1. Sino-French Institute for Earth System Science; College of Urban and Environmental Sciences; Peking University; Beijing 100871 China
2. Centre of Excellence PLECO (Plant and Vegetation Ecology); Department of Biology; University of Antwerp; Universiteitsplein 1 B-2610 Wilrijk Belgium
3. Institute of Tibetan Plateau Research; Center for Excellence in Tibetan Earth Science; Chinese Academy of Sciences; Beijing 100085 China