Eastern hemlock decline in riparian areas from Maine to Alabama

  • Authors: Evans, Daniel; Aust, Michael; Dolloff, C.; Templeton, Ben; Peterson, John
  • Publication Year: 2011
  • Publication Series: Scientific Journal (JRNL)
  • Source: Northern Journal of Applied Forestry 28(2):97-104


Eastern hemlock (Tsuga canadensis) in the Appalachian mountain range is threatened by the introduced hemlock woolly adelgid (Adelges tsugae). Potential impacts on riparian systems are great because of eastern hemlock’s role as a foundation species that influences site soil, vegetation, and stream characteristics. We installed permanent research sites at 49 locations in riparian areas, from Maine to Alabama, to survey eastern hemlock health, measure stand dynamics, and predict near-term forest composition without eastern hemlock. This report summarizes the initial stand measurements from summer of 2008. We found hemlock woolly adelgid present at 25 of 49 stands from Massachusetts to Georgia, and all of these stands had some degree of hemlock decline. New England states, Ohio, western Pennsylvania, Kentucky, and Alabama had good hemlock health and no sign of hemlock woolly adelgid. Eighteen of the 49 sites had no nonhemlock conifer species in the overstory, and 30 of 49 sites had less than 5 m2 ha-1 of nonhemlock conifers. Without eastern hemlock, 25 of the stands would have more than 90% hardwood in the overstory, many of which are in the mid-Atlantic and southern states at sites dominated by shrubs in the understory such as Rhododendron maximum. Competition from shrubs may hinder stand regeneration after disturbance by hemlock woolly adelgid. On the basis of the abundance of hardwood species and lack of conifer species present in the overstory at many infested hemlock-dominated stands, these sites may convert to hardwood-dominated stands, which will affect terrestrial and aquatic ecosystem dynamics.

  • Citation: Evans, Daniel M.; Aust, Michael W.; Dolloff, C. Andrew; Templeton, Ben S.; Peterson, John A. 2011. Eastern hemlock decline in riparian areas from Maine to Alabama. Northern Journal of Applied Forestry 28(2):97-104.
  • Keywords: eastern hemlock, hemlock woolly adelgid, forest insect pests, forest disturbance, shrub competition
  • Posted Date: June 17, 2011
  • Modified Date: July 21, 2011
  • Requesting Print Publications

    Publication requests are subject to availability. Fiscal responsibility limits the hardcopies of publications we produce and distribute. Electronic versions of publications may be downloaded, distributed and printed.

    Please make any requests at pubrequest@fs.fed.us.

    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.