Plant species capacity to drive soil fungal communities contributes to differential impacts of plant–soil legacies

Plant–soil feedbacks occur when plants alter soil conditions in ways that influence growth of subsequent plants. We explored the relative contributions of such legacy effects and contemporary interactions in a greenhouse experiment by crossing three soil microbial inocula conditioned by distinct field plant communities with two greenhouse plant treatments ( Malva parviflora or Sonchus oleraceus ). We evaluated the composition of inocula and final microbial communities after greenhouse cultivation and correlated compositional changes to plant growth. Final bacterial community composition reflected both field and greenhouse plant treatments, but was not associated with greenhouse plant growth. Alternatively, final fungal communities only reflected recent greenhouse plant exposures and were associated with plant growth, albeit differently for the two species. M. parviflora growth correlated with final, but not initial, fungal community composition. S. oleraceus growth correlated with the degree of change between initial and final fungal communities, but only in the highly growth‐suppressive inocula from plots conditioned by plants producing high levels of toxic secondary compounds. Thus, plant sensitivity to microbial legacies can be jointly determined by a plant species' ability to exert selective pressures and the remnant microbial community's responsiveness to plant interactions.