You are here

Harvard Forest >

Harvard Forest REU Symposium Abstract 2019

  • Title: Quantifying Death: Characterizing patterns of oak mortality in North-central Massachusetts in the aftermath of the most recent gypsy moth outbreak. ​
  • Author: Sofia Kruszka (University of Michigan (all campuses))
  • Abstract:

    The oak genus Quercus is an important species group in the eastern United States, supporting an array of wildlife and contributing nutrients to terrestrial and aquatic ecosystems. Larvae of the invasive gypsy moth Lymantria dispar from Europe and Asia defoliate oak tree species, and the weakened oaks are subsequently vulnerable to other forest insects and pathogens. A recent gypsy moth outbreak from 2015-2018 defoliated over 900,000 acres in Massachusetts at its peak in 2017. Despite widespread gypsy moth defoliation in Massachusetts, oak mortality varies among adjacent stands. I investigated the extent of oak mortality in the aftermath of this gypsy moth outbreak. I measured and assessed tree mortality and dieback in ten 0.12-hectare plots in North-central Massachusetts. With this data, I ran linear and logistic regression models to determine the variables that most closely predicted tree condition. I found that a combination of species, plot, canopy exposure, and trunk diameter most significantly predicted mortality of trees of all species (AICc(null) = 670.948, AICc(mod) = 531.875). For oaks, canopy exposure and plot most significantly predicted mortality (AICc(null) = 255.135, AICc(mod) =219.119). Canopy exposure and trunk diameter did not closely relate to dieback for Quercus species, which is not consistent with previous findings. These results suggest that the dynamics between gypsy moths, oaks, and forest conditions of this outbreak are different from past events.

  • Research Category: Group Projects; Invasive Plants, Pests & Pathogens