Functional traits of ectomycorrhizal trees influence their effects on surrounding soil organic matter properties

Abstract

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 hypothesize 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. In support of our hypothesis, we found consistent differences among EM tree genera in function traits. Quercus trees had lower litter quality, lower {delta}13C in SOM, higher {delta}15N 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 categorized as a unified functional guild.