1 Department of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China, 2 Department of
Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA, 3 Department of Forest Ecology, School of Ecology
and Nature Conservation, Beijing Forestry University, Beijing 100083, China
*Corresponding author. E-mail: jyfang@urban.pku.edu.cn