1 Key Laboratory of Hangzhou City for Ecosystem Protection and Restoration, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 310036, China State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
2 College of Nature Conservation, Beijing Forestry University, Beijing 100083, China.
3 Biology Department, University of Massachusetts, Amherst, MA 01003-9297, USA.