Model-based assessment soil loss by wind and water erosion in China's Loess Plateau: Dynamic change, conservation effectiveness, and strategies for sustainable restoration

摘要

Soil erosion is a widespread environmental problem that threatens environmental sustainability. The Loess Plateau (LP) in China is one of the most severely eroded areas in the world. In this study, the soil erosion dynamics were assessed by applying the Revised Universal Soil Loss Equation and the Revised Wind Erosion Equation; further, the underlying drivers for soil erosion processes were investigated. In addition, implications of constraint effects in soil erosion control were discussed. The results showed that there was a substantial reduction in both wind and water erosion between 2000 and 2015; it is considered that vegetation restoration (mainly in relation to government-aided ecological restoration programs), increased precipitation, and a decrease in wind speed may have contributed to these trends. Land cover and soil properties contribute to spatial patterns of soil erosion. Thus, ecological restoration programs have promoted improvements in soil properties, leading to an eventual reduction. Constraint line analysis indicates that vegetation cover has a nonlinear and threshold effect on soil erosion through constraining the water condition (i.e., rainfall). With respect to water erosion, when rainfall is below the threshold (approximately 450–500 mm), it is not sufficient to maintain a good vegetation cover (about 30–40%), and vegetation cannot efficiently prevent soil erosion; however, once rainfall exceeds the threshold, the soil retention function of the vegetation is enhanced and soil loss is substantially reduced. In addition, there is a lower (10%) and an upper (40%) threshold at which vegetation can control wind erosion, which implies that plant cover lower than 10% has a minimal effect on reducing the wind velocity at the soil surface, and the effect of vegetation on reducing wind erosion is at its maximum when plant cover is 40% or above. However, if human intervention is removed, the limited amount of rainfall on the LP would be insufficient to support large areas of trees in the long-term; therefore, the constraint effects of the water condition on vegetation cover need to be considered to improve the efficiency of afforestation and reforestation efforts aimed at mitigating and preventing soil loss.