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Tsuga canadensis - Betula alleghaniensis / Veratrum viride - Carex scabrata - Oclemena acuminata Swamp Forest
Translated Name: Eastern Hemlock - Yellow Birch / Green False Hellebore - Eastern Rough Sedge - Whorled Wood Aster Swamp Forest
Common Name: High-Elevation Hemlock - Yellow Birch Seepage Swamp
Unique Identifier: CEGL008533
Classification Approach: International Vegetation Classification (IVC)
Summary: 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.



Classification

Classification Confidence: Moderate
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.

Vegetation Hierarchy
Class 1 - Forest & Woodland
Subclass 1.B - Temperate & Boreal Forest & Woodland
Formation 1.B.3 - Temperate Flooded & Swamp Forest
Division 1.B.3.Na - Eastern North American-Great Plains Flooded & Swamp Forest
Macrogroup Laurentian-Acadian-North Atlantic Coastal Flooded & Swamp Forest
Group Laurentian-Acadian-Appalachian Acidic Swamp
Alliance Central Appalachian Hemlock - Hardwood Swamp Forest

This is the revised vegetation hierarchy. For more information see Classification Sources and usnvc.org.



Related Concepts from Other Classifications

Other Related Concepts
Related Concept Name: Betula alleghaniensis / Oxalis montana Association: Betula alleghaniensis / Carex scabrata Subassociation
Relationship: F - Finer
Reference: 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.
Related Concept Name: Tsuga canadensis - Betula alleghaniensis / Carex trisperma Association
Relationship: F - Finer
Reference: 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.
Related Concept Name: Tsuga canadensis - Betula alleghaniensis / Veratrum viride - Aconitum uncinatum Association
Relationship: F - Finer
Reference: 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.
Related Concept Name: Tsuga canadensis - Betula alleghaniensis / Veratrum viride - Carex scabrata - Oclemena acuminata Forest
Relationship: = - Equivalent
Reference: 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.
Related Concept Name: Tsuga canadensis - Betula alleghaniensis / Veratrum viride - Carex scabrata Association
Relationship: F - Finer
Reference: 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.
Related Concept Name: Hemlock - Yellow Birch: 24
Relationship: B - Broader
Reference: Eyre, F. H., editor. 1980. Forest cover types of the United States and Canada. Society of American Foresters, Washington, DC. 148 pp.
Related Concept Name: High-Elevation Seepage Swamp
Relationship: B - Broader
Reference: Fleming, G. P., P. P. Coulling, D. P. Walton, K. M. McCoy, and M. R. Parrish. 2001. The natural communities of Virginia: Classification of ecological community groups. First approximation. Natural Heritage Technical Report 01-1. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond, VA. 76 pp.

Ecological Systems Placement

Ecological Systems Placement
Ecological System Unique ID Ecological System Name
CES202.593 Appalachian (Hemlock)-Northern Hardwood Forest
CES202.604 North-Central Appalachian Acidic Swamp
CES202.609 Central Appalachian Stream and Riparian


NatureServe Conservation Status
Global Status: G2 (21Sep2001)
Rounded Global Status: G2 - Imperiled
Reasons: This type appears to be quite rare naturally because of its small patch size, its apparent geographic restriction, and the paucity of suitable, high-elevation seepage wetland habitats. Moreover, within the last decade, several documented stands have undergone rapid degradation and compositional alterations resulting from outbreaks of the exotic insect hemlock woolly adelgid. The long-term integrity of all stands of this vegetation is now considered threatened by the adelgid.

Distribution
Color legend for Distribution Map
United States Distribution: MD, PApotentially occurs, VA
Global Distribution: United States
Global 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.

U.S. Forest Service Ecoregions
Domain Name: Humid Temperate Domain
Division Name: Hot Continental Regime Mountains
Province Name: Central Appalachian Broadleaf Forest - Coniferous Forest - Meadow Province
Province Code: M221 Occurrence Status: Confident or certain
Section Name: Northern Ridge and Valley Section
Section Code: M221A Occurrence Status: Confident or certain
Section Name: Blue Ridge Mountains Section
Section Code: M221D Occurrence Status: Confident or certain


Vegetation

Vegetation Summary: 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 square meters) probably reflects a diversity of microhabitats supporting both typical wetland plants and upland mesophytes.

Vegetation Composition (incomplete)
Species Name Rounded Global Status Growth Form Stratum Charact-
eristic
Dominant Constant
Cover Class %
Con-
stancy
%
Betula alleghaniensis G2 Broad-leaved deciduous tree Tree canopy  
 
 
Tsuga canadensis G2 Needle-leaved tree Tree canopy  
 
 
Acer pensylvanicum G2 Broad-leaved deciduous tree Shrub/sapling (tall & short)    
 
 
Alnus incana ssp. rugosa G2 Broad-leaved deciduous shrub Shrub/sapling (tall & short)      
 
 
Hamamelis virginiana G2 Broad-leaved deciduous shrub Shrub/sapling (tall & short)    
 
 
Lindera benzoin G2 Broad-leaved deciduous shrub Shrub/sapling (tall & short)    
 
 
Aconitum reclinatum G2 Flowering forb Herb (field)      
 
 
Angelica triquinata G2 Flowering forb Herb (field)    
 
 
Chelone glabra G2 Flowering forb Herb (field)    
 
 
Euphorbia purpurea G2 Flowering forb Herb (field)      
 
 
Oclemena acuminata G2 Flowering forb Herb (field)  
 
 
Veratrum viride G2 Flowering forb Herb (field)  
 
 
Viola cucullata G2 Flowering forb Herb (field)    
 
 
Osmunda cinnamomea G2 Fern (Spore-bearing forb) Herb (field)    
 
 
Carex scabrata G2 Graminoid Herb (field)  
 
 


At-Risk Species Reported for this Association
Scientific Name
  (Common Name)
NatureServe Global Status U.S. Endangered Species Act Status
Aconitum reclinatum
  (White Monkshood)
G3  
Euphorbia purpurea
  (Glade Spurge)
G3  


Environmental Setting

Wetland Indicator: Y
Environmental Summary: 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.


Dynamic Processes

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.


Plot Sampling & Classification Analysis

Plots stored in VegBank


Authors/Contributors
Concept Author(s): K.D. Patterson and G.P. Fleming, mod. G.P. Fleming and P.P. Coulling
Element Description Edition Date: 01Feb2008
Element Description Author(s): G.P. Fleming and P.P. Coulling
NatureServe Conservation Status Factors Edition Date: 21Sep2001
NatureServe Conservation Status Factors Author(s): G.P. Fleming and P.P. Coulling

Ecological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).


References
  • 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., P. P. Coulling, D. P. Walton, K. M. McCoy, and M. R. Parrish. 2001. The natural communities of Virginia: Classification of ecological community groups. First approximation. Natural Heritage Technical Report 01-1. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond, VA. 76 pp.

  • Fleming, G. P., P. P. Coulling, K. D. Patterson, and K. M. McCoy. 2004. The natural communities of Virginia: Classification of ecological community groups. Second approximation. Natural Heritage Technical Report 04-01. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond, VA. [http://www.dcr.virginia.gov/dnh/ncintro.htm]

  • 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 K. D. Patterson. 2011a. Natural communities of Virginia: Ecological groups and community types. Natural Heritage Technical Report 11-07. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond. 34 pp.

  • 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.


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