Institute of Soil and Water Conservation,Northwest A & F University,State Key Laboratory of Soil Erosion and Dryland Farming on the Loss Plateau,Yangling 712100,China;
College of Forestry,Northwest A & F University,Yangling 712100,China;
College of Life Sciences,Northwest A & F University,Yangling 712100,China;
College of Forestry,Northwest A & F University,Yangling 712100,China;
College of Life Sciences,Northwest A & F University,Yangling 712100,China;