Abstract:【Objective】Digital soil mapping of soil types commonly adopts a multi-type one-time modeling strategy, but this strategy struggles to fully consider the complex relationship between each soil type and its soil-forming environment. To address this gap, this study proposes a type-by-type random forest modeling strategy. 【Method】Taking Yizheng City, Jiangsu Province, as the study area, 21 environmental covariates and 860 typical virtual sample points extracted from soil species polygons in historical soil maps were used to construct random forest classification models for each soil species individually. The spatial distribution of predicted probabilities for each soil species was output, and the soil species with the highest probability was taken as the predicted result for each pixel. This method was compared with the conventional multi-type one-time random forest modeling strategy.【Result】Results showed that the overall accuracy and Kappa coefficient of the type-by-type multiple modeling strategy were 0.62 and 0.58, respectively, while those of the conventional modeling strategy were 0.61 and 0.57. The difference in overall accuracy between the two strategies was very small in the study area. However, the uncertainty of the former decreased significantly. The spatial mean of the maximum probability under the type-by-type multiple modeling strategy was 0.54, which was 0.08 higher than the spatial mean of the maximum probability under the conventional modeling strategy. Moreover, the type-by-type multiple modeling strategy could output, for each pixel, the probability of the second-most-probable soil species and the confusion index, which helps identify confusion-prone areas such as the northern uplands, where the probability of the second-most-probable soil species is relatively high. The type-by-type multiple modeling strategy had higher prediction accuracy for Horse-liver Soil, Yellow Rigid Soil, Yellow Variegated Soil, Oily Silty Soil,etc , than the conventional modeling strategy, but it did not achieve consistent improvement for all soil species. In addition, the type-by-type multiple modeling strategy could output the importance of environmental variables for individual soil species, facilitating analysis of the relationships between soil species and environmental factors. The results showed that elevation, topographic wetness index, and distance to the Yangtze River could indicate the spatial variation of most soil species.【Conclusion】Therefore, compared with the conventional one-time modeling strategy, the type-by-type multiple random forest model can significantly reduce the uncertainty of soil type prediction, improve the reliability of prediction results, and serve as a useful tool for understanding the relationship between each soil species and its soil-forming environment.

Abstract:【Objective】Accurate prediction of the spatiotemporal distribution of cropland soil organic carbon density (SOCD) is essential for assessing regional carbon sequestration potential. Although existing studies have extensively explored the spatiotemporal dynamics of SOCD using geostatistical methods, machine learning, and process-based models, further improvements are still needed in reconstructing continuous spatiotemporal changes in cropland SOCD, identifying stage-specific patterns, and quantifying uncertainties under complex terrain conditions. 【Method】In this study, Guizhou Province was selected as the study area. Based on 2 295 soil samples collected from four periods between 2006 and 2024, together with 67 covariates, a machine learning model was developed using a space-for-time substitution approach to reconstruct the spatiotemporal dynamics of SOCD in the topsoil layer (0-20 cm). 【Result】SOCD in the cropland topsoil of Guizhou increased from 33.48 to 36.89 t·hm-2 during 2006-2024, with an average sequestration rate of 0.18 t·hm-2·a-1 (95% CI: 0.15-0.23 t·hm-2·a-1). The trend showed clear stage differences, with a faster increase during 2006-2012 (0.22 t·hm-2·a-1) and a slower rate during 2013-2024 (0.14 t·hm-2·a-1). Over the past two decades, about 95% of cropland acted as a carbon sink. Higher sequestration rates were mainly found in Zunyi (0.21 t·hm-2·a-1) and Qianxinan (0.22 t·hm-2·a-1). Among all variables, soil temperature, soil moisture, and organic fertilizer input played the most important roles, with relative contributions of 14.76%, 9.81%, and 9.08%, respectively. 【Conclusion】These results provide a clear picture of how SOCD has changed over time in Guizhou’s farmland and offer a practical approach that can be applied to similar studies in other regions.

Abstract:Phosphogypsum (PG) is an industrial by product generated from wet process phosphoric acid production, with both resource potential and environmental risks. Restricted by its huge output and limited resource utilization pathways, its large scale consumption remains challenging, which seriously hinders the green and sustainable development of China’s phosphorus chemical industry. Based on the bibliometric analysis of relevant publications from the Web of Science Core Collection spanning 2006 2026, this paper systematically reviews the generation, stockpiling and weathering processes of PG, and summarizes the research advances in its ecological utilization. Key obstacles including acid environmental stress, complex impurity components, insufficient structural stability, imbalanced nutrient supply and constrained biological processes are analyzed. By comparing the properties of PG with natural soils, a multi process coupled pedogenic driven research idea for transforming PG into constructed technosols is proposed from the perspective of ecological utilization. That is, hazard free treatment via chemical property regulation, structural improvement through physical property optimization, and functional development driven by biological processes. An artificial soil matrix with controllable environmental risks, stable substrate structure and sound ecological functions can be gradually established to achieve the synergistic goals of ecological disposal and large scale consumption of PG. This paper discusses relevant mechanisms from the aspects of acid base regulation, phosphorus fluorine stabilization, particle mineral and pore structure reconstruction, nutrient regulation and biological colonization. It is considered that soil like utilization of PG still faces challenges such as long term risk prevention and control, long term maintenance of substrate functions and large scale engineering application. Future studies should strengthen research on pedogenic driving mechanisms, ecological safety thresholds and multi solid waste synergistic regulation mechanisms, so as to establish a stable, efficient and replicable technical system for ecological utilization of PG and provide new insights for its large scale consumption.

Abstract:【Objective】This study aimed to investigate the spatial differentiation patterns of land resource suitability and land-use matching characteristics in the farming-pastoral ecotone of Inner Mongolia, and to provide scientific basis and decision support for sustainable land management in this region.【Method】Following the law of the minimum, this study employed random forest, support vector machine, and hot spot and cold spot analysis methods to explore and construct a three-tiered evaluation framework for Suitability Evaluation of Soil for Agricultural Use, consisting of “suitability classification, suitability degree discrimination, and matching analysis”. An empirical study was conducted across 29 banners and counties within the farming-pastoral ecotone of Inner Mongolia.【Results】The results showed that: (1) The regional land suitability exhibits a macro pattern of “farming in the east, pastoralism in the west, interlacing in the middle, and localized forestry suitability.” The southeastern banners and counties serve as the core areas for farming suitability, the central and western areas have prominent grassland characteristics., while localized high-value areas for forestry suitability are closely related to ecological restoration and social demands. (2) The spatial differentiation of suitability degrees is significant: arable land is predominantly moderately and marginally suitable, grassland is mainly highly suitable and concentrated in the typical steppe zone, whereas highly suitable areas for forestry are sporadically distributed. (3) The land-use matching analysis identifies three types of mismatches, namely ecologically overloaded, spatially squeezed, and functionally imbalanced, whose spatial differentiation is coupled with the regional geographical pattern.【Conclusion】This study indicates that land-use mismatches exist in the farming-pastoral ecotone of Inner Mongolia. Future land development and utilization should prioritize stock optimization and functional enhancement to achieve the coordinated development of agricultural growth and ecological protection.

Abstract:This study aimed to explore the effects of long-term nitrogen fertilizer application on the mineral composition and microbial necromass carbon in the soil profile and its mechanism of action on soil organic carbon sequestration. 【Method】This study was based on a 38-year long-term fixed-site fertilization experiment on brown soil. The treatments of no fertilization (CK) and long-term nitrogen fertilizer application (N) were selected as the research objects. Techniques such as soil physical fractionation, biomarker analysis, and X-ray diffraction (XRD) were comprehensively employed to systematically analyze the variation characteristics of mineral composition. The analysis also extended to evaluating microbial necromass carbon, different carbon pools in the soil profile (0-100 cm), and revealing the accumulation characteristics and driving mechanisms of the soil organic carbon pool under long-term nitrogen fertilizer application. 【Result】 The contents of soil organic carbon, particulate organic carbon, and mineral-associated organic carbon significantly decreased with increasing soil depth, while dissolved organic carbon first increased and then decreased, peaking in the 20-40 cm layer in both CK and N treatments. Nitrogen fertilizer application did not change the mineral types in the soil profile, but had a significant impact on the profile distribution characteristics of minerals. Long-term nitrogen fertilization promoted the accumulation of microbial necromass carbon in the soil profile and its contribution to soil organic carbon, but decreased the fungal-to-bacterial necromass carbon ratio in the 0-60 cm layer while increasing it in the 60-100 cm layer. Also, long-term nitrogen fertilization significantly increased the contribution of particulate organic carbon to soil organic carbon in the 20-60 cm soil layer, while significantly reducing the contribution of mineral-associated organic carbon to soil organic carbon in the 20-40 cm soil layer. 【Conclusion】Although long-term nitrogen fertilizer application can enhance the function of the “microbial carbon pump”, the reduction of montmorillonite, the increase of kaolinite, and the increased proportion of fungal residues in the deep soil collectively resulted in the failure of microbial necromass carbon to synchronously transform into mineral-associated organic carbon accumulation. This indicates an “asynchrony” between mineral-associated organic carbon and mineral protection in the deep soil.

Abstract:【Objective】Nitrogen deposition serves as the primary source of external nitrogen input in forest ecosystems, while litter decomposition is the key process of carbon and nitrogen cycling. Both nitrogen deposition and litter decomposition can modulate forest soil nitrous oxide (N2O) emission and methane (CH4) uptake. Moso bamboo (Phyllostachys edulis) forest is a unique forest type in China’s subtropics, with great carbon sequestration potential. However, the effects of nitrogen deposition, litter decomposition, as well as their interactions on Moso bamboo soil N2O emissions and CH4 uptake remain poorly understood. Thus, this study aimed to investigate how different nitrogen forms, litter types, and their interactions affect soil N2O and CH4 fluxes.【Methods】A 180-day constant-temperature microcosm experiment was conducted using the soil from a Moso bamboo forest. Two nitrogen forms (inorganic nitrogen: ammonium nitrate; organic nitrogen: urea + glycine), three litter types (Parathelypteris glanduligera, Moso bamboo, and Ardisia japonica), their pairwise combinations, and a control (no nitrogen or litter addition), totaling 12 treatments, were included in this study to investigate how different nitrogen forms, litter types, and their interactions affect soil N2O and CH4 fluxes.【Result】The results show that both nitrogen and litter additions significantly increased N2O emissions, but an antagonistic interaction appeared when they were applied concurrently and its magnitude was primarily driven by nitrogen form. Nitrogen and litter additions indirectly promoted N2O emissions by mainly altering soil pH, DOC and WSN, and then MBC and MBN. For CH4, both nitrogen and litter additions significantly enhanced CH4 uptake. Their combined application also generated an antagonistic interaction. However, this effect was independent of nitrogen form and litter type. Overall, nitrogen and litter additions promoted CH4 uptake primarily through changing soil pH and increasing DOC and NH4+-N concentrations.【Conclusion】This study revealed that the form of nitrogen deposition and litter type interactively regulate soil N2O emission and CH4 uptake in Moso bamboo forests. These findings provide theoretical support for litter management and greenhouse gas mitigation strategies in Moso bamboo forests under high nitrogen deposition.

Abstract:Apples are widely cultivated on the Loess Plateau due to their remarkable economic and ecological benefits. However, long-term orchard cultivation tends to induce soil desiccation and consequently form a dried soil layer. Studies have demonstrated that converting orchards back to farmland can effectively alleviate soil desiccation, whereas the optimal time required for this conversion remains unclear. Therefore, this study evaluated the suitable duration for converting deep-rooted (Apple orchard, AO) to shallow-rooted vegetation (Croplands) from an ecological and economic perspective, which included soil water storage (SWS), dried soil layers (DSL), crop water use efficiency (CWUE), soil water temporal stability and farmers" income. And the croplands converted by AO included those with conversion periods of 3, 5, and 7 years, which was abbreviated as CCA3, CCA5 and CCA7, respectively. In addition, cropland under continuous cultivation served as the control group (CL). The soil water content (SWC) in 0-10 m soil layer was measured by soil auger method between 2024 and 2025.The results showed the deep SWS followed the order: CL > CCA7 > CCA3 > CCA5 > AO, and there were no significant differences for CCA3, CCA5, and CCA7. The DSL of CCA3, CCA5, and CCA7 all disappeared. There were also no significant differences in CWUE for them. As the conversion years increased, the temporal stability of SWC increased. In addition, as the duration increased, the farmers" income significantly decreased. Therefore,three years may be the appropriate duration for converting orchards to cropland from an ecological and economic perspective. The findings of this study provide an important reference for the rational land use management on the Loess Plateau.

Abstract:【Objective】 Determining the optimal grid resolution for fine-scale characterization of cultivated soil organic carbon (SOC) is essential for developing targeted carbon sequestration and emission reduction strategies in topographically heterogeneous regions. This study examines Fujian Province, a subtropical region featuring complex terrain commonly characterized as "80% mountains, 10% water, and 10% farmland."【Method】 We compiled multi-resolution spatial datasets by integrating comprehensive soil sampling data with environmental covariates, then applied Random Forest modeling to predict SOC spatial patterns.【Result】 Our findings reveal that grid resolution governs the hierarchical importance of environmental predictors. Notably, prediction accuracy exhibits differential sensitivity to resolution across landscape types: SOC predictions for paddy fields and hilly-mountainous terrain demonstrate robustness to resolution variation, whereas those for drylands and plain/terrace landscapes show pronounced sensitivity. Optimal resolutions vary systematically by landform and land use: 0.2 km for the entire province and plain/terrace areas, 0.5 km for hilly-mountainous regions, and 0.1 km for valley/basin zones. Land use-specific optima include 0.1 km for paddy fields, 0.2 km for drylands, and 0.5 km for irrigated land.【Conclusion】 These results highlight the imperative of adopting landscape-specific and land use-tailored grid resolutions to ensure robust SOC prediction in topographically complex terrain.

Abstract:【Objective】The excessive application of chemical fertilizers has turned tea plantation soils into hotspots for nitrous oxide (N2O) emissions in China’s agricultural systems. Therefore, identifying and optimizing farmland management strategies that effectively mitigate N2O emissions from tea plantation soils is of great importance for greenhouse gas reduction in both China and the world. Microbial inoculants show considerable potential for reducing N2O emissions from agricultural soils by modulating soil microbial communities and influencing the activity of N-cycle functional genes. However, how N2O emission pathways and intensities in tea plantation soils respond to the application of microbial inoculants remains poorly understood. 【Method】In this study, the effects of Bacillus and Trichoderma harzianum inoculants on N2O emissions and their underlying process-driven mechanisms in seven typical tea plantation soils collected from different climatic regions across China were investigated. The investigation was conducted through laboratory incubation experiments combined with a δ18O (N2O/H2O) versus δ15NSP dual-isotope mixing model. 【Result】The results showed that bacterial denitrification and nitrifier denitrification were the dominant pathways for N2O production in the tea plantation soils. Addition of Bacillus and T. harzianum reduced N2O emissions from the tea plantation soils by an average of 48.6% and 23.5%, respectively. Both inoculants reduced N2O emissions through shared mechanisms, including increasing soil pH, enhancing N2O reduction via nosZ-mediated activity, and inhibiting fungal denitrification. Moreover, Bacillus addition significantly reduced the gene abundance of ammonia-oxidizing bacteria (AOB), thereby suppressing N2O emissions from the nitrification process. 【Conclusion】In conclusion, the application of microbial inoculants is an effective strategy for mitigating N2O emissions from tea plantation soils. The findings of this study provide data to support the development of fertilization management strategies aimed at reducing N2O emissions from tea plantation soils in China, and offer scientific guidance for promoting the application of microbial inoculants in tea plantation soil management.

Abstract:【Objective】The spatial distribution of mineralogy classes in mineral soils reflects the regional pedogenic environment and soil-forming processes, and this information is essential for understanding soil genesis and development.【Method】This study focuses on Hubei Province, a region with a subtropical climate in China. By integrating legacy soil mineralogy class data, a fuzzy mapping framework was proposed based on an expert knowledge decision tree. The study further investigated the spatial probability distribution and driving factors of soil mineralogy classes using three different models. 【Result】The results showed that the CatBoost model demonstrated the best performance among the three models. The soil mineralogy classes in the study area were predominantly Mixed, Illite mixed, and Siliceous mixed, while Smectite, Kaolinite, and Vermiculite classes were distributed in scattered patches. Based on the validation results, there were differences in mapping accuracy among different mineralogy classes. Among these, mapping results for mixed types, such as Siliceous mixed, were relatively good, while those for single types exhibited higher uncertainty. Further investigation of the characteristics of environmental variables revealed that hydrothermal conditions may influence the spatial differentiation of Mixed and Kaolinite mixed by affecting the intensity of weathering and leaching, while the parent material makes a significant contribution to the spatial distribution of Siliceous mixed and the Smectite mixed.【Conclusion】These research findings contribute to a deeper understanding of soil formation and evolution processes in the subtropical transition zone and provide a reference basis for the systematic classification and naming of soil families in the 3rd National Soil Census.