This work was supported by the National Natural Science Foundation of China(Grant No.40171002);the'Hundred People'Project of the Chinese Academy of Sciences under the leadership of Prof.Wang Genxu;the State Key Project(973)(Grant No.2003CB415201).
Since the 1960s, dramatic changes have taken place in land-use patterns characterized by the persistent expansion of cultivated land and a continuous decrease in natural woodland and grassland in the arid inland river...