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Canopy disturbance and growth dynamics of Carolina hemlock forests infested with hemlock woolly adelgid.

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Bibliographic Details
Title: Canopy disturbance and growth dynamics of Carolina hemlock forests infested with hemlock woolly adelgid.
Authors: Wofford, C.K.1 (AUTHOR) caseykwoff@gmail.com, Forrester, J.A.1 (AUTHOR), Keyser, T.L.2 (AUTHOR), Jetton, R.M.1 (AUTHOR)
Source: Canadian Journal of Forest Research. 6/12/2026, Vol. 56, p1-13. 13p.
Subject Terms: *Insect pests, *Tree growth, *Ecological impact, *Forest degradation, *Nature conservation, *Trees, Conifers
Geographic Terms: Appalachian Mountains, North Carolina
Abstract: Carolina hemlock (Tsuga caroliniana Engelm.) is a rare conifer endemic to the southern Appalachian Mountains. Since the early to mid‐20th century, the non‐native hemlock woolly adelgid (HWA; Adelges tsugae Annand) has threatened the persistence of both Carolina and eastern hemlocks (Tsuga canadensis (L.) Carrière) throughout the Appalachians. To assess the long‐term impacts of HWA within the context of historical growth patterns, we used dendroecological methods to reconstruct establishment dates, disturbance events, and radial growth trends for four Carolina hemlock populations in North Carolina and Tennessee. Establishment was concentrated between 1940 and 1970, after which recruitment sharply declined. Growth release analyses revealed a cyclical disturbance–recovery pattern, with major releases concentrated in the 1970s and 1990s and moderate releases distributed across decades. This cycle was disrupted following the arrival of HWA in each county. Within a decade of infestation, radial growth declined by more than 50% at some sites, and the magnitude of suppression often exceeded that observed following natural disturbance events. These persistent declines suggest long‐term physiological stress under continued pest pressure. The sustained growth suppression indicates that HWA has fundamentally altered the growth dynamics of Carolina hemlock populations. These findings underscore the urgency of conservation interventions before visible canopy decline is observed. [ABSTRACT FROM AUTHOR]
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Description
Abstract:Carolina hemlock (Tsuga caroliniana Engelm.) is a rare conifer endemic to the southern Appalachian Mountains. Since the early to mid‐20th century, the non‐native hemlock woolly adelgid (HWA; Adelges tsugae Annand) has threatened the persistence of both Carolina and eastern hemlocks (Tsuga canadensis (L.) Carrière) throughout the Appalachians. To assess the long‐term impacts of HWA within the context of historical growth patterns, we used dendroecological methods to reconstruct establishment dates, disturbance events, and radial growth trends for four Carolina hemlock populations in North Carolina and Tennessee. Establishment was concentrated between 1940 and 1970, after which recruitment sharply declined. Growth release analyses revealed a cyclical disturbance–recovery pattern, with major releases concentrated in the 1970s and 1990s and moderate releases distributed across decades. This cycle was disrupted following the arrival of HWA in each county. Within a decade of infestation, radial growth declined by more than 50% at some sites, and the magnitude of suppression often exceeded that observed following natural disturbance events. These persistent declines suggest long‐term physiological stress under continued pest pressure. The sustained growth suppression indicates that HWA has fundamentally altered the growth dynamics of Carolina hemlock populations. These findings underscore the urgency of conservation interventions before visible canopy decline is observed. [ABSTRACT FROM AUTHOR]
ISSN:00455067
DOI:10.1139/cjfr-2026-0018