Open Journal of Forestry

Volume 4, Issue 5 (October 2014)

ISSN Print: 2163-0429   ISSN Online: 2163-0437

Google-based Impact Factor: 1.36  Citations  

Spatial Distribution of Hemlock Woolly Adelgid Induced Hemlock Mortality in the Southern Appalachians

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DOI: 10.4236/ojf.2014.45053    3,004 Downloads   4,020 Views  Citations


Hemlock woolly adelgid (Adelges Tsugae Annand, HWA) outbreaks are posing a major threat to eastern hemlock (Tsuga canadensis L. Carr.) and Carolina hemlock (Tsuga caroliniana Engelm.) forest landscapes in the eastern USA. As foundation species, hemlocks play a variety of functional roles in forest landscapes. These species usually occur as isolated canopies and mixed species in landscapes where variation in topography is extreme. Spatially explicit inventory information on HWA induced hemlock mortality at landscape scale does not exist. High resolution aerial imageries enable landscape scale assessment even at the individual tree level. Accordingly, our goal was to investigate spatial pattern and distribution of HWA induced hemlock mortality using a high resolution aerial image mosaic in the Linville River Gorge, Southern Appalachians, western North Carolina. Our study objectives were: 1) to detect dead trees within the Lower Linville River watershed; 2) to estimate the area occupied by dead trees in the forest canopy surface; 3) to investigate the relationship of dead hemlocks and topography; and 4) to define the spatial pattern of the dead trees. We found ca. 10,000 dead trees within the study area, occupying over 7 ha of the canopy surface with an average area of 36 m2 per dead tree. The density of the dead trees was higher in proximity to the Linville River, at higher elevations, and on northern and northwestern aspects. Spatial pattern of the dead trees was generally clustered at all spatial scales. We suggest that although the reduction in plant biomass resulting from herbivory within the landscapes is modest, impact of the clustered distribution of hemlock mortality, especially in the riparian zones, is noteworthy. Our analysis of the pattern of hemlock decline provides new means for projecting future impacts of HWA on the range of hemlock distribution in eastern North America.

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Kantola, T. , Lyytikäinen-Saarenmaa, P. , Coulson, R. , Strauch, S. , Tchakerian, M. , Holopainen, M. , Saarenmaa, H. and Streett, D. (2014) Spatial Distribution of Hemlock Woolly Adelgid Induced Hemlock Mortality in the Southern Appalachians. Open Journal of Forestry, 4, 492-506. doi: 10.4236/ojf.2014.45053.

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[4] When a foundation crumbles: forecasting forest community dynamics following the decline of the foundation species Tsuga canadensis
[5] When a foundation crumbles: forecasting forest dynamics following the decline of the foundation species Tsuga canadensis
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[6] Development of monitoring methods for Hemlock Woolly Adelgid induced tree mortality within a Southern Appalachian landscape with inhibited access
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[7] Influence of soil and topography on defoliation intensity during an extended outbreak of the common pine sawfly (Diprion pini L.)
[8] Hemlock Woolly Adelgid (Adelges tsugae) and Hemlock (Tsuga spp.) in Western North Carolina: What do the Forest Inventory and Analysis Data Tell Us?
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