1 Institute of Ecology, College of Urban and Environmental Sciences, State Key Laboratory for Vegetation Structure, Function and Construction (VegLab), Peking University, Beijing, 100871, China 2 School of Advanced Agricultural Sciences, Peking University, Beijing, 100871, China * Correspondence: Yin Wang, Email: wangyinpku@pku.edu.cn, Tel & Fax: + 86 10 62742799