Impacts of forest restoration on soil erosion in the Three Gorges Reservoir area, China.

Vegetation recovery is a promising strategy to mitigate soil loss risk across different landscapes and human disturbance levels. Uncertainties still exist in the impacts of forest restoration on soil erosion with respect to complicated terrain condition and land-use/cover pattern, especially in mountainous reservoir areas undergoing intensive human activities. Here, we assess the effects of forest restoration on controlling soil erosion in the Three Gorges Reservoir area (TGRA), China. The Revised Universal Soil Loss Equation and time-series data were used to estimate soil erosion and its changes in 2001-2015. The slope of soil erosion at a pixel level was estimated to determine the responses of soil erosion to forest restoration. The results indicate that the conversion of cropland to forest was the dominated land use/cover transformation process in the TGRA from 2001 to 2015. The mean annual soil erosion rate in the TGRA decreased, with an annual drop rate of 1.28%. Changes in the soil erosion rate presented significant spatial variations, with a significant decrease (1.09 t∙ha-1∙yr-1) in the terrain slope zones between 25° and 35°, where intensive forest restoration occurred. Within various land transformation processes, the slope of the mean soil loss rate was the highest (slope = 0.71, P < 0.01) in afforestation areas. Our findings reveal that forest restoration can effectively reduce soil erosion in mountainous reservoir areas, but there are significant variations in the various vegetation recovery processes with the time-lag effect and across elevational gradient. Although most forest restorations occurred in steep slope areas, slope steepness is still the dominated factor in the spatial variation of soil erosion in the TGRA. We suggest forest landscape restoration to fill the scale gap between soil erosion and forest restoration in hilly reservoir areas such as the TGRA.