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 China
2. Institute of Soil and Water Conservation; Chinese Academy of Sciences and Ministry of Water Resources; Yangling Shaanxi 712100 China
3. School of Geography and Tourism; Shaanxi Normal University; Xi'an Shaanxi 710119 China
4. National Demonstration Center for Experimental Geography Education; Shaanxi Normal University; Xi'an Shaanxi 710119 China