8[7]Davidson A,Csillag F.A comparison of three approaches for predicting C4 species cover of northern mixed glass prairie[J].Remote Sensing of Environment,2003,86:70-82.
9[9]Tong C,Wu J,Yong S,et al.A landscape-scale assessment of steppe degradation in the Xilin River Basin,Inner Mongolia,China[J].Journal of Add Environments,2004,59:133-149.
10[10]Prince S D,Brown de Cohtoun E,Kravitz L.Evidence from rain use efficiencies does not support extensive Sahelian desertification[J].Global Change Biology,1998,4:359-374.
