Effects of invasive plant Mikania micrantha on plant community and diversity in farming systems.
To explore the effects of invasive plant Mikania micrantha H.B.K invasion on plant community and diversity in farming systems, the composition, density, importance value, species richness, diversity indices and evenness index were analyzed under five different M. micrantha cover classes (0, 1-25, 26-50, 51-75 and 76-100%). The study took place in farm fields in Longchuan County, Northwest of Yunnan, China. A total of 20 plant species from 20 genera and 10 families were identified. Within communities where M. micrantha occurred, M. micrantha was the most dominant species with the highest population density. Population density and importance values of some dominant species, Ageratum conyzoides, Bidens pilosa, Borreria latifolia, Digitaria sanguinalis and Galinsoga parviflora clearly declined as M. micrantha cover increased and their importance values were significantly negative correlated with M. micrantha cover (p<0.05). The cover of M. micrantha clearly was also negatively correlated with Eleusine indica, Phyllanthus urinaria and Siegesbeckia pubescens (p<0.05). By contrast, population density and importance values for Commelina communis and Kyllinga cylindrical, increased substantially with increased M. micrantha and there were significant positive correlations between their importance values and M. micrantha cover (p<0.05). Maximum values for species richness (17.00), Simpson index (0.86), Shannon-Wiener index (2.10) and Pielou index (0.73) occurred in 1-25% cover of M. micrantha; the next highest values occurred with 0% cover of M. micrantha. Most species richness, diversity and evenness values within M. micrantha cover ranges of 1-25 and 0% were not significantly different but as M. micrantha cover increased, species richness, diversity and evenness values significantly declined, going from 26-100% cover of M. micrantha. Overall, it was concluded that M. micrantha invasion had profound effects on plant community and species diversity in farming systems which must be taken account as we attempt to manage its invasions.