil. However, CM and MS treatments significantly reduced the colloid stability of moderate saline-alkali soil, causing colloidal particles agglomerated. Therefore, in moderate saline-alkali soil, the application of cow manure and maize straw may be more effective than biochar for stability improvement.【Conclusion】The application of organic materials ameliorates the basic physicochemical properties of saline-alkali soil and optimizes the state of soil colloid. Compared with biochar, cattle manure and maize straw, due to their rich functional groups and nutrients, significantly reduced the colloid stability of moderate saline-alkali soil upon application, thereby inducing colloidal aggregation and promoting the formation of microaggregates.

• The Contribution of Microbial Necromass Carbon and Its Influencing Factors in Biocrust-Covered Soils in the Mu Us Desert

  mengyanrong, Baicunlin, Zhao guangwei, Niuxiangwen, SheWeiwei, ZhangYuqing, QinShugao, Yang Jing, Jiang Ya Wen, Li Ming Jie, FengWei

  DOI: 10.11766/trxb202404240168

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  Abstract: 【Objective】Biocrusts are critical surface covers in desert ecosystems that play an essential role in enhancing soil organic carbon (SOC) sequestration through various biological and physicochemical processes. Despite extensive research on biocrust functions, the contribution of microbial necromass carbon (MNC) under biocrust (BSCs) coverage to SOC and its influencing factors remains unclear. This study aims to address this knowledge gap by analyzing the role of cyanobacterial, lichen, and moss crusts in the Mu Us Desert.【Method】Soil samples were collected from the cyanobacterial, lichen, and moss crust layers, as well as from the underlying soil (0–5 cm depth), to investigate their physicochemical properties and amino sugar contents as proxies for MNC. Contributions of fungal necromass carbon (FNC) and bacterial necromass carbon (BNC) to SOC were evaluated, and their relationships with soil pH, nitrogen content, exchangeable calcium ions, soil moisture, and particulate organic carbon (POC) versus mineral-associated organic carbon (MAOC) fractions were assessed.【Result】The results revealed that: (1) MNC constituted approximately 57.7%, 47.9%, and 22.5% of SOC in cyanobacterial, lichen, and moss crusts, respectively, while in the underlying soil, MNC contributed 40.7%, 40.2%, and 28.5% of SOC for the respective crust types. (2) Across all crust types, FNC contributed significantly more to SOC than BNC, with average contributions of 28.4%±10.7% and 11.2%±4.8%, respectively. (3) MNC, especially FNC, had a stronger influence on the POC fraction compared to MAOC, suggesting its dominant role in labile carbon pools. (4) Positive correlations were found between FNC and BNC and soil nitrogen contents (ammonium, nitrate, and total nitrogen) as well as SOC. Conversely, significant negative correlations were observed with soil pH, exchangeable calcium ions, and moisture content. These findings indicate that soil properties strongly regulate the dynamics of MNC in biocrust-covered soils. (5) The spatial variability of MNC contributions highlights the critical role of crust type and underlying soil characteristics in shaping microbial-derived SOC.【Conclusion】This study highlights that the contribution of MNC to SOC diminishes from cyanobacterial to lichen to moss crusts, with FNC consistently being the dominant component. MNC primarily contributes to the POC fraction, underscoring its role in maintaining active carbon pools. Soil nitrogen content, SOC, pH, exchangeable calcium ions, and soil moisture emerged as key factors influencing the accumulation and decomposition of MNC. These insights enhance our understanding of microbial-mediated soil carbon cycling and sequestration mechanisms in arid ecosystems. Furthermore, the findings underscore the importance of preserving biocrust integrity to sustain carbon storage functions in desert landscapes. The results provide a scientific foundation for devising carbon management strategies aimed at mitigating desertification, enhancing carbon sequestration, and fostering sustainable development in desert regions.

• Extraction of Biofilms and Mineral Response Characteristics of Interspecific Interaction in Acidic Purple Paddy

  Yan Guili, Wen Yi, Zhao Sheng, Xiong Xuan, Liu Shanpeng, Jiang Yu, Tang Yuqing, OUYANG Kai

  DOI: 10.11766/trxb202406210252

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  【Objective】Soil minerals, as the main carrier of biofilms, regulate the formation of multi-species biofilms in soil and profoundly affect the types of bacterial interactions within the biofilm.【Method】To further reveal the interaction mechanism between soil active components and multi-species biofilms, this study selected common minerals such as kaolinite, montmorillonite, and goethite in soil, as well as strains extracted from paddy soil, as research objects. Single strains were paired and co-cultured with soil minerals. In situ monitoring was carried out using confocal laser scanning microscopy (CLSM) combined with the crystal violet staining method, to explore the formation of multi-species biofilms and the response of bacterial species interactions within biofilms to soil minerals.【Result】The results show that compared with the pure bacterial system, both kaolinite and montmorillonite treatments significantly inhibited the formation of multi-species biofilms, and the S-1+S-14 combination in the kaolinite treatment system was most inhibited, with a decrease of 42.57% in biofilm biomass. The addition of kaolinite changed the interaction between the S-1+S-2 strain combination from synergistic to neutral and adjusted the S-1+S-8 combination from neutral to antagonistic. However, montmorillonite alleviated the antagonistic interaction between the S-1+S-14 and S-1+S-15 strains, and their interaction relationship shifted to neutrality. The treatment of goethite significantly promoted the formation of multi-species biofilms in the four groups, with the S-1+S-14 combination showing the greatest increase in biofilm biomass (46.45%). Also, the addition of goethite significantly enhanced the synergistic effect of the S-1+S-2 mixed microbial community, causing the interaction between microbial communities in the S-1+S-8 and S-1+S-14 combinations to shift from neutral and antagonistic to synergistic, and adjusting the S-1+S-15 combination from antagonistic to neutral.【Conclusion】This study clarifies the effects of different types of soil minerals on the formation of multi-species biofilms and reveals the potential mechanisms for the transformation of interactions between microbial communities within biofilms. The results of this study can provide theoretical guidance for a deeper understanding of the microbial effects of soil components and soil biological processes, as well as further exploration of soil biological resources.

• Effects of Different Types of Vegetation Restoration on Soil Pore Characteristics in Benggang Erosion Areas

  WANG Qiankun, ZHANG Xin, YANG Wei, PENG Jue, WANG Junguang

  DOI: 10.11766/trxb202408270344

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  【Objective】This study aimed to investigate the impact of different vegetation restoration types on soil pore characteristics in Benggang areas.【Method】Surface soil samples were collected from four vegetation-restored lands (artificial arbor, artificial forest, artificial shrubland, and artificial grassland) in the Benggang erosion area and an unplanted site was selected as the control (eroded land). The pore characteristics of the aggregates (3~5 mm) were visualized and quantified using X-ray microcomputed tomography (μCT) at a voxel resolution of 5.91 μm. Following the imaging, we measured various physical soil hierarchies, including bulk density, aggregate size distribution, and mechanical composition across multiple scales. 【Result】The results indicated that vegetation restoration significantly improved the formation and stability of soil aggregates, leading to notable changes in aggregate pore characteristics and characterized by high anisotropy and fractal dimension. This suggests that different vegetation types not only influence the physical properties of the soil but also enhance its ability to retain water and nutrients, thereby contributing to overall soil structure. The aggregate pore size distribution varied among the different revegetated sites, reflecting the influence of specific environmental conditions and management practices associated with each type of vegetation. The Soil Structure Index (SSI) was used to assess the overall quality of soil structure. The findings revealed that, except for artificial grassland, the SSI values were consistently higher for all vegetation-restored lands compared to the eroded land. The ranking of SSI values followed artificial arbor (0.66) > artificial forest (0.60) > artificial shrubland (0.48) > eroded land (0.31)> artificial grassland (0.25). This hierarchy underscores the significant benefits of arboreal woodlands, particularly citrus orchards, in enhancing soil structure and stability. 【Conclusion】Overall, the results of this study underscore the critical role of vegetation restoration in promoting ecological recovery and improving soil quality in the Benggang erosion areas of South China. By demonstrating the positive impacts of different vegetation types on soil aggregate pore characteristics, this research provides valuable insights for land management and ecological restoration efforts. Future studies could expand on these findings by exploring the long-term effects of various restoration practices on soil health and erosion control, thereby contributing to more effective strategies for sustainable land use and environmental conservation.

• Effects of Different Organic Fertilizers on the Formation, Stabilization, and Turnover of Aggregates in Acidic Soil

  ZHANG Jie, ZHOU Jia, WANG Yongmin, SHI Xiaojun, WANG Shuai, YU Haiyan, XU Qingwei, CHANG Xia, WANG Zeyu, YE Sili, HUANG Haiyang, ZHANG Yuting

  DOI: 10.11766/trxb202407230298

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  【Objective】Acidic soil is not conducive to the formation of water-stable macroaggregates, which in turn affects the level of soil fertility and the normal growth of crops. Research suggests that the application of organic fertilizer is an important way to improve acidic soils, however, the effect of organic fertilizers on the formation processes of acidic soil aggregates remains not clear. Also, there is a lack of evaluation and comparison between different types of organic fertilizers. 【Method】The rare earth oxide tracer method was used to test different organic fertilizers with equal carbon content on purple and red soil for 56 days. Four treatments were set up (no organic fertilizer control as CK; ordinary organic fertilizer as OF; biochar organic fertilizer as BC; and bio-organic fertilize as BO) and used to determine the stability of soil aggregates, the content of organic carbon in each fraction of aggregates, soil respiration, and the turnover path and rate of aggregates.【Results】The results showed that compared with the CK, the addition of organic fertilizer effectively reduced the amount of aggregate fragmentation, promoted the turnover and formation of large aggregates (>0.25 mm), and increased the average weight diameter (MWD) of soil aggregates. The BO treatment had the best effect on improving the stability of soil aggregates, which could be increased by 53.5%～103.35%. Adding organic fertilizer promoted the formation of the 0.25 mm aggregates and by calculating the turnover rate of soil aggregates, it was found that the addition of organic fertilizer reduced the turnover rate of large aggregates and increased the turnover rate of small aggregates (<0.25 mm). It is worth noting that in purple soil, the turnover rate of small aggregates was higher than that of large aggregates, while in red soil, the opposite trend was observed. Also, the addition of organic fertilizer promoted soil respiration and significantly increased the content of organic carbon in individual fractions (P<0.05). The total organic carbon content of different treatments was BC > BO > OF > CK, which increased by 14.50%～27.78% in purple soil and only increased by 6.40%～9.82% in red soil. 【Conclusion】In general, the application of organic fertilizer can effectively reduce the fragmentation process of aggregates, promote the turnover of small aggregates to large aggregates, and improve the stability of aggregates. The application of bio-organic fertilizer was more conducive to improving the level of soil water-stable macroaggregate structure, increasing soil stability, and improving soil structure.

• Research Progress on the Mechanism and Related Application of Soil Bio-driven Aggregates Formation and Stability

  MA Zheng, LI Zhenlun, YANG Yuran, LI Jiabing, ZHANG Xinlei, YANG Luyao, GUO Ruiting

  DOI: 10.11766/trxb202407270307

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  Soil aggregates are an important component and basic unit of soil structure, and their stability is crucial for maintaining soil health and crop productivity. The formation and stability of aggregates are the result of the joint action of biological and non-biological factors, and soil organisms (microorganisms and animals) play a crucial role in this process. A thorough understanding of the relationship between soil organisms and the formation and stability of aggregates is of great theoretical significance in elucidating the process and mechanism of soil quality change. However, systematic summaries of the driving mechanisms and current application status of soil organisms in aggregate formation and stabilization are still lacking. This paper reviews the effects of soil microorganisms and animals on aggregate formation and stabilization and clarifies the aggregate formation process and stabilization mechanisms driven by soil organisms. The study discovers that microorganisms mediate aggregate formation and stabilization through their physical characteristics, secretion of adhesive substances, and decomposition of organic matter, while animals mediate aggregate formation and stabilization through biological disturbance and feeding. Furthermore, the current status of using soil organisms and their products to increase aggregate stability is analyzed, emphasizing the potential application of novel soil biological structural modifiers. In conclusion, prospective research directions are outlined for future investigations. Researchers should concentrate on the following areas: (1) The formation and stabilization mechanism of soil aggregates driven by soil organisms on multi-scale interface processes; (2) The composition and genetic regulation mechanism of microbial extracellular polymeric substances (EPS) and glomalin-related soil protein (GRSP); (3) The influence mechanism of soil archaea and viruses on the formation and stability of aggregates; (4) The formation process and stabilization mechanism of aggregates mediated by soil food web; and (5) Development and application of biological soil structure improvers. This paper aims to provide both theoretical insights and technical guidance for maintaining and improving soil quality.

• Construction and application of synthetic communities: a new strategy to improve soil health

  Fang Linchuan, Hu Ziying, Cui Qingliang, Yang Yang, Liang Yuting, Cai Peng, Qu Chenchen, Gao Chunhui, Jiao Shuo, Liu Yurong, Huang Qiaoyun, Tan Wenfeng

  DOI: 10.11766/trxb202410120392

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  Abstract:

  Abstract: Soil health is an important prerequisite to ensuring food security and maintain the services and functions of terrestrial ecosystems. Soil microorganisms play a key role in regulating nutrient circulation, enhancing rhizosphere immunity, and preventing environmental pollution. Rational development and application of microbial resources is an important means to protect soil health and exert soil functions in the future. However, the heterogeneity and complexity of soil ecosystems limit the identification and utilization of microbial functions. Currently, the development of synthetic biology provides new ways and ideas for using microorganisms to promote soil health. By fully exploiting the metabolic diversity, functional stability, environmental adaptability of microbial communities, and rationally constructing synthetic communities, technical support can be provided for the ecological restoration of soil damaged by environmental pollution or degraded in quality due to agricultural use. This review summarizes the approaches, tools, and application scenarios for constructing synthetic communities and explores their mechanisms in remediating contaminated soils, enhancing soil fertility, and promoting plant resistance to soil-borne diseases and abiotic stresses. Furthermore, future research directions are proposed, including the construction of synthetic community repositories, the development of synthetic biology tools, and the application of artificial intelligence for screening synthetic communities. These strategies are of great significance for achieving precise construction and directional utilization of synthetic communities in a specific range to improve soil health and ensure sustainable use of soil.

• Response of Soil Moisture Storages and Soil Carbon Stocks to Typical Patterns of Farmland Shelterbelt Systems in the Hetao Irrigation Area, China

  LIU Liyuan, FENG Tianjiao, XIAO Huijie, JI Mingxin, LI Junran, WANG Dong

  DOI: 10.11766/trxb202406280264

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  Abstract:

  Farmland shelterbelt systems are crucial for improving soil moisture and carbon conditions, ensuring crop production, and enhancing the quality of the ecological environment. However, while serving as a barrier to agricultural ecosystems, farmland shelterbelts also compete with crops for nutrients and moisture resources, resulting in both positive and negative environmental effects. Therefore, exploring the factors influencing the spatiotemporal variations of moisture and carbon conditions within farmland shelterbelts with typical configuration is essential to effectively enhance the ecological benefits of farmland shelterbelt systems, scientifically constructing shelterbelt forests, and improving the ecological environment. In this study, we selected typical configurations of farmland shelterbelt systems, including two-row, four-row, five-row, and eight-row forest belts in the Hetao Irrigation Area. We measured the soil moisture storage (SMS) and soil carbon stocks (SCS) across various spatial positions at different horizontal distances from the shelterbelts (0.3H, 1H, 2H, 3H, 4H, where H represents the height of mature trees) and at different depths (0-20 cm, 20-40 cm, 40-60 cm, 60-80 cm, 80-100 cm), as well as at different temporal scales (early, mid, and late growing seasons across various months). Additionally, the study examined ecological environmental factors, including soil properties, vegetation attributes, and microclimatic factors, to investigate the key factors influencing soil moisture storage and soil carbon stocks within farmland shelterbelt systems. The results showed that: (1) SMS and SCS were highest in the four-row forest belts, with 240.2 mm and 26.7 kg·m-2, respectively, and lowest in the two-row forest belts, with 195.4 mm and 16.1 kg·m-2, respectively. Overall, the general pattern of soil moisture storage and soil carbon stocks across different shelterbelt configurations was four-row > eight-row > five-row > two-row. (2) For the temporal scale, the highest mean SMS (277.7 mm) was recorded in May, while the highest mean SCS (22.04 kg·m-2) was recorded in October. Regarding the horizontal distance, SMS exhibited an increasing trend with distance from the shelterbelt, whereas SCS displayed a decreasing trend. In terms of vertical depth, SMS increased with depth, while SCS gradually decreased as depth increased. (3) Farmland shelterbelts significantly reduce wind speed, solar radiation, and air temperature while enhancing relative humidity and minimizing soil evaporation, with the four-row forest belts exhibiting optimal microclimatic regulation and overall benefits. (4) The ranking of ecological environmental factors affecting soil moisture storage and soil carbon stocks was as follows: soil properties > microclimate factors > vegetation attributes. By analyzing and evaluating the effects of each environmental factor on SMS and SCS under different patterns of farmland shelterbelt systems, this study provides a theoretical basis and scientific foundation for constructing farmland shelterbelt ecosystems.

• Deliberations on Collaborative Supervision of Risk Control and Remediation for Soil Pollution of Constructed Land

  CHANG Chunying, HUANG Zaoquan, LÜ Mingchao, LI Zhaohui, DENG Yirong

  DOI: 10.11766/trxb202408280345

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  Abstract:

  Soil pollution risk control and remediation is the key to the safe use of constructed land. The effectiveness of this work is influenced by both technological development and environmental management, and the systematic and coherent linkage of supervision is crucial. National and local governments have made diverse attempts at the collaborative supervision of soil environments within constructed land. Utilizing local legislation, regulatory documents, and technical standards, these strategies have progressively honed and standardized the allocation of departmental responsibilities, process supervision, and access management, leading to effectively controlling the environmental risks of contaminated sites. Despite these advancements, there is a clear need for further bolstering the all-encompassing and interconnected nature of coordinated supervision. This thesis, based on the analysis of the natural attributes, socio-economic attributes, and soil remediation particularities of constructed land, systematically reviews the current status and typical issues of constructed land soil pollution risk control and remediation, and provides suggestions on optimization of collaborative supervision. Overall, within the framework of the national institutional system, local governments were focused on refining the scope of supervision, formulating implementation details, and strengthening supervision and implementation to meet national requirements, without imposing additional demands. In addition, the text analyzes issues such as unclear scope of joint supervision, insufficient planning considerations, shallow integration of land transfer, and inadequate integration of land plot information. It advances a suite of recommendations for enhancing the coordinated supervision framework, including clarifying supervisory scopes, alignment of land planning with soil remediation endeavors, specification of land transfer procedures, embracing a unified national land spatial "one map" strategy, and strengthening of oversight through a multiplicity of approaches. Future investigative trajectories may delve into the realms of precision regulation, pivot to green and low-carbon remediation methodologies, and digital transformation of soil pollution oversight, all aimed at significantly elevating the collective impact of coordinated supervision. This study offers valuable insights for enhancing the integrated regulatory framework for soil risk control and remediation on constructed land, thereby ensuring the safe and effective use of such land.

• Study on the Composite Pollution of Degradable Microplastics and Thiacloprid

  TIAN Jiayu, GENG Dongmei

  DOI: 10.11766/trxb202409150367

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  Abstract:

  【Objective】Microplastics (MPs) and neonicotinoid pesticides are widespread pollutants in agricultural soils, however, their interactions have not been fully studied. Thus, this study aims to explore the interactive mechanisms between biodegradable MPs [poly(butylene succinate), PBS] and neonicotinoid pesticide (thiacloprid, THI). 【Method】The interactive and adsorption mechanisms of THI on PBS were investigated through adsorption kinetics and isotherm models by considering the influence of common environmental factors like pH, salinity, and dissolved organic matter. Also, the desorption of pre-adsorbed THI from PBS using pure water and simulated intestinal fluid (SIF) as background solutions was evaluated. In addition, the bioavailability of THI in red and black soils treated with different proportions of PBS was compared and analyzed using thin film diffusion gradient (DGT) technology. 【Result】The results revealed that the adsorption process of THI on PBS was consistent with the pseudo-second-order kinetic model, indicating that chemical adsorption was predominant. Also, the adsorption isotherm analysis indicated that the adsorption of THI by PBS was multi-layered, and the experimental data fitted both the Henry and the Freundlich models well (R2 > 0.99). The results also showed that an increase in pH and salinity promoted the adsorption of THI while changing the concentration of dissolved organic matter had little effect on the adsorption process. Furthermore, the desorption experiments found that using SIF, the maximum amount of THI desorbed was 39.4 μg?g-1, which was 1.16 times higher than that desorbed by pure water, suggesting that THI is more easily desorbed in the SIF environment. Using the DGT technology, it was observed that the bioavailability of THI in soil increased after the addition of PBS, and the increase became more significant as the ratio of PBS added was increased. 【Conclusion】PBS can adsorb and desorb THI, and when added to soil, PBS can affect the bioavailability of THI. These findings provide important information for understanding the impact of MPs on the environmental behavior of neonicotinoid pesticides under actual environmental conditions and offer a new perspective on the environmental risk assessment and management of pesticides.

• Toxicokinetics of Phenanthrene in Enchytraeus crypticus

  XIAO Naichuan, YOU Lelin, LIU Jiawen, DAI Wencai, ZHANG Tingting, GAO Ming

  DOI: 10.11766/trxb202409050359

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  【Objective】Enchytraeus crypticus is a model species widely used in toxicology studies and soil environmental risk assessments. It is known for its low sensitivity to polycyclic aromatic hydrocarbons (PAHs) which are prevalent soil contaminants. However, there remains a lack of toxicokinetic research on this species. This study selected phenanthrene as a representative PAH to investigate its toxicokinetics on E. crypticus under different exposure concentrations. 【Method】Laboratory experiments were conducted to study the toxicokinetics of phenanthrene on E. crypticus at three concentrations: 20, 40, and 80 mg?kg-1. Phenanthrene uptake and elimination were monitored over time. Toxicokinetic modeling was used to calculate the uptake rate constant, elimination rate constant, and bioaccumulation factor (BAF). A comprehensive model was also fitted to assess the overall phenanthrene dynamics. 【Result】The results indicated that phenanthrene rapidly accumulated in E. crypticus during the initial exposure phase and reached steady-state concentrations of 47.83±11.69, 106.8±15.52, and 364.1±51.11 mg?kg-1 at exposure levels of 20, 40, and 80 mg?kg-1, respectively. During the elimination phase, phenanthrene was eliminated at a decreasing rate over time. The uptake rate constants increased significantly with exposure concentration, while the elimination rate constants declined, resulting in elevated BAF values at higher concentrations. E. crypticus exhibited high tolerance and bioaccumulation potential for phenanthrene, with prolonged retention at high exposure levels, posing potential risks to soil ecosystems. 【Conclusion】The study concludes that the concentration-dependent toxicokinetics of phenanthrene, particularly differences in uptake, accumulation, and elimination, could result in varied soil environmental risk assessments. These findings underscore the need for careful consideration of such concentration-dependent dynamics in PAH risk evaluations. Furthermore, low-sensitivity species like E. crypticus should receive special attention in environmental risk assessments to ensure accurate evaluations of PAH-related risks.

• Changes in plant- and microbial-derived soil organic carbon in three temperate mature forests

  Liuxinying, Taoyulan, Wangyanping, Zhaoxuechao, Yang shanwu, Wang shandi, Huang li, Li wenhui, Qingkui Wang

  DOI: 10.11766/trxb202406130233

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  【Objective】Forest ecosystems are the largest carbon pool in terrestrial ecosystems, and forest soils are the largest organic carbon pool in terrestrial ecosystems. Soil organic carbon (SOC) is an important component of the carbon pool in terrestrial ecosystems, and plant- and microbial-derived organic carbon are the key components of SOC. So, an advanced understanding of the effects of forest types on plant- and microbial-derived organic carbon is important. 【Methods】From three types of temperate forests: Pinus densiflora, Robinia pseudoacacia and Quercus acutissima, 0-10 cm mineral soil was collected to analyze the contents of lignin phenols and amino sugars, which are biomarkers of soil organic carbon of plant- and microbial-derived organic carbon. Also, the basic physical and chemical properties of soil, and the community structure and activity of microorganisms were investigated. 【Result】The soil total amino sugars, amino glucans, amino galactose, and cytosolic acids were significantly lower in P. densiflora than in R. pseudoacacia and Q. acutissima, Also, the bacterial, fungal, and microbial residue carbon was significantly lower in P. densiflora than in Q. acutissima and R. pseudoacacia, and the content of microbial residue carbon in R. pseudoacacia and Q. acutissima was 1.9 and 2.3 times higher than that in P. densiflora. The contribution of microbial residue carbon to SOC in R. pseudoacacia, Q. acutissima, and P. densiflora was 56.79%, 57.41%, and 52.55%, respectively. In addition, the content of fungal residue carbon was 12.76-16.56 times higher than that of bacterial residue carbon, and its contribution to organic carbon was much larger than that of bacterial residue carbon. Furthermore, it was observed that the content of total lignin phenol and its three types of monomers (V, S and C) followed R. pseudoacacia>Q. acutissima>P. densiflora with, the content of total lignin phenol in R. pseudoacacia and Q. acutissima being 3 and 2.8 times higher than that in P. densiflora. Also, the acid-aldehyde ratios of Vanillyl-based ((Ad/Al)v) and Syringyl-based ((Ad/Al)s) in the soil of R. pseudoacacia were significantly higher than those in Q. acutissima and P. densiflora, suggesting that the decomposition of soil lignin was higher in the R. pseudoacacia.Random forest model predictions showed that total nitrogen, organic carbon, total phosphorus, pH, and xylanase were the main factors affecting soil microbial, bacterial, fungal residue carbon and lignin phenols. Following the structural equation modeling, it was recorded that soil physicochemical and microbial properties are latent variables that have a strong influence on soil microbial residual carbon and lignin content,【Conclusion】Our results indicate that microbial growth can be promoted by improving soil nutrients and microbial properties. Eventually, increasing microbial and plant-derived organic carbon content and contribution to the SOC pool in temperate forest management can, maximize its carbon sequestration potential.

• Response Characteristics and Influencing Factors of Soil Organic Carbon to Reduced Chemical Fertilizers or Organic Fertilizer Substitution

  Wu Nengxiang, Wang Ping, Liu Yalong, Wang Jingkuan

  DOI: 10.11766/trxb202408190332

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  Delving into the impacts of reduced chemical fertilizers (RCF) and organic fertilizer substitution (OFS) on soil organic carbon (SOC) is crucial for understanding the response processes of agricultural SOC pools to fertilization and achieving sustainable agricultural development early. This study aims to explore the impacts of RCF and OFS on SOC under different climatic conditions, initial soil properties, and land use patterns. Furthermore, it endeavors to estimate the key influencing factors and clarify the natural and anthropogenic conditions conducive to SOC accumulation.【Method】After collecting and sorting out 142 published literature, we analyzed the variation characteristics of SOC content under RCF and OFS using meta-analysis. Thereafter, the influence degrees of various factors on SOC were systematically investigated by the Random Forest Model.【Result】The results revealed that SOC decreased by 2.61% on average under RCF. Notably, greater SOC losses were observed in temperate regions (with annual mean temperature < 10°C and annual mean precipitation < 1000 mm), whereas SOC losses were not significant with changes in altitude. Soils with high initial SOC content favored SOC retention. With soil’s initial pH and available phosphorus content increasing, the overall loss of SOC tended to intensify, with the highest SOC reduction reaching 6.91%, however, the effect of initial available potassium was the opposite. The declines in SOC under RCF were similar in farmland and orchards, while changes in SOC in vegetable fields were not significant. In contrast, SOC significantly increased by 14.39% under OFS, with subtropical regions at low to medium altitudes and annual precipitation < 600 mm being more conducive to SOC accumulation. Except for low levels of initially available nitrogen (50 mg·kg-1), no significant differences in SOC were observed among soils with different initial SOC, total nitrogen, and available nitrogen contents. With initial pH and available phosphorus content increasing, the cumulative effect of SOC enhanced, whereas the effect of initially available potassium was the opposite. Among different land use types under OFS, paddy-upland rotation and vegetable field utilization were most favorable for SOC accumulation.【Conclusion】Under the two fertilization systems, the climatic and environmental conditions in subtropical regions are more conducive to SOC sequestration. Compared to the subsurface soil, the impact of RCF and OFS on SOC in the surface soil was more significant. The decline in SOC of RCF was similar in both farmland and orchards, while the change of SOC in vegetable fields was not significant. In contrast, paddy-upland rotation and vegetable fields were the most favorable practices for SOC accumulation under OFS. Additionally, pH and initially available nitrogen were the most critical factors influencing the changes in SOC with RCF and OFS, respectively. These research results are of great significance for achieving carbon neutrality and sustainable development in agriculture as soon as possible.

• Differences in Soil Carbon Sequestration Effects of Long-term Carbonization Straw Return on Soil in Acidic Red Soil Areas in Southern China

  YANG Xin, XU Lingying, XIA Longlong, ZHAO Xu

  DOI: 10.11766/trxb202405210205

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  【Objective】 Converting agricultural straw into biochar and then returning it to the field has received widespread attention at domestic and abroad as a potential pathway for soil improvement and carbon sequestration and emission reduction in the southern acidic red soil area. 【Method】 Relying on the soil column experiments of rice-wheat (paddy-upland）rotation and millet-wheat (upland-upland) rotation established in June 2011, the organic carbon accumulation characteristics and changes in the organic carbon functional group structure of paddy soils (QP and TP) and upland soils (QU and TU) developed from Quaternary red clay and Tertiary red sandstone soils were observed under long-term straw biochar application (BC0, 0 t·ha-1 per season; BC11.3, 11.3 t·ha-1 per season). The relationship between soil organic carbon quantity, structure, stability indicators and soil properties was analyzed, in order to clarify the differences in carbon sequestration effect of biochar application on different acid red soils. 【Result】 The results showed that soil texture, land use type and their interaction significantly affected soil organic carbon density under biochar treatment. Compared with BC0, the increase in soil organic carbon density from 0-20cm was higher in partial clayey soils (QP, 25.22 kg·m-2; QU, 8.07 kg·m-2 ) than sandy soils (TP, 8.67 kg·m-2; TU, 7.58 kg·m-2 ), and higher in paddy soils (QP, TP) than upland soils (QU, TU) after 11 years of BC11.3 treatment. The results of 13C solid-state NMR showed that under the same farming conditions, there was no significant difference in the composition of organic carbon functional groups and stability indicators of soil with different textures. The ratio of alkyl carbon and o-alkyl carbon in paddy soil is higher than that in dryland soil, and the ratio of aromatic carbon, hydrophobicity index and aromaticity are lower than that in dryland soil. pH, bulk density, field water capacity, and total porosity all significantly affected the soil organic carbon content and its stability indicators after biochar application. 【Conclusion】 The above results show that the organic carbon sequestration of partial clay soil is higher than that of sandy soil after long-term straw carbonization and returning to the field in the sour red soil area of South China, but there is no difference in long-term stability. The sequestration of organic carbon in paddy field is larger than that in upland, but upland is more conducive to the long-term stability of soil organic carbon. In this study, we investigated the mechanism of carbon sequestration effect difference between different soils from soil organic carbon and its structural characteristics, and provided scientific basis for the rational use of straw biochar resources.

• Reduction Effect of Reductive Soil Disinfestation on Soil Biological Co-contamination in Different Farmland Soils

  YU Wenhao, YANG Zhiyi, ZHANG Jingqing, LIU Liangliang, HUANG Xinqi, ZHANG Jinbo, CAI Zucong, ZHAO Jun

  DOI: 10.11766/trxb202405290213

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  [Objective] In recent years, the enrichment of soil-borne pathogens and antibiotic resistance genes (ARGs) has led to biological co-contamination of soil, posing a serious threat to agricultural product safety and human health. [Method] To investigate the synergistic remediation effect of reductive soil disinfestation (RSD) on soil biological co-contamination, intensive farmland soils (black soil, red soil and fluvo-aquic soil) with co-contamination of Ralstonia solanacearum, ARGs, and mobile genetic elements (MGEs) were selected. RSD was applied with 1% ethanol (ET,), alfalfa meal (AL, C/N: 21.2), and molasses (MO, C/N: 12.6), alongside controls of maximum water holding treatment (FCK) and untreated soil (CK). Real-time PCR was used to analyze the changes of R. solanacearum, major ARGs and MGEs before and after treatment, and the reduction rate of relative abundance was used to measure the mitigation effect of RSD treatment on soil biological co-contamination. [Result] The results showed that RSD could effectively reduce a variety of ARGs and MGEs, among which AL and MO treatment could decrease the relative abundance of aadA7, aadA21, tet36, sul1, and IS6100 genes in black soil, with a reduction rate of 28.4%~49.9%. After ET treatment, the relative abundance of aadA7, msrE, tetG, tetM, tet36, intl1, IS6100, and IS26 genes in fluvo-aquic soil decreased significantly, and the reduction rate reached 56.2%~81.6%. Additionally, RSD efficiently reduced the relative abundance of R. solanacearum in soil, and the decrease in red soil and fluvo-aquic soil was 88.0%~92.3% and 76.1%~94.2%, respectively. Correlation analysis showed that there was a certain coupling relationship between the relative abundance of R. solanacearum and ARGs and MGEs. In fluvo-aquic soil, the relative abundance of R. solanacearum was significantly and positively correlated with the relative abundances of most ARGs (aadA7, msrE, tetG, tetM, and tet36) and MGEs (intl1, IS6100, and IS26) genes, indicating that RSD treatment had a good synergistic reduction effect on the biological co-contamination in fluvo-aquic soil. Furthermore, there were considerable differences in the correlation results between the relative abundance of R. solanacearum, ARGs, and MGEs and soil physicochemical properties in different soil types. This indicates that the effectiveness of RSD treatment in remedying soil biological co-contamination varies depending on soil physicochemical properties. [Conclusion] RSD can synergistically reduce soil biological co-contamination caused by the superposition of soil R. solanacearum, ARGs, and MGEs, but its reduction effect is affected by soil and organic material types.

• Temporal dynamics and fraction accumulation characteristics of black soil organic carbon under long-term continuous straw return

  Zhang Jiaqi, wangcui, Wang Mingming, Pan Fengjuan, Hao Xiangxiang, Sui Yueyu

  DOI: 10.11766/trxb202404290176

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  【Objective】Straw returning is an effective measure to increase the amount of soil organic carbon (SOC) in agroecosystems. The objective of this study was to study the temporal dynamic of SOC in Mollisols during long-term straw return. 【Method】Based on an 18-year long-term field experiment using a maize-soybean rotation cropping system in the typical black soil region，the temporal dynamic of topsoil (0-20 cm) organic carbon was studied under three treatments: no fertilizer (NF), mineral fertilizer (NPK), and mineral fertilizer with straw return (NPKS). Furthermore, physical and chemical fraction methods were applied to study the effect of straw return on SOC pools. 【Result】The results showed that: (1) Compared with the initial (2004) soil, the SOC content significantly increased by 12.97% in the NPKS treatment, with an annual increase of 0.18 g·kg-1, and the SOC content significantly decreased by 3.9% in the NF treatment, while no significant change was found in NPK treatment. (2) There was a significant positive correlation between SOC content and year and the cumulative carbon input in the NPKS treatment. In particular, a significant relationship between SOC and cumulative carbon was observed from 2004 to 2015 under NPKS, while not from 2015 to 2022, indicating that the increase of SOC caused by straw return mainly occurred in the first 11 years, and after 11 years, the SOC reached a state of equilibrium. (3) The NPKS treatment increased the carbon content in free light fraction (fLFC), occluded light fraction (oLFC), the heavy fraction (HFC), humic acid (HAC), fulvic acid (FAC), and humin (HMC) by 47.77%, 34.77%, 11.18%, 13.00%, 6.32%, and 11.71%, respectively. Straw return improved the C proportion in labile fractions (fLFC and oLFC) and decreased the proportion of HFC, but the contribution of HFC to SOC improvement was more than 80%. Thus, the stable HFC was a key component for the long-term sequestration of SOC. In addition, straw return increased the ratio of HA/FA, consequently, increasing the humification degree of soil organic matter. 【Conclusion】Long-term continuous straw return can effectively improve the content of SOC and its fractions in black soil, but after 11 years of continuous straw return, SOC will stop growing and reach a new equilibrium. Although the labile SOC was elevated at a higher percentage than the stable SOC，the stable SOC still plays a crucial role in maintaining the stability and quantity of SOC.

• Differences in Soil Erosion Resistance Between Different Vegetation Types of Purple Soil in the Three Gorges Reservoir Area

  FENG T, CHEN Xiaoyan, ZHU Pingzong, PAN Zhenhua, YANG Lan, WANG Dingbin

  DOI: 10.11766/trxb202407080276

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  【Objective】Soil erosion resistance reflects the vulnerability or sensitivity of soil to erosion, which is a critical parameter utilized for soil erosion prediction and is of significant importance for predicting regional soil erosion and adjusting land use patterns. Nevertheless, the potential effect as well as their driving mechanism of vegetation types on soil erosion resistance is still scarce in the purple soil of the Three Gorges Reservoir Area. Therefore, this study aimed to explore the potential effect of vegetation types on soil erosion resistance and decipher the influencing mechanisms of purple soil in the Three Gorges Reservoir area. 【Method】Based on a full field investigation in the Qinling watershed of Zhongxian Country in the Three Gorges Reservoir area, seven typical vegetation types of the coniferous forest of Cupressus funebris Endl. (CF) and Pinus massoniana Lamb. (PM), broadleaf forest of Eucalyptus spp. (E), Citrus reticulata Blanco.(CR), shrub (S), grassland (G) and maize (M) were selected. Combined with the field sampling and indoor analysis, difference analysis, correlation analysis, redundancy analysis and path analysis, the differences as well as the main influencing factors of soil erosion resistance between different vegetation types were comprehensively analyzed. 【Result】The comprehensive soil erosion resistance index (CSRI) varied from 0.05 to 0.72 between different vegetation types, among which maize had the minimum CSRI, then followed by CR, G, E, PM, S and CF. Moreover, CSRI varied significantly between different vegetation types with the CSRI of SL and CR being significantly lower than that of other vegetation types. Compared to M, CSRI of CR, G, E, PM, S, and CF increased by 210%, 407%, 779%, 816%, 1095% and 1217%, respectively. Differences in CSRI between different vegetation types was closely related to near-surface soil properties and vegetation characteristics. Correlation analysis indicated that CSRI was significantly positively correlated with organic matter content, water-stable aggregates content, total porosity, clay content, litter weight of the semi-decomposed layer, and root mass density, whereas significantly negatively correlated with bulk density (p<0.05). The results of redundancy analysis showed that water-stable aggregates, clay, and organic matter contents were the main factors controlling the differences in CSRI between different vegetation types, which could explain 64% of the total differences. However, the influencing mechanism of vegetation types on CSRI in purple soil was different from most previous studies carried out in other regions. Influenced by the formation process of purple soil, variation in CSRI between different vegetation types was dominantly controlled by clay content via its direct effect and indirect effect through increasing organic matter and water-stable aggregates contents. 【Conclusion】Sloping land and orchard land are still the potential areas of soil erosion in the Three Georges Reservoir area since it has the minimum CSRI. Cupressus funebris Endl land can be promoted as soil and water conservation species in the reservoir area. The relevant research results can provide a scientific basis for the adjustment of land use structure and the selection of tree species for soil and water conservation, to realize the green and sustainable development of the Three Georges Reservoir area.

• Regional Differences of Farmland Soil Organic Carbon Pool Changes in Fujian Province from 1982 to 2018

  LONG Jun, ZHANG Liming, HUANG Qian, ZHANG Xiu, BIAN Ana, ZHU Lixia, CHEN Qingsen, XING Shihe

  DOI: 10.11766/trxb202409220371

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  【Objective】Estimating the spatial-temporal changes of farmland soil organic carbon density (SOCD) provides a scientific basis for food security and double-carbon strategy.【Method】In this study, a total of 371,976 polygonal patches and 57,254 sampling sites were used to establish 1:10,000 databases. The raster dataset of soil organic matter content was interpolated using the simple kriging method combining with ancillary variables of terrain information, which was an optimal interpolation established in the earlier study based on the idea of “ideal interpolation method + efficient auxiliary variables”. Then, the SOM content was assigned to each polygonal patch of the farmland map with the help of the spatial analyst tools of ArcGIS v. 10.8 software. Eventually, the SOCD was calculated. Moreover, the gravity center migration model was employed to quantify the regional differences in farmland SOCD changes in Fujian Province from 1982 to 2018. The regions mentioned above referred to different administrative regions of nine cities, soil types of nine soil groups, three land use types of paddy fields, dry-land, and irrigated land, and two climatic zones such as the middle subtropics and south subtropics of Fujian. Also, these nine cities were divided into the southeastern coastal cities and northwest inland cities of Fujian.【Result】The farmland soils in different regions had dual functions of carbon source and sink in the past 40 years. Viewed from the area ratio of farmland soil carbon source and sink, the carbon sequestration capacity or loss intensity of most farmland was concentrated in the range of 0～1 kg·m-2, regardless of administrative regions, soil types, land use types, or climatic zones. Specifically, the farmland SOCDs in the southeastern coastal cities of Fujian were 2.37～2.65 kg·m-2 and 2.23～2.83 kg·m-2 in 1982 and 2018, respectively, which were much lower than those of northwest inland cities (2.92～3.24 kg·m-2 and 2.99～3.30 kg·m-2). It was also found that Putian was the only city to experience a decline in SOCD, with a carbon source effect of 0.31 kg·m-2. In terms of soil types and land use patterns, paddy soils and paddy fields were the most important carbon sink, with SOCD increased by 0.10 kg·m-2, while coastal solonchaks, aeolian soils, and dry-land contributed as a carbon source, with SOCD decreased by 0.23 kg·m-2, 0.22 kg·m-2 and 0.03 kg·m-2, respectively. When it came to climatic zones, the farmland soil in the middle subtropics of Fujian increased from 3.02 kg·m-2 (1982) to 3.16 kg·m-2 (2018) in SOCD, with higher SOCD level and carbon sequestration efficiency than those of south subtropics.【Conclusion】The farmland soil organic carbon pool changes varied greatly with regions in Fujian Province from 1982 to 2018. These changes might have been mainly influenced by a combination of intrinsic soil factors and external factors such as human disturbance. Thus, our work suggests that in formulating policies for farmland carbon sequestration management in Fujian in the years to come, priority should be given to the SOCD level in different regions and their change differences.

• Spectral Characteristics of Dissolved Organic Matter in Soils with Diverse Vegetation Cover in the River-Lake Confluence Area of Hongze Lake

  CHENG Hu, WU Yudong, GUO Yanhui, MIN Ju, LU Haiying, HAN Jiangang, ZHANG Longjiang, JI Rongting

  DOI: 10.11766/trxb202408070322

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  【Objective】Soil dissolved organic matter (DOM) plays an important role in the biogeochemical processes in wetland ecosystems. This study aimed to uncover the total quantity, components, and source features of DOM in the river-lake confluence area of Hongze Lake. 【Method】The spectral characteristics of DOM in soil covered by lake-sedge, reed, poplar, and willow in the river-lake confluence area of Hongze Lake were studied using UV-visible absorption spectroscopy and the three-dimensional fluorescence spectroscopy method. 【Result】The results showed that the DOM content of soil covered by different vegetation was in the order of reed wetlands, lake-sedge wetlands, poplar forests, and willow forests. Additionally, soil within 40 cm of reed wetlands contained a dissolved organic carbon level of 193.2 mg·kg–1. The soil DOM values of A250/A365, SUVA254, SUVA260, and SR ranged from 3.7 to 4.5, 1.3 to 1.8, 0.86 to 1.8, and 3.6 to 4.9, respectively. Moreover, the molecular weight, aromaticity, and hydrophobicity of lake-sedge wetlands soil were significantly higher than those of other soils. As revealed, DOM""s molecular weight, aromaticity, and hydrophobicity decreased in the 20~40 cm soil layer as opposed to the 0~20 cm soil layer. As shown by EEM-PARAFAC, four fluorescence components, terrestrial humic acid-like, marine humic acid-like, fulvic acid-like, and protein-like, have been recognized. Humic acid-like substances were found in all soil layers, with 55.1% to 70.1% being the majority, but the 20~40 cm soil layer saw a rise in protein-like substances, especially in reed wetlands soil. The FI, BIX, and HIX indices of DOM varied depending on the vegetation, with a range of 1.3 to 1.5, 0.47 to 0.72, and 1.7 to 7.4, respectively. The soil DOM properties were greatly influenced by the coverage of different vegetation. Also, terrestrial humic acid-like substances were the dominant soil DOM in the river-lake confluence area of Hongze Lake, with a lesser level of self-obtained and a higher degree of humification. 【Conclusion】In summary, the research results revealed the differences in total DOM content and spectral characteristics of soils with different vegetation cover in the river-lake confluence area of Hongze Lake. It further provides a scientific basis for understanding DOM environmental behavior in the river-lake confluence area, thus, strengthening carbon sequestration efficiency in key areas and enhancing habitat protection.

• Latitudinal Zonal Variation of Surface Properties of Soil Particles with Different Particle Diameters

  YU Linqiao, HE Aizhou, LI Hang

  DOI: 10.11766/trxb202406210248

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  【Objective】The spatial distribution of soil is consistent with the changes in bioclimatic conditions, with the soil mineral and organic composition also showing certain zonal changes. Consequently, the evolution of soil minerals accompanies the changes in soil surface properties. However, it remains unclear how these changes will vary among soil particles of different sizes. The goal of this study was to research the surface properties of soil particles with different diameters of 0-500, 500-1 000, 1 000-2 000, and > 2 000 nm in the latitudinal zonal soils and reveal the zonal changes of soil particle surface properties in different particle diameter ranges. 【Method】The surface electrochemical properties (specific surface area, surface charge amount, charge density) of soil particles were determined by the combined determination method, the organic matter of soil particles was determined by the potassium dichromate method, the mineral composition of soil particles was determined by X-ray diffractometer. 【Result】It was found that: (1) < 2 000 nm soil particles played a major role in the contribution of soil organic matter, secondary minerals, specific surface area, and surface charge while < 500 nm soil particles were the largest contributors to the soil specific surface area and surface charge. (2) With the decrease of latitude, the content of 0-500 nm particles gradually increased, the content of secondary minerals increased, the content of organic matter decreased, and the soil surface charge and specific surface area showed decreasing trends. (3) The soil-specific surface area and surface charge in the high latitude area increased linearly with the increase of the content of organic matter and montmorillonite, and the influence of montmorillonite content was greater than that of organic matter content. There was no obvious linear relationship between the specific surface area and surface charge with the increase of illite content. Also, the soil-specific surface area and surface charge increased linearly with the increase of organic matter content in the low latitude area while there was no obvious linear relationship between the specific surface area and surface charge with the increase of illite or kaolinite content. 【Conclusion】The soil specific surface area and surface charge at high latitudes were mainly affected by the contents of montmorillonite and organic matter, while the soil specific surface area and surface charge at low latitudes were mainly affected by the content of illite and organic matter.

• Impact of Ralstonia solanacearum Invasion on the Interaction Between Bacterial and Fungal Communities in Tomato Rhizosphere

  PENG Junwei, LIU Qin, DONG Yuanhua, LI Jiangang

  DOI: 10.11766/trxb202408290347

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  【Objective】Ralstonia solanacearum, a highly virulent plant pathogenic bacterium, causes bacterial wilt in tomatoes and other crops. This causes host death and significant yield losses, posing a serious threat to agricultural economies. The rhizosphere, as a critical environment for plant-microbe interactions, plays a decisive role in determining the outcome of pathogen invasion and plant health. However, the interactions between bacteria and fungi in the rhizosphere under pathogen invasion remain unclear, thus, limiting the understanding of the microbial changes associated with bacterial wilt disease.【Method】This study investigated the impact of R. solanacearum invasion on the composition and interaction networks of bacterial and fungal communities in the rhizosphere of diseased and healthy tomato plants. Quantitative real-time PCR (qPCR) was employed to quantify microbial abundances, while high-throughput amplicon sequencing was used to characterize the diversity and structure of bacterial and fungal communities. By comparing the microbial co-occurrence network in rhizosphere soils of diseased and healthy tomato plants, the study aimed to elucidate how pathogen invasion affects the microbial community structure and their ecological interactions.【Result】The results showed significant differences in the bacterial communities between the rhizospheres of diseased and healthy plants. The rhizosphere of diseased plants was invaded by a higher abundance of R. solanacearum, while the rhizosphere of healthy plants was significantly enriched with bacteria from the phyla Actinobacteria and Firmicutes, which include a greater number of beneficial bacteria with potential for biological control. Moreover, pathogen invasion reduced the ecological niche breadth and qPCR counts of fungi in the rhizosphere. Co-occurrence network analysis revealed that the bacterial-fungal network in diseased rhizospheres was more complex, with a significantly higher proportion of fungal nodes (46.7% compared to 31.0% in healthy rhizospheres). Among them, Ascomycota species emerged as key network nodes, indicating that pathogen invasion enhanced the close associations between bacteria and fungi (particularly Ascomycota species). In the direct bacterial-fungal interactions, the proportion of negative correlations in diseased rhizospheres (46.3%) was notably higher than in healthy rhizospheres (35.4%), suggesting that pathogen-induced interactions were predominantly antagonistic. Additionally, in the bacteria-fungi networks, Ascomycota and Actinobacteria were identified as key fungal and bacterial taxa, serving as biological indicators in diseased and healthy rhizospheres, with significant positive (R2 = 0.393, P = 0.002) and negative (R2 = 0.523, P = 0.000 2) correlations with pathogen abundance, respectively.【Conclusion】These results elucidate the disruptive effects of R. solanacearum on rhizosphere microbial communities, particularly the bacterial-fungal ecological interactions, and highlight the changes in rhizosphere microbial structures under bacterial wilt. This study provides a theoretical foundation for developing future strategies to control bacterial wilt in tomatoes.

• Evolution Characteristics of the Conversion Threshold of Different Potassium Forms in Two Typical Paddy Soils

  HU Congyue, HAN Guangzhong, YANG Jinling

  DOI: 10.11766/trxb202408060320

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  【Objective】In the past few decades, soil potassium has received less attention than nitrogen and phosphorus, despite that potassium loss in farmland is a common issue due to large crop demand and the relatively small application amount. Soluble potassium resources are relatively unabundant in China. The low self-sufficiency rate and high reliance on imports led to the high cost of potassium fertilizers. Due to the importance of potassium in crop production and the cost and environmental consequences of applying potassium fertilizer, it is worth paying attention to mineral potassium in future agricultural production. It has been found that there is a unique potassium release mechanisms of layered silicate potassium-rich minerals in paddy soils. However, there is currently a lack of systematic research on the changes and influencing factors of different potassium transformation thresholds during the formation of paddy soils, which greatly limits the establishment and development of potassium transformation models for these soils. 【Method】This study selected "potassium-rich" purple paddy soil and "potassium-poor" red paddy soil, and investigated the evolution characteristics and influencing factors of different potassium transformation thresholds during their formation through time series analysis. The aim was to provide theoretical support for reducing the dependence on soluble potassium fertilizers in rice fields. 【Result】 For "potassium-rich" purple paddy soil, traditional rice cultivation in the early stages (within 0-20 years) significantly reduced the total amount of water-soluble potassium and exchangeable potassium in the plow layer (about a 28% decrease). After this period, the transformation thresholds between water-soluble potassium and exchangeable potassium, and between exchangeable potassium and non-exchangeable potassium, remained relatively stable, with thresholds stabilizing between 61±4 and 106±9 mg·kg-1, respectively. For "potassium-poor" red paddy soil, the total amount of water-soluble potassium and exchangeable potassium also decreased significantly in the early stages of rice cultivation (within 0-100 years), reaching very low levels (about a 30% decrease). Subsequently, the transformation thresholds between water-soluble potassium and exchangeable potassium, and between exchangeable potassium and non-exchangeable potassium, stabilized, with thresholds remaining between 32±4 and 64±4 mg·kg-1, respectively. 【Conclusion】During the formation of paddy soils, the potassium forms and transformation thresholds in these soils are closely related to the potassium-rich minerals in clay and silt particles. The potassium release mechanisms of layered silicate potassium-rich minerals can remain stable over a long period during the formation of "potassium-rich" paddy soils. For red paddy soils, especially those with over 200 years of rice cultivation, it is necessary to increase potassium fertilizer input in a sustainable and potassium-balanced manner to avoid negative potassium balance in the fields. There is great potential in using gravel-rich layered silicate potassium minerals as an alternative to traditional potassium fertilizers in paddy fields.

• Effects of Microplastics with Different Concentrations and Particle Sizes on N2O Emissions from Agricultural Soils Under Different Temperature Conditions

  SHI Mengxuan, LI Haochen, ZHOU Pengyu, WAN Quan, CHEN Zonghai, LI Yige, LU Ying, LI Bo

  DOI: 10.11766/trxb202406040221

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  【Objective】Microplastic (MP), with its small size and low degradability, is recognized as a potential persistent organic pollutant in terrestrial ecosystems. MP enters terrestrial ecosystems and affects the soil nitrogen cycling process by changing the soil’s physical, chemical, and biological properties. These changes affect soil N2O emission. Despite having gained global attention, the key factors and mechanism of MP influence on soil N2O remain unclear. Therefore, this study aimed to investigate the effects of MP size and concentrations on N2O emission from agricultural soils at different temperatures and thus explore their potential mechanism. 【Method】Agricultural soils were collected from plots in South China for indoor culture experiments, and five different treatment sets were selected under three temperature gradients (10 ℃, 20 ℃ and 30 ℃): (1) no microplastics (CK); (2) addition of microplastics with a mass concentration of 0.1% and a particle size of 74 μm (Nlp-0.1%); (3) addition of microplastics with a mass concentration of 0.5% and a particle size of 74 μm (Nlp-0.5%); (4) addition of microplastics with a mass concentration of 0.1% and a particle size of 25 μm (Nsp-0.1%); and (5) addition of microplastic with 0.5% mass concentration and a particle size of 25 μm (Nsp-0.5%). Afterward, soil N2O concentration as well as inorganic nitrogen and microbial functional genes were determined. 【Result】Elevated temperature significantly increased soil N2O emissions from agricultural soils (P < 0.001), and the cumulative soil N2O emissions at 30 ℃ were 43.3 and 6.3 times higher than those at 10 ℃ and 20 ℃, respectively. In addition, soil NO– 3-N content gradually increased with increasing temperature. The abundance of AOB amoA, Comammox (com2), nirS, nirK, and nosZ functional genes was the highest at 20℃ and lowest at 30℃. The effects of MP of different sizes on soil N2O emissions and related nitrogen cycle functional genes varied widely. Compared with the CK treatment, the Nlp treatment significantly increased soil N2O emission by 37.5% and 838.7% at 10 ℃ and 20 ℃ (P＜0.001). The Nsp treatment significantly decreased the abundance of com2 and nirK functional genes but significantly increased the abundance of nirS functional genes in soil (P＜0.001). The correlation and random forest analyses showed that soil N2O emission was significantly and positively correlated with temperature and the concentration of NO– 3-N, but significantly and negatively correlated with the abundance of AOA amoA, nirK, nirS, and nosZ functional genes (P＜0.05). Furthermore, it was observed that the nosZ functional genes and temperature were the main factors affecting soil N2O emission. 【Conclusion】Elevated temperatures significantly increased N2O emissions from agricultural soils, and different particle sizes and concentrations of MPs had different effects on soil N2O emissions, and there was an interaction effect between microplastics and temperature. The results of this study can provide a scientific basis for investigating the mechanism of MP on N2O emissions from agricultural soils under global warming conditions and for risk assessment.

• The Biocontrol Effect and Microecological Mechanism of Lysobacter enzymogenes Bio-organic Fertilizer on Salvia miltiorrhiza Root Rot

  YOU Chuan, ZHANG Chi, YUAN Ruoyu, MEI Xinlan, WANG Xiaofang†, XU Yangchun, SHEN Qirong, WEI Zhong

  DOI: 10.11766/trxb202406250260

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  【Objective】Salvia miltiorrhiza Bunge, commonly known as Danshen, is a perennial herbaceous plant that is a traditional and widely used medicinal herb in China. Intensive cultivation has led to frequent outbreaks of soil-borne diseases, notably root rot, which significantly limits the yield and quality of Danshen. 【Method】This study compared the antagonistic abilities of four Lysobacter strains isolated from the rhizosphere of Solidago canadensis against the root rot pathogen Fusarium oxysporum 220. To identify the most efficient fermentation substrate for the selected strain, microbial solid-state fermentation was conducted using tobacco stalk, rice straw, sorghum straw, corn straw, and Solidago canadensis straw. Based on the optimal fermentation substrate, a bio-organic fertilizer (BOF) was prepared. Subsequently, pot experiments were conducted to evaluate the effectiveness of this BOF in controlling Danshen root rot. Finally, based on metagenomic sequencing, the key microbial groups and functional genes enriched by BOF were analyzed. 【Result】The results of the study demonstrated that the Lysobacter enzymogenes strain Le395 exhibited strong antagonistic effects against the root rot pathogen F. oxysporum 220. In the organic fertilizer raw material screening experiment, it was found that the optimal fermentation substrate for strain Le395 was Solidago canadensis straw. In the pot experiment, it was observed that the application of the BOF effectively controlled Danshe root rot disease. Compared to the control group (CK), the disease incidence was reduced by 50.3%, and the disease index decreased by 50.2%. Additionally, the BOF showed significant growth-promoting effects. The above-ground fresh biomass of the plants treated with BOF increased by 163.1%, while the below-ground fresh biomass increased by 147.0% compared to the CK group. Finally, qPCR and metagenomics sequencing analyses revealed that the application of Le395 BOF significantly decreased the abundance of Fusarium and F. oxysporum in the rhizosphere of Danshen. It also increased the abundance of Lysobacter and L. enzymogenes, while modulating the rhizosphere microbial community structure and enhancing the abundance of disease resistance- and growth promotion-related functional genes in the rhizosphere. 【Conclusion】These findings provide a theoretical and technical foundation for developing an ecological and sustainable strategy for controlling Danshen root rot using bio-organic fertilizer.

• Differential Responses of Microbial Necromass to Warming in topsoil and subsoil

  YANG Dongqiao, ZHANG Zihan, LU Mengya, DING Xueli

  DOI: 10.11766/trxb202407080274

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  【Objective】Microbial necromass carbon (MNC) is an important component of the soil organic carbon (SOC) pool and probing the response of MNC to climate change is key to a deeper understanding of the mechanisms of microbial-mediated regulation of SOC formation. There is still a lack of understanding regarding the impact of climate warming on topsoil and subsoil MNC accumulation dynamics in different ecosystems. 【Method】This study conducted a meta-analysis of the effect of warming of 8 sample sites on MNC in different soil layers and its contribution to SOC and on the response of topsoil and subsoil MNC to warming (41 for total amino sugars, 69 for glucosamine, 69 for muramic acid and 26 for galactosamine). 【Result】Warming promoted the accumulation of MNC in different soil layers as a whole, especially in the topsoil (14.3%). This may be related to the differences in plant-carbon input and the spatial heterogeneity of microbial communities in different soil layers under a warming background. However, due to the acceleration of the loss of SOC in the subsoil after warming, the proportion of MNC contribution to SOC in the subsoil (12.5%) was higher than that in the topsoil (11.3%). Furthermore, the positive effect of the accumulation of fungal necromass and their contribution to SOC in different soil layers was greater than that of bacterial necromass, suggesting that the new carbon input directly or indirectly regulated the composition of MNC. Moreover, the impact of warming on the accumulation of MNC in different soil layers is bound up with warming amplitude and years. Lower warming (≤ 2℃) promoted microbial anabolism to increase the accumulation of MNC in the topsoil by 17.2%, while the contribution of MNC in increasing SOC in the subsoil pool was significantly promoted (14.7%) during higher warming (> 2℃). On the timescale of warming, long-term warming (> 5a) changed the microbial activity pattern and had a greater impact on the ratio of MNC to SOC in subsoil (42.8%). Meanwhile, the contribution of microbial necromass to SOC was increased with soil depth in forest and cropland, whereas warming weakened the proportion of subsoil microbial necromass to SOC in grassland. 【Conclusion】Based on our analysis, we suggest that research on the dynamics of microbial-mediated organic carbon accumulation in specific ecosystems in response to warming should focus on the response of microbial necromass in both topsoil and subsoils. This would provide a huge boost to understanding and predicting the sensitivity of SOC dynamics to climate change and its feedback mechanisms.

• Rapid Assessment of Critical Coagulation Concentration of Soil Colloids by Zeta Potential

  yuanlei, xuyingde, renkailu, zuoyan, lishaobo, zhangyun, zhangguangcai, wangjingkuan, gaoxiaodan

  DOI: 10.11766/trxb202403140110

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  【Objective】The sedimentation characteristics of soil colloids are intricately linked to soil fertility and erosion resistance, with the critical coagulation concentration serving as a pivotal parameter for evaluating particle aggregation and dispersion. The rapid and accurate determination of this critical coagulation concentration holds significant importance in assessing soil quality. 【Method】This study evaluates the critical coagulation concentrations of three types of particles: —montmorillonite, humic acid, and brown earth colloids, —by observing the trend in zeta potential variation on their surfaces. Through piecewise linear fitting, the feasibility of determining the critical coagulation concentration using the zeta potential method is verified in conjunction with dynamic laser light scattering. 【Result】The findings reveal that: (1) The absolute value of zeta potential in each system decreases with increasing electrolyte concentration. This decline is rapid in the relatively low electrolyte concentration range but slows down in the higher concentration range. (2) The critical coagulation concentration of montmorillonite and brown earth colloids on the charged surface in potassium and calcium ion systems determined through piecewise fitting with electrolyte concentration changes, aligns with measurements from dynamic laser light scattering. (3) However, there was a significant difference between the critical coagulation concentration measured by the zeta potential and dynamic laser light scattering methods for humic acid colloid with variable charged surface in potassium and calcium systems. 【Conclusion】For montmorillonite and brown earth colloidal particles with constant charged surfaces, the zeta potential method can be used to rapidly and accurately determine their critical coagulation concentrations. This method boasts simplicity, requires minimal sample volume, and offers high efficiency. Conversely, for humic acid colloidal particles with variable charged surfaces, the zeta potential method fails to accurately assess the critical coagulation concentration.

• Effects of Long-term Straw Return on Soil Arbuscular Mycorrhizal Fungi and Their Ecological Network

  SHI Qihuan, Zhang Yanjie, ZHOU Guixiang, ZHANG Jiabao, ZHANG Congzhi, LU Shunbao, JIA Chunhua, LIU Mingfeng

  DOI: 10.11766/trxb202404100150

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  Abstract：【Objective】Arbuscular mycorrhizal fungi (AMF) play a crucial role in soil microbial ecological networks and can form symbiotic structures with about 80% of plants, making them a key component of sustainable soil management. 【Methods】In order to reveal the response mechanism of soil AMF and their ecological network to straw return in the fluvo-aquic soil area of North China Plain, experimental plots with different straw return treatments were chosen under long-term wheat-maize rotation, and high-throughput sequencing and ecological network analyses were applied to elucidate the composition of soil mycorrhizal practices and fertilization treatments. The experiment was set up with five treatments and three replications, including T1: straw removal + PK fertilizer; T2: straw mulching + PK fertilizer; T3: straw removal + NPK fertilizer; T4: straw mulching + NPK fertilizer; and T5: straw burying + NPK fertilizer.【Results】The results showed that: (1) Straw incorporation with NPK fertilizer significantly decreased soil pH and increased the content of soil organic matter, total nitrogen, ammonium nitrogen, available potassium, and available phosphorus (P < 0.05). This suggests that the combination of straw and NPK fertilizer is effective in enhancing soil fertility. (2) Different treatments of straw burial and nitrogen fertilizer application significantly affected the community composition of AMF, however, there was no significant difference in the alpha diversity of the communities. Nevertheless, Glomus and Paraglomus were the main dominant genera of the AMF community in the fluvo-aquic soil, highlighting their important role in these ecosystems. (3) Co-occurrence network analysis revealed seven distinct ecological network modules. Notably, the species abundance in module VI showed a significant positive correlation with several soil nutrient indices, including organic matter, nitrate nitrogen, available phosphorus, available potassium, and total nitrogen (P < 0.05). This module also exhibited a significant positive correlation with N-acetylglucosaminidase activity, an enzyme involved in nitrogen cycling (P < 0.05). Conversely, the species abundance in module VI was significantly negatively correlated with soil pH (P < 0.05).【Conclusion】Different straw returning methods can effectively regulate soil fertility by improving soil physicochemical properties, modulating the structure and diversity of soil microbial communities, and adjusting AMF network interactions. By understanding the complex interactions between AMF communities and soil management practices, we can develop more effective strategies for maintaining soil health and productivity. This research provides valuable insights into the mechanisms by which straw returning and fertilization treatments influence AMF communities and their ecological networks, offering a foundation for future studies and practical applications in sustainable agriculture.

• Effects of Different Straw Returning Methods on the Accumulation of Plant- and Microbial-derived Carbon in Shajiang Black Soil（Vertisol）

  Yu ZiZhou, Guo ZiChun, Ding TianYu, Wang YueKai, Zhang Ping, Peng XinHua

  DOI: 10.11766/trxb202406010218

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  【Objective】Soil organic carbon (SOC) is one of the key factors influencing crop yield in the Shajiang black soil region, and straw returning is an effective method for continuously improving SOC. However, the accumulation characteristics of plant- and microbial-derived carbon and their relative contribution to SOC under different straw returning methods (no-tillage with straw returning, NTS; rotary tillage with straw returning, RTS; deep ploughing with straw returning, DPS) remain poorly understood. Therefore, this study aims to explore these characteristics and contributions of plant- and microbial-derived carbon in 0~10 cm, 10~20 cm and 20~40 cm soil layers of Shajiang black soil under different straw returning methods. 【Method】A seven-year field experiment was conducted using lignin phenols and amino sugars as biomarkers. Mixed soil samples were collected from depths of 0~10, 10~20, and 20~40 cm. The content of plant- and microbial-derived carbon and their contributions to SOC were calculated based on the biomarkers content. 【Results】The results revealed that, RTS and DPS significantly increased the SOC content of each soil layer, with an increase of 113% (P < 0.05). In contrast, the effects of NTS on SOC were mainly concentrated in the 0~10 cm layer after seven years, showing a phenomenon of surface accumulation in SOC. There was no significant difference in lignin phenol content between NTS and RTS (P > 0.05), however, in the 10~20 cm and 20~40 cm layers under DPS treatment, lignin phenol content increased by 57.3% and 36.3%, respectively (P < 0.05), despite a marked decrease in the 0~10 cm layer (P > 0.05). Additionally, the relative contents of Vanillyl (V) and Syringyl (S) phenols under DPS were significantly increased (P < 0.05) and the degree of oxidative degradation of lignin in the 10~40 cm layer was lower than that under NTS and RTS. Furthermore, amino sugar content showed no significant difference between NTS and RTS in each soil layer. However, under DPS, amino sugar content in the 10~20 cm and 20~40 cm layers increased by 45.6% and 35.8% in comparison with RTS, respectively (P < 0.05). The variation trend of Glucosamine (GluN) and Galactosamine (GalN) with soil depth was similar to amino sugar content, but in the 0~20 cm layer, Muramic acid (MurN) content under NTS and DPS was lower than that of RTS, with a highest decrease of 47.2%. Interestingly, DPS promoted the transformation of microbial community towards fungi, with the carbon ratio of fungal necromass to bacterial necromass in the 10~20 cm and 20~40 cm layers increasing by 177% and 58.0%, respectively, compared to RTS (P < 0.05). 【Conclusion】The substantial increase in SOC content primarily results from a significant rise in crop residue content observed in the topsoil (0~10 cm) under NTS and RTS, as well as in the deeper soil (10~40 cm) following DPS. Our findings suggest that DPS promotes the accumulation of plant- and microbial-derived carbon in deeper soil layers, increases the contribution of microbial carbon to SOC and enhances the stability of carbon pool, which is crucial for the efficient utilization of straw resources and improvement of soil quality in Shajiang black soil region.

• Effect of Nitrogen and Phosohorus Addition after Straw Input on the Microbial Community Structure and the Accumulation of Necromass in Paddy Soil

  LU Mengya, WANG Zhiquan, ZHANG Kun, DING Xueli

  DOI: 10.11766/trxb202406220253

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  【Objective】Paddy soil has enormous potential for carbon sequestration and straw inputs in these soils strongly influence the microorganism-mediated turnover of soil organic carbon (SOC). This study aims to explore the microbial processes involved in the formation of SOC in response to straw inputs and to determine the regulatory effects of nitrogen and phosphorus on these microbial processes. 【Method】A 300-day laboratory experiment was conducted to investigate the effects of straw (S) and straw combined with nitrogen and phosphorus nutrient additions (S+NP) on soil microbial communities and their necromass accumulation processes, in a subtropical red loam rice soil. Phospholipid fatty acids (PLFA) and amino sugars (AS) were used as microbial biomarkers to indicate living microbial biomass community and necromass, respectively. 【Result】The results showed that compared to the control (CK) treatment, the S and S+NP treatments significantly increased the total soil PLFA content (P < 0.05) and the increase in fungal biomass (65.1%-30.1%) was greater than that of bacterial biomass (22.6%-34.3%). Fungal biomass was significantly higher in the S+NP treatment than that in the other treatments at the later incubation stage of 300 d, and the ratio of fungal/bacterial biomass (F/B) also significantly increased in straw plus high rate of nutrient supply (P < 0.05). Our results suggested that nitrogen and phosphorus application may affect soil microbial community structure over a longer time after straw amendment, which gradually shifted towards a fungal-dominated community structure with time. The accumulation of microbial necromass was significantly higher in both S and S+NP treatments than in the control throughout the incubation period (P < 0.05), and the dynamics of fungal necromass mirrored the total microbial necromass. However, bacterial necromass reduced remarkably at the end of the incubation and their content was significantly lower in the S+NP treatment than that in the S treatment (P < 0.05), suggesting its decomposition in the later stages of incubation. Further correlation analysis showed significant positive correlations between microbial biomass, microbial necromass and SOC (P < 0.05). This demonstrates the importance of microbial mediated mechanisms driving SOC formation and transformation in paddy fields following exogenous straw application. 【Conclusion】In conclusion, the impact of straw return on soil organic carbon pool in paddy fields is closely related to microbial community structure and its mediation of necromass accumulation process, which may be regulated by extraneous nutrient supply. Furthermore, supplementation with moderate amounts of nitrogen and phosphorus nutrients can facilitate the accumulation of organic carbon fractions of microbial origin over longer time scales, especially the fungal necromass carbon. This will be of significant importance in regulating microbial-mediated organic carbon sequestration processes through on-farm nutrient management practices.

• Research Progress on Ecological Effects and Microbial Degradation of Biodegradable Plastics in Soils

  HAN Yujuan, TENG Ying

  DOI: 10.11766/trxb202405270210

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  Biodegradable plastics are considered ideal replacements for traditional plastics due to their easy biodegradability, and have broad application prospects. Soil is an important destination for various biodegradable plastic waste. A comprehensive understanding of the ecological effects of biodegradable plastics in the soil environment can provide a scientific basis for evaluating the ecological safety of biodegradable plastics, which is the foundation and prerequisite for their large-scale promotion and application. Given that microbial degradation is the main pathway for the degradation of biodegradable plastics in soil, a thorough understanding of the degradation process and mechanism can provide theoretical guidance for achieving efficient and controllable in-situ degradation of biodegradable plastics. This paper first summarized the ecological toxicological effects of biodegradable plastics on soil ecosystems from the perspectives of soil physicochemical properties, soil microorganisms, plants, and animals. Biodegradable plastics entering the soil environment are not only a physical input, but also a chemical input, which can change the physicochemical properties of soil, such as bulk density, porosity, and nutrient content. They can directly or indirectly affect the structure and function of soil microbial communities, and affect the growth and development of plants as well as the survival and reproduction of soil animals. Furthermore, the microbial degradation mechanism of biodegradable plastics in soil and the key factors affecting degradation efficiency were further summarized. Soil microorganisms degrade biodegradable plastics mainly through three key steps: colonization on the plastic surface, secretion of extracellular enzymes that catalyze polymer depolymerization, and mineralization of oligomers or monomers. The degradation rate of biodegradable plastics in the actual soil environment is relatively slow, and their degradation efficiency is affected by various factors such as the properties of plastics, soil environment, and climate conditions. At the same time, the microorganisms and enzymes involved in the degradation of biodegradable plastics were systematically combed. Because of the current research status and shortcomings, the key research directions in the future are prospected, aiming to provide scientific reference for the study of environmental impacts and microbial degradation of biodegradable plastics in soil.

• Progress of soil temperature prediction equation

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

  DOI: 10.11766/trxb202210220581

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  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.