Frontier Theories and Practice of the Soil Underground Loss in Karst Areas

Soil underground loss (SUL) is a distinctive erosion process in karst regions, where soil infiltrates into underground conduits through bedrock fissures, posing a severe threat to land resources. This paper reviews the frontier theories and practice of SUL, clarifying its mechanisms driven by soil properties, geomorphological settings, hydrological constraints, and human disturbances such as vegetation destruction and land cultivation. Conceptually, SUL has evolved from a slope-scale subsurface process to a catchment-scale surface–underground continuum, necessitating an integrated definition. Current estimates of SUL’s contribution to total soil erosion vary widely due to methodological and scale discrepancies. Among influencing factors, slope gradient and rainfall intensity consistently emerge as dominant drivers, while fissure degree and rock exposure rate show context-specific effects, highlighting the complexity of factor interactions. Future research should prioritize integrating field tracing with simulation experiments, establishing long-term observation networks, developing process-based models embedding epikarst conduit geometry, and translating findings into targeted mitigation measures. Advancing these directions will provide robust support for rocky desertification control and sustainable land management in karst regions globally.