1. School of Geographical Science, Northeast Normal University, Changchun 130024, China
2. Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
3. School of Natural Resources, University of Missouri-Columbia, Columbia 65211, USA
4. Northeast Institute of Geography and Agricultural Ecology, Chinese Academy of Science, Jilin 130012, China
5. Remote Sensing Technique Centre, Heilongjiang Academy of Agricultural Science, Harbin 150086, China