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

The Ordos plateau is a relatively independent physiographic unit and a comp lex, quite sensitive ecotone in the semi-arid zone of north China. Shrubs a re the dominant plant life-form of the region. With a progressive decrease in moisture gradient from desert steppe to steppe desert, the ecological re placement of shrub communities is obvious. This paper deals with the distri bution characteristics of shrub community diversity with environmental grad ient changes and analyses the influences of various environment factors on shrub community diversity in the region. The results from this study sugges t that the diversity of shrub communities depends on their spatial structur e, in particular the composition of the herb layer. Shrub community diversi ty gradually decreases from desert steppe to steppe desert. Among various f actors (geographic co-ordinates, annual mean temperature, coldest monthly m ean temperature, annual mean evaporation, annual precipitation, sunshine pe rcentage, annual mean wind velocity and annual mean number of sandstorm day s, etc.), moisture gradient change is the greatest factor affecting shrub c ommunity diversity in the region, but its significance is low. it is possib le that the influences of overgrazing on the shrub communities far exceed t he impact of moisture gradient change. (C) 2001 Academic Press.