[Numerical analysis on ecological gradient of plant communities in Donggou catchment, Hebei Province, China].

Based on DCCA-OAC, the plant communities in Donggou catchment, Bashang region, Hebei Province, were classified into 8 types of community. The environmental gradient, structural gradient and human-disturbance could be well expressed in the ordination plot. Axis 1 reflected the spatial pattern of plant communities along the gradient of altitude and slope, while axis 2 showed the plant community distribution on different aspects. The plant communities showed a distribution gradient along moisture gradient as shown by the combination of both axes of DCCA. The communities exhibited different trends in the synusia and species composition. Betula platyphylla was only existed on the high and steep northern aspect. The dominate species of shrub and herbaceous synusia on northern aspect were Potentilla fruticosa and Carex rigescens respectively, while on southern aspect were Artemisia spp. and Agropyron cristatum. The distribution along altitude and slope also existed among dominate species of each synusia on southern aspect. In addition, human disturbance, including grazing, farming and logging, had significant influence on the temporal and spatial distribution of communities. In general, the better the habitat, the more intensive the human disturbance.