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Harvard Forest REU Symposium Abstract 2008
- Title: Hemlock Forest Vegetation Dynamics: Long-term Responses to Hemlock Woolly Adelgid
- Author: Relena R Ribbons (University of Copenhagen)
- Abstract:
Eastern hemlock (Tsuga canadensis) stands across the eastern United States are being infested by hemlock woolly adelgid (Adelges tsugae) exhibiting mortality within 4-10 years of initial invasion. The purpose of our study was to investigate overstory and understory vegetation dynamics associated with chronic adelgid infestation. In 1995, forest structure, composition, health, and physical site characteristics were examined at eleven sites in central Connecticut. Permanent plots were established at each site and were re-sampled this year. Field methods included overstory dbh measurements, crown classification, T. canadensis mortality levels and understory vegetation identification and percent cover estimates. Overstory mortality was variable across sites, ranging from 10-98% and three field sites originally containing 50-90% hemlock have since lost over 95% of hemlock trees. Hemlock mortality has resulted in a shift in forest structure, to forests dominated by Betula lenta (black birch), Acer rubrum (red maple) and Fagus grandifolia (beech) saplings. Black birch sapling density increased from 125-250 ha-1 to >4,000 ha-1at some sites. In heavily damaged stands, black birch has recently recruited into the tree size category (>8cm dbh). Healthy hemlocks remain at some sites, despite 15 years of adelgid infestation. Research will continue to focus on community vegetation responses to the decline of hemlocks, in existing and future plots.
- Research Category: Invasive Plants, Pests & Pathogens; Large Experiments and Permanent Plot Studies
