Soil erosion is a key environmental issue impacting terrestrial ecosystems, especially in sensitive karst regions. Although it is generally accepted that soil erosion processes are strongly influenced by changes in land use and landscape patterns, there is still uncertainty about the spatial association between soil erosion and landscape patterns, especially when spatial spillover effects are considered. To tackle this problem, this study incorporates a karst desertification factor to optimize the commonly applied Revised Universal Soil Loss Equation (RUSLE) model. Based on this, we investigated soil erosion(SE) and landscape characteristics in two representative karst basins in southern China: the Yeji River (YJR) and Dabang River (DBR) watersheds. Finally, for the first time at the sub-watershed scale, we used spatial econometric modeling to resolve the spatial dependence of soil erosion and investigated the spatial association between landscape and SE. The findings showed SE tended to increase in both watersheds during the study period, with high erosion areas concentrated in the middle and lower reaches of watersheds. Disturbed by natural and anthropogenic activities, the watershed landscape exhibits a general trend toward fragmentation. Spatial econometric analysis confirmed the significant presence of SE spatial spillovers, highlighting the importance of interactions between sub-watersheds. Furthermore, the spatial relationship between the landscape patterns and SE demonstrated their complexity, with landscape connectivity significantly influencing the spatial spillover effects of SE. These findings deepen our comprehension of the drivers of soil erosion in ecologically fragile regions and provide support for regional landscape management and soil preservation efforts.

Rocky desertification has formed a unique vegetation-soil-rock structure (VSRS) on the underlying surface of karst area, resulting in complex surface processes. Despite their significance, the response of runoff generation and erosion processes at binary interfaces to VSRS is still poorly understood. In this study, artificial simulated rainfall experiments were carried out on karst micro-plots with binary structure. Driven by rainfall intensity (R) and VSRS, the runoff and sediment output processes and its hydrodynamic mechanisms at the binary interface were studied. The results showed that the surface runoff rate (SRr) decreased with the increase of moss cover (MC) or rock exposure rate (RE), and increased with the increase of soil thickness (ST), with an amplitude more than or equal to 4.98%. With the increase of R, the surface runoff yield (SR) and runoff leakage (RL) showed an increasing trend, but the SR increased even more. This indicated that SR is more susceptible to R. Surface sediment yield (SS) showed complex changes with increasing test gradients, while sediment leakage (SL) showed a single increase (r >= 0.46, P < 0.05). Runoff and sediment leakage occurred at different VSRS, and the initial rate was greater than 0.09 Lmin(-1) or 0.02 gmin(-1). This suggested that soil and water leakage in karst areas may be widespread. Proportion of SR and SS increased with increasing R, and became the main loss pathway (>54.77 %) during heavy rainfall (120 mm/h). Prediction performance of hydrodynamic parameters for SRr was 12.25 % higher than that for surface sediment rate (SSr), and V was the best factor for SRr (R-2 > 0.84, P < 0.01). This study further enriches the theory of hydrological processes in karst rocky desertification areas, and provides important support for decision-making on soil and water conservation and ecological restoration.

Soil erosion is significantly altering the global carbon cycle, leading to considerable soil organic carbon (SOC) loss, which in turn affects carbon redistribution. However, the assessment of SOC loss in complex environments, such as karst regions, and its causal relationships with environmental factors remain underexplored. To fill it, this study proposes a novel approach for evaluating SOC loss in karst regions. This approach integrates rocky desertification factors to refine the Revised Universal Soil Loss Equation (RUSLE) for analyzing dynamic changes in soil erosion and SOC loss in karst regions. Additionally, causal inference theory is applied for the first time to construct a causal network for SOC loss, with the Tree-Augmented Naive Bayes method used for risk assessment. The findings indicate that the average SOC loss due to soil erosion over the study period was 2.16 x 1010 g C, with SOC loss closely mirroring the spatial patterns of soil erosion. The causal network revealed that rainfall exerted a significant direct causal effect on SOC loss, surpassing vegetation as the dominant factor, with its influence intensifying over time. Exposed bedrock, acting as a moderating factor, added complexity to the SOC loss process in karst regions. High SOC loss areas are mainly found in regions with abundant rainfall, dense vegetation, moderate slopes, high topographic wetness index, and high clay content. These results enhance our understanding of environmental interactions and carbon cycle responses in karst regions, providing a robust scientific basis for regional carbon sink strategies and effective management practices.

Intense land degradation had created a special vegetation-soil-rock complex structure (VCS) on karst slopes, which altered regional soil and water processes. In this study, we investigated the combined effects of heterogeneous VCS on soil erosion/leakage, rainwater transformation and hydrodynamic characteristics at the microplot scale by simulating the karst dichotomous structure slopes with steel tanks and indoor artificial rainfall. The analysis showed that the surface runoff rate decreased with the increase of VCS and the subsurface runoff rate decreased with the increase of VCS. When the rainfall intensity increased to 60-120 mm/h, there was obvious surface runoff yield on the VCS slope. When the rainfall intensity exceeded 60 mm/h, the VCS showed obvious surface sediment yield with an initial rate ranging from 0 to 4.03 gmin(-1). VCS showed obvious underground runoff and sediment yield under different rainfall intensities, and the initial rate was greater than 0.45 Lmin(-1) or 0.13 gmin(-1). This suggests that soil and water leakage from the karst rocky desertification slopes may be generalized. All the erosion flow regimes of VCS slopes were rapid laminar flow or slow laminar flow. The drag coefficient and flow shear increased with the increase of VCS, and the flow power showed a trend of increasing, then decreasing and then increasing. The water flow shear and water flow power showed a power function relationship with the sediment yield rate (R-2 >= 0.2293, P < 0.05). In terms of direct effects, hydrodynamic characteristics had the strongest influence on surface sediment yield (beta = 0.68, P < 0.05), and rock exposure rate had the strongest influence on subsurface sediment yield (beta = 0.56, P < 0.05). In terms of total effect, rainfall intensity was the dominant driver of surface/subsurface sediment yield (beta = 0.75/0.72, P < 0.05). This study provides insights into understanding the mechanism of hydraulic erosion on rocky decertified slopes and provides a theoretical basis for decision-making on soil erosion management in karst areas.

Understanding the influence and mechanism of patchy rock-vegetation-soil landscapes on soil and water loss processes is important for karst desertification hillslopes. However, due to the complexity of surface processes in karst regions, the response of runoff and sediment yields to various landscape types and configurations has not been thoroughly explored. Simulated experiments under different rainfall intensities were conducted in steel troughs that mimicked the dual hydrological structure of karst hillslopes. The study employed multiple linear hierarchical regression to quantitatively investigate the effects of 3 landscape types (rock embedding type (RP), vegetation (moss) cover type (VP), and rock-vegetation composite type (CP)) and 24 configurations on surface/underground runoff and soil loss. The results indicated that rainfall intensity exhibited a strong explanatory power for surface/underground runoff yield and soil loss rates under different landscape types (R-2 > 0.6). Significant surface and underground sediment yields were observed on karst slopes under 30-120 mm/h rainfall conditions. The three landscape types reduced surface runoff and sediment yields, increased underground runoff and exhibited non-stationary effects on underground soil loss. The responses of surface/underground runoff yield rate and soil loss rate to different landscape types and configurations varied. Under rainfall intensities ranging from 30 to 120 mm/h, the average regulation efficiency for surface/underground runoff rates by rock embedding, vegetation cover, and composite types was 0.07/-0.10, 0.23/-0.38, and 0.20/-0.26, respectively. Similarly, the average regulation efficiency for surface/underground soil loss rates was 0.09/-0.07, 0.37/0.01, and 0.36/-0.10, respectively. Vegetation cover and composite types were more effective in regulating runoff and sediment than rock embedding type. Only the mid-slope and down-slope rock configurations had a significant impact on runoff yield rate and soil loss rate. Nearly all vegetation configurations and composite configurations significantly affected surface/underground runoff yield rate and surface soil loss rate, with down-slope vegetation cover proving to be the most effective, followed by mid-slope and uniform. The regression models for surface soil loss rate incorporating the interaction terms of vegetation cover/composite types and rainfall intensity achieved R-2 values of 0.97 and 0.98, respectively. The interaction terms exhibited significant negative effects on surface soil loss rates. The interaction weakened the effect of vegetation cover /composite types on the surface soil loss rate. This study further enriches the theoretical understanding of soil and water loss on karst hillslopes and provides theoretical references for land managers to make sustainable land management decisions.

Sloping farmland constitutes the primary source of soil and water loss in Southwest China. However, research and practice on organic mulching, one of the key soil and water conservation measures, have been relatively limited in karst regions. The questions of whether there are significant differences in the effectiveness of various types for organic mulches in diminishing runoff and sediment on karst sloping farmlands, and whether the interactions between organic application rates and rainfall significantly influence runoff and sediment loss, have not been systematically addressed. Therefore, the study employs simulation experiments to investigate the influence of six application rates (0 %, 30 %, 40 %, 50 %, 60 %, and 70 %) of litter, straw, and biochar under three rainfall intensities (30, 60 and 90 mm/h) for soil and water loss in karst sloping farmlands. A regression model was used to analyze the relationships between rainfall, application rates, interaction terms, and the runoff yield rate (Rr) and sediment yield rate (Sr). The results indicated that Rr and Sr decrease with increasing application rates and increased with prolonged rainfall duration. Runoff and sediment reduction efficiencies (RRE and SRE) rose with higher application rates, and the effectiveness (p < 0.05) of the three organic mulches on Rr and Sr varied significantly. The RRE and SRE for litter were the highest (44.05 %, 81.27 %), followed by straw (34.00 %, 46.53 %), while biochar had the lowest (31.63 %, 35.11 %), and RRE consistently exceeded the SRE. Interaction terms significantly affected the Rr and Sr of litter and biochar (p < 0.05) but did not have a significant impact on straw (p > 0.05). Considering these findings and the cultivation characteristics of karst sloping farmland, and along with the availability and cost, straw is recommended for agricultural practices. This study provides a theoretical foundation and practical guidance for agronomic tillage practices and soil loss control in karst sloping farmlands.

Extreme precipitation is a crucial trigger for soil erosion events in karst regions. However, the existence of a scale effect in suspended sediment characteristics of karst basins and which extreme precipitation variables control this effect remain unclear. To investigate this, we analyzed the scale effect on suspended sediment characteristics using monthly hydrological data from five karst basins of varying scales, consistently monitored from 2012 to 2019. We aimed to clarify the contribution of extreme precipitation to suspended sediment and identify the dominant influencing factors. The results showed a significant negative exponential correlation between basin scale and sediment transport rate (STR). The phenomenon occurs due to two main reasons, first, the increased sediment transit distances with growing basin dimensions, leading to higher sedimentation; second, the unique dual hydrological structure of karst landscapes, which enhances subterranean leakage and further sedimentation. Furthermore, extreme precipitation was found played a crucial role in explaining STR variability, explaining approximately 56 % to 78 % of the observed variance in the five karst basins. Simultaneously, the dominant extreme precipitation factors affecting suspended sediment variability varied with basin scale. Specifically, heavy precipitation days, consecutive wet days, the rainstorm amounts and rainstorm days were identified as the main determinants. These variations are mainly attributed to the watershed's sensitivity to extreme precipitation events and its intrinsic attributes, including dual pathways, land use patterns, and geomorphological types, etc. This study provides theoretical insights into the increasing soil erosion caused by extreme precipitation in karst basins with different scales.

Global climate change has profoundly influenced atmospheric circulation systems, with frequent heavy rainfall events crucial in determining long‐term hydrological trends. However, the specific mechanisms by which atmospheric circulation regulates rainfall variability and subsequently affects river streamflow remain inconclusive, particularly in ecologically fragile and geomorphologically complex karst regions. This study examines a typical karst basin to analyze hydrological variations from 1965 to 2021 and explores the driving mechanisms of large‐scale atmospheric circulation on rainfall and streamflow dynamics. The results indicate that, over the past half‐century, total annual rainfall in the Shibantang Catchment has declined while extreme precipitation indices have increased. Consequently, although the long‐term average discharge has decreased, the proportion of flood‐season discharge has risen. Rainfall variations driven by atmospheric circulation explained 22.3%–76.9% of streamflow fluctuations. The dominant factors influencing streamflow have shifted across different historical periods: human activities had a more significant impact in the late 20th century, whereas climate change has become the primary driver in the 21st century. Furthermore, our findings reveal a strong correlation between climate change in karst regions and the contraction of the Asian polar vortex and its northward displacement. This suggests that atmospheric circulation influences streamflow evolution trends by regulating climate variability. From a global atmospheric circulation perspective, this study elucidates the hydrological variation mechanisms in heterogeneous karst basin, advances karst hydrology theory, and provides scientific support for water resource management and extreme weather adaptation.

Forest parks are vital terrestrial ecosystems that provide multiple ecosystem services (ESs) to both society and nature, including carbon storage, water conservation, soil retention, and tourism-related cultural services. These services are essential for maintaining ecological security and supporting socio-economic development. However, little is known about how ESs vary across forest parks situated in different karst landforms, and integrated re-search on the combined effects of climate, vegetation, karst surface characteristics, and tourism remains limited. In this study, we examine forest parks in Guizhou Province, China, selecting four key ESs—water conservation, soil retention, carbon storage, and cultural services associated with tourism—and evaluate their levels through a comprehensive ecosystem services index (CES). We apply a structural equation model (PLS-SEM) to disentangle how climate, vegetation, karst surface features, and tourism activities drive spatial heterogeneity in CES. The results reveal significant differences among karst land-form units: carbon storage is relatively low in karst plateaus and gorges, whereas water conservation is highest in non-karst areas. Together, the four categories of driving factors explain 71.6–74.2% of the variance in CES, with climate emerging as the dominant contributor to spatial variation. For individual services, the principal drivers differ: normalized difference vegetation index (NDVI) and tourist numbers are jointly shaped by karst surface characteristics and climate, while multi-year average spring precipitation is the most influential factor across forest parks. This study provides new evidence of the socio-ecological mechanisms regulating ESs in karst mountain forestscapes and offers a scientific reference for enhancing and regeneratively managing ecosystem services in these fragile regions.

Palladium (Pd) catalysts are promising for electrochemical reduction of CO2 to CO but often can be deactivated by poisoning owing to the strong affinity of *CO on Pd sites. Theoretical investigations reveal that different configurations of *CO endow specific adsorption energies, thereby dictating the final performances. Here, a regulatory strategy toward *CO absorption configurations is proposed to alleviate CO poisoning by simultaneously incorporating Cu and Zn atoms into ultrathin Pd nanosheets (NSs). As-prepared PdCuZn NSs can catalyze CO production at a wide potential window (-0.28 to -0.78 V vs RHE) and achieve a maximum FECO of 96% at -0.35 V. Impressively, it exhibits stable CO production of 100 h under similar to 95% FECO with no decay. Combined results from X-ray analysis, in situ spectroscopy, and theoretical simulations suggest that the codoping strategy not only optimizes the electronic structure of Pd but also weakens the binding strengths of *CO and increases the proportion of weak-binding linear *CO absorption configuration on catalysts' surfaces. Such targeted adoption of weakly bound configurations abates the energy barrier of *CO desorption and facilitates CO production. This work confers a useful design tactic toward Pd-based electrocatalysts, codoping for steering adsorption configuration to achieve highly selective and stable CO2-to-CO conversion.

In the process of urbanization, human activities have caused significant changes in land use, posing serious threats to ecosystems. Issues such as habitat fragmentation and reduced structural connectivity hinder regional sustainability. The vulnerability of karst areas exacerbates these impacts. Effectively managing the human-environment relationship in karst regions is crucial for maintaining ecological security, currently a focal point of research. Scientific prediction and rational construction of future ecological networks are key to enhancing regional ecological security. Taking Guizhou Province, the central area of southern Chinese karst, as an example, this study utilizes CA-Markov modeling to forecast future (by 2030) land use conditions. On this basis, we constructed the ecological network of Guizhou Province from the perspectives of morphology, habitat quality analysis, and integration. We compared the differences between the networks generated from different perspectives. Finally, we delineated priority protection areas and proposed corresponding protection recommendations. Results indicate an increasing trend in arable land, water bodies, and urban residential land by 2030, with arable land showing the largest change, increasing by 2.79 %, primarily due to conversions from forest land, grassland, and urban land. Using habitat quality, 254 source points are selected, while 191 are selected using MSPA, with an overlap of 106 source points. In highly urbanized areas, source points are predominantly located on administrative boundaries. Corridor construction results indicate variations in certain characteristics between different perspectives but generally show an eastern bias. Corridors overlapped across the three perspectives total 23,578 km. In regions characterized by high human activity in central and western areas, networks constructed based on habitat quality exhibit a more fragmented and isolated spatial pattern compared to those based on morphological criteria. Based on these findings, priority ecological restoration areas are categorized into ecological protection, restoration, and auxiliary regeneration areas, each with corresponding restoration recommendations. This research contributes to understanding the future ecological security patterns in karst regions, providing a scientific basis for biodiversity conservation and ecological environment security in karst areas.

Investigating land cover patterns, changes in carbon stocks, and forecasting future conditions are essential for formulating regional sustainable development strategies and enhancing ecological and environmental quality. This study centers on Guiyang, a mountainous urban area in southwestern China, to analyze the dynamic changes in land cover and their effects on carbon stocks from 2000 to 2035. A carbon stocks assessment framework was developed using a cellular automaton-based artificial neural network model (CA-ANN), the InVEST model, and the geographical detector model to predict future land cover changes and identify the primary drivers of variations in carbon stocks. The results indicate that (1) from 2000 to 2020, impervious surfaces expanded significantly, increasing by 199.73 km2. Compared to 2020, impervious surfaces are projected to increase by 1.06 km2, 13.54 km2, and 34.97 km2 in 2025, 2030, and 2035, respectively, leading to further reductions in grassland and forest areas. (2) Over time, carbon stocks in Guiyang exhibited a general decreasing trend; spatially, carbon stocks were higher in the western and northern regions and lower in the central and southern regions. (3) The level of greenness, measured by the normalized vegetation index (NDVI), significantly influenced the spatial variation of carbon stocks in Guiyang. Changes in carbon stocks resulted from the combined effects of multiple factors, with the annual average temperature and NDVI being the most influential. These findings provide a scientific basis for advancing low-carbon development and constructing an ecological civilization in Guiyang.

Incorporating Ecosystem Service Value (ESV) into land use planning provides a fresh perspective for informed land management decisions. ESV, influenced by socio-economic and natural factors, has complex driving mechanisms, particularly in China's southwestern karst regions. Studying mediating variables helps elucidate these mechanisms. Further research into ecosystem services interactions and effective land use policies in karst areas is needed. This study evaluates the ESV of Guizhou Province, located in southern China's karst region, using the benefit transfer approach. Combining the Guizhou Provincial Land Use Planning Outline (2006-2020) with the multi-objective programming (MOP) model optimized by genetic algorithm and the patch-generating land use simulation (PLUS) model, four future development scenarios were designed. The response of ESV to land use and land cover (LULC) changes at the county scale under four different development scenarios from 2000 to 2020 and in the future was analyzed. A partial least squares structural equation model (PLS-SEM) was used to decouple the driving mechanism affecting ESV. The results show that over the past two decades, with the implementation of various ecological restoration projects, the total ESV has increased. The ESV for natural development scenarios, ecological conservation scenarios, economic development scenarios, and sustainable development scenarios are CNY 238.278 billion, CNY 400.514 billion, CNY 283.201 billion, and CNY 323.615 billion, respectively. The direct impacts of karst surface characteristic factors (KSCF), meteorological factors (MF), socio-economic factors (SEF) and transportation location factors (TLF) on ESV are positive (0.098), negative (-0.098), positive (0.336), and positive (0.109) respectively. The total effect of KSCF on ESV through influencing socio-economic factors and LULC is (-0.738), with SEF playing a complete mediating role. MF indirectly affect ESV by influencing LULC, with LULC playing a complete mediating role in this process. The PLSSEM model shows that under the dominant position of LULC, the interaction between natural environmental factors and socio-economic factors on ESV is very complex. This study offers valuable insights that can guide managers in this region, as well as in other karst regions globally, in the development of sustainable land use policies.

Climate factors and changes in landscape patterns are often recognized as the primary drivers of soil conservation services. The influence mechanism of climate factors and landscape patterns on soil conservation service is scale-dependent and spatial heterogeneous. However, it is not clear whether small watershed scale is more conducive to soil erosion control than large scale such as county scale and township scale. For the purpose of creating land use development plans that take local conditions into account, it is crucial to clarify the effects of climate and landscape pattern factors on soil conservation change. Wujiang River basin (WRB), a typical karst basin located in the catchment of the largest first-level tributary on the upper Yangtze River in China, was used as the study area in this research. Soil conservation services provided by water erosion control (SPC) in WRB from 2005 to 2020 were evaluated using the RUSLE model based on the modified rock exposure rate. By using stepwise regression model and multi-scale geographically weighted regression model (MGWR), the spatial heterogeneity of the influence of different driving factors on soil conservation service was comprehensively studied at the scale of district, township and small watershed. The results show that the SPC fluctuates obviously, but the trend is not significant. Climate factor is the dominant factor affecting SPC. With the change of scale from large to small, the adjusted R2 of the regression model gradually increases, especially the factors related to landscape pattern, and more driving factors can be revealed more comprehensively and effectively. Therefore, the small watershed scale is the best control unit to improve the SPC when formulating the regional management landscape plan. The findings of this research also have benchmark significance for other ecological fragile areas, and can provide more comprehensive suggestions for local ecosystem management and landscape planning.

The source and transport processes of suspended sediment are issues that require further study. The complex relationship between the integrated surface characteristics and the mechanisms of sediment sources and transport in heterogeneous karst watersheds remains unclear. This study proposes a comprehensive assessment framework for sediment sources that combines the surface characteristics of karst watersheds, such as exposed rock and shallow topsoil in karst areas. Additionally, the Karst Surface Characteristic Index (KSCI) is developed to evaluate the potential supply capacity of sediment in karst watersheds. The hysteresis index (HImid) is calculated using a long series of hydrological data to study runoff and sediment relationships in eight watersheds in the karst region of southern China. Results indicated that plan curvature, terrain relief, NDVI, and rock exposure contributed most to KSCI, with these four factors contributing 65%. The Q -SSC hysteresis analysis results based on 445 hydrological events showed that a clockwise hysteresis pattern was the most frequent and efficient pattern of sediment transport in the studied watershed (clockwise hysteresis pattern accounted for 72.3% of 445 hydrological events) owing to the limited sediment supply in the karst watersheds. The quantitative analysis results of HImid and KSCI showed that HImid was closely related to KSCI. With an increase in KSCI, a clockwise hysteresis pattern was more likely to appear, indicating that watershed characteristics exerted a significant influence on sediment transport velocity and efficiency. In terms of spatial distribution, near the outlet of the watershed or the river channel, high KSCI values were distributed, and clockwise hysteresis was more likely to occur. In contrast, at the far end of the watershed outlet or the river channel, high values of KSCI were distributed, and anticlockwise hysteresis was more likely to occur. Our findings further enrich the theory of soil erosion and the runoff -sediment relationship at the watershed scale in karst areas, and serve as valuable decisionmaking references for integrated water and soil sources management.

The medium-intensity karst desertification environment is typically characterized by more rocks and less soil. The abandoned land in the construction areas of the dry-hot river valley hydropower station has more infertile soil, severe land degradation, and very low land productivity. Therefore, it is urgent to improve the soil quality to curb the increasingly degrading land and reuse the construction site. Few studies have focused on the effect of soil restoration and comprehensive evaluation of soil quality with multi-treatment in abandoned land in the dry-hot valley hydropower station construction area. Here, 9 soil restoration measures and 1 control group were installed at the Guangzhao Hydropower Station construction in Guizhou Province, China, for physical and chemical property analysis. In total, 180 physical and 90 chemical soil samples were collected on three occasions in May, August, and December 2022. Soil fertility and quality were evaluated under various measures using membership functions and principal component analysis (PCA). This study showed that almost all measures could enhance soil water storage capacity (The average total soil porosity of 9 soil treatments was 57.56%, while that of the control group was 56.37%). With the increase in soil porosity, soil evaporation became stronger, and soil water content decreased. Nevertheless, no decrease in soil water content was observed in the presence of vegetation cover (soil water content: 16.46% of hairy vetch, 13.99% of clover, 13.77% of the control). They also proved that manure, synthetic fertilizer, and straw could promote total and available nutrients (Soil total nutrient content, or the total content of TN、TP、TK,was presented as: synthetic fertilizer (11.039g kg-2)>fowl manure (10.953g kg-2)>maize straw (10.560g kg-2)>control (9.580g kg-2);Total available nutrient content in soil, or the total content of AN,AP,A,was shown as:fowl manure (1287.670 mg kg-1)>synthetic fertilizer (925.889 mg kg-1)>sheep manure (825.979 mg kg-1)>control (445.486 mg kg-1). They could also promote soil fertility, among which the first two reached the higher comprehensive soil quality. Fertilizer was conducive to improve soil quality and fertility, yet long-term application could cause land degradation like soil non-point source pollution, compaction, and land productivity decline. Ultimately, combining fertilizer with biochar or manure is recommended to improve soil fertility. Biochar and green manure could play an apparent role in soil improvement only when there is abundant soil water. The above views provide theoretical support for curbing soil degradation, improving soil fertility and quality, enhancing land productivity, and promoting the virtuous cycle of the soil ecosystem.

A thorough understanding of the complex response of hydrologic processes to latent factors is of great significance for regional soil erosion and water resources management. However, what kind of mediation effect exists between hydrologic processes and latent factors is not yet clear, especially in heterogeneous karst regions. In this study, the elasticity coefficient method and partial least squares structural equation modelling (PLS-SEM) were used to investigate the mechanism of latent factors on hydrologic processes in karst basins and to explore the mediation effect between latent factors and hydrologic processes. The results show that the runoff of Yeji River Basin decreased during 1997-2004, but increased or stabilized since 2005. On the monthly scale, the runoff in July and December showed an 'inverted V-shaped' change. Both elasticity coefficient method and PLS-SEM showed that climate change contributed the most to runoff (direct effect accounted for 37.94% similar to 61.41%). In PLS-SEM, the total effect sizes of latent factors on runoff were as follows: climate change (0.751 similar to 0.963) > vegetation (0.296 similar to 0.740) > karst characteristics factors (KCF) (-0.454 similar to -0.563) > human activities (-0.036 similar to -0.528) > land use and cover change (LUCC) (-0.036 similar to -0.205). In the typical karst basin, two mediation pathways have been determined: human activities-vegetation/LUCC-runoff, where vegetation and LUCC had a mediation effect of relationships between human activities and runoff; climate change-KCF-runoff, where KCF had a mediation effect of relationships between climate change and runoff. Moreover, PLS-SEM is a preferred method to decouple the complex responses of hydrologic processes in heterogeneous karst basins to climate change and human activities than the elasticity coefficient method. This study conducted further research and exploration on the mechanism of hydrologic processes in heterogeneous karst basins, and provided valuable theoretical references for grassroots water managers to cope with water resources management under the context of future climate change.

Increasingly frequent extreme rainfall as a result of climate change is strongly damaging the global soil and water environment. However, few studies have focused on daily extreme sediment events (DESE) in heterogeneous karst watersheds based on long-term in -situ observations. This study quantitatively assessed the time effect of DESE on rainfall response, decoupled the impact of environmental factors on DESE by using structural equation modelling, and finally explored the modelling scheme of DESE based on the hybrid model. The results showed that DESE had the highest frequency of occurrence in May -July, with dispersed distribution in the value domain. Rainfall with a time lag of 1 day and a time accumulation of 2 or 3 days was an important contribution to DESE ( P < 0.01, R = 0.47 -0.68). Combined effects of environmental factors explained 53.6 % -64.1 % of the variation in DESE. Runoff and vegetation exerted the strongest direct and indirect effects on DESE, respectively (8 = 0.66/ -0.727). Vegetation was the dominant driver of DESE in Dabanghe and Yejihe (8 = -0.725/-0.758), while the dominant driver in Tongzhihe was climate (8 = 0.743). In the future, the risk of extreme sediments should be prevented and resolved through the comprehensive regulation of multiple paths, such as runoff and vegetation. Hybrid models significantly improved the modelling performance of machine learning models. Generalized additive model -Extreme gradient boost had the best performance, while Partial least squares regression -Extreme gradient boost was the most valuable when considering performance and input data cost. Two methods can be used as recommended solutions for DESE modelling. This study provides new and in-depth insights into DESE in

[Objective] The soil erosion issue is very prominent in the karst region of southwest China and significantly affects the sustainable development of the regional economy. However, it is currently not very clear how the characteristic environmental factors of karst basins affect the direct driving force of soil erosion and runoff erosivity. [Methods] Taking the Yeji River Basin in the karst region of southwest China as an example and basing on the long-term and high-frequency field measurement data at the outlet hydrological station of the basin, the spatiotemporal change characteristics of runoff erosivity from 2005 to 2020 were evaluated and the influence of main karst environmental factors on runoff erosivity was analyzed by the Soil and Water Assessment Tool (SWAT) and the Partial Least Squares Model (PLSR). [Results] The average annual runoff erosivity was 2 326.47 m4/(km2·s), with strong spatial heterogeneity. In 2005, the high runoff erosivity was mainly distributed in the northern and central parts of the basin. During 2010—2020, the high runoff erosivity area gradually shifted to the central and southern parts of the basin. In terms of time, benefiting from the implementation of ecological restoration projects such as comprehensive control of soil and water loss in sloping farmland and comprehensive control of rocky desertification since the 11th Five-Year Plan, the runoff erosivity of the Yeji River Basin had been generally decreasing year by year. Lithology, exposed bedrock, and slope were the dominant control factors, which jointly explained 57.7% of the spatiotemporal variation of runoff erosivity in the Yeji River Basin. [Conclusion] These results can provide a theoretical reference for the comprehensive control of soil erosion in karst basins and help to formulate more precise and effective policies and measures to improve the ecological environment of the karst area and promote the sustainable development of the region.

Soil erosion is a prominent environmental problem in karst regions.Exploring the spatiotemporal variability of soil erosion and the factors that influence soil erosion is of great significance for regional soil erosion prevention and control.However,the mechanisms influencing the characteristic features of the karst basins,such as bedrock exposure and lithology,still need to be further explored.This study used GIS technology,the Revised Universal Soil Loss Equation model,Getis-Ord Gi*,and partial least squares regression(PLSR)to identify the dominant factors influencing soil erosion and the spatiotemporal variability of soil erosion in 31 sub-basins of the Dabang River Basin(DRB),a typical karst area of Southwest China,from 2010 to 2020.The results indicated that soil erosion in the DRB from 2010 to 2020 was generally decreasing,the mean soil erosion in the DRB in 2010,2015 and 2020 was 18.46,16.51 and 15.29 t ha-1 a1,respectively.During the study period,the area of slight erosion increased by 26.39％(706.54 km2),while severe erosion enlarged by 26.36 km2.Spatially,the DRB was primarily affected by medium and slight soil erosion.The hot spot areas of soil erosion(key control areas)were mainly concentrated in the central and southern parts of the basin,decreasing each year,and the area of soil erosion hot pots has decreased from 43.22％to 20.60％.PLSR decoupling results show that elevation,bedrock exposure,land use type,interbedded limestone and clastic rock,and vegetation coverage were identified as the key variables affecting soil erosion,explaining 52.8％of soil erosion variability,with a high value of the Variable Importance on Projection(VIP)more than 1.These results can be used as a reference for comprehensive control of soil erosion and water loss in the basin.