1. College of Ecology, Lanzhou University, Lanzhou, China
2. Center for the Pan-Third Pole Environment, Lanzhou University, Lanzhou, China
3. State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment (TPESRE), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China
4. College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China