Contrasting the roles of mycorrhizal compatibility in community development between arbuscular- versus ecto-mycorhizal systems

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.

植物物种与土壤菌根真菌（biotic agents，生物介导因子）之间的反馈调控植物种间相互作用，但目前尚不确定其效应是否为植物群落构建的必要组成部分。温带森林中两类占主导地位的菌根类型——丛枝菌根（arbuscular mycorrhizal）植物与外生菌根（ectomycorrhizal）植物，可驱动截然不同的动态过程：真菌群落组成会随植物群落组成的改变而发生变化，且此类变化会通过（i）植物-真菌相容性（plant-fungus compatibility）与（ii）共享真菌网络（common fungal networks）两条途径，对植物生长产生差异化反馈。本研究旨在探究植物群落构建与菌根类型之间的关联，对比丛枝菌根（AM）与外生菌根（EcM）共生关系对幼苗建成（seedling establishment）的影响。通过模拟成熟树木群落改变土壤真菌组分（即丛枝菌根与外生菌根接种物）、并改变新生幼苗竞争环境的场景，我们发现土壤养分竞争会影响幼苗建成。结果显示，相容性匹配的幼苗其叶、根生物量显著高于不相容幼苗，这一收益源于成熟竞争者通过强化正向养分反馈所带来的益处。尽管植物-土壤反馈同时介导了丛枝菌根与外生菌根共生关系下的树木幼苗相互作用，但相较于丛枝菌根共生，外生菌根共生的相容性效应估计值更为正向。值得注意的是，与丛枝菌根系统相比，外生菌根系统中真菌物种的共享程度更高，且共享真菌网络的结构形成更为显著，这与前述结果相契合。综合以上结果，本研究揭示了幼苗建成与菌根功能分化之间的关联。