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Assessment of landscape correlates of Eastern hemlock decline due to hemlock woolly adelgid

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By: , and 
Edited by: K.A. McManusK.S. Shields, and D.R. Souto

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Abstract

Eastern hemlock (Tsuga canadensis) is in decline throughout its range in the eastern US due to infestation by an exotic insect pest, the hemlock woolly adelgid (Adelges tsugae). In Shenandoah National Park, the hemlock woolly adelgid (HWA) rapidly killed many stands of hemlock after first appearing in the late-1980’s, while having only minor impact in other stands. At present, few investigators have examined the mechanisms that produce this discontinuous impact, although landscape factors are predicted to play a major role (Orwig and Foster, 1998: Perry 1988). In an effort to address possible landscape correlates to hemlock decline, we conducted a preliminary analysis of 5 years of hemlock health estimates in comparison to measures of terrain, stand isolation, and potential dispersal corridors at the stand level. We found that elevation, slope, light conditions, and distance to streams all exhibited relatively strong correlation with hemlock decline, although the relationship varied by year. In addition, there appears to be some evidence of spatial autocorrelation in decline, suggesting that similar environmental conditions are either controlling the adelgid or making hemlock stands more susceptible to HWA. We are using the results of this preliminary analysis to guide more detailed efforts aimed at modeling hemlock stand vulnerability as a result of site, landscape, and regional factors.

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Publication type Report
Publication Subtype Other Report
Title Assessment of landscape correlates of Eastern hemlock decline due to hemlock woolly adelgid
Year Published 1999
Language English
Publisher U.S. Department of Agriculture
Publisher location Newtown Square, PA
Contributing office(s) Leetown Science Center
Description 1 p.
Larger Work Type Report
Larger Work Subtype Other Report
Larger Work Title Proceedings, Symposium on sustainable management of hemlock ecosystems in Eastern North America
First page 134
Last page 134
Conference Title Symposium on sustainable management of hemlock ecosystems in Eastern North America
Conference Location Durham, New Hampshire
Country United States
State Virginia
Other Geospatial Shenandoah National Park
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