Biological Invasions

, Volume 12, Issue 9, pp 3135–3143 | Cite as

The aftermath of an invasion: Structure and composition of Central Appalachian hemlock forests following establishment of the hemlock woolly adelgid, Adelges tsugae

  • Heather L. Spaulding
  • Lynne K. RieskeEmail author
Original Paper


As the highly invasive hemlock woolly adelgid, Adelges tsugae, continues to expand its distribution in eastern North America, affected forests will incur drastic changes in composition and structure. While these changes have been well-studied in dense hemlock forests in the Northeast, relatively little work is known about the effects of the adelgid at the western edge of the range of eastern hemlock, Tsuga canadensis. We evaluated the nature and extent of these changes using vegetation assessments coupled with growth simulations. The woody plant community was assessed in three strata (upper, mid- and lower) and was used to predict forest succession. Using the Forest Vegetation Simulator (FVS), we then projected the growth of hemlock forests 20 years into the future with and without the effects of the adelgid. In forest simulations lacking adelgid invasion, little change in composition or structure is forecast. In contrast, our projections predict a near complete loss of the hemlock forest type within 20 years of adelgid establishment, with widespread conversion to hardwood forest types, most notably white oak-red oak-hickory, chestnut oak-black oak-scarlet oak, and yellow poplar-white oak-red oak. Hemlock loss will result in denser deciduous forests with thinner canopies and multiple gaps, and significant alterations to terrestrial and aquatic wildlife habitat.


Hemlock Tsuga Adelges tsugae Forest vegetation simulator Modeling 



We would like to thank Melanie Antonik, Keith Holmes, Amber Jones, Tommy Kuhlman, Brian Marbert, Aric Payne, and Matt Thomas for their help with vegetation surveys and data entry. Rob Paratley provided taxonomic assistance, Angela Schoergendorfer offered statistical advice, and Talbot Trotter (USDA Forest Service) provided assistance with the Hemlock Woolly Adelgid Event Monitor. We would also like to thank Kyle Napier (Kentucky State Nature Preserves Commission), Merril Flanary (Kentucky Natural Lands Trust Commission), and Rob Watts (Eastern Kentucky University) for help in selecting our study sites. John Obrycki and two anonymous reviewers provided comments on an earlier version of this manuscript. This research was supported by funds from the USDA Forest Service Southern Research Station and the Kentucky Agricultural Experiment Station, and is published as Experiment Station Project 09-08-047.


  1. Anon. (2003) Natural resource information service (NRIS): field sampled vegetation (FSVeg) Common Stand Exam. V1.5.1. USDA Forest Service, Rocky Mountain Research Station, Fort Collins, COGoogle Scholar
  2. Arner SL, Woudenberg S, Waters S, Vissage J, MacLean C, Thompson M, Hansen M (2001) National algorithm for determining stocking class, stand size class, and forest type for forest inventory and analysis plots. USDA Forest Service Northeastern Research Station Internal Rep., Newtown Square, PA 10 pGoogle Scholar
  3. Boettcher SE, Kalisz PJ (1990) Single-tree influence on soil properties in the mountains of Eastern Kentucky. Ecology 71:1365–1372CrossRefGoogle Scholar
  4. Callaway RM, Aschehoug ET (2000) Invasive plants versus their new and old neighbors: a mechanism for exotic invasion. Science 290:521–523CrossRefPubMedGoogle Scholar
  5. Callaway RM, Ridenour WM (2004) Novel weapons: invasive success and the evolution of increased competitive ability Front. Ecol Environ 2:436–443CrossRefGoogle Scholar
  6. Callaway RM, Thelen GC, Rodriguez A, Holben WE (2004) Soil biota and exotic plant invasion. Nature 427:731–733CrossRefPubMedGoogle Scholar
  7. Chornesky EA, Bartuska AM, Aplet GH et al (2005) Science priorities for reducing the threat of invasive species to sustainable forestry. Bioscience 55:335–348CrossRefGoogle Scholar
  8. Clavero M, Garcia-Berthou E (2005) Invasive species are a leading cause of animal extinctions. Trends Ecol Evol 20:110CrossRefPubMedGoogle Scholar
  9. Coleman TW, Clarke SR, Meeker JR, Rieske LK (2008) Forest composition following overstory mortality from southern pine beetle and associated treatments. Can J For Res 38:1406–1418CrossRefGoogle Scholar
  10. Colunga-Garcia M, Haack RA, Adesoji OA (2009) Freight transportation and the potential for invasions of exotic insects in urban and periurban forests of the United States. J Econ Entomol 102(1):237–246CrossRefPubMedGoogle Scholar
  11. D’Amato AW, Orwig DA, Foster DR (2008) The influence of successional processes and disturbance on the structure of Tsuga canadensis forests. Ecol Appl 18:1182–1199CrossRefPubMedGoogle Scholar
  12. Dixon GE (2002) Essential FVS: a user’s guide to the forest vegetation simulator. Internal rep. Fort Collins, CO: US Department of Agriculture, Forest Service, Forest Management Service CenterGoogle Scholar
  13. Donnelly D, Lilly B, Smith E (2001) Southern (SN) variant overview: forest vegetation simulator. USDA Forest Service Forest Management Service Center, Fort Collins, COGoogle Scholar
  14. Evans AM, Gregoire TG (2007) A geographically variable model of hemlock woolly adelgid spread. Biol Invasions 9:369–382CrossRefGoogle Scholar
  15. Ford CR, Vose JM (2007) Tsuga canadensis (L.) Carr. mortality will impact hydrologic processes in southern appalachian forest ecosystems. Ecol Appl 17:1156–1167CrossRefPubMedGoogle Scholar
  16. Forest Health Technology Enterprise Team (2008) The Hemlock Woolly Adelgid event monitor users guide. USDA Forest Service Natural Resources Research Center, Fort Collins, COGoogle Scholar
  17. Godman RM, Lancaster K (1990) Eastern Hemlock. In: Burns RM, Honkala BH (eds) Silvics of North America: 1. Conifers. USDA Forest Service Agric. Handbook 654, USA, pp 604–612Google Scholar
  18. Griffin S (2007) Hemlock Woolly Adelgids in Georgia. Georgia forestry commission. Online:
  19. McClure MS (1990) Role of wind, birds, deer, and humans in the dispersal of hemlock woolly adelgid (Homoptera, Adelgidae). Environ Entomol 19:36–43Google Scholar
  20. McClure MS, Cheah CASJ (1999) Reshaping the ecology of invading populations of hemlock woolly adelgid, Adelges tsugae (Homoptera: Adelgidae), in eastern North America. Biol Invasions 1:247–254CrossRefGoogle Scholar
  21. Mencuccini M (2003) The ecological significance of long-distance water transport: short-term regulation, long-term acclimation and the hydraulic costs of stature across plant life forms. Plant Cell Environ 26:163–182CrossRefGoogle Scholar
  22. Nilsen ET, Walker JF, Miller OK, Semones SW, Lei TT, Clinton BD (1999) Inhibition of seedling survival under Rhododendron maximum (Ericaceae): could allelopathy be a cause? Am J Bot 86:1597–1605CrossRefPubMedGoogle Scholar
  23. Nilsen ET, Clinton BD, Lei TT, Miller OK, Semones SW, Walker FJ (2001) Does Rhododendron maximum L. (Ericaceae) reduce the availability of resources above and belowground for canopy tree seedlings? Am Midl Nat 145:325–343CrossRefGoogle Scholar
  24. Orwig DA, Foster DR (1998) Forest response to the introduced hemlock woolly adelgid in southern New England, USA. J Torrey Bot Soc 125:60–73CrossRefGoogle Scholar
  25. Orwig DA and Foster DR (2000) Stand, landscape, and ecosystem analysis of hemlock woolly adelgid outbreaks in southern New England: an overview. In: McManus KA, Shields KS and Souto DR (eds) Proceedings: symposium on sustainable management of hemlock ecosystems in Eastern North America. USDA General technical report 267. Newtown Square, PA, pp. 123–125Google Scholar
  26. Preisser E, Elkinton J, Abell K, Miller-Pierce M, and Orwig DA (2008) Interactions between hemlock woolly adelgid and elongate hemlock scale in New England hemlock forests. In: Onken B and Reardon R (eds) Fourth symposium on hemlock woolly adelgid in the eastern United States. USDA Forest Service FHTET 2008-01, pp. 212–213Google Scholar
  27. Souto D, Luther T, Chianese B (1996) Past and current status of HWA in eastern and Carolina hemlock stands. In: Salom SM, Tignor TC, Reardon RC (eds) Proceedings of the first hemlock woolly adelgid review. USDA Forest Service, Morgantown, WV, pp. 9–15Google Scholar
  28. Spaulding HL (2009) Forests of the future: simulating the effects of exotic invasive species on forest structure and composition. MS thesis, University of Kentucky, LexingtonGoogle Scholar
  29. Stadler B, Müller T, Orwig D, Cobb R (2005) Hemlock woolly adelgid in New England forests: canopy impacts transforming ecosystem processes and landscapes. Ecosystems 8:233–247CrossRefGoogle Scholar
  30. Sullivan KA, Ellison AM (2006) The seed bank of hemlock forests: implications for forest regeneration following hemlock decline. J Torrey Bot Soc 133:393–402CrossRefGoogle Scholar
  31. Swank WT, Crossley DA (eds) (1988) Forest hydrology and ecology at Coweta. Springer-Verlag, New York, NYGoogle Scholar
  32. Walker JR, Lei T, Semones S, Nilsen E, Clinton BD, Miller OK (1999) Suppression of ectomycorrhizae on canopy tree seedlings in Rhododendron maximum L. (Ericaceae) thickets in the southern Appalachians. Mycorrhiza 9:49–56CrossRefGoogle Scholar
  33. Ward JS, Montgomery ME, Cheah CASJ, Onken BP, Cowles RS (2004) Eastern hemlock forests: guidelines to minimize the impacts of hemlock woolly adelgid. USDA Forest Service NA-TP-03-04, Morgantown, WV 28 ppGoogle Scholar
  34. Weckel M, Tirpak JM, Nagy C, Christie R (2006) Structural and compositional change in an old-growth eastern hemlock Tsuga canadensis forest, 1965–2004. For Ecol Manage 231:114–118CrossRefGoogle Scholar
  35. Wilcoxon F (1945) Individual comparisons by ranking methods. Biometrics Bull 1:80–83CrossRefGoogle Scholar
  36. UK Ag Weather Center (2007). Online:
  37. Walters RS, Yawney HW (1990) Red maple. In: Burns RM, Honkala BH (eds) Silvics of North America: 2. Hardwoods. USDA Forest Service Agriculture Handbook 654, USA, pp 164–179Google Scholar

Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  1. 1.Department of EntomologyUniversity of KentuckyLexingtonUSA

Personalised recommendations