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Harvard Forest Symposium Abstract 2018

  • Title: Microbial and soil biogeochemical responses to multiple global changes
  • Primary Author: Serita Frey (University of New Hampshire - Main Campus)
  • Additional Authors: Mark Anthony (University of New Hampshire - Main Campus); Melissa Knorr (University of New Hampshire - Main Campus); Eric Morrison (University of New Hampshire - Main Campus); Emily Whalen (University of New Hampshire - Main Campus)
  • Abstract:

    Our research continues to focus on how multiple global change factors are impacting terrestrial ecosystems, with an emphasis on soil biota and nutrient cycling processes. We are specifically interested in how environmental changes affect the composition and diversity of soil microbial communities and microbial-mediated carbon and nitrogen cycles. 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. We are conducting this work at three soil warming studies (Soil Warming × Nitrogen Addition, Barre Woods, and Prospect Hill), 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:

    • Soil warming resulted in a cyclic pattern of soil organic matter decomposition and carbon dioxide fluxes to the atmosphere, with phases of substantial soil carbon loss alternating with phases of no detectable loss (Melillo et al., 2017). Several factors affected the degree of soil carbon loss, including depletion of microbially-accessible carbon pools, reductions in microbial biomass, a shift in microbial carbon use efficiency, and changes in microbial community composition.
    • Soil warming resulted in higher aboveground tree seedling growth, but reductions in fine root biomass. Further, soil warming positively influenced plant-soil feedbacks through higher arbuscular mycorrhizal colonization of fine roots (Wheeler et al., 2017).
    • Fungal abundance was reduced by chronic nitrogen amendment at sites where ambient nitrogen deposition was high (~10 kg ha-1 y-1), but fungal abundance was not affected by nitrogen additions in forests with low ambient deposition (~3 kg ha-1 y-1).
    • Fungi exhibit altered physiology in response to long-term environmental change. For example, fungi exposed to more than 25 years of soil N enrichment are less able to decompose plant litter (van Diepen et al., 2017).
    • A reduction in soil and litter manganese concentrations under chronic soil nitrogen amendment may explain observed suppression of decomposition in nitrogen-enriched soils.
    • Community-assembly processes and species interactions are important controls on the function of wood-decay fungal communities, ultimately overwhelming substantial differences in abiotic conditions (Maynard et al., 2018)
    • Environmental change fundamentally restructures the soil fungal community, altering the relative abundance of key fungal functional groups.
    o Mycorrhizal fungi (both ectomycorrhizal and arbuscular mycorrhizal fungi) were the most sensitive fungal guild following 10 years of soil warming, showing an overall decline in fungal species richness and relative abundance. In contrast, soils exposed to 20 years of warming showed an increase in the relative abundance of yeasts and wood decomposers compared to control plots.
    o Garlic mustard invaded plots were differentiated from uninvaded plots by lower variation in fungal community composition (beta diversity) and soil properties, higher fungal richness and community evenness (alpha diversity), and a suite of novel saprotrophic and pathotrophic fungi that were consistently present across the invaded landscape and absent from uninvaded forest patches (Anthony et al., 2017).

    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. Ecosphere 8(9), Article e01951.
    Maynard, D.S., K.R. Covey, T.W. Crowther, N.W. Sokol, E.W. Morrison, S.D. Frey, L.T.A. van Diepen, Mark A. Bradford. 2018. Fungal associations overwhelm abiotic conditions as drivers of community structure and function. Ecology (in press)
    Melillo, J.M., S.D. Frey, K.M. DeAngelis, W. Werner, M. Bernard, F.P. Bowles, G. Pold, M.A. Knorr, and A.S. Grandy. 2017. Long-term Pattern and Magnitude of Soil Carbon Feedback to the Climate System in a Warming World. Science 358, 101-105.
    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.
    Wheeler, J.A., S.D. Frey and K. Stinson. 2017. Responses of red maple seedlings to multiple environmental stresses: interactive effects of invasion, warming, and nitrogen deposition. Forest Ecology and Management 403, 44-51.

  • Research Category: Soil Carbon and Nitrogen Dynamics