Rainfall Predominantly Governs Soil Organic Carbon Loss, Exceeding the Contribution of Vegetation Carbon Sequestration in Karst Watersheds

ABSTRACT 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 × 10 10 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.