1. Institute of Soil and Water Conservation, Chinese Academy of Sciences Yangling Shaanxi 712100 China
2. Univ. of Chinese Academy of Sciences Beijing 100049 China
3. Institute of Soil and Water Conservation, Northwest Univ. of Agriculture and Forestry Yangling Shaanxi 712100 China
4. State Key Lab. of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation Northwest Univ. of Agriculture and Forestry Yangling Shaanxi 712100 China
5. College of Natural Resource and Environment Northwest Univ. of Agriculture and Forestry Yangling Shaanxi 712100 China