Effects of rainfall and rocky desertification on soil erosion in karst area of Southwest China

Monitoring and evaluating the evolution of rocky desertification timely and studying the characteristics of soil erosion under different rainfall patterns are of great scientific significance for regional soil and water conservation, rocky desertification control and ecological environment construction. Four periods of remote sensing image data from 2005 to 2020 were selected to study the evolution characteristics of rocky desertification and its impact on soil erosion in the controlled boundary area of Shibantang hydrological station of Yeji River Watershed, Guizhou Province, China. According to the 408 erosive rainfall events, the soil erosion under different rainfall patterns in the watershed was analyzed. The results showed that: erosive rainfall events in the study area were mainly pattern A, accounting for 57.4% of the total rainfall events; the second was pattern B, accounting for 28.9% of the total rainfall events; the rainfall pattern of C occurred occasionally. Among them, pattern A was the main rainfall pattern leading to soil and water loss and had the largest contribution rate to soil erosion in the watershed. From 2005 to 2020, the area of rocky desertification showed a decreasing trend, accounting for 72.2% from 87.9%. Spatially, rocky desertification has mainly concentrated in the middle south of the watershed since 2010, while the rocky desertification mainly concentrated in the middle and north before 2010. The effects of different grades of rocky desertification on soil erosion were different, and the soil erosion modulus in areas with the medium, severe and extremely severe rocky desertification was generally small. The soil erosion modulus estimated by the RUSLE (Revised Universal Soil Loss Equation) model was still much higher than that calculated by the data measured by the hydrological monitoring station. Therefore, the application of the RUSLE model in karst area needs to be further modified. These results can provide reference for rocky desertification control, soil erosion control and fragile ecosystem restoration in karst area.