1. State Key Lab. of Soil Erosion and Dryland Farming on the Loess Plateau; Institute of Soil and Water Conservation CAS & MWR; Yangling Shaanxi 712100 PR China
2. Univ. of Chinese Academy of Sciences; Beijing 100049 PR China
3. Institute of Soil and Water Conservation Northwest A&F Univ.; Yangling Shaanxi 712100 PR China
4. College of Resources and Environment Northwest A&F Univ.; Yangling Shaanxi 712100 PR China