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Harvard Forest >

Harvard Forest Symposium Abstract 2017

  • Title: From the ground up: development of eastern hemlock seedling, sapling, and canopy growth
  • Primary Author: Molly Wieringa (Harvard University)
  • Additional Authors: David Orwig (Harvard Forest); Neil Pederson (Harvard Forest)
  • 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 investigations 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 well-covered in scientific literature, we have endeavored 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 in the Harvard Forest, we hypothesized that eastern hemlock is capable of employing a competitive regenerative mechanism known as a seedling bank. Within the mega-plot, we selected 100 seedlings from subplots where 48 overstory hemlocks had been cored in 2015. Each core and seedling was visually dated, cross-dated, and used to create growth chronologies for Prospect Hill’s seedling, understory, and overstory strata. We found that seedlings from the mega-plot established primarily between 1960 and 1985, ranged in age from 16 to 85 with an average of 38 years, 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 expected, from the decline of overstory hemlock. The lack of response is 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: Invasive Plants, Pests & Pathogens; Large Experiments and Permanent Plot Studies