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Harvard Forest Symposium Abstract 2017

  • Title: Fungal community responses to multiple, interacting global changes
  • Primary Author: Serita Frey (University of New Hampshire)
  • Abstract:

    Fungal community responses to multiple, interacting global changes

    Serita D. Frey, Mark Anthony, Kevin Geyer, Melissa Knorr, Jessica Moore, Eric W. Morrison and Emily Whalen

    Microbial diversity and community composition are key drivers of ecosystem processes including C and nutrient cycling. Our work has increasingly focused on the fungal component of the microbial community because fungi are the primary decomposers of plant litter in temperate forests and fungi are sensitive to environmental change. We are conducting comprehensive analyses of soil fungal communities in response to several environmental stressors (i.e., climate warming, nitrogen additions, and invasive plants) using marker gene, whole genome, gene expression, meta-genomic and meta-transcriptomic approaches. We are coupling these -omics approaches with culture-based studies, stable isotope analysis, and biogeochemical analyses (e.g., C and N fluxes, microbial biomass, extracellular enzyme activities) to better understand the ecology and evolution of soil fungal communities in the context of abiotic and biotic change and the microbial controls on biogeochemical cycles. This work is being done at several long-term global change experiments at Harvard Forest, including the Soil Warming × Nitrogen Addition (SWaN) Study, the Chronic Nitrogen Amendment Study, the DIRT plots, and across a set of sites invaded by garlic mustard. Key results from the past year include:

    • Environmental change fundamentally restructures the soil fungal community, altering the relative abundance of key fungal functional groups. For example, a decline in the relative abundance of ectomycorrhizal fungi following long-term N addition was offset by an increase in the relative abundance of saprotrophs (Morrison et al., 2016). Likewise, fungal communities associated with garlic mustard invasion had lower ectomycorrhizal but higher saprotrophic and pathotrophic relative abundances, with a suite of novel saprotrophic and pathotrophic fungi differentiating invaded from uninvaded soil (Anthony et al., in review).

    • Fungi evolve and exhibit altered physiology in response to long-term environmental change. For example, fungi exposed to more than 25 years of soil N enrichment have evolved and are less able to decompose plant litter (van Diepen et al., 2017). Fungal isolates from N treatment plots were generally less able to decay plant litter than isolates of the same species from control plots, and the responses of these N isolates did not revert or resemble control isolate responses even when the N isolates were grown in control environments. To our knowledge, this study is the first to test if and how fungal behaviors relevant to a critical ecosystem process evolve in response to long-term environmental change.

    • A change in the fungal species present in the community affects ecosystem functioning. For example, long-term soil warming favors plant symbiotic fungi over free-living saprotrophic fungi – a change which alters the types of decomposition enzymes produced, and ultimately causes a shift in the chemical signature of organic matter, having implications for long-term soil C dynamics. Long-term N deposition favors fungal species that are less active overall and that produce fewer decomposition enzymes, resulting in an accumulation of soil organic matter. The underlying mechanisms driving changes in fungal community structure are still unclear, but something we are beginning to evaluate. For example, intrinsic genomic features of fungi predict growth rates and metabolic efficiency, traits that likely influence community composition. We have also found that a loss of soil and litter manganese (an important co-factor for some key decomposition enzymes), particularly following long-term N additions, may help explain observed shifts in fungal physiology.

    References
    Anthony, M.A., S.D., Frey, and K.S., Stinson. 2017. Fungal community homogenization, shift in dominant trophic guild, and appearance of novel taxa in forests invaded by an exotic plant. ISME Journal (in review).

    Morrison, E.W., S.D. Frey, J.J. Sadowsky, L. van Diepen, W.K. Thomas, and A. Pringle. 2016. Chronic nitrogen additions fundamentally restructure the soil fungal community in a temperate forest. Fungal Ecology 23, 48-57.

    van Diepen, L.T.A., S.D. Frey, E.A. Landis, E.W. Morrison, A. Pringle. 2017. Fungi exposed to chronic nitrogen enrichment are less able to decay leaf litter. Ecology 98(1), 5-11.

  • Research Category: Soil Carbon and Nitrogen Dynamics; Large Experiments and Permanent Plot Studies; Invasive Plants, Pests & Pathogens; Biodiversity Studies