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Harvard Forest Symposium Abstract 2019

  • Title: The depth-resolved response of New England soils to warming
  • Primary Author: Caitlin Hicks Pries (Dartmouth College)
  • Additional Authors: Serita Frey (University of New Hampshire - Main Campus); Owen Krol (Dartmouth College); Pamela Templer (Boston University)
  • Abstract:

    Over half of global soil organic carbon (SOC) is stored in subsurface soils (>20 cm depth), but little is known about the vulnerability of this deeper SOC to climate change. Most soil warming experiments have either only warmed surface soils or only examined the response of the surface carbon dioxide flux, so the sensitivity of SOC at different soil depths and the potential of various soil depths to generate feedbacks to climate change is undetermined. As predictive models of terrestrial carbon storage move toward more mechanistic process representations, we need to understand how the carbon cycle differs across soil depths. We will present depth-explicit measurements of soil CO2 production from two forest soil warming experiments in the Northeastern U.S including long-term climate manipulations at Harvard Forest (the Soil Warming and Nitrogen experiment; SWAN) and Hubbard Brook (the Climate Change Across Seasons Experiment; CCASE). At Harvard Forest, we were unable to detect a response to 12 years of warming at any depth, possibly due to the difficulty of maintaining the +5°C warming treatment during a historically wet year. At Hubbard Brook, deeper soils increased CO2 production in response to warming and decreased CO2 production in response to induced freeze thaw cycles during the winter. We have also used respiration quotients (ratios of CO2 produced to O2 consumed) to connect changes in CO2 fluxes to the carbon sources and processes that contribute to soil respiration. At Harvard Forest, respiration quotients indicate that anaerobic respiration is occurring during periods of thaw in the warmed plots. Our depth-explicit measurements have thus far demonstrated that deeper soils house an active and responsive carbon pool.

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