Threshold effects of vegetation coverage on soil erosion control in small watersheds of the red soil hilly region in China

Vegetation restoration has long been considered as an effective strategy for soil conservation in many hilly regions, which can lead to a significant increase in vegetation coverage. The aim of this paper was to quantify the effect of changes in vegetation coverage on soil erosion control in the red soil hilly region of China. Based on a literature review, a database was collected from 35 typical small watersheds. The database covered extensive geographical locations, including 6 provinces and 1 autonomous region of China, with vegetation coverage ranging from 8% to 96%, and the soil erosion modulus ranging from 67 to 13,000 t.km(-2).a(-1). The results confirmed that vegetation coverage significantly and positively affected soil loss. It also indicated that there is a threshold phenomenon between vegetation coverage and soil loss. The vegetation coverage in the small watersheds could be divided into three threshold zones: the lower threshold (0-40%), the transition zone (40-80%), and the upper threshold (80-100%). In these zones, the vegetation soil conservation efficiency and its changing rates were unlike. Thus, different vegetation restoration strategies should be adopted in these zones. In the lower threshold, it is suitable to adopt artificial restoration; in the upper threshold, natural recovery is more reasonable; and in the transition zone, combination of artificial and natural restoration is preferable. This study revealed the vegetation coverage threshold values and the corresponding restoration strategies with respect to soil erosion control at the region scale, which serve as a scientific basis for decision makers.