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Harvard Forest Symposium Abstract 2013

  • Title: Effects of winter climate change on stem and belowground carbon dioxide efflux in a mixed-hardwood forest
  • Primary Author: Pamela Templer (Boston University)
  • Additional Authors: Andrew Reinmann (Boston University)
  • Abstract:

    Forests of the northeastern U.S. typically have a continuous snowpack in winter, which insulates soils below it. However, winters with a late-developing or intermittent snowpack can result in colder soil temperatures and a greater frequency and depth of soil frost. Climate models project a reduction in snowpack depth and duration by the end of the 21st century in the northeastern U.S., which may have important implications for ecosystem carbon fluxes and the ability of forests to mitigate climate change through carbon uptake and storage in biomass and soils. The objectives of this research were to quantify the effects of reduced winter snowpack and increased soil frost on rates of carbon dioxide (CO2) efflux from soil and tree stems. We are conducting a snow removal experiment in mixed stands of red oak (Quercus rubra) and red maple (Acer rubrum) trees at Harvard Forest in central Massachusetts. Snow was removed from three plots (13m x 13m) during the first four to five weeks of the 2010/2011 and 2011/2012 winters to mimic a later development of snowpack and to induce soil frost.



    During the first year of this multi-year study snow removal increased the depth and duration of soil frost, increased the frequency of freeze-thaw cycles, and impeded soil warming in the spring compared to the reference plots. Aboveground losses of CO2 from tree stems during the growing season were higher for red oak trees than red maple trees, but were not altered by a reduced snowpack and increased soil frost in the previous winter. Stem CO2 efflux was equivalent to 19-24% and 24-34% of belowground losses of CO2 per unit surface area during the growing season for red maple trees and red oak trees, respectively. A reduced snowpack and increased soil frost did not alter rates of heterotrophic respiration (P > 0.05). In contrast, annual rates of total soil respiration increased by 25%, indicating an increased contribution from root and rhizosphere respiration; however, this difference was not statistically significant (P > 0.05), likely due to the high spatial variability in rates of soil respiration. Results of this study to date suggest that a reduced winter snowpack and increased soil frost may not have a large effect on stem efflux of CO2, but may increase total losses of CO2 from mixed-hardwood forests.

  • Research Category: Forest-Atmosphere Exchange
    Regional Studies
    Soil Carbon and Nitrogen Dynamics