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Harvard Forest Symposium Abstract 2014

  • Title: Analysis of Soil Community DNA from a Chronosequence Warming Experiments at Harvard Forest
  • Primary Author: William Rodr√≠guez-Reillo (University of Massachusetts - Amherst )
  • Additional Authors: Jeffrey Blanchard (University of Massachusetts - Amherst ); Kristen DeAngelis (University of Massachusetts Amherst); Serita Frey (University of New Hampshire - Main Campus); Jerry Melillo (Marine Biological Laboratory); Grace Pold (University of Massachusetts Amherst); Linda van Diepen (University of New Hampshire - Main Campus)
  • Abstract:

    Earth's climate is warming, and this is causing both biophysical (e.g., albedo) and biogeochemical (e.g., carbon cycle) feedbacks to the climate system. Increased temperature seems to alter soil organic matter (SOM) processing, and if warming accelerates SOM decomposition, then carbon (C) stored in soils will transfer to the atmosphere, resulting in a self-reinforcing (positive) feedback to the climate system. Though soil microbes are major drivers of soil C cycling, we lack an understanding of how temperature affects SOM decomposition. In addition, unique decomposer communities can also influence organic matter chemistry, which in turn can affect SOM decomposition. Ongoing field warming sites at the Harvard Forest (Petersham, MA) have experienced 5o C above ambient soil temperatures at three replicated experiments for 5, 8 and 20 years. These experiments now correspond to three distinct phases of CO2 emissions observed in the oldest field study site. This chronosequence offers a unique opportunity to understand how climate change affects soil microbial community composition and activity over time. DNA was extracted from the warming plots and sequenced by DOE's Joint Genome Institute to test whether the microbial community shifts, under chronically warmed conditions, towards one better suited to access declining stocks of labile C over short-term warming, and to decompose recalcitrant C compounds over long-term warming. Averaged over all samples bacteria comprise 98% of the total DNA. Fungi, in particular, the Ascomycota and Basidiomycota account for 84% of eukaryotic DNA. Our analyses to date on changes on microbial community structure and function indicate significant differences between organic and mineral layers, some differences between sites, but no strong treatment effect.

  • Research Category: Physiological Ecology, Population Dynamics, and Species Interactions, Soil Carbon and Nitrogen Dynamics