The foundation species Tsuga canadensis (Eastern hemlock) and the distinctive forest ecosystems it creates are under threat due to the invasive hemlock woolly adelgid (HWA). The sap-sucking insect starves the needles of T. canadensis and is decimating its stands across the eastern U.S. However, much less understood is how below-ground dynamics, particularly symbiotic ectomycorrhizal fungi (ECM), impact T. canadensis survival of the HWA. The chief aim of this project was to study how the factors of soil quality, microbial biomass, and neighbor species richness correlate with the ECM abundance of T. canadensis individuals across varying levels of HWA infestation. For this, ECM abundance was estimated via GCMS analysis of ergosterol concentration (in ppm) from fungal in-growth bags deployed for a year beginning in July of 2024 and harvested July of 2025. The other below-ground factors were: soil pH, microbial biomass, baseline NH4 and NO3 levels, nitrogen mineralization, nitrification, and species richness data collected from the same trees at which the fungal in-growth bags were deployed. Most significantly, these data (exception: species richness) were collected and compared across three sites with varying levels of HWA infestation: a control site in New Hampshire and two infested sites at Harvard Forest—one “unhealthy” and one “healthy,” despite infestation beginning in the same year. The goal is to paint a fuller picture than is currently seen about the below-ground dynamics of T. canadensis stands sustaining different levels of HWA influence—particularly regarding the role of ECM. Preliminary results indicate that pH, soil microbial biomass, baseline NH4, and ergosterol levels significantly differ across sites, the latter suggesting that HWA infestation has a detectable effect upon ECM presence in T. canadensis stands. Ergosterol abundance also appears to be positively correlated with baseline NH4 levels. These and further analyses will shed light on the relationships between soil quality, baseline N levels, microbial activity and N demand, and ECM abundance (implicated: activity) in T. canadensis stands under varying levels of stress by HWA. This is information that could be important for forest restoration efforts as well as a deeper understanding of the vast underground theater upon which so much of the above-ground response to invasive species depends—an increasingly relevant ecological predicament.