1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation; Northwest A&F University, No. 26 Xinong Road; Yangling 712100 China
2. College of Hydraulic & Environment Engineering; China Three Gorges University, No. 8 Daxue Road; Yichang 443002 China
3. Institute of Soil and Water Conservation of Chinese Academy of Sciences and Ministry of Water Resources, No. 26 Xinong Road; Yangling 712100 China
4. Agricultural Research Council; Institute for Soil, Climate & Water, Private Bag X79; Pretoria 0001 South Africa
5. USDA-ARS; Grazinglands Research Laboratory, 7207 West Cheyenne Street; El Reno OK 73036 USA