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Harvard Forest REU Symposium Abstract 2019

  • Title: The future of eastern forests without hemlock
  • Author: Samantha Matson (Virginia Polytechnic Institute and State University)
  • Abstract:

    Eastern hemlock (Tsuga canadensis) is a foundation species native to eastern deciduous forests that provides ecosystem services including microclimate control, stream stabilization, and biodiversity. The invasive insect, hemlock woolly adelgid (Adelges tsugae), is spreading across the Northeast and Appalachians, killing hemlock trees and stands and subsequently altering the composition and structure of the forest. Prior work in southern New England has shown that shade intolerant and hardwood species such as black birch are replacing the hemlock forests. Using long term regeneration data and sapling height measurements from the logged and girdled treatments of Harvard Forest’s Hemlock Removal Experiment, I examined four emerging understory trees for relative abundance and rate of growth over time. Unsurprisingly and across both treatments, black birch is by far the most numerous and tallest while pine density is steadily increasing over time. In the girdled treatment, black birch heights are lower than in the logged treatment. The heights of white pine are closer to black birch in the girdled treatment. Annual growth (internode length) measurements in pine show steady rates each year in the girdled treatment while they are declining in the logged treatment. This data supports the idea that pine will take part in the future canopy of this forest, at least in the girdled plots. By continuing with this research, we will be able to test these predicted changes in forest dynamics to New England’s forests without hemlock.

  • Research Category: Invasive Plants, Pests & Pathogens