Quantitative analysis of the Vitex negundo var. heterophylla communities in Taihang Mountain, Shanxi Province

The ecological relationship of species, community and environment of Vitex negundo var. heterophylla communities were studied by using TWINSPAN and DCA. The results of TWINSPAN indicates that the communities could be classified into 13 associations. The classification matrix indicates two environmental gradients, light intensity and soil humidity. The gathered groups of plant quadrates in the space of DCA ordination are consistent with the result of TWINSPAN, which revealed a relationship between plant formations and environmental gradients.The first axis of the twodimensional ordination diagram of DCA obviously reflects the trend of aspect. The second axis expresses the gradient changes of slope. It is considered that the major factors that restrict the formation distribution of the mountain are aspect and slope.