Abstract:Gardner, a famous soil physicist, believes that the current soil science knowledge is too fragmented, it is therefore necessary to build a systematic soil science knowledge system. Churchman, an Australian scholar, pointed out that the new knowledge system of soil science must break the boundaries of each soil science branch. In this paper, the necessity as well as the theoretical and methodological basis of the reconstruction of the core knowledge system of soil science were systematically analyzed. This paper indicates that the quantum mechanical description of soil electric-atom interaction can be the theoretical basis for building core knowledge systems of basic soil science, and the quantitative description of the five macro physical quantities, including electrostatic force, long-range van der Waals force, osmotic force, hydrophilic and hydrophobic force, can break the boundaries of each soil science branch, and then study soil as a whole. Based on the quantum mechanics of soil electric-atom interaction and with the help of five macroscopic physical quantities, the systematic description of soil matrix process, interface process and pore process can be realized. Since the physical, chemical and biological processes in soil can be reduced to the correlation and coupling of soil "matrix processes", "interface processes" and "pore processes" at different scales, it is expected to build a new core knowledge system of basic soil science based on the theory and method proposed in this paper.

Abstract:Soil is a complex with high heterogeneity. The early research on digital soil mapping mainly focused on the lateral variation of soil, with less consideration of the vertical variation and three-dimensional (3D) digital soil mapping. In recent years, the rapid developments of 3D geographic information technology and earth observation and detection technology have greatly promoted research on soil 3D data acquisition, 3D prediction, 3D data modeling, 3D model and visualization. In this paper, we reviewed the existing research on soil prediction and soil model construction in 3D space, to provide suggestions for the application and development of 3D digital soil mapping. We searched the Web of Science database by using 3D soil mapping, 3D GIS, 3D data model, 3D geological modeling, 3D visualization, soil spatial variability, spatial prediction, Kriging interpolation, soil-landscape analysis, depth function, machine learning, geostatistics, random simulation as keywords, and selected the key literatures for analysis based on correlation, citation rate and literature sources. We summarized the popular methodologies for soil spatial variability, 3D spatial soil prediction, soil 3D data model, and 3D model construction, and evaluated the advantages, disadvantages and application scenarios of each method. This review presents the common problems of 3D soil mapping, such as sparse soil profile data, low accuracy of 3D soil prediction, and insufficient information to create the data source for 3D soil modelling, and put forward some feasible research prospects.

Abstract:Soil is the main natural resource for human survival and development. In recent years, the aquatic risks induced by the tire rubber antioxidant N-(1, 3-dimethylbutyl-N'-phenyl-p-phenylenediamine (6PPD) and its ozonated derivative N-(1, 3-dimethylbutyl-N'-phenyl-p-benzoquinone (6PPD-Q) are causing global concern. However, little is known about their behavior in soil and the effects on soil biota. Evidence have shown that soil is an important "aggregation" of tire wear particles (TWPs), and the TWPs entering the environment release various species of additives including rubber antioxidants, silica, metals, etc. Among them, p-Phenylenediamines (PPDs) are the most widely added rubber antioxidants due to their excellent performance, which can be released as TWPs into environmental media and produce derivatives such as PPD-Qs. Therefore, it is of great significance to study the fate and ecological environmental risks of 6PPDs and their derivatives in soil. Focusing on their soil environmental safety and ecological health, we introduce the behavioral characteristics of the occurrence, migration, and transformation of 6PPD and 6PPD-Q in the soil environment; describe the accumulation, transport, and metabolism mechanisms of 6PPD and 6PPD-Q in terrestrial organisms; and elucidate their toxicological characteristics and the related toxicity mechanisms on organisms. It provides a theoretical basis for the ecological risk assessment and prevention of 6PPD and 6PPD-Q pollution.

Abstract:【Objective】 This study aimed to construct a high precision prediction method for soil bulk density to accurately complete the regional soil attribute database.【Method】 Based on the data of 2, 883 typical cropland samples in the Sichuan Basin (including Sichuan Province and Chongqing Municipality) obtained during the second national soil census, this study used correlation analysis, variance analysis, and regression analysis to reveal the statistical characteristics and main controlling factors of the cropland topsoil bulk density in the Sichuan Basin. The traditional pedotransfer functions (PTFs), multiple linear regression (MLR) models, radial basis function neural network (RBFNN) model, and random forest (RF) models were used to establish a soil bulk density prediction model through three modeling methods: whole region, by river basin and by soil type, to fill the missing value of soil bulk density.【Result】 The results show that the cropland topsoil bulk density in the study area ranged from 0.60 to 1.71 g·cm^-3, with a mean value of 1.29 g·cm^-3. Soil organic matter, soil subgroup, and rainfall in summer were the most important factors influencing bulk density. The RBFNN model constructed by the river basin can better capture the nonlinear relationship between soil bulk density and the influencing factors and the spatial non-stationarity of this relationship. The coefficient of determination (R²) and root mean square error (RMSE) of the 432 independent validation samples were 0.519 and 0.095 g·cm^-3, respectively, which were significantly better than those of other methods.【Conclusion】 Therefore, the RBFNN prediction model constructed in sub-basin is helpful to improve the imputation accuracy of the missing values of topsoil bulk density in the Sichuan Basin, and also provides a method reference for the imputation of missing values of soil properties in other regions.

Abstract:【Objective】 Cynodon dactylon is a commonly used herbaceous plant for ecological greening, soil consolidation and slope protection, vegetation restoration, and soil and water conservation. Its developed root system network and unique growth characteristics have a significant impact on the formation and spatial reorganization of soil pores. Current research has mostly focused on the role of the plant’s roots in soil aggregate formation and stability, however, the dynamic impact of root growth on soil pores remains unclear. 【Method】 This study employed a pot experiment, selecting Cynodon dactylon as the model plant and typical purple soil and yellow soil from the mountainous and hilly regions of southwestern China as the culture substrates. Four different treatments were established: purple soil with Cynodon dactylon (G), purple soil control (CK), yellow soil with Cynodon dactylon (YG), and yellow soil control (YCK). The soil profile images under different treatments were continuously collected using the minirhizotron technique. The root traits of Cynodon dactylon and soil pore structure parameters at different stages were quantified through optimized root extraction algorithms and image processing techniques. Combined with statistical analysis, the study explored the dynamic growth of Cynodon dactylon roots and their impacts on the evolution of soil pore structure. 【Result】 The results showed that: (1) Cynodon dactylon grew well in both purple and yellow soils, and the root growth rate was higher in purple soil than in yellow soil. The root length, root surface area, and root volume of Cynodon dactylon in purple soil were nearly three times higher than those under yellow soil cultivation conditions; (2) Compared with the unplanted CK and YCK, the growth of Cynodon dactylon significantly reduced the number of pores, porosity, and fractal dimension of purple and yellow soils, and the reduction effect of roots on soil pores continuously increased with root growth; (3) Redundancy analysis indicated that roots explained 40.60% of the variation in soil pore structure, and root length, root surface area, and root volume were the key root traits that reduced soil pore structure parameters. 【Conclusion】 In summary, through the optimized minirhizotron technique, continuous observation of plant roots and soil pores was achieved on site. It was found that Cynodon dactylon significantly reduced pore number and other parameters during its growth period, providing methodological support for in-situ, non-destructive, and dynamic studies on root-pore interactions, as well as theoretical support for vegetation restoration and soil and water conservation in ecologically fragile areas.

Abstract:【Objective】 The submembrane drip irrigation planting mode has been a major factor in the evolution of physicochemical traits after the reclamation of saline-alkali land in inland arid areas, especially the changes in soil salinity and available nutrient content. 【Method】 In this study, the gray desert soil of Xinjiang was studied by continuous localization survey and observation of the sample plot. The sample plots of Manas in Xinjiang were selected for land reclamation in different years beginning from 1996, and four surveys were carried out from 2010 to 2020. The dynamic changes of soil salinity and fertility traits of gray desert soil under the condition of submembrane drip irrigation cotton after reclamation were monitored at fixed points, and the differences of several plots after different planting years were compared.【Result】 The main resulted suggest that the soil salinity in the topsoil (0-20 cm) was significantly reduced after the reclamation from uncultivated land to farmland, and the average salinity of various plots decreased to 3.71 ·kg^-1 after 6-10 years of reclamation. The average annual decline rate was 1.41 ·kg^-1·a^-1, reaching the level of mild salinization, then with the continued reclamation (11-25 years), the soil salinity was maintained between 2.06-2.11 ·kg^-1, and reaching the non-salinization level. The soil pH in different reclamation years showed a significant downward trend after reclamation. With continued reclamation (11-25 years), the average soil pH remained between 8.2 and 8.5, which was slightly alkaline. With increasing years of reclamation, the soil available phosphorus (P) increased significantly, after 11-25 years of reclamation and planting, the soil average available P level remained between 13.33, and 19.97 m·kg^-1. This indicated that the variation of soil fertility was different with the different reclamation years. The soil organic matter increased significantly after 6-10 years of reclamation while the soil available potassium slowly decreased after 1-5 years of reclamation but slightly increased after 6-10 years. Also, available potassium increased to the original level after 11-16 years and then remained stable. The content of soil inorganic nitrogen increased significantly after 6-15 years of reclamation and remained stable after 16-25 years.【Conclusion】 This study showed that the process of reclamation and utilization of uncultivated land into farmland had a significant effect on the improvement and cultivation of soil P fertility. The uncultivated land reclamation and utilization effectively reduced soil salinity and pH, and it took 6-10 years to change the good land after uncultivated land reclamation. This study provides a theoretical basis for the control of salt content and the improvement of fertilization and farmland productivity during the reclamation process of inland saline-alkali uncultivated land.

Abstract:【Objective】 This study investigated the mechanism of different organic carbon (C) sources to control fertilizer nitrogen (N) transformation and its induced soil acidification. 【Method】 Four types of organic C sources (glucose, sodium benzoate, cellulose, and lignin) with different availability for microorganisms were selected for a 45-day indoor incubation experiment. It was conducted under the condition that the C/N ratio of C source and fertilizer (urea) was 40. The effects were analyzed for the combined application of organic C source and urea on N transformation and soil acidity in Ultisol. 【Result】 The results showed that intensive nitrification occurred when urea was used solely in Ultisol, resulting in a soil pH decrease of 1.17 pH units at the end of the incubation. Compared with the sole application of urea, the combined application of organic C sources and urea significantly enhanced soil respiration, and decreased soil inorganic N by 17.1%-99.4% and soil NO₃^--N by 46.1%-99.9%. However, these organic treatments increased soil microbial biomass N and solid organic N (non-extractable N) by 3.0%-14.8%, and increased soil pH by 0.67-3.11 pH units. These findings suggest that the combined application of organic C sources and N fertilizer promoted the immobilization of fertilizer N by soil microorganisms and soil N sequestration, thereby significantly reducing nitrification and soil acidification induced by N fertilizer. Specifically, as a labile organic C source, glucose facilitated the rapid immobilization of fertilizer N by microorganisms in the early stage and the mineralization of organic N in the later stage. It indicated that glucose could play a role in temporary storage and slow release of fertilizer N in the soil. Cellulose was less easily utilized by microorganisms and also promoted microbial immobilization of fertilizer N. Although cellulose was not as fast as glucose, it had strong immobilization capacity and high C use efficiency, which was conducive to the long-term immobilization of fertilizer N in the soil. Lignin, a resistant organic C source, weakly promoted microbial immobilization of fertilizer N but directly inhibited nitrification. The mentioned C sources regulated the N transformation process and increased the soil pH by approximately 0.6 pH units. Sodium benzoate, as a labile organic acid salt, reduced nitrification directly by inhibiting nitrification and indirectly by promoting microbial N immobilization, although the microbial immobilization of fertilizer N was significantly lower than that of glucose and cellulose. Decarboxylation of sodium benzoate rapidly consumed a substantial amount of H+ and significantly increased the soil pH by approximately 3.0 pH units. 【Conclusion】 The chemical properties of organic C sources, including the complexity of their chemical structure, microbial availability, microbial C use efficiency, and microbial toxicity, are the main factors affecting the transformation process of soil C and N, and consequent soil acidification. The findings obtained in this study provide significant theoretical support for the effective and sustainable management of soil nutrients and acidity in cropland.

Abstract:【Objective】 The increase in global food demand and the consumption of phosphorus(P) fertilizer in modern agriculture have caused P accumulation in extensively managed croplands. Most of the accumulated P deposits exist in sparingly soluble or insoluble species, leading to their low availability, which is almost impossible to use directly by plants or microorganisms. Therefore, improving the utilization of soil accumulated P is not only one of the effective ways to enhance the utilization efficiency of P fertilizers but also relieves the increasing tension of P resources. At present, a large number of macroscopic field experiments have revealed the synergistic promoting effect of nitrogen (N) on P activation and uptake. However, in the N and P interaction, in-situ observation of dissolved N interacting with precipitated P has been lacking. 【Method】 Herein, Ca-P precipitates with different solubilities, namely sparingly soluble (DCPD) and insoluble (HAP), were selected as test materials. Taking aqueous solution as control, five NH₄Cl concentrations (0.5, 5, 50, 500, 1, 000 mmol·L^-1) were set as N sources. The in-situ dissolution kinetics of DCPD and HAP at different N levels were directly observed by atomic force microscopy (AFM). AFM-based dynamic force spectroscopy (DFS) technique was employed to characterize the interaction between ammonium cations and DCPD/HAP surfaces at the molecular scale. 【Result】 The result showed that the surface dissolved immediately, accompanied by the formation of triangular etch pits, following the addition of NH₄Cl. When increasing the NH₄Cl concentration, the surface dissolution rate of DCPD was significantly promoted. The quantitative results further exhibited the dissolved P mass was significantly increased from 27.00 mg·kg^-1 to 145.0 mg·kg^-1 with the increase of NH₄Cl concentration from 0.5 mmol·L^-1 to 1 000 mmol·L^-1. By contrast, the surface morphology of HAP almost remained constant without obvious dissolution even if the NH₄Cl concentration was up to 1 000 mmol·L^-1. The dissolved P mass was 5.00 mg·kg^-1, which was not significant compared with the dissolved P mass of 3.00 mg·kg^-1 in aqueous solution. AFM-based DFS results showed that the interaction force between ammonium cations and DCPD (230.6 pN) was significantly greater than that between ammonium cations and HAP (154.0 pN). Due to the difference in binding strength of ammonium cations on Ca-P surfaces at the molecular level, the hydration layer of mineral surfaces is destroyed at different degrees. As a result, the surface dissolution kinetics of DCPD and HAP were significantly different when regulated by ammonium cations. 【Conclusion】 This research provides method guidance for in-situ observation of nanoscale dissolution kinetics of different Ca-P minerals. It also illustrates the enhanced interface dissolution on negatively charged DCPD induced by ammonium cation to release available P, thus improving the continuous P supply capacity in soils.

Abstract:【Objective】 Soil organic carbon (SOC) pool, the largest C pool in terrestrial ecosystems, can achieve long-term C sequestration. SOC plays a vital role in the global C cycle and is a key link in achieving C peaking and C neutrality goals. Humic acid (HA) is one of the most important and more stable components of soil organic matter, representing a more stable soil C pool. The vegetation coverage type of regional soil affects the quantity, quality and composition of HA, and further affects its aggregation characteristics. In this study, HA in surface soil under bamboo forest (Altitude 580 m) and broad-leaved forest (Altitude 280 m) in Jinyun Mountain, Chongqing, was taken as the research object, and then surface properties and aggregation characteristics of these two HA were clarified. 【Method】 The structural characteristics were evaluated by element analysis, thermal gravimetric analysis, and Fourier infrared spectroscopy. Combined with dynamic light scattering and zeta potential measurement, the aggregation kinetic characteristics of these two HA colloids induced by Na⁺, Mg²⁺ and Ca²⁺ were studied and compared. 【Result】 It was found that HA in bamboo forest soil had higher C/N, C/H, stronger thermal stability and aromatic infrared absorption characteristic spectra, indicating HA in bamboo forest soil had more aromatic functional groups, more complex structure, and higher humification degree. The results of dynamic light scattering showed that the critical coagulation concentrations of Na⁺, Mg²⁺, and Ca²⁺ for the HA colloids of bamboo forest soil were 1 097.9 mmol·L^-1, 8.6 mmol·L^-1, and 5.1 mmol·L^-1, respectively. The HA colloids of broad-leaved forest soil did not aggregate in the Na⁺ system, and the critical coagulation concentrations in Mg²⁺ and Ca²⁺ systems were 80.7 mmol·L^-1 and 20.2 mmol·L^-1, respectively. The zeta potential of HA in bamboo forest soil was much lower than that in broad-leaved forest soil. The absolute value of the zeta potential of HA in bamboo forest soil was 3.43 times that of HA in broad-leaved forest soil, which could be used to explain the difference in aggregation characteristics between the two. The sensitivity of the HA in bamboo forest soil to three cations is much higher than that of HA in broad-leaved forest soil, which can quickly aggregate and form larger particle sizes. 【Conclusion】 The change of coverage vegetation types will cause the corresponding change of HA properties in surface soil. The humification degree of HA in high-altitude bamboo forest soil is higher, and the sensitivity to cations is also higher. The results of this study provide an important reference for understanding the formation and stability of HA after organic matter input into soil.

Abstract:【Objective】 The prevalence and dissemination of antibiotics resistance genes (ARGs) in farmland soils have become a major threat to food security and human health. However, there is still no effective method to remediate ARGs-contaminated farmland soil. Chemical fumigation and reductive soil disinfestations (RSD) are widely used to kill soil-borne pathogens in agricultural production, but it is still unknown whether they are capable of reducing the abundance of ARGs in ARGs-enriched soil. 【Method】 In this study, an ARGs-enriched farmland soil due to long-term application of chicken manure was selected, and soil incubation experiment with seven treatments: CK (control without soil treatment), FCK (maximum water holding capacity treatment), DZ (chemical fumigation with 0.02% dazomet), and RSD with 1% ethanol (ET, TOC: 521.7 g·kg^-1), alfalfa (AL, TOC: 454.9 g·kg^-1, C/N: 21.2), molasses (MO, TOC: 270.1 g·kg^-1, C/N: 12.6) and the mixture of alfalfa and molasses (AM, m/m=1: 1), were conducted to investigate the shifts in absolute abundance and relative abundance of ARGs and mobile genetic elements (MGEs) via real-time PCR. The effects of different treatments on soil ARGs and MGEs were evaluated by reduction rate. 【Result】 Results showed that RSD treatment could decrease the relative abundance of aadA21, msrE, tetG, tetM, and ErmF genes, with the reduction of the aadA21 gene in relative abundance being 50.5%-58.3% in AL-, MO-, and AM-treated soils, while the relative abundances of msrE, tetG, and tetM genes were significantly lowered by ET treatment, with the reduction rate being as high as 80.9%, 78.3%, and 66.9%, respectively. Meanwhile, RSD treatment could significantly decrease the relative abundance of MGEs (IS6100 and IS26 gene), with the reduction rate being 67.7%-74.3% and 38.1%-42.6%, respectively. In addition, the relative abundances of ARGs and MGEs were slightly increased in DZ treatment, with the increasing rate of ARGs and IS26 gene being 21.9% and 42.6%, respectively. 【Conclusion】 Collectively, RSD treatment can decrease soil ARGs contamination by reducing the relative abundance of ARGs and MGEs, limiting the horizontal transfer ability of ARGs, and the reduction effect is related to the type of organic materials used. Moreover, RSD treatment is more effective in reducing the relative abundance of ARGs and MGEs than dazomet fumigation and has the potential for rapid remediation of ARGs-contaminated soil.

Abstract:【Objective】 The degradation of organic pollutants in soil by activated persulfate (PS) with nanoscale zero-valent iron (nZVI) or sulfidized nanoscale zero-valent iron (S-nZVI) is currently one of the research hotspots in in-situ chemical oxidation remediation technologies. Benzene, toluene, ethylbenzene, and xylene (BTEX) are typical odorous pollutants in petrochemical-contaminated sites. Thus, the discovery of remediation technologies aimed to achieve efficient removal of BTEX and the elucidation of the degradation mechanism is of great environmental significance.【Method】 The study established a persulfate oxidation system using biochar-supported sulfidized nano zero-valent iron (S-nZVI@BC) as the activator, explored the degradation of BTEX under different conditions, and compared its effectiveness with other materials for PS degradation. Moreover, based on chemical probe experiments, electron paramagnetic resonance (EPR) experiments, and purge-and-trap-gas chromatography-mass spectrometry (PT-GC-MS), the degradation pathways of BTEX were indicated.【Result】 The results showed that S-nZVI@BC/PS system had the best degradation efficiency on BTEX in the soil at pH = 3, S/Fe = 1/4, Fe/C = 1/2, S-nZVI@BC dosage of 0.01g·g^-1soil, and PS concentration of 30 mmol·L^-1. The degradation rates of benzene, toluene, ethylbenzene, and ortho-xylene in the S-nZVI@BC/PS system reached 96.7%, 98.5%, 96.9%, and 98.4% within 2 h, respectively. The S-nZVI@BC catalytic system showed the best performance among the five different catalytic systems studied in the order of PS < nZVI/PS < nZVI@BC/PS < S-nZVI/PS < S-nZVI@BC/PS. Also, S-nZVI@BC maintained good reaction activity in a wide range of pH 2-9. There were three active free radicals in the system: SO₄˙-, HO˙, and O₂˙-, among which SO₄˙- was confirmed as the main active substance in the reaction process. Based on main free radicals and intermediates, it is indicated that BTEX may have two degradation pathways: Free radical addition and free radical hydrogen extraction reaction.【Conclusion】 Sulfur modification and biochar loading effectively improved the stability of nZVI catalytic performance, and S-nZVI@BC/PS can efficiently degrade BTEX. This study provides theoretical support for the establishment of efficient degradation technology for odorous pollutants in soils.

Abstract:【Objective】 Paddy soils are extensively polluted by heavy metals (HMs) in China and present significant challenges for safe agricultural use. Thus, this study seeks to address the heavy metal pollution in China's paddy soils, focusing on polluted soils from the Dabaoshan mining areas in Shaoguan, Guangdong Province.【Method】 A flooding-drainage incubation experiment was conducted and combined with chemical extraction, diffusive gradients in thin films (DGT) technology, and correlation analyses. Also, the impact of phosphorus (P) and humic acid (HA) addition on soil Fe speciation and the bioavailability of related elements was evaluated. The selection of P and HA concentrations was based on common agricultural practices to ensure the environmental relevance of this study.【Results】 The results revealed that soil pH gradually became neutralized while redox potential (Eh) decreased during the flooding period. The concentrations of acid-soluble Fe²⁺, amorphous Fe, and Fe activation degrees increased from 1.5 g·kg^-1 to 4.8 g·kg^-1, 6.6 g·kg^-1 to 10.1 g·kg^-1, and 21% to 29%, respectively, with a decrease in amorphous Fe content observed in treatments with added P and HA from 2 to 42 days of flooding. After soil drainage, both amorphous Fe(Fe_ox) and Fe activation degree rapidly decreased to 7.4 g·kg^-1 and 21.6%. Regarding CaCl₂-extractable heavy metals, the lowest values were observed after 14 days of flooding, whereas levels of As, Cd, Cu, and Zn rapidly increased to 0.1, 0.4, 0.3, and 7.0 mg·kg^-1, respectively, after drainage. The addition of P and HA in the early flooding stage increased the As content by 80% and 35% compared to the control, respectively, but decreased the contents of Cu, Zn, and Cd, with HA addition, the reduction rates of CaCl₂-extractable Cu, Zn and Cd were over 67%. During flooding, DGT-extracted P and Fe content initially increased then decreased, while Zn content gradually reduced. The addition of P and HA significantly reduced the bioavailable Zn content in the early stages of flooding while the bioavailable content of P and As was primarily controlled by bioavailable Fe.【Conclusion】 During the soil flooding-drainage incubation, significant changes occurred in soil physicochemical parameters including pH, Eh, and speciation of Fe. The addition of P and HA could regulate the bioavailability of elements such as Fe, P, and HMs. These findings offer valuable insights for the remediation of HMs-polluted soils, highlighting the potential for using P and HA in improving soil quality and ensuring safe agricultural production.

Abstract:【Objective】 Cadmium (Cd) is the heavy metal pollutant with the highest over-limit rate in paddy soil in China. The bioavailability and mobility of Cd are affected by dissolved organic matter (DOM) in the soil. Paddy fields are important food production areas in China. As an important ecological agriculture mode in the rice industry, integrated planting and breeding of rice fields is of great significance to rural revitalization. The modification of paddy field environments and fishing can change DOM, but the complexation process between soil DOM and Cd²⁺ in paddy soil and during integrated planting and breeding of rice field process has not been clearly understood. 【Method】 In this study, the complexation process between DOM and Cd²⁺ in rice-shrimp cultivation (RS) and rice monoculture (CK) systems was investigated using a comprehensive array of analytical techniques, including ultraviolet-visible absorption spectrum (UV-Vis), 3D fluorescence spectroscopy, synchronous fluorescence spectroscopy, parallel factor analysis (PARAFAC), 2D correlation analysis (2D-COS), and the modified Stern-Volmer binding reaction model. Herein, RS was taken as an example of integrated planting and breeding of rice fields.【Result】 The PARAFAC analysis showed that soil DOM components of RS and CK were similar, including 1 tryptophan (C1) and 3 humus components (C2, C3, C4). Compared with CK, the proportions of C2 and C4 in soil DOM of RS were lower, while C3 was higher, and C1 was not significantly different. The UV-vis spectrum showed that DOM absorbance in CK was higher than in RS, with the absorption peak mainly located at 200-230 nm. With the increase of Cd²⁺, the change of UV-vis spectrum and UV254 was significantly different between RS and CK. Synchronous fluorescence spectra and 2D-COS analysis showed that paddy soil DOM fluorescence intensity changed with the increase of Cd²⁺, three absorption peaks were found by synchronous fluorescence spectra in DOM of paddy soil, which were the peak of tryptophan at 270 nm and the humus peak at 310 nm and 370 nm, respectively. The binding order between soil DOM and Cd²⁺ in RS was humus (310 nm), tryptophan, and humus (375 nm), respectively. However, in CK, the binding order was tryptophan, humus (375 nm), humus (310 nm). In the Stern-Volmer binding reaction model, the fluorescence intensity of C1 and C4 decreased with the increase of Cd²⁺, but the fluorescence intensity of C2 and C3 was unstable, which showed that the complexation of humus components C2 and C3 with Cd²⁺ had instability. This also led to the failure of fitting C2 and C3 in the model. The complexation constants lgK of C1 and C4 in the soil DOM of RS were 4.25 and 5.03, which were higher than in CK.【Conclusion】 The soil DOM in RS and CK mainly consisted of humus and the material composition ratio of soil DOM in RS was different. The complex process of DOM and Cd²⁺ in paddy soil belonged to static quenching and the aromatic structure affected the stability of DOM and Cd²⁺ complexation. Also, RS influenced the binding ability of tryptophan and fulvic acid DOM to Cd²⁺ whereas the instability of the complexation of humus with Cd²⁺ and the complexation of C4 with Cd²⁺ can enhance the bioavailability of Cd in soil. The results of this research can provide a scientific reference for the study of soil Cd pollution mechanism and pollution prevention in paddy fields.

Abstract:【Objective】 Artificial vegetation plays an important role in the restoration of the ecosystem in Mu Us Sandy Land. Understanding the phosphorus (P) forms in the rhizosphere and bulk soils of typical artificial vegetation can provide a basis for scientific vegetation construction in the area. 【Method】 The rhizosphere soil and bulk soil of seven typical artificial vegetations (Pinus sylvestris, Populus simonii, Amygdalus pedunculata, Amorpha fruticosa, Salix psammophila, Sabina vulgaris, and Artemisia ordosica) in Mu Us Sandy Land were collected and the phosphorus content of different forms were subsequently determined using Jiang-Gu phosphorus fractionation method. 【Result】 The results showed that 1)The total phosphorus (TP) content of Salix psammophila rhizosphere soil was significantly higher than that of other vegetation types while Populus simonii, Amygdalus pedunculata, and Artemisia ordosica increased available phosphorus (AP) content in rhizosphere soil. This indicates that planting Populus simonii and the other 3 vegetation types was beneficial for P activation. 2) The Ca₈-P content in rhizosphere soil of Pinus sylvestris, Amygdalus pedunculata, Amorpha fruticosa, and Salix psammophila was lower than in the bulk soil. The decrease in Al-P and Fe-P in Amorpha fruticose rhizosphere soil was the largest, and the difference in Ca₁₀-P content between rhizosphere and bulk soil was the smallest in Salix psammophila. 【Conclusion】 Al-P and Fe-P showed a significant positive correlation with AP in most vegetation rhizosphere soils and were the main forms involved in soil P transformation. This study provides scientific evidence and directives for the management and planting pattern layout of plantations to promote sustainable P management.

Abstract:【Objective】 Soil microbial carbon use efficiency (CUE) is an important indicator reflecting the regulation of the soil carbon cycle by microorganisms through their metabolism. However, the response and driving factors of soil microbial CUE to different management measures in cropland ecosystems are still unclear. This hinders a deep understanding of soil organic carbon turnover, rapid improvement of soil fertility, and effective mitigation of climate change.【Method】 Published literature worldwide was collected, and 198 paired of relatively independent soil microbial CUE databases under different cropland management measures were established, including ¹³C-labeled substrate(CUE_13C), ¹⁸O-labeled water (CUE_18O) and stoichiometric model (CUE_ST) approaches. It was quantitatively evaluated the response of soil microbial CUE to different cropland management measures under specific climate, soil properties, and experimental conditions by meta-analysis, combining Pearson and regression analysis to study the biotic and abiotic factors that control soil microbial CUE variation.【Result】 (1) Compared with no biochar addition, biochar addition increased soil microbial CUE_13C and CUE_18O by 9.40% and 18.22%, respectively, while CUE_ST decreased by 40.01%. Compared with no fertilization, the application of chemical fertilizers could reduce soil microbial CUE_18O(-4.71%), but increased soil microbial CUE_ST(28.20%), whereas straw amendments led to a decrease in soil microbial CUE_18O and CUE_ST by 14.08% and 28.64%, respectively. Relative to conventional tillage, no or reduced tillage significantly increased soil microbial CUE_13C, CUE_18O, and CUE_ST(-2.12%-15.45%). (2) There were significant differences in the effects of cropland management measures on soil microbial CUE under different climates, soil properties and experiment duration. Cropland management measures in semi-arid and humid areas reduced the soil microbial CUE_13C by 8.80% and increased by 4.69%, but the soil microbial CUE_18O decreased from 44.57% to -2.31%. When the soil organic carbon content was > 12 g·kg^-1, cropland management measures increased the soil microbial CUE_13C and CUE_ST by 7.79% and 12.87%, respectively. In the transition from acidic to alkaline soils, cropland management measures caused the soil microbial CUE_13C to decrease from 12.74% to -7.51%. Also, as soil clay content increased, soil microbial CUE_13C and CUE_ST decreased, while soil microbial CUE_18O showed an increasing trend. With the increase of soil cation exchange capacity, soil microbial CUE_18O and CUE_ST showed a decreasing trend. When the experiment duration was 3-10 years, cropland management measures increased soil microbial CUE_18O by 43.49% while soil microbial CUE_ST decreased by 23.72%. (3) Soil microbial CUE_13C increased with aridity index and decreased with soil pH. Furthermore, the soil microbial CUE_18O increased with soil microbial growth rate and soil microbial biomass carbon. Soil organic carbon, β-glucosidase and N-acetyl-glucosaminidase were positively correlated with soil microbial CUE_ST(P < 0.05) whereas soil clay content was negatively correlated with soil microbial CUE_ST(P < 0.01). 【Conclusion】 Considering climatic factors and soil chemical properties, and the response of microbial activity and function to cropland management measures at a specific site is conducive to adjusting the soil microbial CUE at the microbial community or cell level, thereby effectively promoting soil carbon formation and accumulation in cropland ecosystems.

Abstract:【Objective】 Soil particulate organic carbon (POC) is a key player in the transformation and sequestration of soil carbon pools. However, POC content is significantly regulated by changes in soil environment. Therefore, this study was aimed to clarify the change of POC and its influencing factors with vegetation degradation of alpine wetlands, in an attempt to provide certain basic data for further understanding the responses of soil carbon pool dynamics to climate change and human activities in alpine wetland. 【Methods】 In this study, the swampy meadow of Gahai wetland in the northeastern edge of the Qinghai-Tibet Plateau (QTP) was taken as the study area. In the typical vegetation growth area around Gahai Lake, the spatial instead of temporal method was used to characterize the degree of degradation. Sample plots were set up by selecting lots with gentle terrain and consistent slope orientation. Different vegetation degradation levels were classified according to the indicators of plant species composition, aboveground biomass, community height and cover. Soil samples were collected from four vegetation degradation levels, including non-degraded (ND), slightly degraded (SD), moderately degraded (MD), and heavily degraded (HD) in swampy meadow at Gahai wetland. The contents of soil POC were investigated in in the growing seasons of 2016-2017 by field sampling and laboratory analysis. Three-factor analysis of variance was used to analyze the effects of vegetation degradation, soil layer, sampling time and their interactions on soil moisture, soil organic carbon (SOC) and POC contents. Redundancy analysis was performed to determine the dominant factors affecting the change of SOC components in each vegetation degradation levels. 【Results】 The results showed that vegetation degradation significantly decreased the amount of POC at soil surface layers (0-10 and 10-20 cm), but there was no significant effect on the deep layers (20-40, 40-60, 60-80 and 80-100 cm). As the growing season progresses, the contents of POC at 0-10 and 10-20 cm layers decreased first and then increased in four vegetation degradation levels. However, the contents of POC at the other deep layers did not change significantly. In terms of inter-annual variation, soil POC levels and fluctuations were higher in 2016 than in 2017. Analysis of variance (ANOVA) showed that the sampling time, the vegetation degradation and soil layer had significant effects on the POC content, respectively. Meanwhile, the interaction of sampling time, vegetation degradation and soil layer had a significant effect on soil POC content. To further identify the intrinsic factors affecting changes in POC content. Redundancy analysis was utilized to reveal the differences between the studied factors. The results showed that total nitrogen and below-ground biomass were the main factors driving changes in soil organic carbon fractions. 【Conclusion】 In summary, the process of vegetation degradation in alpine wetlands may impair the accumulation of surface soil carbon pools in the wetlands of the QTP. The original POC accumulation is gradually lost with the increasing degree of vegetation degradation. This phenomenon suggests that vegetation degradation may have transformed the QTP wetlands into a new potential carbon source.

Abstract:【Objective】 In recent years, due to improper use of nitrogen fertilizer, a large accumulation of nitrate in the soil has seriously threatened the soil ecological security of the apple orchard in the loess area. The input of dissolved organic carbon (Dissolved organic carbon, DOC) and intercropping with deep-rooted leguminous crops may be a potentially feasible way to reduce nitrate in the deep soil of the apple orchard, However, research on the feasibility of this approach its effectiveness and influencing factors is currently weak. 【Method】 Therefore, this study set up four treatments in the apple orchard in the northern loess area of Wei River: DOC solution irrigation (D), alfalfa intercropping (M), DOC solution irrigation + alfalfa intercropping (D+M), and control (CK). Various indicators such as nitrate nitrogen, DOC, soil organic carbon (Soil organic carbon, SOC), moisture content, and denitrifying microbial abundance in the 0-600 cm soil layers were measured. 【Result】 The study found that under the D and D+M treatments, the reduction rate of nitrate nitrogen in the 0-400 cm soil profile reached around 50%, but the effect of the single M treatment was not significant. The carbon-to-nitrogen consumption ratio between consumed DOC and nitrate was about 5: 1 in the D treatment, and about 4.35: 1 in the D+M treatment. Both the D and D+M treatments increased the copy numbers of nirS, nirK, and nosZ denitrification genes in the 0-600 cm soil layers, and enhanced the contribution of DOC, SOC, and denitrifying microbes to nitrate reduction.【Conclusion】 Overall, the D+M treatment showed the best nitrate reduction effect and can be considered a feasible measure for controlling deep soil nitrate in orchards in the loess area.

Abstract:【Objective】 Summer fallow after winter wheat harvest in dryland is a common practice on the Loess Plateau. However, due to bare land and intensive rainfall during summer fallow, the leaching characteristics of residual fertilizer nitrogen (N) after crop harvest deserve attention. This study aimed to reveal that the destination of applied N fertilizer after wheat season and the leaching characteristics of residual N fertilizer during summer fallow in dryland of the Loess Plateau. 【Method】 This study was carried out in large lysimeters (3 m×2.2 m×3 m) by the ¹⁵N labeled method. ¹⁵N labeled urea was applied at the beginning as basal fertilizer with the rate of 150 kg·hm^-2.Firstly, the absorption of ¹⁵N labeled fertilizer by wheat and the residual N in the soil after wheat harvest were investigated, and subsequently the ¹⁵N abundance and content changes of residual ¹⁵N labeled fertilizer in the soil profile were measured during the summer fallow of three years (2015—2017). 【Result】 The results showed that the average absorption of nitrogen fertilizer by wheat was 53.9% while the amount of ¹⁵N fertilizer distributed in the soil (0-100 cm) after wheat harvest was 36.3% of the N application rate, with an average of 40.1% being in nitrate form. In the first year, the residual ¹⁵N fertilizer which accumulated in the 0-40 cm soil layer moved downward and accumulated in the 60-80 cm soil layer during the following summer fallow. The ¹⁵NO₃^--N mainly accumulated in the above 80 cm soil layer before summer fallow, but the accumulation peak of ¹⁵NO₃^--N was in the 80-100 cm soil layer at the end of fallow. In the second and third years, the residual ¹⁵N fertilizer and ¹⁵NO₃^--N moved downward about 20 cm, respectively, during summer fallow. After the summer fallow, the amount of residual ¹⁵N fertilizer in the 0-100 cm soil layer decreased, but the amount of residual ¹⁵N fertilizer and ¹⁵NO₃^--N in the 100-200 cm soil layer both increased. Specifically, the amount of residual N in the 100-200 cm soil layer increased by 1.9 and 7.0 kg·hm^-2during the summer fallow of the second and third years, respectively. Also, the amount of ¹⁵NO₃^--N in the 100-200 cm soil layer increased by 2.7 and 7.0 kg·hm^-2during the summer fallow of the second and third years, respectively. 【Conclusion】 During the summer fallow, residual N fertilizer leached significantly. Under normal precipitation conditions, the average downward migration rate of residual N fertilizer during a summer fallow was 20 cm. As the age increased, the residual N fertilizer in the 0-100 cm soil decreased; while it increased in the 100-200 cm soil layer, with nitrate as the main leached form. However, the cumulative total loss of residual N fertilizer in the 0-200 cm soil profile during summer fallow was small, indicating that the redistribution of residual N fertilizer nitrogen in the soil profile was the main mechanism.

Abstract:【Objective】 Azolla has a highly biological nitrogen fixation ability, however, the growth of Azolla is sensitive to ammonium nitrogen in water and is easily affected by water pH. Research suggests that root zone fertilization of fertilizers can effectively reduce the concentration of ammonium nitrogen in floodwater. However, it is unknown whether culturing Azolla under root zone fertilization of fertilizers can stably inhibit ammonia volatilization and increase yield for paddy soils with different pH values. This study aimed to determine the effect of root zone fertilization of fertilizers in combination with Azolla on ammonia volatilization and rice yield in paddy soils with different pH values. 【Method】 A pot experiment was conducted with three types of paddy soil (acid, neutral, alkaline), two methods of fertilization (broadcasting and root zone fertilization of fertilizers), and two modes of rice cultivation (with or without Azolla). The ammonia volatilization potential and grain yields of rice were determined for these 15 treatments. 【Result】 The results showed that: (1) Under the same nitrogen application rate, root zone fertilization of fertilizers treatments only volatilized NH₃-N 1.0-1.8 kg·hm² (calculated by nitrogen), which were 96% lower than surface application of nitrogen fertilizer for the three types of paddy soil, and Azolla-rice co-culture treatments lowered the ammonia volatilization by 17%-50% when compared with those of rice mono-culture treatments; (2) Compared with rice mono-culture treatments, Azolla-rice co-culture treatments produced higher rice yield. Moreover, root zone fertilization of fertilizers combined with Azolla reached the highest rice yield in black soil, increased by 41% compared with the grain yield of black soil surface application without Azolla.【Conclusion】 In conclusion, root zone fertilization of fertilizers can significantly reduce ammonia volatilization for paddy soils with different initial pHs while root zone fertilization of fertilizers combined with Azolla has greater potential for increasing rice yield.

Abstract:【Objective】 Nitrogen (N) deposition is an important global climate change factor affecting soil phosphorus (P) cycling in forest ecosystems. However, understory N application typically applied directly to the ground, has been widely used to simulate N deposition in forest ecosystems in the past. This simulation method may neglect the retention and adsorption effect of the forest canopy, which cannot truly assess the effect of N deposition on soil P cycling. Moreover, organic N is another important component of atmospheric N deposition, but the ecological effect of the organic N deposition has not been fully studied.【Method】 To evaluate the effect of atmospheric N deposition on soil P cycling, a field experiment was conducted involving six treatments: canopy control (CNA-CK), canopy inorganic N addition (CNA-IN), canopy organic N addition (CNA-ON), understory control (UNA-CK), understory inorganic N addition (UNA-IN), and understory organic N addition (UNA-ON) based on the Anji MosoBamboo Ecosystem Research Station of Zhejiang A&F University, in Anji County, Zhejiang Province. The N deposition rate was set at 50 kg·hm^-2·a^-1 (based on the atomic mass of N, the same as below). IN uses ammonium nitrate while ON uses a mixture of 25 kg·hm^-2·a^-1 urea and 25 kg·hm^-2·a^-1 glycine as the N source. The CK treatment involves adding an equal amount of water. Soil P fractions, microbial biomass P, acid phosphatase activity, P cycling functional gene abundance, and some physicochemical properties were measured to investigate the effects of different N deposition simulation approaches and N components on soil P fractions and their driving factors.【Result】 The results showed that canopy N addition (CNA) significantly reduced soil total P, occluded P, and labile P concentrations compared to understory N addition (UNA) with the percentage of 15.1%-26.5%, 18.3%-21.5% and 9.7%-38.3%, respectively. However, soil P fractions did not differ significantly between CNA-ON and CNA-IN treatments, whereas UNA-IN treatment significantly reduced resin P and labile P content compared to UNA-ON treatment. Acid phosphatase activity and pH were the main factors affecting soil P fractions, but N deposition did not significantly influence soil P cycling functional gene abundance.【Conclusion】 Therefore, it was suggested that simulating N deposition via CNA significantly reduced the contents of total P and P fractions such as occluded P and labile P of Moso bamboo forest soils, whereas simulating N deposition via conventional UNA underestimated this reduction effect. Soil P is closely linked to the cycling of soil carbon and N, which are vital for maintaining a balanced nutrient ecosystem. Consequently, future simulation experiments on N deposition should systematically consider the effects of N deposition simulation approaches and N addition components on soil carbon, N, and P cycling processes.

Abstract:【Objective】 Microorganisms play an important role in the biogeochemical cycle of lake ecosystems and are important factors affecting the long-term sequestration of organic carbon in lakes. However, the current understanding of the distribution of sediment microbial communities and their impact on carbon dynamics is still insufficient. 【Method】 In this study, we used high-throughput sequencing to analyze the distribution pattern of microbial communities in sediments of west Dongting Lake. Combined with geochemical parameters such as sediment mechanical composition, total organic carbon, and molecular composition of organic matter, we analyzed the influence of environmental factors on microbial community structure and explored the key factors regulating the structure of sediment microbial communities. 【Result】 Significant differences in microbial community structures were observed among different sediment layers (Bacteria: R² = 0.542, P < 0.001; Fungi: R² = 0.430, P < 0.001). On the one hand, from the shallow layer (0～20 cm) to the deep layer (50～100 cm), the relative abundance of copiotrophic microorganisms (e.g., Proteobacteria) in the sediments significantly decreased while the relative abundance of oligotrophic microorganisms (e.g., Chloroflexi) significantly increased. On the other hand, the abundance of the main functional groups of microorganisms changed significantly with increasing sediment depth. In particular, the functions related to aerobic chemoheterotroph and aerobic ammonia oxidation were significantly more abundant in the shallow sediment than in the subsurface (20～50 cm) and deep layers. The differential distribution of microbial communities in sediments is mainly influenced by changes in organic matter content (Bacteria: R² = 0.532, P < 0.001; Fungi: R² = 0.534, P < 0.001). Our result also revealed that the content of total organic carbon significantly affected the abundance changes of various microbial taxa including Proteobacteria, Chloroflexi, Actinobacteria, Basidiomycota, and Glomeromycota, explaining 76.2% (P < 0.001) and 58.2%(P < 0.01) of the variation in bacterial and fungal community structures, respectively. 【Conclusion】 The variation in the distribution of organic matter was the main reason for the differences in microbial community structure in different sedimentary layers. Thus, this study reveals the role and feedback mechanism of microorganisms in lake ecosystems and is of great significance for exploring the evolution and stability of lake ecosystems.

Abstract:【Objective】 With global climate change and overgrazing, shrub encroachment is extensively occurring in global grasslands. However, relatively little is known about how the structure of bacterial communities shifts with shrub encroachment. Thus, considering the aboveground plant community, soil carbon chemical composition, soil bacterial community structure and network beneath the canopies of three typical shrub species (Potentilla fruticosa, Spiraea alpina, and Caragana microphylla) as well as in adjacent grassland (as a control), the effects of shrub encroachment on the structure of soil bacterial communities and soil carbon pools were explored.【Method】 16S rRNA gene sequencing was used to investigate the bacterial communities and co-occurrence features among bacterial taxa while Fourier transform infrared spectroscopy (FTIR) was conducted to assess the soil organic carbon (SOC) chemical composition.【Result】 Shrub encroached grasslands (Potentilla fruticosa and Caragana microphylla) showed significant changes in aboveground plant community composition (P < 0.01) while the aboveground plant community diversity and richness remained constant (P > 0.05). The biomass of the three shrub plots was significantly higher than that of grassland (P < 0.05) whereas underground biomass showed no significant difference (P > 0.05). Shrub encroachment had no significant effects on SOC and total nitrogen (TN) contents, but weakened the differences of SOC contents between top- and subsoils, as shown by significantly higher SOC contents in the topsoil of the grassland than in its subsoil (P < 0.05), with no such trend in the three shrub plots.The SOC chemical composition in both top- and subsoils of the three shrublands and grassland was dominated by aromatics(except for deep soil in Caragana microphylla plots), with no significant difference in aromatic content between shrub and grassland plots (P > 0.05). However, the Caragana microphylla plots exhibited a surface-aggregated distribution of aromatics (P < 0.05). Random forest model analysis revealed that the distribution of Acidobacteria and Actinobacteria was the most important predictor of shrub encroachment in top and subsoils (P < 0.01). According to Non-metric multidimensional scaling (NMDS) analysis, the bacterial community composition of alpine grassland was significantly altered by shrub encroachment. Moreover, plant community composition and SOC chemical compositions were the main explanatory factors affecting bacteria community composition in both depths. Functional prediction analysis identified four biological metabolic pathways, including cellular processes, environmental information processing, metabolism, and genetic information processing, with metabolism being enriched in shrub plots (P < 0.05). Based on topological parameters of total links, complexity, and natural connectivity, the results showed that the soil bacterial network of shrublands was more complicated and stabilized than that in grasslands, and mutualism or commensalism may play an important role in establishing the bacterial community structure. 【Conclusion】 In summary, the results of this study suggest that shrub encroachment had an important regulatory effect on soil bacterial community structure and soil carbon pool. The results enrich the literature on soil microbial community in alpine grassland and provide a theoretical basis for the effect of soil carbon source and sink in alpine grassland.

Abstract:【Objective】 This study aimed to clarify the effects of different return methods of organic matter on the characteristics of soil microbial communities.【Method】 The changes of soil microbial community abundance and structure under single application of maize straw, sheep manure and combined application with biochar were analyzed by quantitative PCR and high-throughput sequencing based on two years of field experiments in dry cropland red soil.【Result】 The results showed that: (1) Compared with the control (no material), the soil pH and nutrient content of sheep manure alone increased significantly, while the single application of straw had no significant effect on them. Compared with straw and sheep manure alone, soil organic carbon content under the treatment of biochar co-application with straw or sheep manure was significantly increased by 133.5% and 81.47%, respectively. (2) The abundance of bacteria and fungi under the treatment of sheep manure treatment significantly increased by 448.7%and 1 709%, respectively, and the abundance of bacteria under the treatment with biochar was further increased by 35.34%. Straw alone only increased fungal abundance. Single straw application and its combination with biochar significantly reduced bacterial diversity and richness but had no significant effect on fungal diversity. (3) Straw, sheep manure and biochar alone changed the structure of bacterial and fungal communities, and there were significant interaction effects. Functional predictive analysis showed that the combination of biochar and organic materials reduced carbohydrate metabolism and the abundance of potential plant pathogens. Available phosphorus, pH, total nitrogen and available potassium were the main factors affecting the abundance and structure of soil microbial communities.【Conclusion】 In summary, the combined application of sheep manure and biochar can effectively improve the fertility of dryland red soil, increase the abundance of soil microorganisms, and reduce the number of potential pathogens. Thus, the combined application of sheep manure and biochar can be used as an effective measure to improve the fertility of dryland red soil and maintain soil health.

Abstract:【Objective】 Soil extracellular enzymes, as the catalysts of soil biochemical reactions, directly drive soil element cycling and energy flow processes and play indispensable roles in the biogeochemical cycling of carbon, nitrogen, and phosphorus in desert ecosystems. Winter snow is a key climatic factor regulating soil element cycling. Soil extracellular enzyme activities respond sensitively to the changes in winter snow cover and the relatively stable hydrothermal conditions highly alter soil extracellular enzyme activities under the winter snow cover. Thus, changes in the winter snow cover will trigger fluctuations in soil extracellular enzyme activities, significantly influencing the nutrient cycling processes in desert ecosystems which are water-scarce and nutrient-poor.【Method】 In order to investigate the effects of winter snow cover changes and arbuscular mycorrhiza (AM) fungi on soil enzyme activities in the Gurbantunggut Desert under the background of a “warm and humid” trend, we conducted a long-term field experiment simulating winter snow cover changes and in situ inhibition of AM fungal activities with a split-area randomized block experimental design. The following treatments were adopted; for the primary zone, the control (40 mm water increase, W) and an AM-inhibition treatment (40 mm water increase with the addition of benomyl, BW); for the subplot zone, including three levels, 100 % snow cover increase (+S), natural snowfall (CK), and 100 % snow cover decrease (-S). Soil samples were collected from 0-10 and 10-20 cm soil layers, soil physicochemical properties, and soil enzyme activities which are related to soil carbon, nitrogen, and phosphorus cycling were determined to uncover the effects of AM fungi on soil enzyme activities and microbial metabolism limitation under the background of winter snow cover changes in the desert ecosystem.【Result】 (1) AM fungi significantly increased the aboveground net primary productivity of plant community, decreased the content of soil available phosphorus and ammonium nitrogen, but increased the content of soil organic carbon. The activities of soil enzymes related to soil carbon, nitrogen, and phosphorus cyclings were decreased under the natural snow cover and increased snow cover in the AM fungi treatments. In contrast, AM fungi treatments increased the activities of soil enzymes which are related to the soil carbon and nitrogen cyclings under decreased snow cover. (2) Based on the vector analyses, our results indicated that soil microbial activities were co-limited by soil carbon and phosphorus in desert ecosystems. Furthermore, we found that AM fungi decreased soil microbial carbon limitation under the natural snow cover and increased snow cover treatments, but there was no consistent pattern in the effects of AM fungi on soil microbial carbon and phosphorus limitation under the decreased snow cover treatment.【Conclusion】 AM fungi play an important role in promoting plant available phosphorus and ammonium nitrogen uptake, enhance soil enzyme activities which are related to soil carbon and nitrogen cyclings, and alleviate soil microbial carbon limitation in desert soils under the background of winter snow cover changes. Importantly, our results revealed the effects of winter snow cover changes and AM fungi on soil extracellular enzyme activities and soil microbial metabolism limitation. This contribution will provide a reference in the understanding of belowground ecological processes and feedbacks, and a scientific basis for the protection and ecological restoration constructions for desert ecosystems in the future.