Drivers of the negative diversity-invasibility relationship: nutrient availablity, allelopathy, soil biota and soil legacy effects

ABSTRACT Elton’s diversity-invasibility hypothesis predicts that high-diversity native communities should be less easily invaded than low-diversity communities. Although various mechanisms have been proposed to explain it, it remains unclear which of those mechanisms is more important and whether they operate simultaneously. Using one pool of native plant species and one pool of invasive alien plant species that naturally co-occur in China, we here tested in four separate experiments whether nutrient availability, allelopathy, soil microbiota and soil-legacy effects can all mediate the diversity-invasibility relationship. While soil-nutrient availability, allelopathy, soil biota and soil-legacy effects separately influenced biomass production of alien plant species and native plant communities, our results suggest that only soil biota and allelopathy influenced diversity-invasibility relationship in our study system. Importantly, by excluding the potential effects of allelopathy and soil biota in the nutrient-competition experiment, nutrient competition alone is not necessarily related to the negative diversity-invasibility relationship.