1. Postgraduate Candidate, Key Laboratory of Agricultural Soil and Water Engineering of Ministry of Education in Arid Areas, Northwest A&F Univ., Yangling 712100, China.
2. Associate Professor, State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F Univ., Yangling 712100, China; Key Laboratory of Agricultural Soil and Water Engineering of Ministry of Education in Arid Areas, Northwest A&F Univ., Yangling 712100, China (corresponding author).