School of Economics & Management, Inner Mongolia University, Hohhot 010021, P.R.China;
School of Economics & Management, Inner Mongolia University, Hohhot 010021, P.R.China;
Sino-US Center for Conservation, Energy and Sustainability Science in Inner Mongolia, Hohhot 010021, P.R.China;
Agricultural Information Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, P.R.China;