1. College of Resources and Environment; Northwest A&F University; Yangling 712100 China
2. College of Forestry; Northwest A&F University; Yangling 712100 China
3. Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau; Northwest A&F University; Yangling 712100 China
4. Institute of Soil and Water Conservation, CAS&MWR; Yangling 712100 China
5. Beijing Key Laboratory of Lignocellulosic Chemistry; Beijing Forestry University; Beijing 100083 China