1. School of Geography and Tourism, Shaanxi Normal University, Xi’an, China
2. National Demonstration Center for Experimental Geography Education, Shaanxi Normal University, Xi’an, China
3. Institute of Surface-Earth System Science, Tianjin University, Tianjin, China
4. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, College of Natural Resources and Environment, Northwest A&F University, Yangling, China