Do the phenolic acids in forest soil resist the exotic plant invasion?

Allelopathy helps in the success of some invasive plants (i.e. Novel Weapons Hypothesis). The invasive plants exert allelopathic inhibitory effects on natives, but it is unclear, how the invaders are affected by the allelochemicals released by native plants. We have developed a GC-MS based approach to analyze the phenolic acids in forest soil and their allelopathic effects on three worst invasive plants (Ipomoea triloba L., Mikania micrantha Kunth and Wedelia trilobata (L.) Hitchc.) in South China. We identified eight phenolic compounds (benzoic acid, p-hydroxybenzaldehyde, trans-cinnamic acid, p-hydroxybenzoic acid, vanillic acid, 3,4-dihydroxybenzoic acid, p-coumaric acid and ferulic acid) in the forest soil, and found that individual phenolic acids were seldom strong enough to effectively inhibit the growth of invasive plants, however, their mixtures had inhibitory effects on invaders. Our work provides an evidence, how the native forest community resists the exotic plant invasion through allelopathy.