Dynamic Characteristics of Cynodon dactylon Root Growth and Its Influence on Soil Pore Evolution
In situ Dissolution Kinetics of Ammonium Nitrogen Interacting with Precipitated Calcium Phosphate Determined by Atomic Force Microscopy
Mechanism of Degradation of Typical Malodorous Benzene Congeners in Soil by Activated Persulfate with Sulfidized Nano-zero-valent Iron Loaded on Biochar
Soil Iron Speciation Transformation and in-Situ Monitoring of Element Bioavailability During the Flooding-drainage in Polluted Paddy Soils
Research of Paddy Soil Dissolved Organic Matter Composition and Its Binding Process with Cd2+
Effects of Changes in Organic Matter Distribution in Lake Sediments on Microbial Community Structure
- Dynamic Characteristics of Cynodon dactylon Root Growth and Its Influence on Soil Pore Evolution
- In situ Dissolution Kinetics of Ammonium Nitrogen Interacting with Precipitated Calcium Phosphate Determined by Atomic Force Microscopy
- Mechanism of Degradation of Typical Malodorous Benzene Congeners in Soil by Activated Persulfate with Sulfidized Nano-zero-valent Iron Loaded on Biochar
- Soil Iron Speciation Transformation and in-Situ Monitoring of Element Bioavailability During the Flooding-drainage in Polluted Paddy Soils
- Research of Paddy Soil Dissolved Organic Matter Composition and Its Binding Process with Cd2+
- Effects of Changes in Organic Matter Distribution in Lake Sediments on Microbial Community Structure
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Thoughts for the Reconstruction of Core Knowledge System of Basic Soil Science: Necessity, Theoretical and Methodological Basis
LI Hang, LIU Xinmin, TIAN Rui, LI Rui, TANG Ying
2025,62(1):1-13, DOI: 10.11766/trxb202403120105
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.
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A Review of Soil 3D Prediction and Modelling Techniques
XIE Xianli, XIA Chengye, YIN Biao, LI Anbo, LI Kaili, PAN Xianzhang
2025,62(1):14-28, DOI: 10.11766/trxb202311140473
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.
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Environmental Behavior and Terrestrial Ecological Risks of Typical Rubber Antioxidants and Their Derivatives: A Review
JIANG Jinlin, WU Huiyi, WANG Lei, DONG Shunan, CAO Shaohua
2025,62(1):29-39, DOI: 10.11766/trxb202308310345
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.
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Methods of Filling in Bulk Density Gaps of Cropland Topsoil in the Sichuan Basin
LI Aiwen, LI Wendan, SONG Liangying, RAN Min, CHEN Dan, CHENG Jinli, QI Haoran, GUO Conghui, LI Qiquan
2025,62(1):40-53, DOI: 10.11766/trxb202311270498
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.
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Dynamic Characteristics of Cynodon dactylon Root Growth and Its Influence on Soil Pore Evolution
ZHANG Jing, RAN Yiguo, MA Donghao, CHEN Lin, WU Yingbo, HUANG Ping
2025,62(1):54-68, DOI: 10.11766/trxb202310310446
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.
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Long-term Observation of Effects on Soil Salinity and Fertility in Saline-alkali Land Reclamation under Drip Irrigation
HUO Weige, PENG Yi, ZHANG Shaomin, LIU Shenglin, BAIDENGSHA Maimaiti Aili, FENG Gu
2025,62(1):69-80, DOI: 10.11766/trxb202309080368
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.
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Inhibition Mechanisms of Acidification Induced by Urea Application Using Organic Carbon Sources with Different Availability for Microorganisms in Ultisol
GUAN Peng, WANG Ruhai, SHI Renyong, LI Jiuyu, XU Renkou
2025,62(1):81-91, DOI: 10.11766/trxb202308140323
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.
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In situ Dissolution Kinetics of Ammonium Nitrogen Interacting with Precipitated Calcium Phosphate Determined by Atomic Force Microscopy
2025,62(1):92-101, DOI: 10.11766/trxb202309210395
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.
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Properties and Aggregation Characteristics of Humic Acid in Surface Soil under Two Forest Vegetations of Jinyun Mountain
2025,62(1):102-113, DOI: 10.11766/trxb202309280403
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.
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Effects of Dazomet Fumigation and Reductive Soil Disinfestation on Antibiotic Resistance Genes in Farmland Soil
YU Wenhao, LI Shu, LIN Yulan, ZHANG Jingqing, XU Chenwei, LIU Liangliang, ZHANG Jinbo, CAI Zucong, ZHAO Jun
2025,62(1):114-126, DOI: 10.11766/trxb202309100369
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.
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Mechanism of Degradation of Typical Malodorous Benzene Congeners in Soil by Activated Persulfate with Sulfidized Nano-zero-valent Iron Loaded on Biochar
LI Yanlu, YANG Xinglun, BIAN Yongrong, MA Zhiyong, GU Chenggang, SONG Yang, XIANG Leilei, WANG Fang, JIANG Xin
2025,62(1):127-140, DOI: 10.11766/trxb202310240433
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.
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Soil Iron Speciation Transformation and in-Situ Monitoring of Element Bioavailability During the Flooding-drainage in Polluted Paddy Soils
ZHAO Wantong, WANG Yufeng, LIU Zhe, HUANG Qiaoyun, YI Ceng, FENG Xionghan, WANG Xiaoming
2025,62(1):141-152, DOI: 10.11766/trxb202310210430
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(Feox) 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.
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Research of Paddy Soil Dissolved Organic Matter Composition and Its Binding Process with Cd2+
LIANG Yihao, NI Caiying, LI Yanliang, XIAO Luochang, JIAN Minfei
2025,62(1):153-164, DOI: 10.11766/trxb202310180426
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.
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Phosphorus Speciation Characteristics of Typical Artificial Vegetation Rhizosphere Soil in Mu Us Sandy Land
HAN Chaoqun, WANG Jiao, ZHAO Chunlei, SHAO Ming'an
2025,62(1):165-176, DOI: 10.11766/trxb202403290141
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.
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Response Mechanisms of Soil Microbial Carbon Use Efficiencies to Cropland Management Measures
ZHANG Chenyang, SUN Liyang, XU Minggang, LI Jianhua, CAI Andong
2025,62(1):177-188, DOI: 10.11766/trxb202309020351
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(CUE13C), 18O-labeled water (CUE18O) and stoichiometric model (CUEST) 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 CUE13C and CUE18O by 9.40% and 18.22%, respectively, while CUEST decreased by 40.01%. Compared with no fertilization, the application of chemical fertilizers could reduce soil microbial CUE18O(-4.71%), but increased soil microbial CUEST(28.20%), whereas straw amendments led to a decrease in soil microbial CUE18O and CUEST by 14.08% and 28.64%, respectively. Relative to conventional tillage, no or reduced tillage significantly increased soil microbial CUE13C, CUE18O, and CUEST(-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 CUE13C by 8.80% and increased by 4.69%, but the soil microbial CUE18O 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 CUE13C and CUEST by 7.79% and 12.87%, respectively. In the transition from acidic to alkaline soils, cropland management measures caused the soil microbial CUE13C to decrease from 12.74% to -7.51%. Also, as soil clay content increased, soil microbial CUE13C and CUEST decreased, while soil microbial CUE18O showed an increasing trend. With the increase of soil cation exchange capacity, soil microbial CUE18O and CUEST showed a decreasing trend. When the experiment duration was 3-10 years, cropland management measures increased soil microbial CUE18O by 43.49% while soil microbial CUEST decreased by 23.72%. (3) Soil microbial CUE13C increased with aridity index and decreased with soil pH. Furthermore, the soil microbial CUE18O 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 CUEST(P < 0.05) whereas soil clay content was negatively correlated with soil microbial CUEST(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.
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Temporal Dynamics and Content of Soil Particulate Organic of Gahai Wetland in Gansu Province During Vegetation Degradation Succession
MA Weiwei, LIU Qiang, LI Guang, CHANG Wenhua
2025,62(1):189-200, DOI: 10.11766/trxb202309040355
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.
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Study on the Reduction of Nitrate in Deep Soil of Apple Orchard in Loess Area by Irrigation of Dissolved Organic Carbon Solution and Intercropping of Alfalfa
DAI Hongwei, DING Yanhong, GAO Xiaodong, LI Changjian, REN Min, SONG Xiaolin, ZHAO Xining
2025,62(1):201-213, DOI: 10.11766/trxb202310280440
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.
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Leaching Characteristics of Residual Fertilizer Nitrogen in the Dryland of Loess Plateau During the Summer Fallow Period
XIA Mengjie, WANG Huimin, LEI Shuang, ZHAO Mengzhen, FENG Hao, ZHOU Jianbin
2025,62(1):214-222, DOI: 10.11766/trxb202308250340
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.
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The Influence of Root Zone Fertilization in Combination with Azolla and Soil pH on Ammonia Volatilization
ZHU Tong, LI Hong, ZHOU Yanping, ZHENG Jicheng, YIN Bin, YAO Yuanlin
2025,62(1):223-232, DOI: 10.11766/trxb202301180026
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.
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Effect of Canopy Nitrogen Deposition on Soil Phosphorus Fractions in a Moso Bamboo Forest
WEI Jingwei, XIAO Xiangqian, ZHUO Shoujia, JIANG Wenting, SUN Hongyang, CHEN Youchao, LI Yongfu, YU Bing, CAI Yanjiang
2025,62(1):233-245, DOI: 10.11766/trxb202309110372
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.
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Effects of Changes in Organic Matter Distribution in Lake Sediments on Microbial Community Structure
ZENG Aoqi, NIE Xiaodong, LIAO Wenfei, LIAO Shanshan, RAN Fengwei, LIU Yi, LI Zhongwu
2025,62(1):246-260, DOI: 10.11766/trxb202311200488
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.
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Effects of Shrub Encroachment on Soil Carbon Pool and Soil Microbial Community Structure in Alpine Grassland
TENZING Droma, MA Wenming, MA Xiangli, MU Xianrun
2025,62(1):261-272, DOI: 10.11766/trxb202310260437
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.
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Effects of Single Application of Organic Amendments and Their Combination with Biochar on Microbial Community Composition in a Red Soil
XU Yimeng, ZHANG Lei, BAI Meixia, ZHOU Yan, QIN Hua, XU Qiufang, CHEN Junhui
2025,62(1):273-284, DOI: 10.11766/trxb202308200332
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.
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Effects of AM Fungi on Soil Extracellular Enzyme Activities under the Background of Winter Snow Changes in a Desert Ecosystem
XUE Hui, YANG Rong, QIN Wenhao, DONG Qianqian, JI Zhanquan, JIA Yangyang
2025,62(1):285-296, DOI: 10.11766/trxb202310300444
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.
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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
Abstract:
【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.
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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
Abstract:
【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.
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Characteristics of Perched Water Recharge in the Dam Land of Yangjuangou Small Watershed on the Loess Plateau
DOI: 10.11766/trxb202406240256
Abstract:
【Objective】Check dams, as one of the core projects for soil erosion control in the Loess Plateau region, have played an irreplaceable role in preventing soil erosion and improving the ecological environment. By intercepting runoff and depositing sediment, check dams effectively reduced soil erosion, which in turn improved the local ecological environment and agricultural production conditions. However, despite the remarkable success of check dams in soil and water conservation, research on the perched water in dam lands on the Loess Plateau remains insufficient, particularly in understanding the recharge process and mechanisms of the perched water. The study is of great significance for the comprehensive understanding of the ecological function and hydrological role of check dams.【Method】Based on this, dam lands were selected in typical watersheds of the Loess Plateau as the research object, and using iodide and bromide ions as tracers, along with water level monitoring and chlorine mass balance method, the recharge process of perched water in the dam land was systematically traced. The core objective of the study was to reveal the recharge process and mechanism of perched water in dam land under different land use types, and to provide a scientific basis for water resource management.【Result】The results showed that soil moisture in the dam land under different land use types followed the order: farmland > shrubland > arbor land > grassland. Different land use types had a significant impact on the recharge rate of perched water in the dam land. Specifically, the recharge rate of farmland was the highest, followed by arbor land, then grassland, with shrubland having the lowest recharge rate, ranging from 32.94 to 60.96 mm·a-1. This difference reflects the influence of different vegetation types and land management practices on the perched water recharge process, providing important clues for understanding the hydrological functions of different ecosystems. Furthermore, it found that when the precipitation exceeded 15 mm·d-1, water could infiltrate into the perched water and quickly recharged it. At this time, the vertical infiltration rate of water was about 0.13 to 0.15 m·d-1. However, this recharge process was not immediately completed as there was a lag time of about 6 to 11 days, suggesting that the recharge of perched water has a time-lag effect. In addition, the results of iodine ion tracer experiments showed that the perched water in the dam land had good connectivity, with a horizontal water transport rate of 6 m·d-1. This finding suggests that the perched water has a strong hydraulic connection, which could realize the horizontal distribution and redistribution of water within a certain range, and thus form a relatively stable hydrological cycle system on a local scale.【Conclusion】Overall, this study not only reveals the recharge process and mechanism of perched water in the dam land, but also provides an important theoretical reference and scientific basis for further understanding of the perched water in the dam land. Through these research results, the water resource dynamics of the dam land can be better grasped, and technical support can be provided for soil and water conservation and ecological restoration in the Loess Plateau region. These studies can provide strategies to optimize the management and maintenance of check dams, and further promote the protection and improvement of the regional ecological environment.
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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
Abstract:
【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.
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Effects of Sustained Low Level Organic Fertiliser and Chemical Fertiliser Blending on Soil Fertility and Multifunctionality inOasis Farmland
WANG Bing, ZHANG Yuchen, WANG Xinyue, WU Maolin, PENG Yi, HUANG Wei, FENG Gu, YAN Qiwen, JIANG Ping’an, LIU Yunhua, SHENG Jiandong
DOI: 10.11766/trxb202404130153
Abstract:
【Objective】The usage of organic fertilizers in arid zones is limited, which necessitates investigating the most suitable amount required for optimum agricultural productivity, and clarifying the degree of influence on soil physicochemical properties, microbial communities, and multifunctionality in oasis farmland when applied in low amounts in combination with chemical fertilizers.【Method】A field experiment was conducted in Hailou Town, Shaya County, Xinjiang from 2021 to 2023. High-throughput sequencing (16S rRNA and endogenous transcribed spacer region) technology was used to determine and analyze the extent of the effects of organic fertilizer application on soil nutrient physicochemical properties, microbial community composition, and diversity, and to explore the response of soil multifunctionality to organic fertilizer dosage. Four treatments were set up: NPK (chemical fertilizer only), NPK + OM3 (3 000 kg?hm-2 cattle manure + chemical fertilizer), NPK + OM6 (6 000 kg?hm-2 cattle manure + chemical fertilizer), and NPK + OM12 (12 000 kg?hm-2 cattle manure + chemical fertilizer).【Result】The results showed that: (1) Application of organic manure significantly increased soil organic carbon, total nitrogen, available phosphorus, available potassium and nitrate nitrogen, and significantly decreased soil pH; (2) NPK + OM6 and NPK + OM12 treatments significantly increased microbial (Chao1 and Shannon index) and fungal (Shannon index) diversities, and significantly changed the community structure; (3) The relative abundance of Blastomonas, Acidobacilli and Glomus increased, but that of Actinomycetes and Campylobacter decreased with the increase in manure application rate; (4) The application of organic fertilizer can change the composition and diversity of bacterial community by changing soil nutrients and pH, thereby improving soil versatility.【Conclusion】Soil nutrients and microbial community composition and diversity increased significantly with the increase of organic manure application. Three years of organic manure application (3 000-6 000 kg?hm-2) could maintain soil multifunctionality at a high level by increasing soil nutrient content and improving microbial community composition and diversity. Considering the limited amount of organic fertilizer and the cost of fertilization, the application of 3 000-6 000 kg?hm-2 organic fertilizer in crop production in oasis farmland can achieve the effect of improving the multi-function of soil.
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Latitudinal Zonal Variation of Surface Properties of Soil Particles with Different Particle Diameters
YU Linqiao, HE Aizhou, LI Hang
DOI: 10.11766/trxb202406210248
Abstract:
【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.
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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
Abstract:
【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.
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Comparison of Digital Soil Mapping Methods in Plain and Hill Mixed Regions
MENG Ke, HUANG Wei, FU Peihong, LI Wenyue, FENG Ling
DOI: 10.11766/trxb202406210251
Abstract:
【Objective】Digital soil mapping is a burgeoning and efficient method to express the spatial distribution of soil. Based on a data mining algorithm, this method establishes a soil-landscape relationship model to infer soil mapping by using raster data as an expression and computer-assisted. The key to improving the accuracy of digital soil mapping is constructing a suitable soil-landscape relationship model. However, the commonly used methods of digital soil mapping cannot meet the application requirements of soil mapping given the complicated nature of terrains consisting of plains and hills. How to fully consider the main links of the soil-landscape relationship model to accurately infer the spatial distribution of soil types needs further discussion. 【Method】The northern part of Chengmagang town, Macheng City, Hubei province was selected as the study area. It was divided into two terrain units, plains and hills. Based on the 28 environmental variables, Decision Tree (DT), Random Forest (RF), Gradient Boosting Decision Tree (GBDT), and Extreme Gradient Boosting (XGBoost) were used to select optimal mapping methods for each region. Then, the optimal variables combination was selected according to the factor importance ranking of each region. Moreover, the optimal mapping methods were used to establish a soil-landscape relationship model linking soil types to the optimal variable combinations, upon which soil type mapping was inferred for each region. Soil-type mapping results for plain and hilly areas were combined as the soil-type mapping result of the terrain region. Finally, the mapping accuracy of the whole region was compared with the terrain region to further explore ways to improve the accuracy of soil-type mapping in Plain and Hill Mixed Regions. 【Result】Under different terrain conditions, the performance of each inference mapping method was different as well as the optimal inference mapping method. The performance of RF and XGBoost was superior to other algorithms. Specifically, the RF performed better in whole and plain regions while the XGBoost was the best algorithm in the hill region. The model accuracy was further effectively improved through variable screening, with the maximum increase of overall accuracy and Kappa coefficient being 4.96% and 0.059 in the whole region, respectively. However, the model accuracy improvement was not obvious in the plain region, with the increase of overall accuracy and Kappa coefficient being 1.43% and 0.018, respectively. Also, the increase in overall accuracy and Kappa coefficient was 2.82% and 0.03 in the hill region. Compared with the whole mapping method, the inference mapping method based on terrain zoning had the highest accuracy, and the overall accuracy and Kappa coefficient were 73.05% and 0.69, respectively. Meanwhile, the plain region required more remote sensing factors to participate in inference mapping compared to the whole and hill regions. 【Conclusion】The inference mapping accuracy in plain and hill regions can be effectively improved by optimizing the mapping method, selecting environment variables, and adopting appropriate mapping way. This study can provide some references for the screening of environmental variables, the selection of mapping algorithms, and the construction of mapping ways of inference mapping in plain and hill regions. It provides promising and practical examples and technical support effective for promoting the improvement of the accuracy of inference mapping in complex terrain areas.
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Change of Rill Erosion Microtopography on Saturated Loess Slope and its Response to Hydraulic Parameters
TAN Qingfang, CHEN Fengting, HUANG Yuhan, ZHAO Mingquan, CHANG Zhiyong, WU Di, YU Xinxiao, HUAGN Zixuan, WEI Juan
DOI: 10.11766/trxb202405210206
Abstract:
【Objective】This study aimed to investigate the relationship between the hydraulic characteristic parameters of rill erosion and the changes in microtopography of the eroded, which is an important mechanism for investigating rill erosion.【Method】In this study, the loess was selected as the research material, and four slopes gradients(5°, 10°, 15°, 20°) and four flow rates (2, 4, 8, 16 L·min-1) were set. The limited rills with a width of 0.1 m were used to simulate the rill erosion experiment, combined with Structure-from-Motion (SfM) photogrammetry, the relationship between the hydraulic characteristic parameters of rill erosion on slopes and microtopographic variation were analyzed.【Result】The results showed that under the experimental conditions, the flow velocity ranged from 0.23 to 0.92 m·s-1 and slope had a greater influence on flow velocity than the flow rate. The ranges for the Reynolds number and Froude number were from 255 to 2358 and 1.89 to 5.90, respectively. These hydraulic characteristic parameters increased with an increase in both slope and flow rate (P<0.05), while the resistance coefficient exhibited the opposite trend. Surface roughness, relief amplitude, and surface incision depth varied within the ranges of 0.33 to 2.35 cm, 0.47 to 4.35 cm, and 0.53 to 2.53 cm, respectively. The surface roughness, relief amplitude, and surface incision depth were positively correlated with flow velocity, Reynolds number, and Froude number, but negatively correlated with the resistance coefficient. Additionally, surface roughness, relief amplitude, and surface incision depth increased in linear and power function trends with increasing flow velocity and Reynolds number.【Conclusion】As the slope and flow rate increased, all hydraulic characteristic parameters and microtopography factors of the eroded, except for the resistance coefficient, showed a significant increasing trend, indicating that the microtopography was evolving towards conditions that favored erosion. The surface roughness, relief amplitude, and surface incision depth showed a significant positive correlation with changes in flow velocity and Reynolds number. Additionally, the responses of these three microtopographic factors to changes in flow velocity and Reynolds number followed linear and power function relationships. When the flow was low, the variation in surface roughness was the greatest. As the flow rate increased, both the surface relief and the surface incision depth gradually increased, indicating that the downcutting effect of runoff during the erosion process was intense, leading to a continuous increase in rill erosion depth. Our research results can provide a theoretical basis for the control of soil and water loss in loess slope cultivated land and the study of regional ecological restoration.
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Construction of Pedotransfer Function for Predicting Soil Bulk Density in Cultivated Land of Northeast China Using Random Forest
WANG Xiaopan, WANG Changkun, SUN Haijun, GUO Zhiying, LIU Jie, GAO Lei, MA Haiyi, YUAN Ziran, YAO Chengshuo, PAN Xianzhang
DOI: 10.11766/trxb202406180242
Abstract:
【Objective】Soil bulk density (BD) is crucial for understanding the physical condition of black soil in cultivated land of Northeast China and advancing its utilization and protection. The traditional cutting ring method for determining BD is time-consuming and laborious, making the evaluation of BD on a large spatial scale difficult. The pedo-transfer function (PTF) can estimate BD information using readily available soil variables. However, there is currently a lack of research on PTF models specifically targeting the whole of Northeast China, and the importance of potential soil attribute variables for PTF model construction remains to be elucidated.【Method】By incorporating soil organic matter (SOM), moisture content (MC), and soil texture-related variables as input features, we constructed PTF models capable of predicting BD on a large scale. Furthermore, we delved into the significance of these soil attribute variables in the constructed PTF models. Additionally, we assessed the suitability of existing published PTF models for BD prediction in the black soil of Northeast China.【Result】The optimal predicted R2 values of published PTF were 0.17, 0.22, and 0.26, respectively, for the topsoil, subsoil, and all soil samples, and Root Mean Squared Errors ( RMSE) were 0.16, 0.13, and 0.15 g·cm-3, respectively. Also, the optimal predicted R2 values of PTF for the topsoil, subsoil, and all soil samples based on the proposed RF method were 0.22, 0.45, and 0.37, respectively, while the RMSE values were 0.16, 0.11, and 0.14 g·cm-3, respectively.【Conclusion】The published PTF models had low BD prediction accuracy and were difficult to use for BD prediction on the scale of black soil in Northeast China whereas the PTF model constructed in this study has the potential to predict BD on the scale of black soil in Northeast China. Among the variables, SOM was the most important variable for predicting BD in the black soil of Northeast China, followed by MC, while soil texture-related variables had a relatively small impact.
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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
Abstract:
【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.
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Research Progress and Hotspot Analysis of Long-distance Electron Transport and Environmental Effects of Cable Bacteria
LIU Hao, WANG Zhijie, LIU Dandan, HUANG Lingyan
DOI: 10.11766/trxb202406070226
Abstract:
Cable bacteria, a recently discovered type of microorganism found in marine and freshwater sediments, have the unique ability for long-distance electron transfer. Their capacity to link sulfide oxidation in deep anoxic layers with oxygen reduction in surface aerobic layers over spatial distances has garnered significant attention. This electron transfer not only influences sediment pH migration but also affects sediment potential, creating electric fields that impact the cycling of various elements in sediments, thus influencing the ecological environment. Research on cable bacteria"s electron transfer and environmental effects has been prominently featured in top international journals like Nature and PNAS, making it a current research focus. This article summarizes existing research on cable bacteria, covering their classification, habitats, structural characteristics, motility, electron transfer abilities, and environmental impacts. Through bibliometric methods, the literature is analyzed to identify current research trends and future directions, providing insights for further exploration of cable bacteria"s physiological traits and environmental effects.
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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
Abstract:
【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.
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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
Abstract:
【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.
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Developments and Prospects of Research on Size Exclusion Effects in the Transport of Colloids in Porous Media
WANG Changxi, SHEN Chongyang, LIAO Renkuan
DOI: 10.11766/trxb202406180241
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.
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Study on Soil Aggregate Stability and Influencing Factors in Granite Benggang Area of Southeast Guangxi
PENG Ziye, XIE Meixia, LIN Xingchi, DING Erdongzi, LIU Chuhan, HE Lin, LIN Zhe, DUAN Xiaoqian
DOI: 10.11766/trxb202405020182
Abstract:
【Objective】Soil aggregate is the basic unit of soil structure, and its stability is an important index to evaluate soil erosion. This study aimed to evaluate the stability and influencing factors of soil aggregates in the granite Benggang area, explore the relationship between aggregate stability and Benggang erosion, and provide a scientific basis for the prevention and control of Benggang erosion. 【Method】In this study, the typical Benggang in the granite area of southeastern Guangxi was taken as the research object. The dry sieving method and Elliott wet sieving method were used to determine the particle size distribution of soil aggregates in the Benggang erosion area, and the soil samples containing coarse particles were desanded to further analyze the effect of aggregate stability on Benggang erosion. 【Result】The results showed that: (1) The soil mechanically stable aggregates in the granite Benggang area were mainly >2 mm, and the water-stable aggregates were mainly <0.25 mm. The wet sieve average mass diameter of soil aggregates decreased first, then increased and then decreased with the deepening of soil layer. The sanding correction of granite soil reduced the wet sieve error, and the disaggregate reduction decreased with the increase of soil depth, indicating that the stability of deep soil aggregates was poor. (2) The results of correlation analysis showed that the average mass diameter, macro-aggregate content, and disaggregate reduction were significantly positively correlated with soil organic matter, free iron oxide content, silt and clay content, and significantly negatively correlated with pH and sand content. (3) Utilizing redundancy analysis, the study identified that organic matter content and clay content accounted for 89.82% and 7.64% of the variation in soil aggregate indicators, respectively, and explained 97.46% of the total variance. Increasing the levels of soil organic matter and clay content can significantly enhance the stability of soil aggregates, thus mitigating the risk of Benggang erosion. 【Conclusion】This study clarified the stabilization mechanisms of aggregates in the granite red soil region and their influence on Benggang erosion and provides a scientific basis for regional ecological security and sustainable agricultural development.
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Effects of Organic Fertilizer Combined with Antibiotics on C and N Erosion Loss of Purple Soil Slope
FENG Hua, FANG Linfa, WU Changjie, XIAO Ran, LANG Ming, DENG Yan, Prakash Lakshmanan, MA Lihua, LI Zhaolei, ZHANG Fusuo, CHEN Xinping
DOI: 10.11766/trxb202404290177
Abstract:
【Objective】Partial substitution of chemical fertilizer with organic fertilizer is an effective approach for the resource utilization of agricultural wastes in China. Nevertheless environmental exposure to veterinary antibiotics from livestock manure leads to the risk of environmental pollution. Antibiotics can limit the activity of soil microorganisms that play a pivotal role in carbon (C) and nitrogen (N) cycling within soil systems. However, the combined impact of soil antibiotic residue through the soil hydraulic erosion process on soil C and N loss of slope farmland remains unclear. A deep understanding of this mechanism is important for the prevention of nutrient loss and control of non-point source pollution of slope farmland in the Three Gorges Reservoir Area. 【Method】In this study, indoor hydraulic erosion experiments with artificial rainfall were conducted to simulate the process of antibiotics"" impact on C and N erosion loss, and five treatments were set up: 1) CK, no fertilization control; 2) NP, only chemical fertilizer; 3) OMNP, organic fertilizer substituting 30% chemical phosphorus fertilizer; 4) OMNPT, oxytetracycline (OTC) contaminated organic fertilizer substituting 30% chemical phosphorus fertilizer; and 5) OMNPQ, enrofloxacin (ENR) contaminated organic fertilizer substituting 30% chemical phosphorus fertilizer. 【Result】The results showed that: (1) Compared with the application of chemical fertilizer, partial substitution of chemical fertilizer with organic fertilizer significantly reduced the hydraulic erosion of slope land; however, organic fertilizer with antibiotics exposure had no significant effect on erosion process compared to OMNP. (2) The residual concentrations of OTC and ENR in soil were 32.30 μg·kg-1 and 25.55 μg·kg-1, respectively. OTC loss was dominated by runoff (loss mass, 178.60 μg) while ENR loss was dominated by sediment (loss mass, 79.18 μg). (3) Compared with the application of chemical fertilizer only, partial substitution of chemical fertilizer with organic fertilizer significantly reduced total organic carbon (TOC) loss by 8.94% to 11.54%, mineral-associated organic carbon (MAOC) loss by 11.23% to 13.97%, total nitrogen (TN) loss by 22.00%, nitrate nitrogen (NO– 3-N) loss by 29.68%, and ammonium nitrogen (NH+ 4-N) loss by 27.81%. The application of organic fertilizer with antibiotics exposure had no significant effect on the loss of TOC, dissolved organic carbon (DOC), particulate organic carbon (POC) and MAOC, but increased the risk of soil N loss. Compared with the organic fertilizer without antibiotics, the loss fluxes of TN, NO– 3-N and NH+ 4-N in organic fertilizer with antibiotics exposure replacing chemical fertilizer were significantly increased by 22.77% to 37.73%, 19.46% to 22.77% and 190.10% to 253.38%, respectively. Also, it was observed that antibiotics altered the microbial community structure of soil and sediment, which was probably the main cause of increased soil nitrogen loss during erosion processes. (4) Pearson correlation analysis revealed that antibiotic exposure suppressed bacterial abundance and microbial biomass carbon (MBC), and promoted C and N loss. However, the two antibiotics had different effects on soil C and N loss, and only ENR exposure concentration had significant effects on TOC loss and NO– 3-N loss. Compared with the application of organic fertilizer without antibiotics, antibiotics (OTC and ENR) increased the proportion of soil C and N loss by 0.80% to 2.94% and 22.77% to 37.73%, respectively. 【Conclusion】The partial substitution of chemical fertilizer with organic fertilizer can reduce soil erosion and nutrient loss of slope land. However, this action may also result in the contamination of soil with antibiotics, which could subsequently lead to the increased nitrogen loss of slope farmland.
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Dynamics of Soil Moisture and Its Response to Rainfall in Caragana Korshinskii Plantation in Loess Hilly Region
LIANG Jing, WANG Guoliang, XU Xiaoyang, LIU Ying, MAO Jirong, ZENG Yan
DOI: 10.11766/trxb202404220165
Abstract:
【Objective】The seasonal dynamics of soil water and its changes along the soil depth restrict the growth and development of Caragana korshinskii plantation. Thus, by exploring the effects of precipitation types and rainfall on soil water content in the loess hilly area, this study seeks to clarify whether precipitation replenishment could meet the water demand of the growing season of Caragana korshinskii forest, and provide theoretical support for the ecological construction of artificial Caragana korshinskii forest in the loess hilly area.【Methods】The analyses in this study are based on precipitation and soil moisture data of Ansai Lime stick forest in Shaanxi Province from 2019 to 2023. The monthly dynamic changes of soil water under Caragana korshinskii forest at different depths were analyzed, and the response process of soil water to different precipitation types and rainfall during the growing season was investigated. The precipitation data was recorded every 30 minutes, and the soil water data were repeated at three monitoring points on the slope and under the slope, with the monitoring frequency of once an hour. The soil volumetric water content at 10 depths (10, 20, 30, 50, 70, 100, 200, 300, 500, 1 000 cm) was monitored. 【Results】(1) The precipitation in the study area could be divided into 5 types according to the characteristics of precipitation: light rain, moderate rain, large rain, heavy rain, and very torrential rain. Most of the precipitation events in the study area belonged to moderate rain type, with 59 events accounting for 46% of the total events. (2) Soil moisture content was affected by precipitation, and the annual variation of 0~100 cm soil moisture content showed a "double peak" pattern. In May to August, when Caragana korshinskii was growing vigorously, the seasonal dry layer appeared in the 50~100 cm soil layer. The occurrence time of the dry layer was closely related to the precipitation of the year, and the dry layer disappeared after sufficient precipitation recharge. (3) There was a significant positive correlation between rainfall type and soil water infiltration depth (R2 > 0.81), in which the infiltration depth of heavy rain and heavy rain was the deepest, reaching 100~200 cm, followed by moderate rain 10~70 cm, while light rain was limited to 0~10 cm. The response time of surface and deep soil of heavy rain was the shortest, followed by heavy rain, while the response process of light rain was relatively slow. Also, the soil water supply of rainstorm were significantly higher than that of other rainfall types, accounting for 87.5% of the secondary precipitation, followed by heavy rain (36.2%) and long-duration moderate rain (29.7%), while the precipitation of light rain and short-duration moderate rain was mostly lost in the form of evapotranspiration. 【Conclusion】(a) Most precipitation events in the study area belonged to the moderate rain type. The recharge efficiency of light rain and moderate rain was low, and more was loss in the form of evapotranspiration. Although the occurrence frequency of heavy rain was low, it played an irreplaceable role in replenishing soil water. (b) During the flourishing period of Caragana korshinskii growth in summer, the 50~100 cm soil layer generally had different degrees of seasonal drought, which adversely affected the normal growth of vegetation. However, the infiltration depth of heavy rain and rainstorm events reached approximately 50 cm and replenished soil water, and the annual precipitation could meet the needs of Caragana korshinskii growth.
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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
DOI: 10.11766/trxb202404290178
Abstract:
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.
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Differential Responses of Microbial Necromass to Warming in topsoil and subsoil
YANG Dongqiao, ZHANG Zihan, LU Mengya, DING Xueli
DOI: 10.11766/trxb202407080274
Abstract:
【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.
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Mechanisms of Organic Carbon Sequestration and Stabilization Mediated by the Soil “Mineral Carbon Pump (MnCP)”
Xiao Ke-Qing, Li Xinnan, Xing Wen, Feng Mengxi, Zhang Ming, Zhao Yao, Zhu Yong-Guan
DOI: 10.11766/trxb202404250169
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 coping with global climate change. Soil minerals are important components of the soil solid phase, and their interactions with soil organic carbon can directly affect soil interfacial activity, physicochemical properties and fertility. The mineral carbon pump (MnCP) concept emphasizes the key role of soil minerals in driving the active organic carbon sequestration, and describes the functional orientation of minerals in the process of soil organic carbon stabilization. In this paper, we systematically reviewed the concept of MnCP with the main line of mineral-mediated soil carbon sequestration, introduced the five mechanisms underlying MnCP-mediated carbon sequestration, the regulatory factors, and the development of related characterization techniques, and finally proposed the key scientific questions to be further investigated under the framework of MnCP.
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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
DOI: 10.11766/trxb202404120152
Abstract:
【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.
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Spatial Differentiation Characteristics of Soil Erosion and Degradation in Black Soil Cropland of Northeast China
TIAN Zhiyuan, LU Huizhong, MA Rui, ZHAO Yan, LIANG Yin
DOI: 10.11766/trxb202404210164
Abstract:
【Objective】Soil erosion is a significant cause of degradation in black soil. To make matters worse, there is little or no comprehensive evaluation of soil erosion-degradation in black soil cropland in Northeast China. Thus, clarifying the spatial differentiation characteristics of soil erosion and degradation, as well as the different soil erosion-degradation types will be conducive to the implementation of soil protection and restoration technologies tailored to local conditions.【Method】Based on the physical and chemical properties of soil samples collected during two periods of soil survey, the soil species survey in the 1980s and the soil series survey in the 2010s, a comprehensive soil quality index was constructed in this paper via principal component analysis, considering soil thickness, soil organic matter content, total nitrogen content, total phosphorus content, total potassium content, pH value, and bulk density. The spatial distribution maps of soil properties in the 1980s and 2010s were created with a 90 m resolution using environmental covariates and the random forest model. Fuzzy membership functions were built to evaluate soil quality, and soil degradation was the difference between the quality from these two periods. A total of 15 erosion-degradation types of black soil were classified based on two aspects: the intensity of soil erosion types and the degree of soil quality degradation.【Result】The results showed that about one-third of the cropland in Northeast China experienced erosion-degradation. Among them, water erosion is extensive and causes serious degradation. The most typical type was mild water erosion-serious degradation (occupying 23.7% of erosion croplands), which was distributed in the east of the Great Khingan Mountains, the north of the Lesser Khingan Mountains, the south of the Songnen Plain, and the north of the Changbai Mountains. Other types include mild water erosion-slight degradation (16.4%), severe water erosion-serious degradation (14.1%), mild water erosion-no obvious degradation (7.4%), severe water erosion-slight degradation (6.8%), and severe water erosion-no obvious degradation (3.1%). Additionally, the main type of wind erosion was severe wind erosion-slight degradation type (10.1%), which was distributed in the middle of the Songliao Plain and Horqin Sandy Land. This was followed by mild wind erosion-slight degradation (8.3%), severe wind erosion-serious degradation (3.2%), mild wind erosion-serious degradation (2.3%), mild wind erosion-no obvious degradation (1.9%), and severe wind erosion-serious degradation (1.3%). The land area of freeze-thaw erosion-degradation types was small (1.4%),having mild intensity and concentrated in the western foothills of the Great Khingan Mountains.【Conclusion】Overall, our study reveals that the higher the quality of black soil, the more likely it is to suffer serious degradation, which is greatly influenced by severe erosion. Also, the degradation caused by water erosion was the most serious. According to the different spatial distribution of erosion-degradation types, distinct black soil protection and sustainable utilization technologies should be promoted.
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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
DOI: 10.11766/trxb202403220128
Abstract:
【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.
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Stoichiometric Ratio and Influencing Factors of Soil Nutrients Under Farmland, Forestland, and Grassland in Eastern Xizang Autonomous Region
DU Yuanyuan, ZHAO Wen, HUANG Laiming
DOI: 10.11766/trxb202404270171
Abstract:
【Objective】The investigation of soil nutrient content and stoichiometric ratios is of great significance for gaining a deeper understanding of the nutrient cycling and balance mechanisms within ecosystems. The Xizang Autonomous Region, situated on the southwestern Qinghai-Tibetan Plateau, functions both as an ecologically fragile area and a crucial ecological security barrier for China. This research examined the soil nutrient stoichiometric ratios and their influencing factors under different land use patterns in the alpine region of the Xizang Autonomous Region. The objective was to assess nutrient limitations in the study area and provide a foundation for effective nutrient management in these sensitive ecosystems. 【Method】This study focused on three land use types (farmland, forestland, and grassland) across an east-west transect in the eastern Xizang Autonomous Region. Soil samples were collected at different depths (0-10 cm, 10-20 cm, and 20-30 cm) to measure basic physical and chemical properties (including clay content (Cy), bulk density (BD), porosity (Ps), soil water content (SWC), soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), Alkali-hydrolyzable nitrogen (AN) and available phosphorus (AP)). The longitude (LON), latitude (LAT), and altitude (ALT) of each sampling site were recorded using GPS, while environmental factors such as mean annual temperature (MAT), mean annual evaporation (Ea), mean annual precipitation (MAP), and vegetation normalization index (NDVI) were extracted using ArcGIS. Variance analysis was employed to assess differences in the contents of SOC, TN, AN, TP, and AP, along with their corresponding nutrient stoichiometry ratios (C:N, C:P, N:P, and AN:AP) among farmland, forestland, and grassland. Additionally, correlation analysis and redundancy analysis were conducted to identify the factors influencing nutrient stoichiometric ratios across the three land use types. 【Result】The findings revealed no significant differences in SOC, TN, or AN contents among the different land use types (P > 0.05). However, TP and AP contents in farmland were significantly higher than those in forestland and grassland. Moreover, soil C:N did not vary significantly with depth across any of the land use types. The AN: AP ratio in the 10-20 cm soil layer of grassland was significantly higher than that in farmland and forestland, while the C:P and N:P ratios in the 20-30 cm soil layer of farmland were significantly lower compared to forestland and grassland. Farmland soils exhibited greater nitrogen limitation, evidenced by lower AN contents and reduced N:P. Redundancy analysis indicated that SOC, TN, BD, Ps, MAT, and Ea were among the common influencing factors for the 0-30 cm soil nutrient stoichiometric ratios in farmland (16.2%-41.7%), forestland (17.3%-33.9%), and grassland (11.0%-26.9%). Interestingly, the influence of environmental factors on the soil nutrient stoichiometric ratios under different land use types decreased with increasing soil depth. 【Conclusion】Overall, this research enhances the understanding of the key factors influencing soil fertility under different land use types and offers valuable guidance for optimizing nutrient management in the alpine region of Xizang Autonomous Region.
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Effects of Organic Amendments and Their Combination with Biochar on the Stability of Aggregates in Red Soil
ZHANG Xin, WU Qifeng, ZHOU Yan, MA Xiaomin, XING Jiajia, PENG Liyuan, QIN Hua, CHEN Junhui
DOI: 10.11766/trxb202405180201
Abstract:
【Objective】This study aimed to elucidate the effects of different organic amendments (including corn straw, sheep manure, and biochar) application on the stability of soil aggregates and biological binding agents and to provide a scientific basis for carbon sequestration and fertilization improvement of red soil.【Method】The distribution of soil aggregates in different size and the contents of biological binding agents in aggregates were analyzed following six-year successive application of corn straw and sheep manure alone and in combination with biochar.【Result】Compared with the non-amended control, the contents of soil aggregates with particle size > 2 mm and 2-1 mm and the mean weight diameter (MWD) of soil aggregates were significantly increased by application of straw and sheep manure alone. In particular, the MWD and the aggregates of > 0.25 mm were significantly increased by 50% and 27.66% under straw amendment, while increased by 103.13% and 36.17% under sheep manure application alone, respectively. However, biochar alone or in combination with organic amendment did not affect the particle size distribution of soil aggregates. There were no significant interactions between biochar and the organic amendment on the particle size distribution. The organic amendment had a significant effect on the soil organic carbon (SOC) and microbial biomass carbon (MBC) content of aggregates of each particle size. Also, the contents of SOC, MBC, total glomalin-related soil proteins (T-GRSP), and polysaccharides in macroaggregates (> 0.25 mm) were significantly increased by straw, sheep manure, and biochar application alone. Compared with the sole application of straw and sheep manure, biochar co-application significantly increased the SOC content in macroaggregates by 207% and 151%, the MBC by 78% and 62%, the T-GRSP by 15% and 20%, and the polysaccharide content by 24% and 22%, respectively. Biochar and organic amendment had a significant interactive effect on the SOC and MBC content in macroaggregates, silt, and clay particles. In addition, the combined application of biochar and organic amendment had a significant interactive effect on the content of polysaccharides. Random forest regression model analysis showed that the contents of easily extractable glomalin-related soil proteins (EE-GRSP), T-GRSP, and polysaccharides in aggregates were the key factors affecting the MWD.【Conclusion】These findings suggest that long-term successive application of straw and manure could significantly increase the stability of soil aggregates by increasing the MBC, T-GRSP, and polysaccharide in the macroaggregates. The combined application of biochar can promote the accumulation of biological binding agents in macroaggregates, which is more conducive to improving the structural stability and the potential of carbon sequestration and fertilization of red soil.
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Distribution Characteristics of n-Alkanes and Compound-specific Carbon Isotopes in Black Soil of Songnen Plain and Their Implications
QIU Zifei, SHI Yonghui, LI Jingjing, YANG Fei, LONG Hao, ZHANG Ganlin
DOI: 10.11766/trxb202405190202
Abstract:
【Objective】Normal alkanes (n-alkanes) are relatively stable components of soil organic matter. Identifying the composition and occurrence mechanisms of n-alkanes in black soil is of great significance, as it can reveal the source of organic matter and the changes in the soil-forming environment. The purpose of this study was to evaluate the influence of soil-forming processes on the n-alkane index of black soil and to explore the indicative significance of n-alkanes in black soil.【Method】In this study, samples from three typical soil formation processes of Isohumosols in the Songnen Plain were collected, including the HL profile naturally developed under relatively stable terrain conditions, the YA profile affected by erosion and accumulation under unstable terrain conditions and the SH profile with evident animal disturbance processes. The ultrasonic extraction method was utilized to extract free n-alkanes from the soil. The distribution characteristics and compound-specific carbon isotopes were analyzed. 【Result】The results showed that the HL and YA profiles were unimodal, with the main peak being C31 and the odd-even predominance, while the SH profiles were bimodal, with the main peak being C23 and C31. The ∑C25~35 and CPI values of HL and SH sections decreased with the depth of the section, while the ∑C25~35 and CPI values of the YA section increased in the buried layer. The mean δ13Calk values of HL and YA profiles ranged from -29.30 to -30.27‰ and -29.79 to -32.60‰, respectively. Our results indicate that the buried layer is found to enhance the retention of n-alkanes, while disturbance may disrupt other indicators of n-alkanes in situ records. Furthermore, the analysis of n-alkanes and their carbon isotopes suggests that soil organic matter primarily originates from terrestrial higher plants, particularly C3 plants. Since the Holocene period, herbaceous plants dominate the black soil area of the Songnen Plain, with the proportion of woody plants gradually increasing during the development of black soil. Combining the data from 14C dating, it is inferred that the climatic conditions during the last deglaciation likely played a role in the initial development of black soil, while the warm and wet climate of the Middle Holocene contributed to the maturity of black soil.【Conclusion】These results confirm that n-alkanes in black soil can reflect the impact of soil erosion-deposition and disturbance on n-alkanes. Thus, this study will provide a basis for revealing the changes in organic matter sources during the formation of black soil and reflect the soil-forming environment of black soil.
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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
DOI: 10.11766/trxb202402030059
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.
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Evolution Patterns and Underlying Sequestration Mechanisms of Organic Carbon Components in Soil Aggregates under Long-term Rice Cultivation
Zhang Yingchun, Wang Ping, Liu Yalong, Wang Jingkuan
DOI: 10.11766/trxb202402200074
Abstract:
【Objective】Paddy soil is a type of anthropogenic soil formed through long-term water cultivation and ripening, which has a high organic carbon storage and carbon sequestration potential. Clarifying the protection mechanisms of organic carbon in paddy soil can provide a theoretical basis for carbon sequestration, emission reduction, and sustainable utilization of paddy soil. 【Method】Using a 1000-year chronosequence of paddy soils formed through coastal reclamation in Eastern China, we investigated the distribution characteristics and evolution patterns of occluded/free and particulate/mineral-bound organic carbon within soil aggregates under long-term rice cultivation. This was achieved through methods such as force-stable aggregate fractionation and physical particle/density grouping. 【Result】While soil organic carbon (SOC) gradually accumulated under long-term rice cultivation, the contents of particulate organic carbon (POC) and mineral-bound organic carbon (MOC) also increased. However, MOC was the dominant form, accounting for 64.40%~87.89% of the total SOC pool. The distribution patterns of different size soil aggregates were consistent, with macroaggregates (74.0%~77.6%) being the most abundant, followed by microaggregates (9.2%~15.9%) and silt and clay-sized microaggregates (8.6%~15.7%). Therefore, over 70.00% of SOC was stored in the macroaggregates. The organic carbon content of aggregates of all particle sizes increased with the increase of paddy cultivation age and grain size, which were 7.39~13.78 g·kg-1, 1.72~2.74 g·kg-1 and 0.66~1.92 g·kg-1. Among different types of soil aggregates, mineral-bound organic carbon (MOC) was the dominant form. In macroaggregates, occluded microaggregates, and free microaggregates, the MOC contents were up to 2.9, 1.1, and 3.2 times higher than POC, respectively. The protective effect of occluded microaggregates on POC was stronger than free microaggregates, with the POC content in occluded microaggregates being up to 1.5 times higher than in free microaggregates. 【Conclusion】Long-term rice cultivation is beneficial for SOC sequestration under the physical protection of soil aggregates. The protective effect of occluded microaggregates on POC is a potential mechanism for carbon sequestration in paddy soil.
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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
Abstract:
【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.
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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
Abstract:
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.
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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
Abstract:
【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.
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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
Abstract:
【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.
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Research Progress on Ecological Effects and Microbial Degradation of Biodegradable Plastics in Soils
DOI: 10.11766/trxb202405270210
Abstract:
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.
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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
DOI: 10.11766/trxb202401290049
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.
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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
DOI: 10.11766/trxb202403120106
Abstract:
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.
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The Synergistic Effect of a Phage-Probiotic Combination on Suppressing Bacterial Wilt Disease
XI Ningbo, WANG Shuo, LI Tingting, WANG Xiaofang, XU Yangchun, SHEN Qirong, WEI Zhong
DOI: 10.11766/trxb202405160200
Abstract:
【Objective】Bacterial wilt disease, caused by soil-borne Ralstonia solanacearum, has led to significant yield reductions or even crop failures in tomatoes, potatoes, and tobacco, severely limiting the safe supply of agricultural products. Rhizosphere microorganisms play a crucial role in mitigating soil biotic impediments. Probiotics can inhibit pathogens through antagonism or nutrient competition, while phages can target pathogens through specific infections. However, the single use of either probiotics or phages often results in unstable effects, and the high-density fermentation cost of these strains is considerable. 【Method】To establish an efficient and stable technology for reducing soil biotic impediments, this study constructed combinations of antagonistic-competitive and nutrient-competitive beneficial bacteria with phages. It explored their synergistic effects in reducing soil wilt disease through in vitro microplate and greenhouse pot experiments. The potential mechanisms of synergy between probiotics and phages were also investigated. 【Result】 The results showed that most combinations of phages and probiotics exhibited synergistic effects, significantly enhancing the inhibition of pathogenic R. solanacearum growth and the reduction of bacterial wilt disease. Notably, the combination of the antagonistic-competitive beneficial bacterium T-5 with phages resulted in an 89.19% reduction in pathogenic bacterial growth compared to the control. Greenhouse experiments indicated that the synergistic effect reduced the disease index by an average of 58.18%, with the combination of the nutrient-competitive beneficial bacterium WR21 and phages significantly reducing the disease index by 67.28%. Further studies revealed that even at lower concentrations of beneficial bacteria, the phage-bacteria synergy remained effective. At a concentration of 104 CFU?g-1 substrate, the combination of T-5 with phages reduced the disease index by 21.56% and the number of rhizosphere pathogenic bacteria by 19.21% compared to the application of beneficial bacteria alone, demonstrating a strong synergistic effect. Additionally, the study explored the impact of phage-beneficial bacteria combinations on the characteristics of pathogenic R. solanacearum. The results showed that the phage-nutrient-competitive beneficial bacteria combination significantly reduced the pathogen""s carbon source utilization ability, with the WR21 and phage combination reducing the number of carbon sources utilized by the pathogen by 87.9%. Furthermore, under the dual stress of phages and antagonistic-competitive beneficial bacteria, the sensitivity of the pathogen to the antagonistic substances produced by T-5 increased by 64.10%. 【Conclusion】This study highlights the potential of phage-beneficial bacteria combinations in mitigating bacterial wilt disease and preliminarily elucidates the potential mechanisms behind their synergistic effects. These findings provide theoretical and technical support for the development of efficient soil biological obstacle reduction techniques.
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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
DOI: 10.11766/trxb202403110102
Abstract:
【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 (SOCw), and soil pH, and significantly negatively correlated with silt content. The gross nitrification rate was significantly negatively correlated with SOCw 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.
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Impacts of Simulated Erosion and Fertilization on Soil Quality and Corn Yield in Northeastern Black Soil Region
WANG Zhiqiang, LI Yangyang, ZHANG Xiaoping
DOI: 10.11766/trxb202401220038
Abstract:
【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, ?-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, ?-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.
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Amelioration of Acidic Purple Soil with Calcareous Purple Mudstones
CHEN Jingjing, GUO Xinyi, LI Zhongyi, YU Junfeng, WU Wenchun, ZHOU Jia
DOI: 10.11766/trxb202403170116
Abstract:
【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.
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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
DOI: 10.11766/trxb202402030060
Abstract:
【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.
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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
DOI: 10.11766/trxb202401290047
Abstract:
【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.
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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
DOI: 10.11766/trxb202402170070
Abstract:
【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.
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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
DOI: 10.11766/trxb202401090018
Abstract:
【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.
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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
DOI: 10.11766/trxb202311240495
Abstract:
【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.
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Effects of Folsomia candida on Soil Microaggregates Under Different Nitrogen Addition
YOU Lelin, ZHANG Tingting, DAI Wencai, XIAO Naichuan, ZHAO Huan, ZHANG Yarong, XIE Jun
DOI: 10.11766/trxb202404080148
Abstract:
【Objective】This study aimed to investigate the impact of different nitrogen fertilizer application rates on the growth and reproduction of Folsomia candida and their effects on soil micro-aggregates.【Method】Soil samples from field experiments with varying nitrogen application rates (N0: 0 kg·hm-2, N90: 90 kg ·hm-2, N180: 180 kg·hm-2, N270: 270 kg·hm-2, N360: 360 kg·hm-2) were cultivated to examine the differences in Folsomia candida reproduction, total body weight, and their effects on soil micro-aggregates over different cultivation periods (28 d, 42 d, 56 d).【Result】The results indicated that nitrogen application significantly affected soil pH, with the N360 treatment showing a decrease of 0.9 pH units compared to the N0 treatment (P < 0.05). The reproduction of Folsomia candida showed significant differences among the nitrogen treatments as the cultivation period extended. After a 56 d cultivation period, the reproduction number in the N0 treatment was 1.10-1.53 times higher than that in the other treatments (P < 0.05). The total biomass of Folsomia candida larvae generally followed the same trend as the reproduction, with the lowest values observed in the N360 treatment across all cultivation periods. Also, Folsomia candida significantly increased the quantity of 0.05-0.01 mm micro-aggregates by 11.3%-48.4% compared to the untreated soil samples, and significantly decreased the quantity of 2-0.25 mm small aggregates by 27.9%- 60.9%, with more pronounced effects as the cultivation period extended (P < 0.05). The mean weight diameter (MWD) and geometric mean diameter (GWD) of soil under all nitrogen treatments were significantly lower than those of the untreated soil samples (P < 0.05).【Conclusion】The growth and reproduction of Folsomia candida were inhibited by nitrogen fertilization, and high densities of Folsomia candida can increase the content of soil micro-aggregates but destroy small aggregates, leading to reduced soil stability. The results of this study will provide a scientific reference for improving soil structure.
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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
DOI: 10.11766/trxb202312260540
Abstract:
【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.
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Dynamic Changes of Microbial Community Metabolisms Along Soil Profile in Response to Exogenous Carbon and Nitrogen Addition in Mollisols
HU Yaohua, CAI Yuanfeng, CAO Weiwei, JIA Zhongjun
DOI: 10.11766/trxb202402040062
Abstract:
【Objective】 Soil profile is a model system for deciphering the formation and maturation of organic matter-centric fertility. However, the physiological metabolic potential of the soil profile microbial community and the mechanism of its transformation of labile carbon are not clear.【Method】The metabolic mechanisms of soil microbial communities under exogenous carbon and nitrogen input scenarios were investigated by using 13C-labeled glucose and ammonium nitrate to cultivate soils in the surface (0~10 cm), middle (30~40 cm), and deep (90~100 cm) layers of a typical thin-layered black soil. The insoluble organic carbon (13C-SOC) synthesized by microbial growth and reproduction, 13CO2 produced by heterogeneous metabolism, the priming effect, the efficiency of 13C-carbon utilization, and their nitrogen limitation features were determined.【Result】The increase in soil respiration intensity after exogenous 13C-glucose addition was in the order of surface (3.2-fold), middle (11.3-fold), and deep soil (14.5-fold) compared to the control water treatment; the relative priming effect was 43.5%, 150.5%, and 267.0%; carbon utilization efficiency was 34.9%, 37.3%, and 32.9%, respectively. Approximately 45%~50% of glucose was isomerized and metabolized to 13CO2. Also, the number of soil microorganisms increased by about 85.0% in the surface and middle layers and 1.9 times in the deep layer while the 13C-SOC of insoluble cellular biomass synthesized by microorganisms using glucose was 111.6±11.7 mg kg-1 (surface soil), 119.5±3.4 mg kg-1 (middle soil), and 105.2±21.6 mg kg-1 (deep soil). However, the proportion of the total soil organic carbon, in descending order was 0.98% (surface layer) < 1.70% (middle layer) < 4.76% (deep layer). Interestingly, the 13C-SOC tended to increase after nitrogen addition although it was not statistically differentiated, however, it significantly suppressed the relative priming effect. High-throughput sequencing revealed that surface, middle, and deep soil microbial communities clustered independently regardless of carbon and nitrogen treatments under glucose addition conditions. Micrococcaceae were significantly increased in the surface soil and were probably the main contributor of organic carbon from insoluble microbial sources whereas Nocardioides were the main contributors of organic carbon from microbial sources in the middle and deep soil.【Conclusion】These results suggest that the deep soil, despite its lower diversity and abundance, can utilize exogenous and readily decomposable organic carbon to rapidly colonize and produce insoluble organic carbon of microbial origin and its total new carbon inputs were almost identical to those of the surface soil. Soil microbial communities in black soil profiles developed strong functional plasticity during long-term adaptation to geo-climatic variability, which provides an important basis for the stability of soil ecosystem structures and functions.
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Effects of Bacterial Residue Organic Fertilizer on Tomato Growth and Soil Antibiotic Resistance Genes Accumulation
CUI Gege, ZHANG Yaozhong, YANG Tianjie†, WANG Shimei, HUANG Yishuo, XU Yangchun, SHEN Qirong
DOI: 10.11766/trxb202402180072
Abstract:
【Objective】Bacterial residue is a solid waste produced during the fermentation process of antibiotic synthesis intermediate (6-aminopenicillanic acid). Improper treatment will endanger environmental safety and increase the risk of the spread of antibiotic resistance genes (ARGs). At present, composting is the main method for treating residues due to its harmless and resourceful characteristics. Thus this study was designed to investigate the effects of composted bacterial residue organic fertilizer on tomato growth and soil ARGs accumulation and to assess the ecological risks of residue organic fertilizer. 【Method】In a field experiment, the tomato plant was used as the research object and the effects of organic fertilizer fermented from bacterial residue of penicillin synthesis intermediates on tomato growth, soil physicochemical properties, bacterial community structure, and the diversity and abundance of antibiotic resistance genes were analyzed【Result】The results showed that the application of residue organic fertilizer can increase the aboveground dry biomass of tomatoes in the field, and continuous application for two seasons can increase the vitamin C content of tomato fruits and soil nitrate nitrogen content. After being treated with organic fertilizer, there was no significant change in the diversity of bacterial communities in the rhizosphere soil. However, compared with conventional fertilization, the abundance of Proteobacteria significantly increased, while the abundance of Chloroflexi significantly decreased. There was no significant change in the diversity of ARGs in tomato soil after the application of residue organic fertilizer, but the amino glycoside resistance gene aada1 and sulfonamide resistance gene sul (II) were significantly higher than those in conventional compound fertilizer treatment. Also Luteimonas sp. was positively correlated with tetracycline, aminoglycoside, and sulfonamide resistance genes. 【Conclusion】After applying microbial residue organic fertilizer in tomato rhizosphere soil, there was no enrichment of β-lactam ARGs. However the risk of accumulation of tetracycline, aminoglycoside, and sulfonamide ARGs in rhizosphere microorganisms needs further evaluation.
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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
DOI: 10.11766/trxb202401030007
Abstract:
【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.
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Effect and Mechanism of Food Waste Compost on the Stability of Paddy Soil Aggregates
DOI: 10.11766/trxb202402240077
Abstract:
【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 MWDYoder, MWDLB-fast, and MWDLB-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.
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Variation of the Increased CH4 Emissions in Paddy Fields with Straw Incorporation across 11 Consecutive Years
YANG Zhengyu, LI Zongming, LI Yanyan, SHEN Jianlin, WU Jinshui
DOI: 10.11766/trxb202402230076
Abstract:
【Objective】 This study aimed to explore the variations of the increased methane (CH4) emissions and its mechanisms in paddy fields with straw incorporation across 11 consecutive years, so as to provide a scientific basis for the accurate assessment of CH4 emissions under long-term straw incorporation.【Method】A typical double-cropping rice field in the subtropical region was selected as the research subject, and the fertilizer only treatment (CON), low amount of straw incorporation treatment (3.0 t?hm-2, LS) and high amount of straw incorporation treatment (6.0 t?hm-2, HS) were set up. The field experiment was conducted for 11 years (2012—2022) with CH4 fluxes and related soil and environmental factors measured in the early and late rice seasons across the 11 years.【Result】The results showed that in the 11th year of straw incorporation, CH4 emissions in both the LS and HS treatments were substantially higher than those in the CON treatment, with the highest emissions recorded in the HS treatment, followed by the LS and then the CON treatment (HS > LS > CON). However, it was noted that the increment in CH4 emissions due to straw incorporation in the 11th year had diminished by 75.1% and 83.5% when compared to the increment in the first year (P < 0.05). In the 11th year, the contents of soil organic carbon (SOC), ammonium nitrogen (NH4+-N), and dissolved organic carbon (DOC) in the LS and HS treatments showed significant increases by 7.90% and 20.8% (LS and HS treatments, the same as below), and 15.0% and 25.7%, 19.5%, and 31.3%, respectively, compared to the CON treatment (P < 0.05). However, the redox potential (Eh) and soil bulk density (BD) exhibited significant reductions of 14.1% and 21.7%, and 10.3% and 7.76%, respectively (P < 0.05). Furthermore, the abundance of the mcrA and pmoA genes, which are instrumental in methanogenesis and methane oxidation processes, respectively, as well as the mcrA/pmoA gene ratio, were significantly enhanced in the LS and HS treatments compared to the CON, which increased by 96.0% and 152%, 12.7% and 34.8%, and 73.9% and 85.8%, respectively (P < 0.05). Through redundancy analysis, it was determined that in the 11th year of straw incorporation, CH4 emissions in the paddy field displayed a significant positive correlation with the abundance of mcrA and the mcrA/pmoA ratio in the soil (P < 0.05). The decrease in BD and the rise in Eh, induced by the increase in SOC content, likely fostered the augmentation in pmoA gene abundance, which might be the principal reason for the undermined increase in CH4 emissions for the straw treatments observed in the later stages of the experiment.【Conclusion】 In the subtropical regions, relative to CON, the increases in CH4 emissions under long-term straw incorporation was reduced by approximately 80% (P < 0.05) compared to the increase under short-term straw incorporation due to the changes in SOC, BD, and Eh. Therefore, the assessment of CH4 emissions from paddy fields with straw incorporation needs to be dynamically adjusted according to the year of duration of straw incorporation.
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The Decomposition Characteristic of Crop Straws and Their Released Dissolved Organic Matter Properties
DOI: 10.11766/trxb202311130472
Abstract:
【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, bean, 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 bean straw showed a different order. The dissolved organic carbon (DOC) content released by the corn, wheat, bean, 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, bean, 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.
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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
DOI: 10.11766/trxb202311170480
Abstract:
【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.
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Hot Moments and Hot Spots and the Associated Influencing Factors of Denitrification along Farmland Soil Profiles in Southern China
Zhou Han, Wang Xiaomin, Wei Zhijun, Ma Xiaofang, Zhang Yumeng, Shan Jun, Yan Xiaoyuan
DOI: 10.11766/trxb202401020003
Abstract:
【Objective】Denitrification is the primary pathway for removing NO3?-N in agricultural soil profiles, converting NO3?-N into N2, and reducing the risk of NO3?-N accumulation. However, due to methodological limitations, previous studies have mainly focused on the accumulation patterns in soil profiles or the transformation of NO3?-N in the surface soil, with less attention to its removal throughout the entire soil profile. Thus, the rate of denitrification and absolute amount of nitrate removal capacity along the soil profile remain unclear. Furthermore, the existence of “hot moments” and “hot spots” for denitrification in soil profiles is still unknown. 【Method】To evaluate the NO3?-N removal capacity of typical farmland profiles in southern China and to explore the hot moments and hot spots of denitrification, paddy fields (rice-wheat rotation), vegetable fields, and vineyard in the Taihu Lake region were selected for this study. Near in-situ incubation of flooded and non-flooded layers of the soil profile (0-300 cm) of these fields was performed using the Membrane Inlet Mass Spectrometer (MIMS) and Robotized continuous flow incubation system (RoFlow) over a year.【Result】Our results showed that the soil denitrification rate exhibited distinct hot moments and hot spots across the three planting patterns. Denitrification hot moments in rice fields were primarily observed in October during the rice season, with a rate of 17.6±1.0 nmol N g?1 h?1. The denitrification hot moments of vegetable fields and orchards mainly occurred in March, with rates of 44.2±2.5 nmol N g?1 h?1 and 45.3±7.5 nmol N g?1 h?1, respectively. The hot spots of denitrification in the paddy field occurred in the topsoil (0-20 cm) with an average rate of 3.4±0.4 nmol N g?1 h?1. The denitrification hot spots of the vegetable field and orchard mainly occurred at 20-100 cm, with average rates of 11.7±1.3 nmol N g?1 h?1 and 9.4±2.3 nmol N g?1 h?1, respectively. Also, the removal rate of NO3?-N in these denitrification hot spots exceeded 90%, and almost all NO3?-N in the soil profile was removed under the three planting patterns. Correlation analysis results indicated that the soil NO3?-N content was the primary limiting factor for denitrification. 【Conclusion】Our study reveals that the farmland soil profiles under the three planting patterns in the Taihu Lake area exhibit high denitrification rates with distinct denitrification hot moments and hot spots, effectively removing NO3?-N from the soil profile. These findings deepen our understanding of the NO3?-N removal process in farmland soil profiles, holding significant implications for accurately assessing the cumulative risk and removal capacity of NO3?-N in high N input areas of southern China.
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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
DOI: 10.11766/trxb202401110021
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.
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Effects of Experimental Warming on Soil Microorganisms: A Meta-Analysis
ZHAO Wenyu, MIAO Run, CHENG Cheng, WANG Qi
DOI: 10.11766/trxb202402180071
Abstract:
【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.
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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
ZHANG Liming, LI Jing, CHEN Weiming, SUN Jiarui, XIE Xilin, ZHANG Hua, SHEN Jinquan, LIAO Wenqiang, XING Shihe
DOI: 10.11766/trxb202402070064
Abstract:
【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 global warming (GW) 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_GW), 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_GW, 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. The results of grey relational analysis-structural equation modeling also indicated that the clay content, bulk density, and organic fertilizer application rate were most closely associated with the carbon sequestration rate in rice fields of Zhangzhou, followed by the annual average temperature, precipitation, and pH levels. 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. Among subclasses of rice soils, acid sulfate paddy soils were most affected, with -23.05% and 8.10% changes in carbon sequestration rate caused by warming and extremely high temperatures, 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.
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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
DOI: 10.11766/trxb202402040063
Abstract:
【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.
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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
DOI: 10.11766/trxb202311120469
Abstract:
[Objective] The approach of reducing chemical fertilizer usage while increasing the application of organic materials 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 materials (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 materials 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.
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Progress of soil temperature prediction equation
Zhang Jianbin, Gao Zhi Qiu, Tong Bing, Wang Linlin
DOI: 10.11766/trxb202210220581
Abstract:
Soil temperature (especially surface temperature) is a key physical quantity in the interaction between land and atmosphere, and plays a very important role in the earth system. Soil temperature prediction technology has always been the core scientific problem in land surface model, numerical weather prediction and climate prediction. This paper systematically reviews the research progress of soil temperature prediction equation, from the classical heat conduction equation to the heat conduction convection equation that takes into account the physical process of vertical movement of soil moisture, from the single sine wave approximation to the Fourier series approximation of the daily change of surface temperature, from the assumption that the diurnal change of convection parameters is constant to the consideration of its diurnal change, and emphatically summarizes the creation, improvement and solution of the soil heat conduction convection equation. Finally, this paper reviews the application of heat conduction convection equation in the study of surface energy balance, vertical movement of soil moisture, water flux, earthquake and frozen soil heat transfer. At the same time, it is pointed out that the influences of soil water phases and plant roots on the heat conduction-convection equation is warranted for the future research of soil temperature prediction equation.
Supervisor: Chinese Academy of Sciences
Sponsor:Soil Science Society of China
Editor-in-Chief:Xu Renkou
Address:71 East Beijing Road, Nanjing 210008, P. R. China
Zip Code:210008
Phone:+86-25-86881237
Email:actapedo@issas.ac.cn
ISSN:0564-3929
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