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Harvard Forest REU Symposium Abstract 2005

  • Title: Ten year revisit of stand dynamics associated with hemlock woolly adelgid infestation in southern Connecticut
  • Author: Kelly M Walton (State University of New York College of Environmental Science and Forestry)
  • Abstract:

    Hemlock woolly adelgid (HWA) is an invasive insect from Japan that has slowly spread across the eastern United States since it entered Virginia in 1950. HWA is a little understood pest that is causing a gradual decline of eastern and Carolina hemlocks on the east coast. To increase understanding of forest dynamics following long- term HWA infestation, I visited 8 hemlock stands in south- central Connecticut. At each site I counted the mortality of hemlocks, and examined the understory vegetation dynamics by counting percent cover of herbs, shrubs, and seedlings in 1 m2 plots. Also, I cored hemlock and hardwood trees to look for growth trends in response to continued hemlock deterioration. The mortality of hemlocks is dramatic, with 7 of the 8 sites having near or above 80% mortality in 2005, compared to 2 of 8 sites in 1995. In the understory many of the plots show an increase in hayscented fern or black birch. Most of the hardwoods are showing sudden increases in radial growth and hemlocks show dramatic decreases to a fraction of a millimeter per year since HWA infestation in the late 1980s and early 1900s (figure 1). The overall outlook for hemlock forests in south- central Connecticut is continued deterioration, high mortality, and extremely low radial growth on remaining live hemlock trees. The forest is being transformed from sparse vegetation to high fern and black birch cover as the hemlocks die, causing a shift toward a hardwood dominated forest in the future.

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