Establishing Native Plant Communities to Improve the Management of the Invasive Weed Mikania micrantha

Using multiple species in native plant communities may improve control efficiency compared with single-species use. We conducted field investigations to assess the effects of Artemisia argyi, Portulaca oleracea, and their mixtures on the growth and reproduction of Mikania micrantha, followed by a greenhouse de Wit replacement series to compare different combinations of M. micrantha, A. argyi, and P. oleracea in terms of multispecies competition, phytoallelopathy, and photosynthesis. Field investigation showed that compared with M. micrantha monoculture (Group D), aboveground biomass, total stem length, flower biomass, inflorescence biomass, seed biomass, and seed number of M. micrantha increased in the P. oleracea community (Group B), though only seed number was significantly higher (p < 0.05). In contrast, in the A. argyi community (Group A) and the mixed community of A. argyi and P. oleracea (Group C), all these indicators decreased significantly (p < 0.05), in the order: Group C < Group A < Group D < Group B. This indicates that the mixed community (Group C) most strongly suppressed M. micrantha growth and reproduction. The effects of A. argyi, P. oleracea, and their mixture on the growth of M. micrantha in the greenhouse experiments mirrored the trends observed in field investigations. Calculated indices (relative yield, relative yield total, competitive balance index, and change in contribution) of A. argyi, P. oleracea, and their mixed population on M. micrantha demonstrated a higher competitive ability and higher influence of the combination of the two species compared with either A. argyi or P. oleracea alone. The interspecific phytoallelopathy experiment demonstrated strong allelopathic potential of A. argyi versus M. micrantha (p < 0.05) but showed no significant effect on P. oleracea. The net photosynthetic rate (Pn) of M. micrantha was generally lower in communities with both competitors compared with single-species communities. Our results suggest that, compared with a single plant population, the mixed population of A. argyi and P. oleracea exhibited a markedly enhanced ecological control capability through increased relative competitive ability, strengthened allelopathic inhibition, and markedly reduced photosynthetic efficiency of M. micrantha.