Abstract: This paper studied the distribution characteristics of shrub community diversity with environmental gradients and the influence of environmental factors on community diversity. The results show that the shrub community diversity was decided by the spatial arrangement of community,especially,the composition of herb layer.From desert steppe to steppe desert,the shrub community diversity was gradually decreased. Among the ecological factors such as geological coordinates,annual average temperature,coldest and hottest monthly temperature,annual evaporation,sun radiate percentage,wind velocities and sand storm days,water gradient was the main factor affecting biodiversity.Nevertheless,the influence of water gradient was not at a significant level,because the effect of overgrazing and human's destroying on shrub community was far greater than that of water gradient change.

Key words: Erdos plateau, Shrub community, Biodiversity, Water gradient, residual nitrate-N, summer fallow, leaching, winter wheat, nitrogen mineralization.