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Harvard Forest REU Symposium Abstract 2017

  • Title: The Effects of Long Term Soil Warming on Soil Respiration and Carbon Storage
  • Author: States D Labrum (Columbia State Community College)
  • Abstract:

    Soil organic matter (SOM) contains the largest carbon pool in the terrestrial ecosystem. As the earth warms, accelerated microbial respiration will increase the flux of carbon released from the soil into the atmosphere. Warming may result in a self-reinforcing feedback loop affecting climate - SOM decay accelerates due to increased microbial respiration, and soil organic carbon is transformed to atmospheric CO2, which leads to further warming and decreased soil carbon storage. In the Prospect Hill Soil Warming Experiment, warming has increased annual carbon fluxes, but we noted a pattern of decreased soil respiration in the heated plots relative to the control at any given temperature, a phenomenon we refer to as thermal acclimation. To understand what drives thermal acclimation, we incubated soils in the laboratory, using heated and control soils separated by horizon at six temperatures. We observed relationships between temperature and respiration qualitatively similar to field data. We found a decrease in microbial biomass in heated soils explained much of the decrease in respiration relative to control soils. In a second set of incubations, we amended the soils with sucrose to remove potential substrate limitation, which further minimized the difference in respiration between the treatments. We conclude that the reduction in microbial biomass and substrate limitation are primarily responsible for thermal acclimation. Previous studies from the Prospect Hill experiment have provided evidence of functional and structural changes in the microbial community, leading us to hypothesize that those changes could explain the pattern of soil acclimation over the 26-year experiment.

  • Research Category: Soil Carbon and Nitrogen Dynamics; Large Experiments and Permanent Plot Studies; Forest-Atmosphere Exchange