Study on shrub community diversity of Ordos Plateau, Inner Mongolia, Northern China

The Ordos plateau is a relatively independent physiographic unit and a complex, quite sensitive ecotone in the semi-arid zone of north China. Shrubs are the dominant plant life-form of the region. With a progressive decrease in moisture gradient from desert steppe to steppe desert, the ecological replacement of shrub communities is obvious. This paper deals with the distribution characteristics of shrub community diversity with environmental gradient changes and analyses the influences of various environment factors on shrub community diversity in the region. The results from this study suggest that the diversity of shrub communities depends on their spatial structure, in particular the composition of the herb layer. Shrub community diversity gradually decreases from desert steppe to steppe desert. Among various factors (geographic co-ordinates, annual mean temperature, coldest monthly mean temperature, annual mean evaporation, annual precipitation, sunshine percentage, annual mean wind velocity and annual mean number of sandstorm days, etc.), moisture gradient change is the greatest factor affecting shrub community diversity in the region, but its significance is low. It is possible that the influences of overgrazing on the shrub communities far exceed the impact of moisture gradient change.