Contrast in Mycorrhizal Associations Leads to Divergent Rhizosphere Metabolomes and Plant–Soil Feedback Among Grassland Species

Species-specific feedback between plants and soil microbial communities is an important driver of vegetation dynamics. Arbuscular mycorrhizal (AM) fungi colonise most terrestrial plants but are not expected to generate specific feedbacks due to low host specificity. We tested whether variation in mycorrhizal associations and associated rhizosphere metabolomes among co-existing temperate grassland species leads to species-specific plant-soil feedback. More mycorrhizal plant species showed more divergent plant-soil feedback: they experienced reduced growth and mycorrhizal colonisation in soils originating from weakly mycorrhizal species, but feedback became neutral in soil from species with similar mycorrhizal strategies. The species with the most self-promoting soil feedback was characterised by strong metabolome shifts related to stress and immune responses following soil inoculum manipulation, while the metabolomes of species with more negative feedback were unresponsive. This study demonstrates that AM fungi can generate species-specific plant-soil feedback, which can be predicted from plant mycorrhizal strategies and rhizosphere chemistry.