1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation; Northwest A&F University; Yangling Shaanxi 712100 PR China
2. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau; Institute of Soil and Water Conservation, Chinese Academy of Sciences, Ministry of Water Resources; Yangling Shaanxi 712100 PR China
3. College of Environmental Science and Technology; Hunan University; Changsha 410082 PR China
4. Oregon State University Agriculture Program at Eastern Oregon University; Oregon State University; La Grande OR USA