1. Beijing Technology and Business University, School of International Economics and Management, Beijing 100048, China
2. Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Chaoyang District, Beijing 100101, China
3. School of Cultural Industry and Tourism Management, Henan Univerisity, Kaifeng 475001, China
4. State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China