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CEGL008533 Tsuga canadensis - Betula alleghaniensis / Veratrum viride - Carex scabrata - Oclemena acuminata Swamp Forest

Type Concept Sentence: No Data Available

Common (Translated Scientific) Name: Eastern Hemlock - Yellow Birch / Green False Hellebore - Eastern Rough Sedge - Whorled Wood Aster Swamp Forest

Colloquial Name: High-Elevation Hemlock - Yellow Birch Seepage Swamp

Hierarchy Level:  Association

Type Concept: This community is currently known from scattered sites in the Northern Blue Ridge and Ridge and Valley provinces of Virginia. Similar communities have been observed in the High Allegheny Mountains of Virginia and West Virginia, the Maryland Blue Ridge, and the Ridge and Valley of east-central West Virginia. Occurrences in Pennsylvania also seem likely. The type appears to be limited to higher-elevation montane wetlands in a portion of the Central Appalachians where Rhododendron maximum is infrequent to absent. Sites are usually located in high-elevation valleys or slope concavities, in diffuse stream headwaters and lateral, groundwater-saturated flats along larger streams. Occasionally, stands occupy gentle depressions or basins influenced by seasonally perched groundwater but without flowing streams. Elevation ranges from 670-1170 m (2200-3840 feet), though most occurrences are above 900 m (3000 feet). Habitats are flat to moderately sloping and typically have >20% surface cover of boulders and stones weathered from metabasalt, granitic rocks, or sandstone. Stream-bottom habitats have pronounced hummock-and-hollow microtopography, with moss-covered mounds and intertwining roots of Betula alleghaniensis, mucky pools, and braided drainage channels. Canopy dominance is shared by Tsuga canadensis and Betula alleghaniensis in variable proportions. Minor canopy associates include Acer rubrum, Fraxinus americana, Pinus strobus, Quercus alba, and Quercus rubra. Small-tree and shrub layers are open to sparse, with Acer pensylvanicum, Hamamelis virginiana, Ilex verticillata, and Kalmia latifolia the most frequent species. Alnus incana ssp. rugosa is a dominant shrub in one sampled plot. Rhododendron catawbiense is scattered in some stands of this community in the southern part of the Northern Blue Ridge but does not form dense stands. The herb layer is well-developed and usually lush with forbs.

Diagnostic Characteristics: No Data Available

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: Several formerly outstanding, mature examples of this community type on the Blue Ridge have been devastated by the near-complete removal of Tsuga canadensis from the canopy. In these areas, defoliation by the adelgid has resulted in 90-100% hemlock mortality and the release of massive numbers of shrub and birch seedlings in the understory. These sites are now so dense with shrub and sapling thickets and fallen hemlock trees that they can scarcely be traversed on foot. Impacts on the herbaceous flora of the stands has not been fully assessed, but at some sites, the newly opened canopies appear to have stimulated the invasion of exotic weeds such as Alliaria petiolata.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: No Data Available

Floristics: Canopy dominance is shared by Tsuga canadensis and Betula alleghaniensis in variable proportions. Minor canopy associates include Acer rubrum, Fraxinus americana, Pinus strobus, Quercus alba, and Quercus rubra. Small-tree and shrub layers are open to sparse, with Acer pensylvanicum, Hamamelis virginiana, Ilex verticillata, Kalmia latifolia, and Lindera benzoin the most frequent species. Alnus incana ssp. rugosa is a codominant shrub in a few areas on the northern Blue Ridge. Rhododendron catawbiense is scattered in some stands of this community in the southern part of the northern Blue Ridge but does not form dense stands. The herb layer is well-developed and lush with forbs, including the typically abundant species Veratrum viride, Oclemena acuminata (= Aster acuminatus), Angelica triquinata, Chelone glabra, and Viola cucullata. Carex scabrata and Glyceria melicaria are characteristic, colonial graminoids in many stands. Osmunda cinnamomea is the most abundant fern. Additional herbs occurring frequently at low cover include Maianthemum canadense, Athyrium filix-femina ssp. asplenioides, Anemone quinquefolia, Thalictrum pubescens, Trautvetteria caroliniensis, Oxypolis rigidior, and Viola macloskeyi ssp. pallens. Herbs that appear to be less frequent but locally abundant or important in the type include Aconitum uncinatum, Aconitum reclinatum, Thelypteris noveboracensis, Impatiens capensis, Actaea podocarpa (= Cimicifuga americana), Dryopteris cristata, Chrysosplenium americanum, Saxifraga micranthidifolia, and Circaea alpina. The mean species richness of plot-sampled stands (n = 45 taxa per 400 m2) probably reflects a diversity of microhabitats supporting both typical wetland plants and upland mesophytes.

Dynamics:  The Tsuga canadensis component of this community has been devastated in recent years by outbreaks of the introduced insect pathogen hemlock woolly adelgid (Adelges tsugae). Massive habitat disturbances caused by large canopy gaps and fallen hemlocks are initiating compositional changes whose outcomes are not at all clear at this time.
Environmental Description:  Sites are usually located in high-elevation valleys or slope concavities, in diffuse stream headwaters and lateral, groundwater-saturated flats along larger streams. Occasionally, stands occupy gentle depressions or basins influenced by seasonally perched groundwater but without flowing streams. Elevation of plot-sampled stands in Virginia ranges from 670 to 1170 m (2200-3840 feet), though most occurrences are above 900 m (3000 feet). Habitats are flat to moderately sloping (0-11°) and typically have >20% surface cover of boulders and stones weathered from metabasalt, granitic rocks, or sandstone. Stream-bottom habitats have pronounced hummock-and-hollow microtopography, with moss-covered mounds and intertwining roots of Betula alleghaniensis, mucky pools, and braided drainage channels. Regardless of underlying bedrock type, soils usually have a shallow organic horizon and are very strongly to extremely acidic (mean pH in plots = 4.4), with low base status. However, there may be some groundwater enrichment of these habitats in Blue Ridge areas underlain by volcanic and plutonic rocks.
Geographic Range: This community is currently known from scattered sites in the Northern Blue Ridge and Ridge and Valley provinces of Virginia. Similar communities have been observed by Virginia Division of Natural Heritage ecologists in the High Allegheny Mountains of Virginia and West Virginia, the Maryland Blue Ridge, and the Ridge and Valley of east-central West Virginia (Pendleton County). Based on the description of "Hemlock - mixed hardwood palustrine forest" in Fike (1999), occurrences in Pennsylvania also seem likely. The type appears to be limited to higher-elevation montane wetlands in a portion of the Central Appalachians where Rhododendron maximum is infrequent to absent.

Nations: US

States/Provinces:  MD, PA?, VA


Confidence Level: Moderate

Confidence Level Comments: No Data Available
Grank: G2

Greasons: No Data Available
Type Name Database Code Classification Code
Class 1 Forest & Woodland Class C01 1
Subclass 1.B Temperate & Boreal Forest & Woodland Subclass S15 1.B
Formation 1.B.3 Temperate Flooded & Swamp Forest Formation F026 1.B.3
Division 1.B.3.Na Eastern North American-Great Plains Flooded & Swamp Forest Division D011 1.B.3.Na
Macrogroup 1.B.3.Na.2 Pin Oak - Green Ash - Blackgum Swamp Forest Macrogroup M503 1.B.3.Na.2
Group 1.B.3.Na.2.f Red Maple - Blackgum - Green Ash Swamp Forest Group G902 1.B.3.Na.2.f
Alliance A3416 Yellow Birch - Eastern Hemlock Swamp Forest Alliance A3416 1.B.3.Na.2.f
Association CEGL008533 Eastern Hemlock - Yellow Birch / Green False Hellebore - Eastern Rough Sedge - Whorled Wood Aster Swamp Forest CEGL008533 1.B.3.Na.2.f
Concept Lineage: No Data Available

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: > Betula alleghaniensis / Oxalis montana Association: Betula alleghaniensis / Carex scabrata Subassociation (Fleming and Moorhead 1996)
> Tsuga canadensis - Betula alleghaniensis / Carex trisperma Association (Rawinski et al. 1994)
> Tsuga canadensis - Betula alleghaniensis / Veratrum viride - Aconitum uncinatum Association (Rawinski et al. 1996)
= Tsuga canadensis - Betula alleghaniensis / Veratrum viride - Carex scabrata - Oclemena acuminata Forest (Fleming and Coulling 2001)
> Tsuga canadensis - Betula alleghaniensis / Veratrum viride - Carex scabrata Association (Rawinski et al. 1996)
< Hemlock - Yellow Birch: 24 (Eyre 1980)
Concept Author(s): G.P. Fleming and P. P. Coulling (2001)

Author of Description: G.P. Fleming and P.P. Coulling

Acknowledgements: No Data Available

Version Date: 02-01-08
  • Eastern Ecology Working Group of NatureServe. No date. International Ecological Classification Standard: International Vegetation Classification. Terrestrial Vegetation. NatureServe, Boston, MA.
  • Eyre, F. H., editor. 1980. Forest cover types of the United States and Canada. Society of American Foresters, Washington, DC. 148 pp.
  • Fike, J. 1999. Terrestrial and palustrine plant communities of Pennsylvania. Pennsylvania Natural Diversity Inventory. Pennsylvania Department of Conservation and Recreation, Bureau of Forestry, Harrisburg, PA. 86 pp.
  • Fleming, G. P., K. D. Patterson, and K. Taverna. 2017. The natural communities of Virginia: A classification of ecological community groups and community types. Third approximation. Version 3.0. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond, VA. [http://www.dcr.virginia.gov/natural-heritage/natural-communities/]
  • Fleming, G. P., and K. D. Patterson. 2009a. A vegetation classification for the Appalachian Trail: Virginia south to Georgia. Virginia Department of Conservation and Recreation, Division of Natural Heritage. In-house analysis, March 2009.
  • Fleming, G. P., and P. P. Coulling. 2001. Ecological communities of the George Washington and Jefferson national forests, Virginia. Preliminary classification and description of vegetation types. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond, VA. 317 pp.
  • Fleming, G. P., and W. H. Moorhead, III. 1996. Ecological land units of the Laurel Fork Area, Highland County, Virginia. Natural Heritage Technical Report 96-08. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond. 114 pp. plus appendices.
  • Rawinski, T. J., G. P. Fleming, and F. V. Judge. 1994. Forest vegetation of the Ramsey''s Draft and Little Laurel Run Research Natural Areas, Virginia: Baseline ecological monitoring and classification. Natural Heritage Technical Report 94-14. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond. 45 pp. plus appendices.
  • Rawinski, T. J., K. N. Hickman, J. Waller-Eling, G. P. Fleming, C. S. Austin, S. D. Helmick, C. Huber, G. Kappesser, F. C. Huber, Jr., T. Bailey, and T. K. Collins. 1996. Plant communities and ecological land units of the Glenwood Ranger District, George Washington and Jefferson national forests, Virginia. Virginia Department of Conservation and Recreation, Division of Natural Heritage. Natural Heritage Technical Report 96-20. Richmond. 65 pp. plus appendices.
  • Young, J., G. Fleming, P. Townsend, and J. Foster. 2006. Vegetation of Shenandoah National Park in relation to environmental gradients. Final Report (v.1.1). Research technical report prepared for USDI, National Park Service. USGS/NPS Vegetation Mapping Program. 92 pp. plus appendices.
  • Young, J., G. Fleming, W. Cass, and C. Lea. 2009. Vegetation of Shenandoah National Park in relation to environmental gradients, Version 2.0. Technical Report NPS/NER/NRTR--2009/142. National Park Service, Philadelphia, PA. 389 pp.