Shandong Research Institute of Regional Economy Shandong Economic University Jinan 250014 China;
College of Population Resources and Environment Shandong Normal University Jinan 250014 China;
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 Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China;