1. State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences; Chinese Academy of Sciences; Shuangqing Road 18, Haidian District Beijing 100085 China
2. College of Resources and Environment; University of Chinese Academy of Sciences; Beijing 100049 China
3. State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography; Chinese Academy of Sciences; Urumqi 830011 China
4. Fundación CEAM; c/Charles R. Darwin 14, Parque Tecnológico, Paterna 46980 Valencia Spain
5. Research Centre for Soil-Plant System; Council for Agricultural Research and Economics; Rome Italy
6. National Research Council; Via Madonna del Piano 10 50019 Sesto Fiorentino Italy
7. Department of Environmental Science and Engineering; Beijing Technology and Business University; Beijing 100048 China