The effects of plant–soil feedback on invasion resistance are soil context dependent

There is growing interest in understanding the role that plant-soil feedbacks (PSFs) may play in invasion resistance. However, recent studies have shown that there is great uncertainty in explaining community patterns by PSF studies regarding invasions. This uncertainty may be partly because soils used for PSF studies are usually collected from open areas rather than natural communities, thus ignoring the effects of community contexts that may specifically influence the soil feedbacks of community residents to invaders. We performed a two-phase pot experiment to study the soil feedback initiated by ten co-occurring native and exotic species to a forest invader, Phytolacca americana, and the experiments were performed in forest soil and open area soil. The context-dependent mechanisms were further explored by studying different components of PSF. The results showed that natives and exotics had positive and negative effects on P. americana in the open area soil, respectively, but both had negative effects in the forest soil. Nutrient limitation was more important for the PSF in open area soil, whereas biotic factors were likely the primary mechanisms explaining the PSF in forest soil. Additionally, the litter-mediated allelopathy of dominant Quercus acutissima caused the strongest inhibition of the invader. These results suggest that native species can effectively resist invasion by producing negative PSF depending on the community context. Evidence that exotic species promote invasion through positive PSFs was not obtained. This study provided preliminary insights into the possibility of bridging PSF studies and community patterns.