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Harvard Forest Symposium Abstract 2008

  • Title: Temperature Sensitivity of Carbon Retention in Woody Debris in a Temperate Forest
  • Primary Author: Minda Berbeco (Tufts University)
  • Additional Authors: Colin Orians (Tufts University)
  • Abstract:

    Carbon retention in woody debris varies with many environmental factors, such as temperature and moisture availability. The effects of climate change (specifically warming) on carbon retention in woody debris is not yet well understood. As the soil is warmed, organisms that decompose woody debris, such as fungi, invertebrates and microbes could be given a longer active season to degrade wood. This in turn would speed the rate of wood degradation. Such increased decomposition would have significant implications for the carbon cycle as carbon is returned to the atmosphere more quickly than under current soil temperatures. Alternatively, the soil warming could result in a decrease in moisture availability within the woody debris. This would then decrease decomposer activity, slowing decomposition and increasing carbon retention in the wood. We are using the soil warming plot in Barre Woods, where the soil is being warmed to 5º C above ambient temperature, to investigate this question.

    We know from our previous research that Red Oaks have a longer carbon retention time than other species such as Sugar Maple or American Beech. We are testing the hypothesis that differences in chemistry and wood structure result in variation in decomposition among species. Wood chemistry strongly influences the decomposition of debris; more complex carbon compounds degrade more slowly. However it is not yet clear how increased warming will interact with this internal chemistry to further influence decomposition. The variation could also be due to wood structure, as more porous debris can retain larger amounts of moisture for greater periods of time. This in turn could create better environments for decomposers, resulting in higher decomposition rates. Warming could make this variation even more distinct as moisture becomes a limiting factor with less porous species.

    To date we have found no difference in the tree mortality or woody debris accumulation between the soil warming and control plots. As a consequence, the decomposition rate alone will become the sole factor controlling carbon retention in the woody detritus carbon pool. To test this hypothesis we placed several litter bags in the soil warming plot and its control with woody debris of two size classes and four locally dominant tree species. The bags will be harvested once a year for three years to assess carbon, nitrogen and lignin loss as well as changes in density.

  • Research Category: Soil Carbon and Nitrogen Dynamics