[1] Humboldt Univ, Dept Geog, Unter Linden 6, D-10099 Berlin, Germany
[2] Leibniz Ctr Agr Landscape Res ZALF, Eberswalder Str 84, D-15374 Muncheberg, Germany
[3] Chinese Acad Sci, Inst Geog Sci & Nat Resources Res, Beijing 100101, Peoples R China
[4] State Key Lab Resources & Environm Informat Syst, Beijing 100101, Peoples R China