Land-use patterns critically regulate soil organic carbon (SOC) dynamics through differential impacts on particulate (POC) and mineral-associated organic carbon (MAOC) fractions, thereby shaping terrestrial carbon sequestration potential. This study aimed to elucidate how contrasting land-use systems influence SOC stabilization mechanisms in fragile karst ecosystems. SOC fractions and microbial necromass carbon (MNC) were quantified across two restored systems (forestland and grassland) and three intensively managed croplands (sugarcane, maize, and banana) in a subtropical karst region. Agricultural systems experienced substantial SOC losses (18.4–57.0

Soil total phosphorus (STP) is a key component of the terrestrial phosphorus cycle, and its spatial distribution pattern profoundly influences ecological security and the stability of food production. This study integrates 20,372 nationwide plot monitoring records and, based on the Random Forest algorithm, constructs a 1 km resolution layered spatiotemporal map of STP across China for the period 2000-2020. The results show that China's STP exhibits an overall "central high, northern-southern low" spatial pattern, with South China identified as a contiguous low‑phosphorus region (<0.4 g/kg). Vertically, STP decreases by approximately 25.8% with increasing soil depth. The study further reveals regional differentiation characteristics of STP variation: the mid‑temperate zone serves as the core area of phosphorus accumulation, while the middle‑lower Yangtze River region and the Sichuan Basin are identified as hotspots of phosphorus loss. Solar radiation (SR) is the main positive driver of phosphorus enrichment in plateau regions (affecting 29.1% of the national area, ca. 2.65 × 106 km²), whereas wind speed is the primary negative driver of phosphorus loss in arid regions (affecting 32.7% of the national area, ca. 2.98 × 106 km²). Temperature (Tmp) exhibits a bimodal regulatory pattern. This study systematically elucidates the integrated impacts of natural and anthropogenic factors on the spatiotemporal pattern of STP, proposes a multi‑scale analytical framework for soil phosphorus cycling, and provides both data support and scientific basis for the zonal management of phosphorus resources and sustainable agricultural development.

Carbonate rock weathering and soil formation is a key link in the global carbon cycle, but the response mechanism to climate and human activities remains unclear. This study quantifies the spatio-temporal dynamics of soil formation rate (SFR) of carbonate rocks in China based on 1km resolution data (2003-2020) and reveals its driving mechanism by integrating thermodynamic models and structural equation models. The results show that the multi-year average SFR in China is 29.93 t/km²/yr, presenting a latitudinal zonal pattern of “high in the southwest and low in the northeast”, with the peak value in the area between 20°N and 25°N. Lithology is the basis of spatial differentiation, and the mean SFR_CA (104.65 t/km²/yr) is 9.5 times that of SFR_HC. Precipitation is the core driving factor, with a contribution rate of 41.26%. CO₂ shows significant spatially differentiated regulatory effects, inhibiting soil formation in 47.41% of the area. The impact of human footprint is complex, with weak positive effects coexisting with extensive negative dominant areas. The study reveals that the multi-level feedback network of "human-climate-geology" is the key driving force for reshaping the soil formation pattern of karst, providing a new theoretical basis for assessing the soil formation pattern under global change.

Although the global population continues to grow,the coming decades will witness the most rapid expansion of urban population in human history,primarily,driven by large-scale rural-to-urban migration.This migration alleviates human pressure significantly in rural areas,promotes the transformation of land use patterns and ecosystem restoration,and profoundly reshapes regional land spatial configurations.These changes directly or indirectly affect local ecological environments,thereby presenting both new opportunities and challenges for biodiversity.The southwestern region of China serves as a critical ecological security barrier for the country.It is not only a key area for global vegetation greening and plant diversity conservation,but also a typical region experiencing marked rural-urban migration and a pronounced decline in rural population.The ongoing and accelerating outflow of rural population in this region is profoundly reshaping local human-land relationships.Moreover,its distinctive karst landforms and ecological fragility make it highly sensitive to human disturbances.While large-scale rural population decline is reshaping the ecological environment,it also creates opportunities for ecosystem restoration.However,the response mechanisms of plant diversity to rural population decline and its threshold effects remain unclear,which hinders a deeper understanding of the coupling mechanisms in human-earth systems and constrains the scientific rigor and effectiveness of regional ecological conservation strategies. This study focuses on southwestern China as the research area.Based on vascular plant species richness data,the spatial pattern of plant diversity from 2000 to 2020 was reconstructed using a Random Forest model.The K-means algorithm was employed to identify urban-rural boundaries,revealing the spatiotemporal evolution characteristics of the rural population and examining the impact of rural population decline on plant diversity and its threshold effects.Using the human footprint index to characterize human pressure,the relationship between the release of human pressure induced by rural population decrease and the increase in biodiversity was analyzed.Through relative contribution rate decomposition,the driving contributions of climate change and human pressure were quantified.The study addresses the following key questions:(1)Spatiotemporal patterns of population decline in southwestern rural China;(2)Impacts of population decline on the spatial distribution of plant diversity and underlying mechanisms;(3)Threshold responses of plant diversity to changes in population density;(4)Relative contributions of climate change and human pressure to plant diversity changes. The results indicate that between 2000 and 2020,southwestern China experienced a rural population decrease of approximately 137 million,a 5.23％reduction in human pressure,and a significant 44.32％increase in plant diversity.Over 60％of the areas with rural population loss showed significant increases in plant diversity,with an average increase of approximately 0.73 species per 100 km2,across an area of 266,600 km2,Further analysis revealed a nonlinear relationship between rural population density and plant diversity:when population density fell below 336.68 persons·km-2,population decline exerted a suppressive effect on plant diversity;within the range of 336.68 to 956.73 persons·km-2,this suppressive effect gradually weakened;and when density exceeded 956.73 persons·km-2,population decline transitioned to a positive facilitative effect.Decomposition of driving factors showed that changes in rural human pressure contributed 38.64％to plant diversity changes,while climatic factors accounted for 61.36％,indicating that climate change remains the dominant factor influencing regional plant diversity. This study quantifies and reveals for the first time the nonlinear relationship and key thresholds between rural population decline and plant diversity in southwest China.It systematically elucidates the response mechanisms of plant diversity to population decline and human pressure,and clarifies the relative contributions of human activities and climate change.By analyzing the response patterns of plant diversity to rural population outmigration and identifying critical thresholds of population density effects,this research provides a scientific basis for understanding the mechanisms by which rural-urban migration influences biodiversity.The findings offer important insights for biodiversity conservation and regional sustainable development in southwest China.

Abstract Carbonate weathering carbon‐sink (CWCS) is a critical yet inaccurately quantified component of terrestrial carbon sequestration. However, the mechanisms through which climate change and vegetation dynamics drive the spatial heterogeneity of CWCS remain unclear. We integrated multi‐source data to identify altitude thresholds and nonlinear response characteristics of CWCS driven by climatic and vegetation globally. Our findings show that global carbonate weathering sequestered 127.60 ± 7.70 Tg C yr−1 from 1950 to 2014, equivalent to 3.65% of global forest carbon sink. We identified a dichotomous pattern in CWCS at an altitude threshold of 3,000 m: rates decreased below but increased significantly above this elevation. This altitude threshold marks a fundamental shift in climate sensitivity and driving mechanisms, meaning that warming inhibits carbonate weathering in warm lowlands, while high‐altitude cold regions accelerate carbonate weathering through enhanced glacial snowmelt (percent contribution: 20.71%–38.96%) and vegetation–carbon dioxide feedback (NDVI threshold: 0.33–0.67). By 2100, global CWCS is projected to increase by 14.51%–24.90% compared to historical period (1950–2014). High‐altitude cold regions are projected to emerge as pivotal growth areas for CWCS in the future (2015–2100), contributing 45.02%–59.50% of newly added CWCS, despite accounting for only 28.41% of carbonate areas. Our results demonstrate that climate warming has transformed cold high‐altitude regions into indispensable engines for enhancing terrestrial carbon sink.

Meteorological drought, one of the most destructive natural hazards, is driven by both precipitation deficits and high evaporative demand. While precipitation has traditionally been considered the dominant driver, recent studies suggest an increasing influence of evaporative demand. However, it remains uncertain whether these findings represent individual regional cases or a boarder emerging global trend. To address this, we developed a systematic framework using a standardized precipitation evapotranspiration index (SPEI) variant experiment to attribute drought drivers across 292 major global basins. Our historical analysis (1970-2024) reveals a widespread global transition: 48.1% of the global basin area (6.43 & times; 107 km2) transitioned from precipitation-dominated to evaporative demand-dominated drought. This transition, accelerating after 2000, originated in arid continental interiors and expanded outwards, leaving precipitation-dominated areas only one-tenth the size of evaporative demand-dominated ones. Future projections from bias-corrected coupled model intercomparison project phase 6 models indicate this transition is largely irreversible, as over 80% of historically transitioned basins are projected to maintain evaporative demand-dominated through 2100. Basins that have not yet transitioned are also projected to transition toward either evaporative demand-dominated or precipitation and evaporative demand co-dominated drought states. Under the shared socioeconomic pathway (SSP) 5-8.5 scenario, the global area of evaporative demand-dominated droughts is projected to be 17.6% larger by 2100 than under SSP1-2.6 scenario. These findings highlight the urgent need for both climate mitigation to slow these transitions and proactive adaptation to address the new reality of drought driven by evaporative demand.

Understanding the relationship between plant diversity (PD) and terrestrial productivity (NPP) holds theoretical significance. Studies indicate that PD can enhance NPP, but a threshold effect exists. Most existing research focuses on simple communities and static experiments. The dynamics of this relationship on a global scale, especially how soil available phosphorus (OlsenP), a limiting resource prevalent in ecosystems, affects the threshold effect of PD on NPP, is unclear. Here, we constructed a high-resolution dynamic spatial map of global OlsenP concentrations from 2000 to 2020 using 34,336 global data points and machine learning methods. Through the control variable method and elasticity analysis, the threshold patterns of PD effects on NPP and their changing patterns along the OlsenP gradient were quantified for the first time at the global scale and in different ecological zones. It was found that OlsenP raised the upper limit of PD impacts on NPP by approximately 0.98 at the global scale during the 20-year period, but there were significant differences across ecological zones. Threshold ceilings rose from 11.87 to 13.29 in Flooded Grasslands & Savannas and from 12.05 to 13.11 in Montane Grasslands & Shrublands, while Tropical & Subtropical Coniferous Forests saw a 0.37 decrease. These findings revealed that the upper limit of the PD impacts on NPP under the OlsenP perturbation, the threshold effect of PD on NPP will produce strong regional heterogeneity, which provides new theoretical support and data reference for understanding how soil limiting resources regulate the relationship between biodiversity and terrestrial ecosystem productivity.

Weathering is a crucial geological process where surface rocks and minerals are gradually transformed into loose deposits or soil through both physical crushing and chemical decomposition in the natural environment. This dynamic process is intrinsically linked to the entire evolution of the Earth's surface system. Weathering is a fundamental driver of surface topography, leading to the erosion and eventual flattening of steep mountains and promoting the accumulation of nutrient-rich soil in plain areas. It also directly supports the development and maturity of the pedosphere, provides a basic carrier for terrestrial ecosystems, and plays an indispensable role in global material circulation. Crucially, the continuous weathering processes of the Earth fundamentally influence the resilience and recovery capacity of ecosystems by precisely regulating material and energy exchange across the six fields. In the field of global carbon cycle, the chemical weathering of silicate minerals is a fundamental, long-term geological process that acts as a major carbon sink, removing atmospheric carbon dioxide by converting it into dissolved bicarbonate and carbonate ions, thus acting as a crucial natural mechanism to slow global warming. In the aspect of element supply, nitrogen, phosphorus, potassium, and other nutrients released into the biosphere through the natural process of weathering are fundamental for the stability and operation of ecosystems. Traditional geography, while studying the interaction and formation of natural and human elements on the Earth's surface, has not fully recognized the ecological significance and functional value of weathering as a crucial interface connecting life and the environment. This leads to the following three shortcomings in understanding weathering. (1) The disconnection between geological time scales and ecological process research limits the thorough analysis of ecological response mechanisms of climate change events. (2) Biogeochemical cycle models generally face challenges in accurately quantifying biologically driven weathering. (3) An effective quantitative index for the influence of human activities on the flux of weathered materials has not been established. Therefore, the establishment of the "weathering geography" discipline is essential for managing critical environmental challenges and preserving ecological balance. In this paper, the hierarchical research model of geography (from individual organisms to ecosystems) is combined with the mineral geochemical analysis methods of geology to bridge traditional disciplinary boundaries, and the disciplinary system of "rock weathering-material migration-biological response" in weathering geography is constructed. Weathering geography is a new interdisciplinary subject formed by the intersection of ecological geology and geography. It mainly takes the lithosphere, pedosphere, biosphere, atmosphere, hydrosphere, and human sphere as the research objects. By analyzing the influence of physical, chemical, and biological weathering processes on ecosystems and ecological processes, weathering geography integrates the three-dimensional dynamic processes of lithospheric material decomposition, biosphere element utilization, and human sphere intervention and adjustment. This paper reveals the general laws and causes of the relationships between various components of ecosystems and ecological processes in different environmental gradients. Furthermore, a multi-sphere interactive feedback theoretical system of "water-rock-soil-gas-life-people" is constructed. At the same time, it is emphasized that establishing a multi-scale coupling system of "in situ observation-model inversion-application verification" is crucial for realizing a comprehensive, whole-chain analysis from element cycles to continental weathering patterns. This system will reveal the coupling mechanism of energy flow and material circulation in the Earth's surface system, provide a new theoretical tool for ecological simulation in extreme environments, address the cognitive deficiency of traditional geography by linking the complex interactions between deep geological processes and surface ecological responses, and offer a new paradigm for solving the complexity crisis in ecosystem modeling.

The geological substrate is increasingly recognised as an important modifier of soil respiration (Rs) dynamics, yet it remains underrepresented in global carbon cycle assessments. Using a global synthesis of field-based Rs measurements spanning 1990-2022, we examined the temporal trajectories of Rs and identified contrasting patterns between karst and non-karst landscapes. Breakpoint analyses revealed coherent temporal transitions in non-karst systems around 2013 and 2016, characterised by early positive trends followed by increased variability during intermediate periods, and indications of renewed increases in recent years. In contrast, karst systems exhibited no consistent breakpoints and displayed less temporally coherent responses across sites and periods. Multivariate models explained a greater proportion of variance in karst systems (adjusted R2 = 0.51) than in nonkarst systems (adjusted R2 = 0.48), indicating that Rs variability in karst landscapes may be more consistently associated with a limited set of substrate-specific predictors. Biome type, ecosystem type, climate zone, and elevation were significant predictors across both substrates, whereas climatic variables (MAT and MAP) were not significant in karst systems once other factors were accounted for, indicating weaker direct climate coupling and greater context dependence. Monte Carlo upscaling estimated that mean annual global Rs increased from 92.06 Pg C during the pre-breakpoint period (1990-2012.5) to 106.57 Pg C during the post-breakpoint period (2016.5-2021). Non-karst landscapes showed a pronounced rise consistent with continued Rs acceleration, whereas karst ecosystems exhibited a smaller, non-significant increase indicative of partial attenuation of surface CO2 efflux. Together, these results highlight the importance of explicitly accounting for geological heterogeneity when assessing large-scale trends in soil respiration and carbon-climate interactions.

Abstract Atmospheric moisture transport and precipitation recycling processes are key to understanding regional water cycle under climate change. Using the two‐layer Water Accounting Model (WAM‐2layers) with ERA5 reanalysis data, we analyzed the atmospheric net moisture flux across the Yellow River Basin from 1980 to 2023. We further applied re‐tracking experiments to separate source and sink dynamics by trend categories. The results show that the basin gains atmospheric moisture flux at an average rate of 0.37 mm day−1, with peaks exceeding 1.6 mm day−1 in the southwest. Regions with decreasing net moisture flux are dominated by external moisture advection and evaporation losses, with 89.1% of precipitation from advected moisture and 10.9% from recycling. In contrast, regions with increasing net moisture flux show stronger internal regulation through enhanced moisture recycling, with evaporation contributing 74.2% of the moisture budget and net moisture gain the remaining 25.8%. These regions also exhibit stronger source–sink linkages, with correlations exceeding 0.4 and reaching about 0.6. These findings demonstrate that regional water availability in the Yellow River Basin is governed not only by moisture flux magnitude but also by the organization of atmospheric moisture transport pathways.

The soil formation rate (SFR) in karst carbonate rocks is a vital parameter linking atmospheric carbon dioxide sequestration to pedogenic processes, and it significantly regulates terrestrial carbon cycling. However, the relationship between SFR and ecosystem carbon use efficiency (CUEe) under climate change, as well as its primary driving factors, remains unclear. Utilizing multi-source remote sensing data and global hydrochemical ion concentration datasets, we quantified the spatiotemporal evolution, future sensitivity dynamics, and driving mechanisms of CUEe and SFR from 1982 to 2100. The global SFR flux in karst regions is approximately 22.02 t & centerdot;km(-2)& centerdot;yr(-1), while CUEe is approximately 0.465, with the two variables exhibiting a significant spatial correlation (r = 0.37, p < 0.05). Under future climate scenarios, SFR shows an increasing trend, whereas CUEe exhibits a gradual decrease, leading to a weakening correlation, particularly under the SSP5-8.5 scenario (r = 0.09, p < 0.05). The sensitivity of CUEe to SFR (Scue-sfr) exhibits an overall decreasing trend, with a significant breakpoint occurring around 2030 across all scenarios, indicating a weakening of the positive feedback between SFR and CUEe over time. Furthermore, attribution analysis reveals that soil moisture (SM) emerges as the dominant driver of variations in Scue-sfr under the future SSP3-7.0 and SSP5-8.5 scenarios, with a relative contribution of approximately 20-24%. The results suggest that global warming and aridification may decouple the synergistic interaction between SFR and CUEe, providing essential evidence for carbon cycle projections and ecological restoration approaches in the context of climate change.

Southwest China's karst region has rapidly dissolving carbonate rock,shallow soils,and connected surface-subsurface drainage.Water,soil,and element cycles therefore respond quickly to climate and land-use change.For the Institute of Geochemistry's 60th anniversary,we review its karst biogeochemical and ecological research through Watershed Earth System Science(WESS)and Earth Critical Zone science.The synthesis uses long-term observations,flux measurements,isotope tracing,remote sensing,and socioeconomic surveys.Results show that the dual structure controls water pathways and whether soil is eroded at the surface or lost underground.Carbon,nitrogen,and sulfur are repeatedly retained and transformed at canopy,moss,soil,and bedrock interfaces,creating rapid responses to acid deposition,fertilization,and climate anomalies.Carbonate Weathering coupled with Aquatic Photosynthesis(CCW)links weathering-derived inorganic carbon to biological uptake and organic-carbon preservation.Ecological projects,urbanization,and migration jointly affect rocky-desertification recovery and regional carbon storage.The studies connect interface reactions with watershed transport and Socio-Ecological System(SES)governance.They inform zoned restoration,regional carbon accounting,and sustainable rural development.

Abstract Biochar applied in ecological restoration shows a significant dose-dependent effect. Therefore, determining an appropriate rate for specific environments is essential in practical applications. To this end, we integrated soil profiles and biogeochemical and microbiome datasets from six major ecosystems (agricultural, grassland, forest, coastal wetlands, desert, and polar tundra), constructed a global biochar remediation threshold map, and investigated the driving mechanisms of threshold formation. Simultaneously, differentiated application frequency strategies tailored to each ecosystem are proposed. The results showed that the appropriate thresholds for different ecosystems were 5–30 t ha−1 (agricultural), 5–40 t ha−1 (grassland), 5–40 t ha−1 (forest), 10–50 t ha−1 (coastal wetlands), 10–40 t ha−1 (desert), and 20–60 t ha−1 (polar tundra). Within the threshold range, in combination with customized application frequency, biochar enhances ecological functions by increasing soil water-holding capacity (by approximately 10–14.3%), reducing greenhouse gas emissions (by approximately 16.4–31.5%), lowering soil heavy metal content, and increasing soil organic matter. Exceeding the threshold can cause sharp fluctuations in soil pH, increases in bioavailable polycyclic aromatic hydrocarbons, and decreases in microbial diversity, thereby inhibiting remediation. Inadequate application frequency also weakens the ecological restoration efficacy of biochar. The thresholds are environmentally dependent. The threshold window can be expanded or narrowed by the joint regulation of preparation parameters, soil characteristics, climate, and human management. Based on this, we propose a framework of “threshold identification–mechanism analysis–targeted intervention” and customized application paths for ecosystems (e.g., on-farm biochar + fertilizer single/strip application, low-dose staged application in grassland, forest low-dose dispersal single intervention, combination of wetland surface and spot combined with seasonal application, desert inter-root precision single application, and zoned management of medium and low doses in polar regions). The framework provides a quantitative and mechanistic basis for formulating standards for the production and application of biochar and for promoting precise remediation. Graphical Abstract

The southwest karst region of China is characterized by unique landscape patterns,a fragile ecological environment,and intense human disturbances.Identifying the spatial heterogeneity of ecosystem services(ES)and exploring the spatiotemporal correlations between ES and human activity intensity are crucial for achieving sustainable development.However,previous studies have often overlooked the complex spatiotemporal dynamics and nonlinear relationships between human activities and ES.To address this gap,this study selected four key ES indicators,namely water yield(WY),soil retention(SR),net primary productivity(NPP)for carbon storage,and biodiversity index(BI).Combined with the Human Footprint Index(HFI),we evaluated the spatiotemporal evolution of ES and their responses to human activity intensity.The results show that from 2000 to 2020,the total ecosystem services(TES)in the southwest karst region exhibited a fluctuating upward trend,with an increase of 20.26％.The central part of Guizhou Province witnessed the most significant improvement.During the same period,HFI increased by 12.84％.Nevertheless,TES and HFI showed a significant negative correlation in 55.05％of the study area.Threshold analysis revealed a hump-shaped nonlinear relationship and threshold effects between TES and HFI,indicating that moderate HFI can promote the enhancement of ES,but once the threshold is exceeded,ES will decline.The responses of TES to HFI varied significantly across different regions,reflecting the heterogeneity and vulnerability of the karst ecological environment.This study quantifies the threshold-based constraint relationship between ES and HFI in the southwest karst region,providing both theoretical support and practical pathways for formulating differentiated management strategies in ecologically fragile areas.

Soil organic carbon (SOC) is crucial for ecosystem functioning and global carbon cycling, with vegetation restoration playing a vital role in enhancing SOC sequestration and stability. However, in the karst regions of southwest China, how vegetation restoration regulates SOC sequestration potential and underlying mechanisms remains poorly understood. This study aims to quantify changes in SOC fractions and microbial necromass (MNC, FNC, BNC) under different vegetation restoration types in karst ecosystems, identify key regulating factors, and provide mechanistic insights to enhance SOC stabilization and guide sustainable land use strategies. We examined the impacts of vegetation restoration, including maize and soybean rotation (MS, as the control), natural restoration after being abandoned from cropland (RC), pure forest restoration (PF), forage grass restoration (RG), forest-grass mixed restoration (FG), and mixed forest restoration (MF), on soil POC, MAOC, microbial necromass and its contribution to SOC in karst ecosystems. Vegetation restoration enhanced microbial necromass, particularly FNC, which accounted for 78.9–85.3

Global change is accelerating the chemical weathering of silicate rocks and the associated phosphorus release. However, the effects of phosphorus release on the global patterns of plant phosphorus limitation remain unclear. Here, we show that approximately 47% of the exposed areas in global silicate rocks are subject to phosphorus limitation of vegetation growth, as estimated using the ratio of leaf nitrogen to phosphorus resorption efficiency. Phosphorus-limited areas are projected to expand markedly with global warming, and the proportion may reach 54 - 59% according to two model scenarios (the shared socioeconomic pathways SSP2-4.5 and SSP5-8.5). Nevertheless, phosphorus release from accelerated chemical weathering of silicate rocks mitigates this limitation, with a relative contribution of approximately 15.5%. This work highlights the implications of accelerated chemical weathering of silicate rocks and its resulting phosphorus release for the global patterns of phosphorus limitation, providing a scientific foundation for phosphorus management strategies.