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Harvard Forest REU Symposium Abstract 2019

  • Title: The Light of their Lives: Canopy Change and its Effect on the Seedlings of the ForestGEO Plot
  • Author: Brianna Martinez (Bryn Mawr College)
  • Abstract:

    External conditions such as environmental factors affect any organism’s ability to grow and survive. Many biotic and abiotic factors contribute to a tree’s growth, such as insect infestation, light abundance, and water availability. Healthy hemlocks (Tsuga canadensis) and red oaks (Quercus rubra) populations are dwindling because of infestation of harmful insects. Because these trees are abundant in forests, Hemlock wooly adelgid and gypsy moth are a major threat to forest ecosystem dynamics by weakening eastern hemlock and defoliating red oak populations respectively over time. Due to this phenomenon, the canopy in areas with dense populations of these species are predicted to thin, affecting the competitive environment on the forest floor. Seedling census was taken in subplots in the ForestGeo plot in Harvard Forest to determine the growth and survivorship of eastern hemlock and red oak seedlings as a result of changes in the canopy. To determine how much the canopy has changed, hemispherical canopy photos are taken in the same plots as the seedling census, and light levels are quantified. Using a Turkey’s Honest Significant Difference Test, we found there is significant difference in percent canopy openness across the three-year timespan of our study (F2,316=16, P< 0.0001). In the same time period that the amount of eastern hemlock and red oak seedlings, which are light intolerant, decreased. We will use Integral Projection Models to project growth and survival rate of seedlings to better understand forest ecosystem dynamics.

  • Research Category: Group Projects; Large Experiments and Permanent Plot Studies; Physiological Ecology, Population Dynamics, and Species Interactions