Impact of invasion of exotic plant Alternanthera philoxeroides on interspecies association and stability of native plant community

Alternanthera philoxeroides is an exotic species in China affecting the biodiversity, composition, structure and stability of native communities. The interspecific association of 12 main species and stability of native plant communities invaded by A. philoxeroides were analyzed via variance ratio (VR), chi-square (χ²) correction test, Jaccard index and improved Godron M’s measure in Shangrao City. The study shows that the native communities non-invaded by A. philoxeroides exhibits positive associations on the whole. There are a number of species pairs with positive associations, and some positive associations are very significant. However, species pairs with negative association appear in native plant communities invaded by A. philoxeroides. The number of species pairs with positive associations reduces sharply compared with the un-invaded communities, and the community exhibits negative association on the whole. Competition among species increases in invaded native communities reducing the stability of certain disadvantaged species due to weak competitiveness. Based on the results of interspecific associations, all species with close relations in local communities invaded by A. philoxeroides disparts into two distinct ecological groups with certain interconnection. Invasion of A. philoxeroides decreases the stability of native community and the number of certain species gradually decreases or are even completely replaced. It is observed that rapid A. philoxeroides invasion induces significant negative effect on native species. Controlling measure and invasive mechanism of A. philoxeroides should be strengthened.