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Latebreaking Poster

Session: Biogeochemistry (Latebreaking)

LB 5-43 - Oak mortality leads to increased diversity and shifting community composition of soil fungi in a temperate hardwood forest

Thursday, August 10, 2023
5:00 PM – 6:30 PM PDT
Location: ESA Exhibit Hall
Oak-dominated forests in the northeast United States are susceptible to many pathogens, such as oak wilt, which has affected populations in the midwest and eastern United States. In addition to the impacts on aboveground tree mortality, spread of these pathogens into eastern U.S. forests may drive changes in key soil fungal groups, such as ectomycorrhizal fungi. Using a longterm oak girdling experiment at Black Rock Forest in New York, USA, we looked for patterns in shifting fungal community composition following large scale oak mortality to better understand the interactions between canopy tree composition, soil fungal diversity, and forest function. We collected soil samples and soil environmental variables in 10 year old plots that included treatments of total 100% oak girdling (O), 50% oak girdling (O50), non-oak girdling (N), and a control without girdling (C). We then sequenced the fungal community using the ITS1-F and ITS2 reverse primers and classified the communities using the UNITE fungal reference and FUNGuild databases. We compared fungal alpha diversity, beta diversity and community composition as well as EcM abundance across the treatment groups through linear regressions and redundancy analysis. Alpha diversity was significantly greater in the O and O50 plots compared to the control, but was not higher in the non-oak girdled plots. There was an increase in saprophytic fungal abundance and a decrease in EcM fungal abundance in all the disturbed plots, but the difference was only significant in the O and O50 plots. ECM fungi showed a strong negative correlation with the fungi Archaeorhizomycetes suggesting that this is the fungal taxa that replaced EcM following the loss of canopy oak trees. Girdling treatments significantly affected fungal community composition, as did soil nitrogen levels, C:N ratios and soil pH. The increase in alpha diversity in only the oak girdle plots provides evidence of competition release as EcM fungi are removed from soils where they previously dominated. The shift from EcM to saprophytic fungi following disturbance is well documented, and significant in terms of carbon cycle implication given increased soil respiration in saprophytic-dominated communities. The large variation in pH between treatments, likely driven by tannic acid in oak leaves, and the effect of pH on fungal diversity highlight the complex feedbacks and co-determined successional dynamics of the canopy and fungal communities.