Abstract
A.M. Cortese. Ectomycorrhizal tree islands are reservoirs of ectomycorrhizal fungi in northeastern secondary maple forests. 165 pages, 20 tables, 8 figures, 2023. New Phytologist style guide used.
Land use legacies have increased the abundance of arbuscular mycorrhizal (AM) trees and decreased the abundance of ectomycorrhizal (EM) trees in northeastern North America. Much of the region is comprised of post-agricultural secondary forests dominated by AM Acer spp. (maple) with scattered EM trees such as Betula spp. (birch), as well as some residual forest patches dominated by EM trees. For my dissertation, I studied how EM colonization, fungal richness and community composition of birch seedlings are influenced by distance of soils from a residual forest edge as well as established EM trees under growth chamber conditions. I also studied how scattered EM birch trees and soil inoculum from EM-dominated forest patches influence EM fungal colonization, fungal richness, and community composition of Tsuga canadensis (hemlock), Pinus strobus (pine), as well as Quercus montana and,Q. rubra (oak) seedlings under field conditions. Finally, I studied how scattered EM birch trees and EM-forest soil inoculum influence growth of pine and hemlock under growth chamber conditions. My results show that soils from EM tree-dominated forests support greater abundance and richness of EM fungi than nearby secondary forests, mostly due to effects of established EM trees. I also found that scattered EM trees are associated with EM fungi mostly lacking from surrounding secondary forests which can enhance the growth of hemlock seedlings. Soil inoculum from local EM tree-dominated forests can be used to introduce native EM fungi where lacking which can enhance the growth of pine and hemlock seedlings. EM fungal communities in areas without EM trees are depauperate and are dominated by fungi that form resistant spore banks in soils. My results show that a lack of EM fungi in post-agricultural secondary forests could be a land use legacy that inhibits the natural regeneration of EM trees. However, existing EM trees and soil inoculum can be used to introduce EM fungi into these forests to enhance EM tree seedling establishment.