Chinese Academy of Sciences (CAS) - Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences (CAS) - Northwest Institute of Eco-Environment and Resources, affiliation not provided to SSRN, Chinese Academy of Sciences (CAS) - Northwest Institute of Eco-Environment and Resources, affiliation not provided to SSRN, Lanzhou University, Lanzhou University, Lanzhou University, Chinese Academy of Sciences (CAS) - Northwest Institute of Eco-Environment and Resources, Lanzhou University, Lanzhou University, affiliation not provided to SSRN and affiliation not provided to SSRN