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Harvard Forest Symposium Abstract 2011

  • Title: The impacts of a reduced winter snowpack on heterotrophic and rhizospheric soil respiration in a mixed-hardwood northern forest
  • Primary Author: Andrew Reinmann (Boston University)
  • Additional Authors: Pamela Templer (Boston University)
  • Abstract:

    In northern forests, soil frost is a natural event that occurs when there is insufficient snow accumulation to insulate soils in winter. Northern forests typically have a continuous snowpack for much of the winter. However, winters with a late-developing or intermittent snowpack occasionally occur and may result in colder soil temperatures and a greater frequency and severity of soil frost. Such variability in winter climate can affect rates of soil respiration and may contribute to interannual variability in ecosystem carbon exchange. Climate models predict 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 belowground carbon fluxes. We are conducting a snow removal experiment to quantify the impacts of a reduced winter snowpack on soil respiration. We hypothesized that a reduced winter snowpack and increased soil frost would lead to (1) increased rates of rhizospheric soil respiration, but reduced rates of heterotrophic soil respiration, with a net reduction in total soil respiration, and (2) a delay in early growing season plant dynamics such as leaf-out time, carbon fixation, and rhizospheric respiration.



    To examine the impacts of a reduced snowpack on carbon dynamics of a northern forest, we established six 13m x 13m plots in the Prospect Hill Tract of Harvard Forest. Snow was removed from three plots in early-winter beginning in December 2010. Total soil respiration and its heterotrophic and rhizospheric components are being quantified in each plot when snow is absent. Timing of leaf-out, root growth, and canopy photosynthesis are also being measured in these plots. The relationships between above- and belowground carbon fluxes will be examined. Preliminary results from the first winter of snow removal indicate that while shallow soil frost (<5 cm depth) was present prior to snowpack development (late-December), the presence of a snowpack in the reference plots facilitated thawing of the frozen soils beneath it. In contrast, soil frost depth in the snow removal plots increased throughout the winter to a maximum depth of 20 cm. A reduced snowpack also increased the frequency of freeze-thaw events in the top 5-10 cm of the soil.

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