Response of Soil Erosion to Climate and Subsequent Vegetation Changes in a High-Mountain Basin

Abstract

Soil erosion is one of the global threats to the environment. Further, climate and vegetation changes have pronounced effects on soil erosion in high-mountain areas. In this study, the revised universal soil loss equation (RUSLE) was improved by developing a method for calculating snowmelt runoff erosivity based on a simulated snowmelt runoff and the observed sediment load, using which the soil erosion rate in the upper Heihe River Basin (UHRB) was calculated. The proposed approach provides an effective method for estimating the soil erosion rate and identifying the causes for its change in high-mountain areas. The normalized difference vegetation index (NDVI) was significantly and positively correlated with both precipitation and temperature in the region and exhibited a significant increasing trend. The increase in NDVI led to a decrease in the soil erosion rate (for the annual, rainfall, and snowmelt periods), although erosive rainfall and snowmelt runoff showed increasing trends, indicating the dominating impact of vegetation cover on soil erosion. The average soil erosion rate of UHRB was 806.2 t km−2 a−1 from 1982 to 2015. On average, soil erosion during rainfall and snowmelt periods contributed to 90.67% and 9.33% of annual soil erosion, respectively. However, the resultant soil erosion rate caused by 1 mm of snowmelt runoff was about 1.9 times that caused by 1 mm erosive rainfall. Soil erosion during the snowmelt period was particularly sensitive to temperature and showed consistent responses to climate and vegetation changes in UHRB and its two tributaries. An increasing NDVI promoted by climate change and anthropogenic factors played a major role in alleviating soil erosion, and the warming exerted intense impacts on soil erosion during the snowmelt period. These findings would be helpful for proposing effective measures for soil conservation in high-mountain areas under climate and vegetation changes.