Shengsheng Gong1, Haichao Xie2, Fahu Chen2,3. 1. College of Urban and Environmental Sciences/Research Institute of Sustainable Development, Central China Normal University, Wuhan, 430079 China. 2. Key Laboratory of Alpine Ecology, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101 China. 3. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing, 100101 China.