1. State Key Laboratory of Earth Surface Processes and Resource Ecology (Beijing Normal University), College of Resources Science & Technology, Beijing Normal University, Beijing, 100875, China
2. Department of Geography, The University of Western Ontario, London, ON, Canada N6A 3K7
3. Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, International Institute of Earth System Science, Nanjing University, Nanjing 210093, China