Yihe Lü1,2, Ting Li1,3, Kun Zhang1,3, Bojie Fu1,2. 1. State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , Beijing 100085, China. 2. Joint Center for Global Change Studies , Beijing 100875, China. 3. University of Chinese Academy of Sciences , Beijing 100049, China.