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Harvard Forest REU Symposium Abstract 2012

  • Title: Ungulate Response to Simulated Hemlock Woolly Adelgid and Salvage Logging Disturbance
  • Author: Andrew J Moe (Vermilion Community College)
  • Abstract:



    Declines in Eastern Hemlock (Tsuga canadensis) forests resulting from infestation of Hemlock Woolly Adelgid (HWA; Adelges tsugae) and associated salvage logging operations are expected to result in widespread transition to hardwood-dominated forest communities in the Northeast. Moose (Alces alces) and white-tailed deer (Odocoileus virginianus) are large herbivores that utilize hemlock and surrounding hardwood stands, and are often associated with recently disturbed habitat . Still—little is known about how these herbivores will interact with HWA to shape regenerating hardwood stands or whether these animals will forage differently in logged vs. insect-killed stands.

    Ungulate activity—browsing, pellet groups, and camera traps—was assessed at the Harvard Forest Hemlock Removal Experiment, which consists of two blocks of four replicate treatments: girdled hemlocks, simulating HWA outbreak, salvage logging, hemlock control, and hardwood control. In addition, understory woody vegetation—stem density, stem height, diameter, and composition—was sampled in recently constructed (November 2011) 15x30m exclosures and paired control plots at each of the treatments.

    Browsing intensity (proportion of stems browsed) and pellet group density were strongly correlated, and browsing was more intense in the logged than in the girdled and undisturbed plots. Images recorded from the camera traps (number of individuals, duration of visit, and activity during visit) did not differ among treatments and were uncorrelated with browsing intensity and pellet groups. As expected, no significant differences in stem density, stem height, or browsing intensity had emerged yet between the fenced and control plots after only 8 months. Overstory treatments, were, however, significant predictors of stem height and stem density.

    As stem height was greatest in the logged plots, and stem density was highest in the girdled plots, this apparent preference of ungulates for the logged plots over the girdled plots suggests that stem vigor (i.e. growth rate) may be a more important factor than stem density in attracting ungulates to disturbed sites. These results suggest that preemptively logged hemlock stands may yield superior foraging habitat to HWA killed stands. Ungulates, in turn, may have greater browsing impacts in salvage logged areas than in HWA-infested areas.

  • Research Category: Biodiversity Studies