Date of Award

Fall 2026

Abstract

Tuberculate ectomycorrhizae (TECM) of oak are understudied, morphologically unique ectomycorrhizal (ECM) fungal structures whose initial observation at the Harvard Forest long-term ecological research site (Petersham, MA) were confined strictly to warmed plots. This study provided the first quantification of oak-associated TECM under experimental warming, characterizing their lifecycle and ecological role. We quantified and characterized TECM over three sampling periods during the growing season (May, June, August) of 2025 at two soil warming experiments at Harvard Forest: Barre Woods and Prospect Hill. We also identified the fungi associated with TECM structures, along with sclerotia found in the same samples. We quantified nutrient profiles of TECM and ECM roots over the three sampling periods to test whether TECM provide elevated nutrient exchange. We found that TECM were confined to warmed plots and displayed seasonal development with three distinct morphological stages. Hemileccinum rubropunctum was the confirmed fungal symbiont of Quercus-TECM. We also documented that microbes associated with TECM have nitrogen (N) fixation capacity, fixing N at rates comparable to nodules of a known N-fixing tree species (Alnus incana). We found that TECM are sites of elevated nutrient concentrations which are most active during August when the TECM are most highly colonized. These findings highlight the importance of understanding the role of TECM in temperate forests and how their ecological role is shaped by warming.

Document Type

Master's Thesis

First Advisor

Serita D Frey

Second Advisor

Matthew Smith

Third Advisor

Stuart Grandy

Department or Program

Natural Resources

Degree Name

Master of Science

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