1. Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, CAS , Beijing 100101 , China
2. University of Chinese Academy of Sciences , Beijing 100049 , China
3. Natural Resources Institute Finland (Luke) , Helsinki , Finland
4. Institute of Crop Sciences, Chinese Academy of Agricultural Sciences , Beijing 100081 , China
5. International Maize and Wheat Improvement Center (CIMMYT) , Texcoco , Mexico