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K. L. Martin & P.C. Goebel 2010. Impact of hemlock decline on successional pathways and ecosystem function
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Impact of hemlock decline on successional pathways and ecosystem
function at multiple scales in forests of the central Appalachians, USA
Katherine L. Martin * & P. Charles Goebel
School of Environment & Natural Resources, Ohio Agricultural Research &
Development Center, The Ohio State University, 1680 Madison Ave.,
Wooster, OH 44691, USA
Abstract
Hemlock woolly adelgid (HWA) is an invasive, exotic insect causing widespread mortality in
Tsuga canadensis (L.) Carr forests of the eastern United States. T. canadensis is considered a
foundation species that dominates ravine and riparian forests across the central and southern
Appalachian Mountains. We are working to clarify how the loss of T. canadensis will affect
ecosystem function in forests of the central Appalachians at both local and landscape scales.
Using a chronosequence approach, we are examining forests within regions classified as longterm
invaded (> 10 years), recently invaded (5-10 years), and intact (not invaded). Initial
analyses indicate hemlock is particularly dominant immediately adjacent to streams, with few
other species in any of the vegetation layers. As this evergreen with poor quality leaf litter
declines, light availability and decomposition rates are increasing, changing the successional
pathways of these forests and providing resources for additional species including invasive,
non-native plant species.
Keywords: Central Hardwood Forest, Ecological disturbance, Hemlock woolly adelgid,
invasive species, Tsuga canadensis
1. Introduction
The forested landscape of eastern North America has been reshaped over the past two centuries
by introduced pests and pathogens (Lovett et al. 2006). Tsuga canadensis (L.) Carr has been an
influential canopy tree species throughout these forests from the last major glacial maximum
approximately 10,000 ybp (Allison et al. 1986, Heard and Valente 2009). Yet, an invasive
insect may eliminate it from most of its range within the next few decades. Described as a
foundation species (Ellison et al. 2005), the demise of T. canadensis will result in widespread
changes throughout forests of eastern North America. Throughout its range extending from the
southern Appalachian Mountains north to New England, the upper Great Lakes and eastern
Canada, T. canadensis dominates ecosystem processes. This evergreen conifer contributes a
unique landscape component, adding beta and gamma diversity in a matrix of largely deciduous
forests. This may be particularly important in the central and southern portions of its range,
where T. canadensis is largely restricted to riparian and cove forests along headwater streams.
In the majority of cases, it composes over half of the basal area and there is little functional
redundancy with any of the co-occurring deciduous hardwoods.
Introduced in Virginia in the 1950’s, the pest insect hemlock woolly adelgid (Adelges tsugae
Annand; hereafter HWA) has spread from northern Georgia to southern Maine and continues to
* Corresponding author. Tel: 01 330 202 3549 - Fax: 01 330 263 3658
Email address: martin.1678@osu.edu
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.