Objective To clarify the newly introduced pollution fingerprints during a single hydrological regulation cycle in the Three Gorges Reservoir Area， and accurately identify the sources and driving mechanisms of heavy metals under different hydrodynamic conditions. Methods In the typical riparian water-level fluctuation zones （Shibaozhai， Guojiaba， and Xiangxi River） in the middle and lower reaches of the Three Gorges Reservoir Area， intact net-deposited sediments across a complete hydrological cycle were collected using in-situ sediment columns. The potential ecological risk index （PERI）， canonical correspondence analysis （CCA）， and positive matrix factorization （PMF） were applied to systematically analyze the pollution characteristics， sources， and environmental driving mechanisms of heavy metals （As， Cd， Cr， Cu， Mn， Ni， Pb， Zn）. Results 1） Pollution characteristics： Cd was the primary pollution factor， with its average content significantly higher than the background value of the reservoir area. The ecological risk level in the reservoir center was significantly higher than that in the reservoir head， and the high-risk hotspots were concentrated in the deep flooding zone （145~155 m）. 2） Driving mechanisms： Flooding duration explained 54.5% of the variance in heavy metals， serving as the primary driving factor. The "hydraulic sorting effect" driven by long-term flooding facilitated the preferential adsorption and accumulation of fine particles and heavy metals in low-elevation areas. 3） Source apportionment： The PMF model identified three pollution sources， namely traffic/industrial sources （mainly contributing to Cd and Pb）， agricultural/mixed sources （mainly contributing to As， Cu， and Ni）， and natural sources （mainly contributing to Mn）. Among these， the contribution rate of industrial sources to Cd was nearly 100%. Conclusion It is confirmed that the net-deposited sediments can effectively retrace short-term pollution inputs in the reservoir area and confirm the interception effect of the midstream backwater fluctuation zone as a "sediment filter" and its vertical enrichment mechanism， thereby providing a scientific basis for the refined management and zoned prevention and control of heavy metal pollution in the water-level fluctuation zone of the Three Gorges Reservoir Area.

Objective This study aims to examine whether and how conservation tillage improves the climate adaptability of grain production， revealing its heterogeneous effects from a dual-dimensional perspective of proactive response and passive adaptation. Methods Based on panel data from 44 sample counties in Heilongjiang Province， China， from 2012 to 2022， a dual-dimensional evaluation framework was established incorporating proactive response and passive adaptation. The Tobit models， system generalized method of moments （GMM）， double machine learning， and spatial Durbin models were employed to empirically test the impacts of conservation tillage on climate adaptability. Results 1） From 2012 to 2022， the climate adaptability of grain production in Heilongjiang Province exhibited an overall evolution pattern of first declining and then rising， with 2017 as a key turning point. Spatially， the pattern evolved from a scattered distribution of high-value areas in the early stage to a distinct east-west differentiation， with high-value areas in the east and low-value areas in the west. 2） Conservation tillage had a significantly positive effect on proactive response， but no significant effect on passive adaptation. The system GMM results showed that the first-order lag term of climate adaptability was significantly positive， indicating that the adaptability improvement showed evident path dependence and dynamic accumulation characteristics. Spatial analysis further demonstrated that the direct and indirect effects of conservation tillage on proactive response were 0.119 and 0.711， respectively， with indirect effect playing a dominant role， indicating a significant spatial spillover effect. 3） The effect of conservation tillage on improving proactive response was more pronounced in regions with higher levels of economic development and flatter terrain. Conclusion Conservation tillage can significantly improve the climate adaptability of grain production， mainly by strengthening proactive response， and exhibits evident path dependence and spatial spillover characteristics. The research findings provide a basis for optimizing agricultural climate adaptation policies from a dual-dimensional perspective and for enhancing the resilience of grain production systems.

Objective This study aims to investigate the morphological change process of scour holes at the headcut of ephemeral gullies on slopes with typical herbaceous communities and their main controlling factors. Methods Field runoff scouring experiments were conducted on slopes covered by three typical herbaceous communities in the loess hilly-gully region （Stipa bungeana， Lespedeza davurica， and Artemisia gmelinii）. Close-range photogrammetry was applied to monitor morphological change processes of scour holes. Results 1） Significant differences in root mass density and soil properties were observed among different herbaceous communities. In the topsoil layer （0~0.2 m）， the Artemisia gmelinii community exhibited significantly higher root mass density， root length density， total porosity， saturated water content， and aggregate mean weight diameter than the other two communities， while soil bulk density， cohesion， and penetration resistance showed the opposite pattern. 2） Herbaceous communities significantly affected the morphological characteristics of scour holes and their change processes. Morphological parameters， including width， height， depth， area， volume， shape factor， and depth-to-diameter ratio， showed fluctuating variations with scouring duration， following an increase-decrease-increase trend. Significant differences in morphological development of headcut scour holes at gullies were observed among different herbaceous communities， with the slowest development in the Artemisia gmelinii community， followed by Lespedeza davurica and Stipa bungeana. 3） Pearson correlation and partial least squares （PLS） analyses showed that root mass density， root length density， total porosity， saturated water content， and aggregate mean weight diameter significantly affected scour hole depth. PLS structural equation modeling （PLS-SEM） indicated that vegetation root traits and aggregate mean weight diameter were key factors affecting scour hole depth development， with total effects of -0.65 and -0.53， respectively. Vegetation roots significantly increased soil aggregate stability， thereby inhibiting scour hole development. Conclusion The findings provide important theoretical support for understanding mechanisms by which vegetation restoration influences headward erosion in ephemeral gullies.

Objective This study explores the spatiotemporal dynamics of vegetation net ecosystem productivity （NEP） and identifies its key driving factors in typical karst regions， providing a theoretical basis for the scientific understanding of carbon cycling mechanisms and the formulation of differentiated carbon neutrality strategies. Methods Vegetation NEP in Guizhou Province from 2000 to 2020 was quantitatively assessed based on an improved Carnegie-Ames-Stanford Approach （CASA） model and an empirical equation for soil microbial respiration. Theil-Sen Median trend analysis， Mann-Kendall significance test， Hurst index， and optimal parameters-based geographical detector were applied to systematically analyze the spatiotemporal variation trends， characteristics， and key driving factors of vegetation NEP in Guizhou. Results 1） During the study period， NEP across Guizhou increased significantly， indicating a continuous enhancement of carbon sequestration capacity. Spatially， NEP decreased from the south-central and southwestern regions to the northern and eastern regions. Vegetation NEP in karst regions ［278.20 g/（m²·a）（based on C）］ was significantly lower than that in non-karst regions ［326.83 g/（m²·a）（based on C）］， suggesting that differences in geological background were the core reason for divergence in carbon sequestration potential. 2） Across the province， changes in NEP mainly remained stable （50.31%） or showed an increasing trend （46.98%）. Increasing trends were concentrated in the western and northeastern regions， while decreasing trends were distributed in the central and eastern regions. Mean Hurst index was 0.48， and areas with Hurst index below 0.5 accounted for 61.59%. 3） Lithology （q=0.41）， as the core natural background factor， directly determined basic habitat conditions such as soil development， water retention， and nutrient conservation， while sunshine duration （q=0.35） was the key meteorological factor. Together， they established the inherent carbon sequestration potential of the region. The interactive effects of multiple factors were stronger than those of single factors. Notably， the interaction between sunshine duration and land use had explanatory power of 50%， representing the key driving factor regulating spatiotemporal patterns of carbon sequestration. Conclusion These findings provide scientific data support and decision-making reference for ecological conservation and restoration， carbon sequestration function enhancement， and sustainable development in ecologically fragile karst regions.

Objective This study aims to investigate the regulatory effects of electric field treatment （ET） on soil microecology in rocky desertification areas under different climatic conditions. Methods Using severely rocky desertified soil as the research subject， a laboratory simulation of the rocky desertification soil habitat along with drought and rainfall processes was conducted. The effects of a continuously operating 20 V electric field treatment on soil physicochemical properties and the structure and functions of bacterial communities were investigated. Results Compared with the control （CK）， the electric field treatment significantly increased the contents of soil organic carbon， alkaline hydrolyzable nitrogen， and available potassium during both the dry and rainy seasons， and inhibited the loss of available phosphorus during the dry season. However， the electric field treatment significantly decreased soil water content and pH. Under the electric field treatment， the richness and diversity indices of the soil bacterial communities were significantly reduced in both the dry and rainy seasons. The community structure composition at the genus level differed significantly between the dry and rainy seasons， while the composition at the phylum level remained unchanged. During the dry season， the electric field significantly enriched Proteobacteria， Sphingomonas， Flavisolibacter， and Chthoniobacter. During the rainy season， it significantly enriched Actinobacte-riota， Cyanobacteria， Bradyrhizobium， Mesorhizobium， Dyella， Burkholderia-Caballeronia-Paraburkholderia， Catenulispora， Amycolatopsis， Mucilaginibacter， and Edaphobacter. During the rainy season， electric field treatment significantly increased the relative abundance of functions such as photosynthesis （chloroplast） and nitrogen fixation in the soil bacterial community. Redundancy analysis （RDA） indicated that soil alkaline hydrolyzable nitrogen， available phosphorus， and water content were the main environmental factors driving the evolution of the bacterial community. Conclusion Electric field treatment can optimize bacterial community structure and enhance its ecological functions by regulating key soil factors， thereby promoting nutrient cycling and system restoration in rocky desertified soil and providing a theoretical basis for ecological management in rocky desertification areas.

Objective This study investigates the variation patterns of runoff in glacier-fed inland rivers and their underlying mechanisms under climate warming， aiming to support water security in arid regions of Northwest China. Methods The Keriya River on the northern foot of the Kunlun Mountains was selected as the study object. Based on hydrological and meteorological data from 1961 to 2019， this study systematically assessed runoff variation characteristics and the driving mechanisms of climate change using the Mann-Kendall trend test， Pettitt method for abrupt change detection， wavelet period analysis， and partial correlation analysis. Hydrological regime changes before and after 2016 were compared from the perspective of reservoir construction. Results 1） Runoff of the Keriya River showed a highly significant increasing trend （p<0.001）， jointly regulated by dominant cycles of 28， 18， and 6 years， with no detectable abrupt structural change. 2） The climate in the basin exhibited asymmetric warming characteristics， with the warming rate of minimum temperature （0.055 ℃/year） being 2.2 times that of maximum temperature （0.025 ℃/year）， and precipitation increased following a stable 23-year cycle. 3） Runoff variation followed a "temperature-dominated， precipitation-assisted， lagged response" pattern， with minimum temperature as the core driving factor and showing a 1-year lag effect. 4） After a reservoir was constructed， a preliminary peak-shaving and valley-filling regulatory effect was observed， with the runoff coefficient of variation decreasing by 48.91%. The increase in runoff during the non-flood season was significantly greater than in the flood season. Conclusion Runoff increase of the Keriya River is primarily dominated by snow and glacier melt induced by nighttime warming， and the basin is currently in a gain period of glacial meltwater. Reservoir operation has already produced a peak-shaving and valley-filling regulatory effect on natural hydrological processes， but it has not altered the long-term increasing trend driven by climate. The findings provide a scientific basis for water resources management in alpine inland river basins under climate change.

Objective This study aims to analyze the impact of spatiotemporal changes in land use patterns on regional carbon storage in Heilongjiang Province， predict future evolution under multiple scenarios， and quantitatively identify the main driving factors of spatial differentiation in carbon storage. Methods Based on four periods of land use data in Heilongjiang Province from 1990 to 2020， the PLUS-InVEST-Geodetector model was coupled to analyze changes in land use patterns and their carbon effects. Future land use and carbon storage in 2060 were simulated under four scenarios： Natural development， cultivated land protection， ecological protection， and urban development. Results From 1990 to 2020， carbon storage in Heilongjiang Province showed a net decrease of 53.46×10⁷ t， with a spatial pattern of high in central regions and low in surrounding areas， high in the north and low in the south， and high in mountainous areas and low in plains. The conversion of forest land to cultivated land， grassland， and unused land was the primary pathway for carbon loss. Multi-scenario simulations indicated that carbon storage in 2060 followed the order： ecological protection scenario （2 012.71×10⁷ t） > natural development scenario （2 000.59×10⁷ t） > urban development scenario （1 996.01×10⁷ t） > cultivated land conservation scenario （1 992.08×10⁷ t）. Geodetector analysis revealed that the spatial differentiation of carbon storage was mainly influenced by factors such as elevation， distance to water bodies， and normalized difference vegetation index （NDVI）. Interactions among factors were mainly characterized by two-factor enhancement and nonlinear enhancement， with the strongest interactions observed between digital elevation model （DEM） and annual precipitation， DEM and distance to rivers， population density and DEM， and DEM and NDVI. Conclusion During the historical period， the conversion of forest land to cultivated land and grassland in Heilongjiang Province led to a continuous net decrease in carbon storage. Future projections indicate that carbon storage is the highest under the ecological protection scenario， with factor interactions centered on DEM dominating the spatial differentiation of carbon storage. Therefore， it is necessary to control the conversion of land types with higher carbon density to those with lower carbon density， strictly implement black soil protection policies， and adopt ecological protection measures. The impacts of natural and socio-economic factors should be comprehensively considered when formulating regional ecological protection and economic development policies， so as to promote the sustainable development of the regional economy in Heilongjiang Province.

Objective To address the limitations of existing nature relationship index （NRI） in depicting the human-nature relationship at the individual level in ecologically fragile regions， and their inability to identify regional differences and key constraining factors， this study aims to reveal the overall level， spatial differentiation， major obstacles， and intrinsic trade-offs and synergies of farmers′ relationship with nature in northern Shaanxi. Methods Taking NRI as a theoretical reference， the macro human-nature relationship framework was downscaled to the individual farmer level. An indicator system of the farmers′ relationship with nature index （FRNI） was constructed， consisting of three first-level dimensions， six second-level dimensions， and sixteen third-level indicators. Based on 522 household questionnaires conducted in 25 counties/districts of northern Shaanxi form July to August 2025， index measurement， the obstacle degree model， and Spearman correlation analysis were employed to analyze the overall level， spatial pattern， key obstacles， and trade-offs and synergies of farmers′ relationship with nature. Results 1） The average FRNI in northern Shaanxi was 0.53， indicating a moderate overall level. Among the three first-level dimensions， the "nature is safeguarded" dimension scored the highest （0.61）， the "nature is thriving and accessible" dimension ranked in the middle， and the "nature is used with care and respect" dimension scored the lowest （0.46）. This suggested that although government-led ecological governance and environmental protection have established a certain foundation， farmers remained relatively weak in resource conservation， ecological care， and active participation. 2） The FRNI in northern Shaanxi showed an overall spatial pattern of "higher in the south and lower in the north"， with different dimensions showing differentiated spatial structures. This indicated that regional differences in farmers′ relationships with nature resulted from the combined effects of natural endowment， agricultural production practices， ecological governance efforts， and farmers′ livelihood structures. 3） The main obstacles to improving FRNI were concentrated in limited accessibility to nature， weak water-saving behaviors， and insufficient farmer participation. Overall， relationships among the indicators were dominated by synergies， with a few indicators showing significant trade-offs. Based on obstacle identification and analysis of trade-offs and synergies， a systematic improvement pathway was proposed， which is prioritizing key obstacles， mitigating major trade-offs， and amplifying synergies. Conclusion The perception-based FRNI effectively characterizes the overall status， spatial differences， and key shortcomings of farmers′ relationships with nature in ecologically fragile regions. In northern Shaanxi， improving farmers' relationship with nature depends not only on ecological improvement， but also on the coordinated enhancement of accessibility to nature， water-saving behavior， and farmer participation， with targeted governance tailored to local conditions. The findings provide a support for evaluating farmer-nature relationships， diagnosing critical obstacles， and informing policy in the Loess Plateau and similar ecologically fragile regions.

Objective This study aims to systematically review the history of soil erosion mapping at the national and global scales prior to the widespread application of remote sensing and GIS， clarify its scientific achievements and historical contributions， explore its practical implications for contemporary digital soil erosion mapping， and promote further advancement in this field. Methods Classic maps and related literature from the mid-1920s to the late 1990s， both in China and worldwide， were systematically collected and analyzed. By examining the historical development trajectory and technical methods employed， this study assesses their scientific achievements and historical value， providing key insights for modern digital soil erosion mapping. Results Soil erosion mapping at national， major geographical unit， and global scales was systematically conducted during this period. Representative outputs include soil erosion maps of the United States， the former Soviet Union， and China， soil erosion maps of severely eroded regions such as the Loess Plateau， and the global soil erosion map. These maps were primarily compiled based on the degree of damage observed in soil profiles or used river sediment transport rate as a proxy indicator to evaluate erosion intensity， and spatial representation of soil erosion was achieved through manual cartographic methods. Conclusions The nearly 80 years of regional soil erosion mapping worldwide have achieved systematic foundational outcomes. Theoretically， it established soil erosion classification systems and an ontological framework， provided historical baseline data， and formed classic paradigms. Practically， it promoted soil and water conservation legislation and the establishment of soil conservation institutions in multiple countries， laying the foundation for global monitoring networks. Its scientific concepts and legacy data provide four insights for contemporary digital mapping， including focusing on erosion-specific themes， integrating classical cartographic theories， deeply utilizing historical data， and constructing a new paradigm of soil erosion mapping in the digital era.

Objective This study aims to investigate the evolution patterns of soil organic carbon （SOC） in abandoned farmland of karst areas and identify the transition threshold of carbon pool from quantitative expansion to structural stabilization. Methods A typical abandoned farmland of karst areas in Guizhou was selected as the research subject. A space-for-time substitution method was adopted to analyze the differences in SOC content and its fractions， including easily oxidizable organic carbon （EOC）， particulate organic carbon （POC）， light fraction organic carbon （LFOC）， and heavy fraction organic carbon （HFOC）， in the 0~20 cm soil layer across farmland （CK） and succession sequences （5， 10， and 15 a of abandonment）. The carbon pool management index （CPMI） and the HFOC/SOC ratio were used to evaluate carbon pool stability. Results 1） After 15 a of abandonment， SOC content in the 0~10 cm soil layer increased by 70.1% compared with CK， with accumulation mainly occurring in the first 10 a. 2） EOC and POC showed an inverted "U"-shaped pattern with increasing abandonment years and peaked at 10 a， increasing by 91.5% and 107.1%， respectively， in the 0~10 cm soil layer compared with CK. HFOC showed a highly significant continuous linear increase （R²>0.9）， with its contribution remaining at 88%~90%. 3） The 10 a of abandonment was the threshold for carbon pool functional transition from an activity-driven quantity increase stage to a stability-driven quality stabilization stage， at which CPMI peaked and then declined， while the stability ratio increased. 4） Carbon pool remodeling showed a vertical differentiation pattern with earlier transformation in the surface layer and a lagged response in deeper layers. The 0~10 cm soil layer exhibited significantly higher sensitivity to succession and faster stability improvement than the 10~20 cm soil layer. The first axis of redundancy analysis （RDA） explained 57.27% of the variations， and abandonment years were the dominant factor driving changes in carbon fractions. Conclusion 10 a is the key turning point for carbon pool functional remodeling in karst areas， and vegetation restoration promotes the transition from active accumulation to chemical stabilization. This finding emphasizes the importance of focusing on carbon pool transformation in surface soils and enhancing carbon sequestration capacity by utilizing strong mineral protection in calcium-rich habitats.