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.

Abstract:【Objective】 To ensure the sustainable development of agriculture, this study aimed to clarify the temporal and spatial changes of soil organic matter, bulk density, and driving factors for Nenjiang City's “thinning and hardening” list. 【Method】 Nenjiang City is located in the core area of typical black soil distribution in China. In 2023, a field survey was conducted at the same locations as the Second National Soil Survey to reassess the current soil conditions. The key soil properties measured in this study included soil organic matter, bulk density, and other physicochemical characteristics at two soil depths(0-20 cm and 20-40 cm). The "point-to-point" method was used to visually reflect the spatiotemporal changes in soil properties over the past 40 years. Furthermore, correlation analysis and redundancy analysis were employed to explore the factors influencing the changes in soil organic matter and bulk density in Nenjiang City. 【Result】 The distribution of soil organic matter and bulk density in Nenjiang City showed significant spatial differences. The organic matter was higher in the east and lower in the west, and the bulk density was higher in the southwest and lower in the northeast. The results showed that in the past 43 years, with the intensities of human activities such as agricultural production, the organic matter content of cultivated soil in the Nenjiang black soil area showed an overall decreasing trend, with that of the surface decreasing by 11.89% and the subsurface by 6.99% compared with 1980. It was observed that locations initially having higher organic matter content experienced a significant decline. In addition, the bulk density of cultivated land in the Nenjiang black soil area showed an overall upward trend, with that of the surface increasing by 12.14% and the subsurface by 17.09% compared with 1980. In different soil types, the decline in average organic matter content was the greatest in black soil, while the average organic matter content in meadow soil increased. At the same time, the average bulk density increased across all soil types, with the greatest increase observed in dark brown earth. In addition, among the factors influencing soil organic matter, total nitrogen, tillage layer thickness, total phosphorus, and slope were all positively correlated with changes in soil organic matter. Among these, total nitrogen and total phosphorus showed the strongest correlation with organic matter variation. On the other hand, changes in soil bulk density were more strongly influenced by clay content, climatic factors (effective accumulated temperature and annual precipitation), and topographic factors (slope). 【Conclusion】 Based on the above results, the changes in soil organic matter and bulk density in Nenjiang City are influenced by multiple factors, including soil properties, climate, and topography. Future efforts should focus on addressing issues such as soil fertility improvement and the elimination of plowpans in the southwestern part of Nenjiang City.

Abstract:【Objective】 Clarifying the historical trajectory of soil erosion in karst regions and investigating the mechanisms of soil and water loss are of great significance for evaluating the ecological restoration potential of regional reforestation and advancing soil and water conservation efforts. While substantial research achievements have been made in soil erosion studies over the past five decades, the evolutionary mechanisms of soil erosion in Chongqing's karst areas over the past century remain unclear. 【Method】 This study focused on a mature Tiankeng in Banxi Town, Youyang County, Chongqing Municipality, located in a typical karst region of Southwest China. The research employed the radioactive nuclide dating methods of ¹³⁷Cs and ²¹⁰Pb to establish a chronological sequence of the sediment profile within the Tiankeng. By integrating sedimentary environmental indicators with historical records of human activities, the soil erosion history over the past century in the Xiaojiazhai karst sub-catchment (where the Tiankeng resides) was reconstructed. In parallel, the findings were compared with research results from the Zhongliang Mountain karst depression and Changjiawa depression in Chongqing to investigate the impacts of human activities on soil erosion processes in the karst areas of Chongqing Municipality at a centennial scale. 【Result】 The results indicated that the soil erosion history in the study area could be divided into three phases: 1897–1955, 1955–1965, and 1965–2023. Over the past century, the sedimentation rate and average erosion modulus in the sub-catchment exhibited significant variations. During 1955–1965, the sedimentation rate and erosion modulus reached 2.30 cm·a⁻¹ and 1109 t·km⁻²·a⁻¹, respectively, which were markedly higher than those of the other two phases. Comparative analysis of soil erosion histories from the Changjiawa Depression in Wushan County and the Zhongliang Mountain Depression in Chongqing revealed that sedimentation rates and erosion moduli in karst sub-catchments of Chongqing over the past century followed a consistent pattern of initial increase followed by decline, with peak erosion modulus values occurring in the late 1950s. To further assess the influence of precipitation on erosion modulus, a correlation analysis between precipitation data and erosion modulus in Youyang County was conducted. The results demonstrated no significant correlation (R² = 0.0059) between precipitation and erosion modulus over the past century, suggesting that precipitation variation likely did not dominate the pronounced changes in soil erosion within the Tiankeng area during this period. Also, the high erosion modulus phase (1955–1965) coincided with extreme drought events and large-scale deforestation in the late 1950s, coinciding with a drastic reduction in forest coverage during this period. Additionally, abrupt increases in δ¹³C_org values and magnetic susceptibility within the sediment profile provided further evidence of the combined impacts of extreme drought and intensive human activities on environmental degradation. These findings suggest that extreme drought and deforestation during this period were critical drivers of intensified soil erosion in Chongqing's karst regions. 【Conclusion】 The study highlights that regional environmental changes caused by intense human activities far exceeded those resulting from natural conditions and thus, provides novel insights into century-scale soil erosion processes in Chongqing’s karst catchments. The findings enhance understanding of regional desertification mechanisms and inform targeted strategies for soil-water conservation.

Abstract:【Objective】 Soil quality is a prerequisite for achieving sustainable crop production. However, due to its low pH and acid buffering capacity, the red soil is prone to losing its quality, thus, necessitating continuous research in quality management practices. Therefore, this study aimed to evaluate the quality enhancement potential of organic fertilizers of plant and animal sources when applied to red soil. 【Method】 Based on a long-term positioning experiment in Yingtan, Jiangxi Province that started in 2011, we analyzed the effects of equal carbon inputs of organic materials of plant sources such as straw (NPKS) and biomass charcoal (NPKB) on top of chemical fertilizers (NPK) and hog manure of animal sources (NPKM) on soil quality and productivity of red soil sloping cropland. The objective of this study was investigated by subjecting our samples and/or data to CT tomography, metagenome sequencing, and random forests. 【Result】 The results showed that the dosing of the three organic materials had significant differences in enhancing the quality of red soil, and the organic fertilizer of animal origin (NPKM) was better than that of plant origin (NPKS and NPKB) compared with the NPK treatment. Also, the NPKM significantly improved the soil pore structure, which led to an increase of 53% and 60% in macro-porosity and connected porosity, respectively (p < 0.05), whereas the NPKS and NPKB treatments had no significant effect. Moreover, NPKM significantly improved soil chemical properties including pH, soil organic carbon (SOC), and total nitrogen by 0.9 pH units, 89%, and 63%, respectively, compared to the NPK treatment. Of the plant-derived organic materials, only NPKB significantly increased SOC content (P<0.05). In addition, the soil microbial diversity was significantly increased in the NPKM treatment, with Shannon's index increasing from 1.8 to 2.0 and Simpson's index decreasing from 0.3 to 0.2. Furthermore, NPKB only significantly increased Shannon's index, while NPKS significantly decreased Simpson's index (P<0.05). The application of different organic materials changed the distribution of the community structure of the dominant flora at the phylum level, decreased the relative abundance of Chloroflexi, and increased the relative abundance of Proteobacteria, with the greatest change observed in the NPKM treatment. Dosing of organic materials significantly increased peanut yield, with the most significant increase of 104% in the dosing of pig manure. 【Conclusion】 The result of this study revealed that the main factors affecting peanut yield were TN, SOC, pH, and microbial abundance, thus, providing an important scientific reference for the efficient fertilization of red soil sloping cropland.

Abstract:【Objective】 Soil degradation on the Loess Plateau has become a major obstacle to regional sustainable development. Therefore, assessing soil quality is crucial for the conservation and rational use of soil resources. 【Method】 Based on data for soil physical, chemical, and biological indicators related to soil quality, this study applied the Soil Quality Index method to carry out a comprehensive and systematic evaluation of soil quality across the Loess Plateau. 【Result】 The results indicate that(1)soil quality exhibits a three-tier spatial distribution: the lowest quality occurs in the Mu Us Sandy Land and arid northwest, moderate quality in the central–western hilly zones, and the highest quality in the southern, eastern, and northern mountain regions as well as the loess hilly–plain area; (2)under different land-use and geomorphic conditions, soil quality declines in the order forestland > cropland > grassland > unused land and mountain > loess plateau > plain > loess hills, and within major agricultural areas, cropland quality decreases in the sequence Fen-Wei Plain > Yinchuan Plain > loess plateau > loess hills; (3)soil nutrients(total nitrogen, organic matter, total phosphorus), biological activity(nematode abundance, soil respiration intensity), and texture(clay and silt content)jointly dominate soil quality. 【Conclusion】 This study reveals that soil quality on the Loess Plateau follows a distinct three-tier spatial pattern with significant differences among land-use types and landforms, primarily governed by nutrients, biological activity, and texture. These findings provide an important foundation for the conservation and improvement of soil resources on the Loess Plateau.

Abstract:【Objective】 Straw incorporation is a vital agricultural practice that positively impacts soil structure improvement, erosion mitigation, and fertility enhancement. Given the increasing pressure on agricultural systems to maintain high productivity while minimizing environmental degradation, scientific evaluation of soil quality under straw incorporation holds significant implications for advancing efficient straw utilization and achieving high crop yields. Soil quality assessment can guide farmers and policymakers in optimizing straw use efficiency, thereby supporting long-term crop productivity and ecological sustainability. This study focuses on evaluating the effects of different straw management strategies on paddy soil quality under a rice-rapeseed rotation system. It aims to analyze the impact of straw incorporation methods on soil physicochemical properties and elucidates the mechanisms of straw incorporation through soil quality assessment, providing theoretical support for sustainable soil management in rice-rapeseed rotation systems. 【Method】 To study the impact of straw incorporation on soil quality, three straw management practices were implemented: no straw return (CK), straw mulching (T1), and straw plowing (T2). Field experiments and laboratory analyses were conducted to assess differences in soil aggregate stability, nutrient distribution, and stoichiometry. The soil quality index (SQI) was calculated using the minimum data set (MDS) method while pathway analysis was employed to explore the mechanisms by which soil physicochemical factors affect soil quality. 【Result】 The results revealed that (1) Compared with the CK and T2 treatments, straw mulching significantly increased the content of soil >1 mm water-stable aggregates. The mean weight diameter (MWD) and geometric mean diameter (GMD)of soil aggregates increased by 6.60% and 23.58%, respectively, indicating that straw mulching enhanced structural stability.(2)T1 increased the organic carbon content of aggregates with different particle sizes, among which the nutrient levels of 2～1 mm aggregates were the highest. Notably, the >5 mm aggregates demonstrated the greatest nutrient contribution capacity, highlighting their role in long-term carbon sequestration. (3) T1 significantly increased the carbon-nitrogen ratio (C/N) and the carbon-phosphorus ratio (C/P). On the contrary, these ratios decreased under T2. (4) The soil quality assessment results based on the MDS revealed that T1 achieved the highest SQI, which was superior to CK and T2 whereas pathway analysis demonstrated that the direct influence of aggregate stability on SQI was the strongest (path coefficient = 0.681). 【Conclusion】 Straw mulching optimizes soil quality by promoting the formation of large aggregates, enhancing aggregate stability, improving organic carbon sequestration, and balancing ecological chemometrics. It is the most effective strategy for improving soil health in rice-rapeseed rotation systems. In contrast, the benefits of straw plowing are limited, possibly due to carbon loss caused by disturbance. These findings provide farmers with actionable insights, indicating that straw mulching should be prioritized over plowing to maximize soil quality.

Abstract:【Objective】 The Northeast Black Soil Region, a vital grain production base in China, suffers from serious soil erosion due to natural and anthropogenic factors. Numerous studies on soil and water conservation measures have been conducted by scholars both domestically and internationally. However, most existing research focuses on evaluating either specific regions or individual measures, while lacking a comprehensive assessment of both the combined benefits and practical applicability of different conservation approaches. 【Method】 We collected 414 sets of research data from 59 published papers on slope erosion of northeastern black soils during 2000-2023 and conducted a comprehensive meta-analysis to evaluate the efficacy of 18 soil and water conservation measures. Our analysis focused on their capacity to mitigate slope runoff and sediment, while examining their responsiveness to variations in slope gradient and soil characteristics. Furthermore, we assessed the regional applicability of these conservation measures based on their performance across different environmental conditions. 【Result】 The analysis revealed that soil and water conservation measures demonstrated substantial effectiveness on black soil slope cultivated land, with average control efficiencies of 63.1% for runoff reduction and 73.2% for sediment control. Integrated measures consistently outperformed individual interventions in terms of overall effectiveness. Among the evaluated measures, all except biochar improvement (Bi) and adding sand (As) demonstrated statistically significant impacts on both runoff and sediment reduction. Particularly noteworthy was the performance of bamboo trenches between ridges (Bt), which achieved exceptional control efficiencies of 98.9% for runoff and 99.9% for sediment reduction. This was closely followed by the combined approach of subsoiling tillage + straw mulching + ridge-furrow intervals (SSR), which yielded control efficiencies of 92.4% and 99.4% for runoff and sediment, respectively. The effectiveness of these conservation measures showed significant spatial variability, being strongly influenced by slope gradient and soil characteristics. Optimal performance was observed on slopes ranging from 4-6°, where average control efficiencies reached 66.4% for runoff reduction and 80.6% for sediment control. Soil-specific analysis indicated that dark brown forest soil exhibited the highest runoff reduction capacity (78.7%) while chernozem demonstrated superior sediment retention properties (96.4%). Furthermore, the most consistent synergistic relationship between runoff and sediment reduction efficiencies was identified in mid-slope sections with gradients of 7-9°, suggesting an optimal range for implementing these conservation measures. 【Conclusion】 This study evaluates the applicability of various soil and water conservation measures for Northeast China's black soil region, based on their effectiveness in reducing runoff and sediment yield. Based on the Relatively Reduced Evaluation Index (RREI) for runoff and sediment, ridge plant belt (Rp) and five other highly effective water conservation measures were prioritized for implementation from a soil and water conservation perspective. For comprehensive consideration of both conservation effectiveness and socio-economic feasibility, three measures; bamboo trenches between ridges (Bt), no-tillage + straw mulching (NTS), and subsoiling tillage + straw mulching + ridge-furrow intervals (SSR), are recommended as priority conservation practices for cultivated slopes in Northeast China's black soil region. Future research on soil and water conservation measures should simultaneously consider their long-term ecological benefits, economic viability, and social acceptability, as these factors are critical for ensuring the sustainable implementation of such conservation practices.

Abstract:【Objective】 Timely and accurate measurement of in situ soil pH is crucial for agricultural production and soil pollution remediation. However, the long-term stability of pH electrodes in soil monitoring remains a challenge. 【Method】 This study evaluated the effectiveness of three types of pH electrodes: spherical glass combined pH electrodes, conical glass combined pH electrodes, and an antimony (Sb) metal pH electrode, for monitoring the pH of acidic Ultisol over 350 days. Additionally, in situ soil pH values from incubated soil were measured using an extra conical glass combined pH electrode. 【Result】 The slopes of all three electrode types showed minimal changes before and after embedding in soil. The slope ranges for the spherical glass, conical glass, and Sb metal electrodes were –58.07 to –60.30, –50.79 to –55.65, and -34.38 to –35.24 mV/pH, respectively, with the spherical glass electrode showing the highest sensitivity. Correlation analysis between in situ monitored pH values and those measured with the extra conical glass electrode revealed significant correlations for the spherical glass and Sb metal electrodes (P<0.01), with correlation coefficients (r) of 0.74, 0.75, 0.56, and 0.80, respectively. In contrast, no significant correlation was observed between the pH values measured by the conical glass electrode and the extra electrode, with r values of –0.38 and 0.15, respectively (P>0.05). 【Conclusion】 These findings suggest that both the spherical glass and Sb metal electrodes are suitable for long-term soil pH monitoring. However, the spherical glass electrode with a protective device is recommended for short-term, high-accuracy monitoring, while the Sb metal electrode is more suited for long-term monitoring applications.

Abstract:【Objective】 Cadmium (Cd) is the major pollutant in China's agricultural soils, threatening soil environmental quality and the safety of agricultural products. Thus, reducing Cd contamination in polluted soils is crucial for improving soil environmental quality. Given that different rice varieties show a 10 to 32-fold difference in their ability to accumulate Cd and rice plants generally have a high biomass (16.3-22.7 t·hm^–2), their potential to reduce soil Cd levels is unparalleled. 【Method】 In this study, multi-year and multi-location field trials were conducted using a high Cd-accumulating rice variety, W4, and field management measures were applied, such as draining paddy fields from the booting stage to maturity, to enhance soil Cd availability. The removal efficiency and stability of W4 in removing soil Cd were evaluated. 【Result】 In a three-year consecutive field trial conducted in Changshu (soil Cd: 0.35 mg·kg^–1, pH: 5.61), results showed that the straw biomass of W4 was 13.6 to 16.1 t·hm^–2 and 1.4 to 1.6 times higher than that of local conventional rice varieties. Its straw Cd concentration was 6.85 to 7.44 mg·kg^–1, 3.3 to 4.5 times higher than conventional varieties, and its grain Cd concentration was 2.38 to 3.38 mg·kg^–1, 6.3 to 9.4 times higher. The amount of Cd removed from the topsoil per season was 101.9 to 132.2 g·hm^–2, with a removal efficiency of 11.8% to 16.5%, 4.7 to 8.9 times higher than that of conventional rice. In a field trial in Xiangtan, Hunan Province (soil Cd: 0.89 mg·kg^–1, pH: 5.50), the straw and grain yields of W4 were 13.8 t·hm^–2 and 6.5 t·hm^–2, with Cd concentrations of 10.22 mg·kg^–1 and 6.05 mg·kg^–1, respectively. The Cd removal amount in the aboveground part was 180.6 g·hm^–2, with a removal efficiency of 7.4%. Model calculations suggest that the use of this high Cd-accumulating rice variety could reduce soil Cd from 1.0 mg·kg^–1(safe use threshold for farmland)to 0.3 mg·kg^–1(risk screening value)within nine planting seasons. 【Conclusion】 Given the low technical and cost barriers of rice cultivation, the use of high Cd-accumulating rice presents a simple, green, and efficient technology for reducing soil Cd levels in China.

Abstract:【Objective】 Industrialization and urbanization have led to the emission of pollutants that can migrate and impact the functions of natural ecosystems. Therefore, it is important to understand the environmental behavior and fate of these pollutants as well as the factors influencing their ecotoxicity. This study aims to investigate the characteristics, sources, and environmental impact of polycyclic aromatic hydrocarbons (PAHs), a class of persistent organic pollutants, in the soil of typical forest and grassland ecosystems. 【Method】 Soil samples were collected from five typical forests and three typical grassland ecosystems in China. Soil physicochemical properties and PAH concentrations were measured, and the composition of PAHs was analyzed. The source apportionment of PAHs was carried out using diagnostic ratio methods and positive matrix factorization methods. 【Result】 The total PAH concentrations in the soil of grassland ecosystems ranged from 7.11 to 137.42 μg·kg^–¹, while in forest ecosystems, it ranged from 10.87 to 976.47 μg·kg^–1. The highest PAH level (208.82–976.47 μg·kg^–¹)was detected in Beijing Xishan Forest. Traffic emissions and coal combustion were the main sources of soil PAHs in forest ecosystems, contributing 41.6%–55.9% and 18.3%–31.8%, respectively. In grassland ecosystems, coal combustion was the dominant contributor to the content of PAHs in soil, accounting for 39.6%–50.2%, except in Zhangbei Bashang Grassland, where traffic emissions prevailed. Biomass combustion contributed more to grassland PAHs than to forest soils. 【Conclusion】 Although soil PAH levels in most natural ecosystems remain relatively low, the influence of human activities on PAH pollution in these ecosystems cannot be overlooked. Continuous efforts in pollutant emission reduction and environmental risk management are essential to protect the functions of natural ecosystems.

Abstract:【Objective】 Atrazine is a chlorotriazine herbicide, which interferes with photosynthesis in some broadleaf plants and is widely used on corn, sorghum, and sugarcane. Residual atrazine may persist in agricultural soil for an extended period due to its long half-life, posing threats to succeeding crops and human health. The fate of atrazine in the environment is normally regulated by lots of pedological and microbial factors. However, the biodegradability of atrazine across soil types as well as the underlying microbial mechanisms remains elusive. In this study, it is aimed to compare the mineralization dynamics of atrazine and bacterial community responses in three typic agricultural soils. 【Method】 Three upland soils classified as black soil (BS), fluvo-aquic soil (FA) and red soil (RS), were collected from corn fields located in geographically distinct areas of China. Soil microcosms spiked with a ¹⁴C tracer were established and mineralization of atrazine to CO₂ was monitored during an 56-days incubation. In parallel, the soil bacterial communities in atrazine-added or clean soil (as a control) microcosms were examined using quantitative PCR and 16S rRNA gene sequencing. 【Result】 The fastest mineralization of atrazine occurred in the FA soil, while the RS showed minimal mineralization activity. The accumulative mineralization over 56 d was 75.2%, 35.5%, and 0.810% of the initially added tracer in the FA, BS, and RS, respectively. Fitting the CO₂ curves with the Gompertz model obtained distinct parameters of accumulative mineralization, maximal rate, and lag time for the three soils. Atrazine markedly increased the abundance of the triazine hydrolase (trzN) gene in the FA and BS soils, and caused significant enrichment of Paenarthrobacter in FA. In light of the well-documented degradation capacity of Paenarthrobacter-related bacteria, this genus perhaps played a major role in atrazine mineralization in the FA soil. Nevertheless, it was impossible to link any taxon to atrazine degradation in the BS microcosms. Nevertheless, an acidic pH (4.16) might account for the particularly low mineralization in the RS. Moreover, the three soils displayed contrasting bacterial community responses to atrazine contamination. In the FA, atrazine was used as a growth substrate, enhancing interspecies cooperation as indicated by increased positive correlation in the co-occurrence network whereas the BS community was less sensitive to atrazine. Residual atrazine severely impacted the structure and diversity of the bacterial community in RS, implicating potential ecological risks to this acidic soil. 【Conclusion】 These findings highlight the substantial differences in atrazine mineralization and resultant bacterial community responses in different soils, indicating an association between herbicide residue and soil type, thus providing a scientific basis for the safe use and pollution control of herbicides.

Abstract:【Objective】 Biosynthetic nano-selenium (SeNP), as a new type of functional fertilizer, has been widely applied into selenium-enriched agricultural production. To date, the effects of SeNP on antibiotic resistance genes (ARGs) and their host microbes in different types of soil are not well understood. This study was designed to investigate the effects of SeNP on the abundance of ARGs and bacterial community structure in the rhizosphere soil of Brassica rapa L. growing in different types of soil. 【Method】 Pot experiments were conducted to analyze the effects of foliar application of different concentrations of SeNP on plant growth, soil properties, bacterial community structure, and the abundance of ARGs and mobile genetic elements (MGEs) in two types of soils (neutral and alkaline). 【Result】 The results showed that foliar application of 1-5 mg·L^–1 SeNP could effectively improve the growth indicators of plants and the content of alkaline hydrolyzable nitrogen in the rhizosphere soil. Compared with the control, the bacterial community abundance in neutral soil increased by 27.09%, significantly. In contrast, the bacterial community abundance in alkaline soil decreased by 14.56%, significantly. And the absolute abundance of ARGs and MGEs also decreased significantly compared to the control group. Foliar application of SeNP not only promoted the increase in the relative abundance of beneficial bacteria (i.e., Gemmatimonadetes, Nitrospirae, and Acidobacteria) in different soils, but also reduced the abundance of potential host bacteria (Chloroflexi) for ARGs in alkaline soil. 【Conclusion】 Biosynthetic SeNP can be served as a potential candidate material to control the spread of soil ARGs effectively. However, the impacts of SeNP on soil antibiotic resistance may vary with different soil types. Thus, further evaluation should be carried out in combination with the characteristics of field soil, providing a reference for the efficient and safe application of SeNP in agricultural production.

Abstract:【Objective】 The heavy use of pesticides such as chlorothalonil (CTN) in agricultural production inevitably has an impact on the soil's ecological environment, thus, exacerbating nitrous oxide (N₂O) emission from farmland soils, considered an important emission source of greenhouse gasses. However, there are few studies on how CTN affects agricultural soil N₂O emission and its associated microbial mechanism. 【Method】 In this study, the response characteristics of N₂O emission in three kinds of farmland soils (S1-vegetable field soil, S2-rice field soil, and S3-wheat field soil) to different concentrations of CTN were studied through indoor culture experiments. The concentration gradients of chlorothalonil were set as 0(CK), 5(T5), 10(T10) and 25 mg·kg^–1(T25). The abundance of microbial functional genes was analyzed simultaneously through real-time quantitative PCR. 【Result】 The results showed that (1) Compared with CK, the treatments of T5, T10, and T25 in the acidic vegetable field soil of S1 led to an increase of 1 868%, 1 264%, and 232% in N₂O emissions, respectively. In the S2 neutral paddy soil, T5, T10, and T25 respectively led to an increase of 4%, 138%, and 334% in N₂O emissions, while for the alkaline wheat field soil S3, T5, T10, and T25 led to an increase of 230%, 119%, and 23% in N₂O emissions respectively. (2) The addition of CTN changed soil physicochemical and microbial characteristics, and significantly increased soil dissolved organic carbon (DOC) content, ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), nitrite-reducing bacteria (nirK, nirS), N₂O reducing bacteria (nosZ), and total bacteria (16S rRNA) genes abundance. Correlation analysis showed that the increase in N₂O emissions was mainly related to the increase in soil carbon and nitrogen substrate contents whereas the abundance of microbial functional genes was mainly attributed to the increase in the gene abundance of total bacteria, ammonia-oxidizing bacteria, and nir-type denitrifying bacteria, as well as the increase in soil DOC content. 【Conclusion】 CTN can increase soil DOC content and microbial gene abundance, and eventually lead to an increase in soil N₂O emission. Also, the effect of CTN on soil N₂O emission depends on soil properties and application concentration. The results of this study provide a scientific basis for further understanding of soil N₂O emission driven by CTN application and its microbiological mechanism and also have important significance for understanding the potential ecological and environmental risks of agricultural CTN application.

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

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

Abstract:【Objective】 Soil aggregates are the basic units of soil structure, and soil organic carbon (SOC) is the core of soil fertility. However, the effect of freeze-thaw on soil aggregate stability and SOC characteristics in black soils and the influencing factors remain timidly understood. Thus, this study utilized the rare earth element tracer technology to investigate the turnover path of soil aggregates and the quantitative characterization of SOC under freeze-thaw action through indoor experiments. 【Method】 Black soils of cultivated and forest lands of Heshan Farm, Nenjiang City, Heilongjiang Province were used for this study. The experiments were set up considering several freeze-thaw cycles of 0, 3, 6, 10, 15, and 25 through indoor cultivation. Also, the dry and wet cycle method was used to label the soil aggregates with different grain sizes (5-2 mm, 2-0.25 mm, 0.25-0.053 mm, and < 0.053 mm) while the rare earth element concentration was determined by Na₂O₂alkali fusion method. In addition, the aggregate turnover processes, the changes in soil aggregate stability (Mean weight diameter, MWD), particle size distribution, aggregate turnover paths, and SOC under freeze-thaw cycling were evaluated at the different cycles. 【Result】 The results showed that the freeze-thaw cycle accelerated the transition between neighboring aggregates, which led to a more drastic transition from aggregates of various particle sizes to those of 2-0.053 mm. With the increase in the number of freeze-thaw cycles, the MWD and 5-2 mm aggregate content decreased gradually while the 2-0.053 mm aggregate content increased gradually. The turnover time of soil aggregates increased with the increase in the number of freeze-thaw cycles, and the increase of 0.25-0.053 mm aggregates was the most significant. There was no significant change in the SOC content of the whole soil after freeze-thaw treatment. However, as the number of freeze-thaw cycles increased, the SOC content of 5-2 mm aggregates increased, and the SOC content of aggregates of other particle sizes decreased. 【Conclusion】 Therefore, the freezing and thawing effect affects the intrinsic process of soil structure dynamics by intensifying the destruction and formation of soil aggregates in the turnover process, reducing the stability of soil structure and changing the SOC content. The results of the study further revealed the microstructural evolution characteristics of the black soil under freeze-thaw action and its quantitative characterization of SOC, thus, providing a theoretical basis for the in-depth study of the turnover of black soil aggregates of various grain sizes and soil structure changes under freeze-thaw erosion.

Abstract:【Objective】 In winter oilseed rape production, there is a widespread practice of overapplying nitrogen fertilizer in pursuit of high yields, which leads to low economic returns and significant nitrogen losses, thereby increasing environmental risks. Determining the appropriate nitrogen fertilizer application rate is crucial for achieving high yields and environmental sustainability in winter oilseed rape. 【Method】 Field experiments were conducted in three major winter rapeseed production areas in the middle and lower reaches of the Yangtze River–Jingmen in Hubei Province, Chizhou in Anhui Province, and Zhenjiang in Jiangsu Province-from 2019 to 2020. Five nitrogen fertilizer application rates (0, 90, 180, 270, and 360 kg·hm^–2) were set to investigate the effects of nitrogen fertilizer rates on winter oilseed rape yield, nitrogen accumulation, residual inorganic nitrogen in soil, and apparent nitrogen balance. The relationship between yield and nitrogen input-output balance was comprehensively evaluated to determine the appropriate nitrogen fertilizer application rate for winter rapeseed that is both high-yielding and environmentally friendly. 【Result】 The results showed that nitrogen application significantly increased oilseed rape yield, with a trend of increasing yield as the nitrogen application rate increased. When the nitrogen application rate reached 270 kg·hm^–2, the yield tended to stabilize, with an average yield of 3 146 kg·hm^–2 for the two varieties at each of the three experimental sites. The trend of nitrogen accumulation in the aboveground parts was consistent with that of yield. When high or excessive nitrogen was applied, the nitrogen accumulation in non-seed organs significantly increased. Compared with 270 kg·hm^–2, when the nitrogen application rate increased to 360 kg·hm^–2, the average nitrogen accumulation in plants increased by 6.85%, and the proportion of nitrogen in non-seed organs increased by an average of 0.49 percentage points. The residual inorganic nitrogen in the soil at the oilseed rape harvest stage and the nitrogen balance of the soil-plant system were positively correlated with the nitrogen application rate, showing a trend of slow growth followed by a sharp increase as the nitrogen application rate increased. When the nitrogen application rate was 270 kg·hm^–2, the average residual inorganic nitrogen and apparent nitrogen surplus were 40 kg·hm^–2 and 95 kg·hm^–2, respectively. 【Conclusion】 Based on the allowable apparent nitrogen surplus for maintaining crop yield and soil fertility (80 kg·hm^–2), the recommended nitrogen fertilizer application rates for the three experimental sites in Hubei, Anhui, and Jiangsu were 207, 219, and 250 kg·hm^–2, respectively, with corresponding average yields of 3 083, 3 054, and 3 149 kg·hm^–2, and residual inorganic nitrogen in the topsoil of 22, 45, and 51 kg·hm^–2, respectively. These recommended rates can ensure stable winter oilseed rape yields while controlling the risk of nitrogen loss, contributing to achieving the dual goals of high yield and environmental friendliness in winter oilseed rape production.

Abstract:【Objective】 This study aimed to explore the growth conditions of Echinochloa and its impact on soil nutrients under varying degrees of alkaline stress. 【Method】 Using the salinized sandy soil of the Mu Us area, this study set up five alkaline stress treatments based on the degree of salinization: pH 8.4, pH 9.0, pH 9.4, pH 9.7, and pH 10.0, with bare soil as control (CK). Growth dynamics and soil nutrient variations were monitored to evaluate the suitability of Echinochloa for vegetation restoration in alkaline degraded sandy areas. 【Result】 The results showed that when the pH increased from 8.4 to 9.4, the plant height and leaf area of Echinochloa did not decrease. However, a further increase in pH resulted in a significant decrease in plant height and leaf area. The treatment with pH 9.0 had the highest average number of tillers, followed by the treatment with pH 9.4. The net photosynthetic rate(P_n) and water use efficiency (WUE) of Echinochloa in pH 9.0 treatment were 26.39%-53.74% and 21.22%-36.36% higher than those in other treatments, respectively. After planting Echinochloa the content of soil organic matter (SOM) and nitrate nitrogen (NO₃^–-N) in the 0-10 cm soil layer significantly decreased, total nitrogen (TN) content in the 0-60 cm soil layer significantly decreased, whereas the ammonium nitrogen (NH₄⁺-N) content significantly increased. The tiller number and plant height of Echinochloa were significantly positively correlated with photosynthetic characteristics, and the root length density (RLD) was significantly positively correlated with the changes in SOM, TN, total phosphorus (TP) and available phosphorus (AP), and significantly negatively correlated with the change in NH₄⁺-N. 【Conclusion】 The pH 9.0 treatment promoted the growth of Echinochloa, however, growth of the above-ground part was hindered when pH was higher than 9.7, while root growth was hindered when pH was higher than 9.4. Cultivated Echinochloa mainly affected soil N nutrition, reducing the content of soil TN and NO₃^–-N, and increasing the content of NH₄⁺-N. These findings indicate that Echinochloa possesses strong alkaline stress tolerance and enhances soil nitrogen mineralization, confirming its suitability for vegetation restoration in alkaline degraded sandy soils of the Mu Us region.

Abstract:【Objective】 The black soil region of northeastern China is experiencing serious soil erosion problems. Although there are various types of soil erosion in this region, hydraulic erosion is still the most dominant form leading to soil degradation. However, current research efforts remain insufficient in examining how hydraulic erosion impacts soil microbial communities, particularly regarding the effects and mechanisms of single rainfall events on the soil microbial biodiversity and community structure. This study investigated how a single rainfall event influences the diversity and community structure of soil microorganisms and the mechanisms through which such alterations would occur. 【Method】 In this study, the experimental rolling hillslope cropland was selected in a typical black soil region of northeastern China for the field artificial rainfall experiments and field observations. In order to recognize the effects of the single rainfall event on soil microbial diversity and community structure in rolling hillslope cropland, three types of runoff plots were set up: bare land plots, soybean plots, and corn plots. The soil microbial diversity and community structure before and after the artificial rainfall event were examined through the application of bacterial 16S rRNA and fungal ITS third-generation high-throughput gene sequencing technology. Then the variations of soil microbial diversity and community structure were compared before and after the artificial rainfall event. Moreover, the microbial populations that were most sensitive to the single rainfall event were recognized and their influences on soil carbon and nitrogen cycling as well as soil nutrient storage were investigated. 【Result】 The rainfall event produced contrasting effects on microbial diversity across different types of runoff plots. In bare land runoff plots, the rainfall event triggered an increase in both soil bacterial and fungal Alpha diversity. However, in soybean runoff plots, bacterial Alpha diversity declined and fungal Alpha diversity exhibited an upward trend. In contrast, corn runoff plots experienced simultaneous reductions in both bacterial and fungal Alpha diversity. The single rainfall event demonstrated no statistically significant impacts on the dominant populations of soil bacteria and fungi across the three runoff plots. However, significant differences in the relative abundance of specific bacterial and fungal species were observed (P<0.05) and these sensitive映瑩档敲敢捩潡汬漠杰楯捰慵汬⁡慴湩摯敳渠癷楥牲潥渠浲敥湣瑯慧汮⁩敺晥晤攮挠瑁獭潮晧†獴潨楥氠⁢敡牣潴獥楲潩湡椠湳⁰牥潣汩汥楳測朠⁴桨楥氠汲獥汬潡灴敩⁶捥爠潡灢汵慮湤摡督楥琠桯⁦戠氼慩挾歃⁨獬潯楲汯⁦楬湥⁸湩漼爯瑩栾攠慳獩瑧敮物湦⁩䍣桡楮湴慬⹹ increased by 2.37% after the rainfall event in the bare land runoff plots, whereas the relative abundance of Thaumarchaeota significantly decreased by 3.22%, and the relative abundance of Actinobacteria significantly decreased by 3.39%. In soybean runoff plots, the relative abundance of Bacteroidetes significantly increased by 3.69% after the rainfall event, the relative abundance of Verrucomicrobia significantly increased by 1.85%, while the relative abundance of Actinobacteria significantly decreased by 2.22%. In corn runoff plots, the relative abundance of Planctomycetes significantly decreased by 1.71% after the rainfall event. Among the fungal species, the relative abundance of Sordariomycetes significantly increased by 7.28% after the rainfall event while the relative abundance of Leotiomycetes significantly decreased by 6.74% after the rainfall event in bare ground runoff plots. Also, the relative abundance of Sordariomycetes in soybean runoff plots significantly increased by 7.08% after the rainfall event while the relative abundance of Tremellomycetes significantly decreased by 4.06%. In the corn runoff plots, the relative abundance of Dothideomycetes significantly increased by 7.35% after the rainfall event while the relative abundance of Mortierellomycetes significantly decreased by 3.11%. 【Conclusion】 This study revealed that single rainfall events have significant effects on the alpha diversity of soil bacteria and fungi in all three types of runoff plots at different magnitudes. Furthermore, the single rainfall event significantly impacted the relative abundance of specific bacterial and fungal dominant species with statistically significant differences before and after the single rainfall event (P<0.05). These results provide important data and a theoretical basis for precise regulation o�������������������������������������������������������������������������������������������������������������������������������

Abstract:【Objective】 The application of straw and biochar is one of the most important measures to improve soil fertility, but whether the abundance of Fusarium graminearum (Fg) concurrently changes during the decomposition process remains unclear. This study aimed to investigate the Fg abundance dynamics with the decomposition process of straw and its derived biochar, and the potential association of it with the variations in properties of organic materials and compositions of fungal communities. 【Methods】 An indoor cultivation experiment was conducted by simulating adequate field conditions for Fg inoculum. Four treatments were designed: (1) maize straw(S), (2) biochar plus Fg(BF), (3) maize straw plus Fg(SF), and (4) biochar plus maize straw plus Fg(BSF), among which the maize straw and biochar were added with the equivalent carbon mass. 【Result】 Our results showed that the Fg abundance at 7, 21, 42, and 70 days was on average in the order of BF>SF>BSF, and the Fg abundance from the BSF treatment was 84.07% and 69.11% lower than that from the BF and SF treatments, respectively. Correlation analysis showed that the Fg abundance was significantly positively related to total carbon (TC), total nitrogen (TN), total phosphorus (TP), and total potassium (TK) of residual organic materials at 7 and 70 days, and these nutrients were all highest in BF treatment. Besides, the fungal community compositions of organic materials significantly differed between treatments, which were driven by both the Fg abundance and the properties of residual organic materials. We further discovered that the significant enrichment of BF treatment by Dirkmeia and Exophiala may be associated with the occurrence of some plant diseases, while the BSF treatment was remarkably enriched with Sarocladium and has biocontrol potential. 【Conclusion】 The above results indicate that the dynamic change of the Fg abundance during the decomposition of organic materials may be mediated by the conjunct effect of the variations in the nutrients content of residual organic materials and it-induced transformation on fungal community composition. Our study provided a novel directive for selecting suitable organic materials to improve soil fertility in terms of the perspective of preventing and controlling Fusarium head blight.

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

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

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%-130.1%) was greater than that of bacterial biomass (22.7%-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.

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

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

Abstract:【Objective】 Extracellular enzymes in soil play a crucial role in mediating the ecosystem's responses to environmental drivers, and their stoichiometry can be used to assess the resource limitation for microorganisms. The conversion from pure forest plantations to mixed forest plantations is an important approach to achieve sustainable forest development. The current study on ecosystem responses to forest conversion has predominantly concentrated on soil nutrients, carbon (C) sequestration capacities, timber productivity metrics, and silvicultural landscape attributes. However, the effects of this conversion on extracellular enzymes and their stoichiometric characteristics in soil remain poorly understood. 【Method】 Here, the 5-year-old mixed forests of Prunus persica ‘Atropurpurea’ + Malus × micromalus, Cunninghamia lanceolata + Phoebe zhennan + P. persica ‘Atropurpurea’ and Cinnamomum camphora + Metasequoia glyptostroboides as well as pure forest plantation soil of E. grandis were investigated. All forest plantations were recently constructed after clear-cutting the E. grandis plantations. It was determined the effect of mixed forests on soil physical and chemical properties, microbial biomass, extracellular enzymes, and their stoichiometric characteristics. Moreover, the correlation between soil extracellular enzymes and stoichiometry with various soil properties was analyzed, and the main controlling factors affecting the extracellular enzymes and stoichiometry in soil were explored. 【Result】 The results showed that: (1) The three mixed forests increased β-1, 4-N-acetylglucosaminidase and l-leucine aminopeptidase activities, but decreased that of β-1, 4-glucosidase and acid phosphatase activities in soil. (2) The vector length of extracellular enzymes ranged from 0.68 to 0.88, while the vector angle ranged from 72.59° to 81.18°, indicating that microorganisms were co-limited by C and phosphorus (P) in all the forest plantation soils. (3) The three mixed forest plantations reduce microbial C and P limitations by increasing organic C, total nitrogen (N) content, pH, microbial biomass C: N ratio in soil, and C: P and N: P ratios in soil. However, the microorganisms were still co-limited by C and P. Therefore, in the early stage of mixed forest plantation construction, organic and P fertilizer can be applied to reduce resource limitations of soil microorganisms in the study area. (4) Total N and microbial biomass N were the key controlling factors influencing extracellular enzyme activity and enzyme stoichiometry in all the forest plantation soils. 【Conclusion】 Collectively, these findings suggest that the conversion of pure forest plantations to mixed forest plantations alleviates the microbial C and P limitations in soil. Notably, extracellular enzymes and their stoichiometric characteristics in soil are influenced by interactions among vegetation, soil properties, and forest microclimate factors. Thus, future studies should prioritize analyzing how mixed forest plantations affect these parameters through plant diversity assessments (e.g., tree and understory vegetation), and understory microclimate monitoring.

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