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Harvard Forest Symposium Abstract 2016

  • Title: Carbon flux patterns and altered microbial community structure and function at the Prospect Hill Soil Warming Experiment, Harvard Forest
  • Primary Author: Jerry Melillo (Marine Biological Laboratory)
  • Additional Authors: Michael Bernard (Marine Biological Laboratory); Frank Bowles (Research Designs); Kristen DeAngelis (University of Massachusetts Amherst); Serita Frey (University of New Hampshire - Main Campus); Grace Pold (University of Massachusetts - Amherst ); William Werner (Marine Biological Laboratory)
  • Abstract:

    The Prospect Hill soil warming experiment was designed to study how the terrestrial carbon-cycle will feedback to the climate system as the world warms based on observations of C fluxes, N availability, and microbial community structure and function. In 1991, 18 6x6 m plots were established in the Prospect Hill Forest Tract of Harvard Forest and assigned to three treatments: heated plots warmed 5 deg C above ambient soil temperature using resistance cables, disturbance control plots identical to heated plots that receive no electricity, and undisturbed control plots. We have observed a pattern of soil carbon fluxes that can be broken into three distinct phases: an ephemeral increase (relative to control plots) during the first ten years (Phase I), a seven-year period during which there was no significant response (Phase II), and a resumed increase that is currently ongoing (Phase III). We also observed a transient increase in rates of nitrogen mineralization during Phase I, but rates have dropped to control levels when measured during phases II and III. Soil warming has led to changes in microbial community function and structure. Lab incubations with 13C labeled compounds have revealed that efficiency of phenol utilization was greater in soil taken from heated plots relative to the control at higher soil temperatures; whereas, metagenomic studies show that Actinobacteria, Acidobacteria and Alpha-proteobacteria have responded strongly to warming. Long-term warming is likely creating more niche space in organic layer soils, which is manifested as increased bacterial alpha diversity, shifting beta diversity, and increased abundance of bacteria. Further studies promise to illuminate the C cycling pathways in these communities that are responding to warming and associated changes in microbially available carbon.

  • Research Category: Large Experiments and Permanent Plot Studies
    Soil Carbon and Nitrogen Dynamics