Functional traits of ectomycorrhizal trees influence surrounding soil organic matter properties

Ectomycorrhizal (EM) effects on forest ecosystem carbon (C) and nitrogen (N) cycling are highly variable, which may be due to underappreciated functional differences among EM-associating trees. We hypothesise that differences in functional traits among EM tree genera will correspond to differences in soil organic matter (SOM) dynamics. We explored how differences among three genera of angiosperm EM trees (Quercus, Carya, and Tilia) in functional traits associated with leaf litter quality, resource use and allocation patterns, and microbiome assembly related to overall soil biogeochemical properties. We found consistent differences among EM tree genera in functional traits. Quercus trees had lower litter quality, lower δ¹³C in SOM, higher δ¹⁵N in leaf tissues, greater oxidative extracellular enzyme activities, and higher EM fungal diversity than Tilia trees, while Carya trees were often intermediary. These functional traits corresponded to overall SOM-C and N dynamics and soil fungal and bacterial community composition. Our findings suggest that trait variation among EM-associating tree species should be an important consideration in assessing plant–soil relationships such that EM trees cannot be categorised as a unified functional guild. Read the free Plain Language Summary for this article on the Journal blog.