Spatial–Temporal Evolution of Soil Erosion in a Typical Mountainous Karst Basin in SW China, Based on GIS and RUSLE

In this study, we address the characteristics of the spatial and temporal evolution of soil erosion in karstic mountainous area of Houzhai River Basin of southwest China. The study uses GIS, erodibility test results, actual surveys of soil types, a revised universal soil loss equation for estimating soil erosion in 1973, 1990, 2002, and 2013, and an analysis of the spatial and temporal distribution of the evolution law of soil erosion for almost 40 years. Results show the following: (1) The soil erosion modulus of the Houzhai River Basin exhibits a decrease from 222.72 t km−2 year−1 in 1973 to 103.82 t km−2 year−1 in 2013. (2) The intensity level of soil erosion changes across space. The most active area is mainly concentrated in the upstream peak cluster depression. Areas with a slope of 8°–25° account for 40.81 % of the total erosion contribution rate, indicating that these are the main areas where erosion occurs. (3) The global and universal classification standard of soil erosion shows that the Houzhai River Basin areas above 65 % do not undergo micro-erosion. The rocky desertification is a serious problem, which explains why grading standard soil erosion intensity is inapplicable to karst areas. (4) The average soil erosion modulus in the basin is generally low (i.e., below 1000 t km−2 year−1), which indicates strong karstification in the karst areas. This process can occur through subsurface pores, fissures, holes, and underground leakage phenomena, which underestimate the amount of soil erosion in the karst areas. A comprehensive analysis of a long time series reveals that soil erosion in the karst areas is a complex process which requires further detailed studies.