1. College of Water and Soil Conservation, Beijing Forestry University, Beijing 100083, China
2. Ji County Station, Chinese National Ecosystem Research Network (CNERN), Beijing Forestry University, Beijing 100083, China
3. State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
4. State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China