Contrasting the roles of mycorrhizal compatibility in community development between arbuscular- versus ecto-mycorhizal systems. root associated fungus metagenome

Feedback between plant species and the soil mycorrhizal fungi (biotic agents) shapes interspecific plant interactions, but it remains uncertain whether its effects are an essential component of plant community development. Two most dominant mycorrhizal types in temperate forests, arbuscular mycorrhizal and ectomycorrhizal plant species, can drive distinct dynamics in which the composition of the fungal community changes due to associations with plant community composition, and these changes differentially feed back on plant growth through the effects of (i) plant-fungus compatibility and (ii) common fungal networks. Here we investigate how plant community development is linked with mycorrhizal types, contrasting the effects of arbuscular mycorrhizal (AM) versus ectomycorrhizal (EcM) associations on seedling establishment. By simulating the scenario where established tree community modifies the soil fungal component (i.e., AM versus EcM inocula) and alters the competitive environment for new seedlings, we found that competition for soil nutrients influenced seedling establishment. The results showed that compatible seedlings had significantly greater leaf and root biomasses than incompatible seedlings, a benefit from the presence of established competitors through enhancing positive nutrient feedbacks. While plant-soil feedback mediated tree-seedling interactions for both AM and EcM associations, the estimated compatibility effects were more positive for EcM relative to AM associations. Notably, this coincided with the more pronounced sharing of fungal species and more structured formation of common fungal network in EcM systems compared to AM systems. Together these results suggest the link between seedling establishment and mycorrhizal functional differentiation.