Mycorrhizal fungi are ubiquitous plant mutualists, and can be classified into two types: ecto- (EM) - dominant in temperate forests and arbuscular (AM) - globally dominant. Both types form mycorrhizal networks (MNs), consisting of fungal hyphae that connect plants of the same and different species. The degree to which the MNs of adult trees facilitate or inhibit other plants, specifically seedlings, is unclear. This study examines how the MNs of adult trees of differing species and mycorrhizal type affect mycorrhizal colonization, growth, and survival of EM seedlings. Quercus rubra seedlings were planted under four adult tree species of varying mycorrhizal types: Q. rubra (EM), Q. velutina (EM), Acer rubrum (AM), and Carya glabra (AM/EM). Seedlings were separated into treatment groups: control (C), bagged control (BC), and disturbed (D). D and BC treated seedlings were planted in bags allowing hyphae to pass while blocking roots. D seedlings’ connection to the MN was consistently disrupted. Seedlings were collected at the end of the growing season and survival and biomass were recorded. Additionally, a subset of the seedlings were examined for EM colonization.
Results/Conclusions
Seedling survival differed significantly by both adult tree species and treatment. Both BC and D seedlings had higher survival than C seedlings, and within those groups seedlings planted near the con-generic Q. velutina experienced the highest survival, while seedlings planted near the con-specific Q. rubra had the lowest. Seedling survival was higher in the D group when compared to BC across all adult trees except for A. saccharum. Between BC and D EM colonization differed significantly by treatment with D seedlings exhibiting lower levels of colonization across all adult species. Across all treatments colonization was highest for near Q. velutina seedlings. Our data indicate that survival of Q. rubra seedlings can be negatively impacted when seedlings are connected to the MN. Survival is lowest near con-specifics, while being near a con-generic is the most beneficial. This work represents an important additional step in advancing our understanding of the role that MNs play in how temperate forest communities assemble.