Can allelopathy be used to efficiently resist the invasion of exotic plants in subtropical forests?
Mature subtropical forests can resist the invasion of Mikania micrantha, a notorious exotic invasive plant, but the underlying mechanism for this resistance is still debated. In this study, we explored whether allelochemicals produced by the dominant species in a subtropical forest were sufficient to inhibit the invasion of M. micrantha. Allelopathic effects of three tree species (Syzygium rehderianum, Cryptocarya concinna and C. chinensis) on the germination and vegetative growth of M. micrantha were investigated. The results showed that aqueous extracts from the leaves of all tree species had allelopathic inhibitory effects on M. micrantha seed germination at a concentration of 5% aqueous extract. Variations were observed in the allelopathic effects of the tree species on germination rate (GR), germination energy (GE) and radicle length (RL), but all the tree species had the same synthetic allelopathic effect (SE). Reduced height, biomass, Chlorophyll (Chl a/b), Carotenoid/Chlorophyll (Car/Chl), antioxidant capacity, nonphotochemical quenching coefficient (NPQ) and increased specific leaf area (SLA) were observed in M. micrantha planted with the tree species. The allelopathic potential of the tree species on M. micrantha in a vegetative growth stage was weak. Our results indicated allelopathy alone was not sufficient to inhibit the invasion of exotic plants in subtropical forests, but the combination of allelopathy and shading may be sufficient.