1. College of Natural Resources and Environment, Northwest A&F University, Yangling, Shannxi 712100, China
2. Institute of Soil and Water Conservation, Northwest A&F University, 712100, Yangling, China
3. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conversion, Northwest A&F University, 712100, Yangling, China