Eupatorium odoratum community structure and its effects on species richness of native vegetation community under different habitats in Karst Area of Guangxi

Eupatorium odoratum, which is a worldwide perennial invasive alien weed, usually spreads rapidly, and poses a serious threat to crops, forest, native vegetation and biodiversity. In order to understand characteristics of Chuomolaena odorata community structure in different habitats and its effects on plant species richness of native vegetation community, three C. odorata communities from different habitats were chosen for establishing three sample plots (plot A, B and C) in Longzhou county and Pingguo county of Guangxi. Plant species composition, structure characteristics, distributions of C. odorata and its effects on plant species richness of native vegetation in each plot were investigated and analyzed. The results showed that there were a total of 79 species, which belonged to 50 genera of 45 families, under the three habitats. The community structures were simple, including there layers (tree, shrub and herb) in plot A, two layers (shrub and herb) in plot B and C, but the plant species, quantity and vertical structure were different. Through the principle component analysis of 36 species with occurring frequency 10%, we found that the human disturbance and light condition were the key factors affected the C. odorata community structure, which contributed 42.88% and 24.17%, respectively. According to the two factors, all the samples could be divided into three cluster groups. The analysis of relationship between the importance value of C. odorata and plant species richness of the communities indicated that when the former reached to 0.51，the latter decreased with the rise of the former, which demonstrated a significant correlation between them. This study suggests that the invasion of C. odorata has an adverse effect on biodiversity, but the effect depends on the intensity of human disturbance.