Institute of Tourism, Beijing Union University, Beijing 100101, China;
Land and Water Division, Natural Resources and Environment Management Department, Food and Agriculture Organization, Rome 00153, Italy;
Institute of Geographic Sciences and Natural Resources research, Chinese Academy of Sciences, Beijing 100101, China;
Institute of Geographic Sciences and Natural Resources research, Chinese Academy of Sciences, Beijing 100101, China;
Institute of Tourism, Beijing Union University, Beijing 100101, China;
