Soil erosion resistance of "Grain for Green" vegetation types under extreme rainfall conditions on the Loess Plateau, China

Objectives: Soil erosion, which is pronounced on the Loess Plateau of China, is generally caused by heavy rain or thunderstorms. To control soil and water losses and improve the eco-environmental condition of the Loess Plateau, the Chinese Central Government issued the "Grain for Green (GFG)" policy in 1999 to restore vegetation on previously farmed steep lands. This study will explore the value of the "GFG" policy by examining the response of three different "GFG" vegetation types (grassland, woodland and orchard) in controlling erosion from an extreme rainfall event in the Northern Shaanxi Province on the Loess Plateau of China. Methods: The vegetation types, coverage, biological soil crust (BSC) coverage, plant species diversity, slope gradient, gully erosion of different "GFG" vegetation types under extreme rainstorm conditions (called "727" rainstorm) were assessed using field surveys. Results: It was found that the grassland and woodland are more effective at reducing gully erosion than orchards, and compared with the sloping farmland, the conversion of sloping farmland to grassland or woodland can reduce gully erosion by more than 90%, whereas conversion of sloping farmland to orchards actually increases gully erosion by more than 60%. Furthermore, having a high surface vegetation cover and well-developed BSC were the most important factors in reducing soil erosion. Conclusions: The "GFG" measures are beneficial in reducing soil erosion on the Loess Plateau, and rehabilitation efforts should focus on grassland and/or woodlands rather than attempting to achieve dual goals with economic gain (i.e., from orchard crops), as it appears that orchards are not conducive for controlling soil erosion