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Harvard Forest REU Symposium Abstract 2016

  • Title: From the Ground Up: Defining Hemlock Undergrowth on Prospect Hill
  • Author: Molly M Wieringa (Harvard University)
  • Abstract:

    Eastern hemlock (Tsuga canadensis) is an integral component of New England forests, fulfilling a unique niche in the temperate forest environment. This study continues previous investigation into the post-regenerative processes of hemlock, which is currently under attack from the invasive pest, hemlock woolly adelgid (Adelges tsugae). While hemlock is a species extensively studied in the scientific literature, we endeavor to widen the scope of study regarding its earlier life stages. Given hemlock’s shade-tolerance and longevity, and observation of seedling growth on the Prospect Hill mega-plot, we hypothesized that eastern hemlock is capable of employing a competitive regenerative mechanism known as a seedling bank. Within the mega-plot, we aged 100 seedlings (< 1 cm DBH) from subplots where 48 overstory hemlocks had been cored in 2015. Each core and seedling was visually cross-dated, and used to create growth chronologies for Prospect Hill’s seedling, understory, and overstory strata. Results suggest that seedlings from the mega-plot ranged in age from 16 to 85 with an average of 38 years, established primarily between 1960 and 1985, remained under 200 cm in height for that time, and have responded to disturbance with release numerous times. Seedlings did not show a release during the last decade, as proposed, most likely due to indiscriminate adelgid infestation. Regardless, these data suggest that eastern hemlock is capable of exhibiting the behavior of a seedling bank, allowing the species to maintain dominance within a forest.

  • Research Category: Historical and Retrospective Studies