Cleavitt, Nat , Eschtruth, Anne , Battles, John , Fahey, Tim .
Contrasting responses of bryophytes and vascular plants to eastern hemlock decline following a hemlock woolly adelgid outbreak.
Ecosystems dominated by eastern hemlock in the Delaware Water Gap National Recreation Area (DEWA) are currently being altered by effects of the exotic hemlock woolly adelgid, chronically elevated atmospheric deposition and several drought years. We used permanent plot data from 1994, 1995 and 2003 to examine changes in understory conditions and vegetation for two hemlock stands in the DEWA. Vegetation changes are compared and contrasted for the bryophytes and vascular plants and in-depth analyses are presented for bryophyte community changes. In comparison to the vascular flora, bryophytes had overall higher richness, faster turnover, and greater shifts in species composition. Among the bryophytes, the importance of colonist species increased between surveys and several nitrophillous species recently colonized both ravines. These results suggest a complex response to regional perturbations (e.g., nitrogen deposition, increase in small-scale disturbance and fluctuations in annual precipitation). Bryophytes and vascular plants are shown to respond to different aspects of perturbation effects and this contrast is rooted in the differential constraints imposed by their divergent physiologies. Monitoring programs designed to evaluate "forest health" should adopt a whole-flora (bryophytes and vascular plants) approach which considers the utility of mobility statistics to increase detection and interpretation of perturbation effects.
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1 - Cornell University, Department of Natural Resources, 8F Fernow Hall, Ithaca, New York, 14853-3001, USA
2 - University of California, Berkeley, Environmental Science, Policy, and Management, 151 Hilgard Hall, Berkeley, California, 94720-3110, USA
3 - Cornell University, Department of Natural Resources, 12 Fernow Hall, Ithaca, New York, 14853-3001
hemlock woolly adelgid.
Presentation Type: Oral Paper
Location: Salon F - Austin Grand Ballroom/Hilton
Date: Wednesday, August 17th, 2005
Time: 11:30 AM