Arbuscular mycorrhizal fungi help explain invasion success of Solidago canadensis.
The importance of soil microbes as a whole has long been recognized in plant invasions, yet relatively few studies address the relative importance of different soil microbial guilds. To this end, we collected soils that were conditioned by plants in 18 pairs of invaded and uninvaded communities and conducted an assemblage experiment (invasive Solidago canadensis and five native plants) via four inoculations. Arbuscular mycorrhizal fungi (AMF) increased the growth of S. canadensis and its competitive suppression (the potential of S. canadensis to suppress its neighboring native plants). The positive feedback effect of AMF on S. canadensis was stronger than their negative feedback effect on five native plants. Solidago canadensis grew larger and had lower competitive suppression in conspecific soils than heterospecific soils. These findings suggest that AMF play a crucial role in driving S. canadensis invasions and also highlight that conspecific and heterospecific soils contribute to the success of S. canadensis through different pathways.