Effects of slope forest and grass vegetation on reducing rainfall-runoff erosivity in Three Gorges Reservoir Region

The study on the relationship between biological regulating measures and soil and water losses, is of great significance to the soil and water conservation and the ecological reconstruction of the environment in Three Gorges Reservoir Area. Seven standard runoff plots were built on the seven natural slopes with different biological regulating measures for observing the runoff and sediment yield produced under these slope biological regulating measures (Koelreuteria bipinnata + Cassia suffruticasa, traditional planting, hedgerows, closed forest, natural restoration, economic forest and control plot). The results showed that the treatments of biological regulating measures affected runoff and sediment generation significantly. Runoff and sediment yield reduced rapidly with the biological regulating measures, the values in control plot were higher, but lower in Koelreuteria bipinnata + Cassia suffruticasa plot and hedgerows plot. Runoff erosion power was positively related with sediment yield. It was suggested that runoff erosion power can be used to better simulate erosion dynamics. The presentation of the effect of different biological regulating measures on erosion by the ratio of runoff erosion power/erosion volume reflects the existence of critical biological regulating measures, which can be used to evaluate regulatory effects of biological regulating measures on soil erosion dynamics.