1. Assistant Professor, Key Laboratory of West China’s Environmental System (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou Univ., Lanzhou 730000, China.
2. Ph.D. Student, Key Laboratory of West China’s Environmental System (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou Univ., Lanzhou 730000, China.
3. Professor, Key Laboratory of West China’s Environmental System (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou Univ., Lanzhou 730000, China; Dept. of Geography, Western Michigan Univ., Kalamazoo, MI 49008 (corresponding author).
4. Associate Professor, Key Laboratory of West China’s Environmental System (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou Univ., Lanzhou 730000, China.
5. Research Associate, Key Laboratory of West China’s Environmental System (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou Univ., Lanzhou 730000, China.
6. Assistant Dean, John Carroll Univ., University Heights, OH 44118.