Spatial distribution of hemlock woolly adelgid induced hemlock mortality in the Southern Appalachians

  • Authors: Kantola, Tuula; Lyytikäinen-Saarenmaa, Päivi; Coulson, Robert N.; Strauch, Sheryl; Tchakerian, Maria D.; Holopainen, Markus; Saarenmaa, Hannu; Streett, Douglas A.
  • Publication Year: 2014
  • Publication Series: Scientific Journal (JRNL)
  • Source: Open Journal of Forestry 4(05)
  • DOI: 10.4236/ojf.2014.45053

Abstract

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.

  • Citation: Kantola, Tuula; Lyytikäinen-Saarenmaa, Päivi; Coulson, Robert N.; Strauch, Sheryl; Tchakerian, Maria D.; Holopainen, Markus; Saarenmaa, Hannu; Streett, Douglas A. 2014. Spatial distribution of hemlock woolly adelgid induced hemlock mortality in the Southern Appalachians. Open Journal of Forestry. 04(05): 492-506. 16 p.
  • Keywords: Adelges Tsugae, Eastern Hemlock, Southern Appalachians, Spatial pattern, Topography, Tree Mortality, Tsuga
  • Posted Date: January 5, 2015
  • Modified Date: July 13, 2015
  • Print Publications Are No Longer Available

    In an ongoing effort to be fiscally responsible, the Southern Research Station (SRS) will no longer produce and distribute hard copies of our publications. Many SRS publications are available at cost via the Government Printing Office (GPO). Electronic versions of publications may be downloaded, printed, and distributed.

    Publication Notes

    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
    • Our online publications are scanned and captured using Adobe Acrobat. During the capture process some typographical errors may occur. Please contact the SRS webmaster if you notice any errors which make this publication unusable.
    • To view this article, download the latest version of Adobe Acrobat Reader.