Institute for Forest Resources & Environment ofGuizhou, Guizhou University, Guiyang 550025, China;
Tibet Agricultural and Animal Husbandry College, Nyingchi 860000, China;
College of Forestry, Northwest A&F University, Yangling 712100, China;
Tibet Agricultural and Animal Husbandry College, Nyingchi 860000, China;
College of Forestry, Northwest A&F University, Yangling 712100, China;