Common (Translated Scientific) Name: Yellow Birch - (Eastern Hemlock) / Great Laurel / (Highland Doghobble) Forest
Colloquial Name: Blue Ridge Hemlock - Northern Hardwood Forest
Hierarchy Level: Association
Type Concept: This association occurs in the Great Smoky Mountains and high mountain areas of southwestern Virginia, and at lower elevations in protected mountain settings in West Virginia. This community is found on steep, mostly north-facing slopes, and on slopes and flats along and above streams. These forests occur on midslope or toeslope positions, protected by higher landforms, where solar exposure is very low. The elevations of samples range from as low as 320 m in West Virginia (1040 feet) to around 1350 m (4400 feet), but the community can probably occur as high as 1524 m (5000 feet) or until Picea rubens begins to dominate. Sites are rocky, often with many large boulders and talus. Soils are stony with heavy litter layers and pockets of colluvium. This forest is affected by occasional disturbance by ice, wind and landslides. This mixed forest type has an open to closed canopy dominated by Betula alleghaniensis and/or Tsuga canadensis, although either of these species may be locally dominant at a small scale. In some stands, Acer rubrum, Betula lenta, Liriodendron tulipifera (at lower elevations), Tilia americana var. heterophylla, Picea rubens, or Quercus rubra can be important in the canopy or occur as minor associates. Other minor canopy and subcanopy species may include Fagus grandifolia, Prunus serotina, and Magnolia acuminata. The tall-shrub stratum is over 2 m in height, very dense (50-100% coverage) and dominated by Rhododendron maximum. Other minor shrubs commonly include Acer pensylvanicum, Amelanchier laevis, Amelanchier arborea, Clethra acuminata, Hamamelis virginiana (West Virginia), Ilex montana, and Vaccinium erythrocarpum. The ground layer is dominated by leaf litter, fallen trees and rocks. Herbaceous cover is sparse to moderate and is composed of scattered plants typical of mid- to high-elevation acidic forests. Composition can be quite variable among stands, but some of the more characteristic species include Dryopteris intermedia, Oclemena acuminata, Polystichum acrostichoides (West Virginia), Viola blanda, and Viola rotundifolia. The bryophyte layer can be well-developed and diverse. This association grades into forests dominated by Picea rubens or Tsuga canadensis at higher elevations.
Diagnostic Characteristics: No Data Available
Rationale for Nominal Species or Physiognomic Features:
Classification Comments: This association is a high-elevation acidic cove forest and is characterized by species indicative of montane, infertile environments, a dense shrub layer of Rhododendron maximum, and a mixed deciduous-evergreen to mostly deciduous canopy. Species richness is typically low, ranging from 4 to 38 species per sample with an average of 19 species per 400-square-meter sample. Analysis of plot samples from the Great Smoky and Virginia mountains, and from Fayette and Raleigh counties, West Virginia, shows the most constant species as Betula alleghaniensis, Rhododendron maximum, Tsuga canadensis, and Dryopteris intermedia.
Some stands in West Virginia may be better classified as Tsuga canadensis - Betula alleghaniensis - Prunus serotina / Rhododendron maximum Forest (CEGL006206), a seemingly more diverse and lower-elevation type. Forests of high-elevation coves at Salt Pond Mountain in Giles County (e.g., War Spur Branch), where Picea rubens is codominant with or subordinate to Tsuga canadensis and Betula alleghaniensis, are tentatively placed here. Some of these stands, however, may be better classified as wetlands and require additional investigation.
Similar NVC Types:
Liriodendron tulipifera - Betula lenta - Tsuga canadensis / Rhododendron maximum Forest, note:
Tsuga canadensis - Betula alleghaniensis - Prunus serotina / Rhododendron maximum Forest, note:
Picea rubens / Betula alleghaniensis / Bazzania trilobata Forest, note:
Picea rubens - (Betula alleghaniensis, Aesculus flava) / Rhododendron (maximum, catawbiense) Forest, note:
Tsuga canadensis - (Betula alleghaniensis, Quercus rubra) / Ilex montana / Rhododendron catawbiense Forest, note:
Acer rubrum var. rubrum - Betula lenta - Magnolia fraseri / (Rhododendron maximum, Kalmia latifolia) Ruderal Forest, note: is a post-disturbance forest, some stands of which could resemble CEGL007861 without Tsuga.
Picea rubens - (Betula alleghaniensis, Aesculus flava) / Viburnum lantanoides / Solidago glomerata Forest, note:
Tsuga canadensis - Halesia tetraptera - Magnolia fraseri / Rhododendron maximum / Dryopteris intermedia Forest, note:
Tsuga canadensis - Betula alleghaniensis - Acer saccharum / Dryopteris intermedia Forest, note:
Tsuga canadensis - Acer saccharum - Fagus grandifolia / Dryopteris intermedia Forest, note:
Physiognomy and Structure: No Data Available
Floristics: This mixed forest has an open to closed canopy codominated by Betula alleghaniensis and/or Tsuga canadensis, although either of these species may be solely dominant over small areas. In some stands, Acer rubrum, Betula lenta, Liriodendron tulipifera (at lower elevations), Tilia americana var. heterophylla, Picea rubens, or Quercus rubra can be important in the canopy or occur as minor associates. Other minor canopy and subcanopy species may include Fagus grandifolia, Prunus serotina, and Magnolia acuminata. The community has a very dense (50-100% cover), evergreen tall-shrub stratum (>2 m tall) dominated by Rhododendron maximum. In the Great Smoky Mountains, a dense low-shrub stratum dominated by Leucothoe fontanesiana is typical, but this species is absent from Virginia and West Virginia examples of the type. Other minor shrubs commonly include Acer pensylvanicum, Amelanchier laevis, Hamamelis virginiana (in West Virginia stands), Ilex montana, and Vaccinium erythrocarpum. Herbaceous cover is sparse to occasionally moderate and is composed of scattered plants typical of mid- to high-elevation acidic forests. Composition can be quite variable among stands, but some of the more characteristic species include Dryopteris intermedia, Oclemena acuminata, Polystichum acrostichoides (in West Virginia stands), Viola blanda, and Viola rotundifolia. Some additional herbaceous species found in this community include Arisaema triphyllum, Dennstaedtia punctilobula, Huperzia lucidula, and Medeola virginiana. In Southern Appalachian stands with very dense evergreen shrub layers, species richness can be extraordinarily low (<10 taxa per 1000-square-meter sample), but in stands with somewhat more open shrub layers, richness can exceed 30 taxa per sample. The bryophyte layer can be well-developed and diverse; mosses and liverworts collected from West Virginia plots include Anomodon attenuatus, Aulacomnium heterostichum, Bryhnia graminicolor, Bryoandersonia illecebra, Campylium chrysophyllum, Hypnum curvifolium, Hypnum imponens, Loeskeobryum brevirostre, Mnium stellare, Plagiothecium denticulatum, Platyhypnidium riparioides, Thuidium delicatulum, Bazzania trilobata, Leucobryum glaucum, and Mnium hornum. The regionally rare plants Botrychium oneidense and Prenanthes roanensis are minor components of this vegetation type.
Dynamics: The Tsuga canadensis component of Virginia stands has been devastated by outbreaks of hemlock woolly adelgid over the past several decades, leading to more open canopy conditions, along with increased regeneration and greater importance of Betula alleghaniensis in most stands.
Environmental Description: This community occurs on steep, mostly north-facing mesic slopes, and on toeslopes and flats along streams. It typically occupies mid- to lower slope and valley-bottom topographic positions that are well-protected by higher landforms. These sites have low solar exposure and may be subject to cold-air inversions. Elevations (of plot-sampled stands) range from 320-750 m (1040-2400 feet) in West Virginia, to 915-1450 m (3000-4800 feet) in the Virginia mountains, and to 1030-1450 m (3400-4800 feet) in the Great Smoky Mountains. Lower elevation stands may intergrade with Betula lenta-dominated forest types. Sites are often rocky, with many large boulders and stones and pockets of colluvium. Soils, weathered from sandstone, acidic shale, or metamorphic igneous rocks, have dense, root-rich duff layers. Samples collected from plots are highly acidic (mean pH = 3.7 to 4.8) with low base status and moderately high organic matter content (mean = 20%). On stream-bottom sites, local areas of seepage are not uncommon, and habitats may be somewhat transitional to a saturated hydrologic regime. Sites occupied by this forest are affected by occasional ice, wind, and landslide disturbances.
Geographic Range: This community has been documented in the Great Smoky Mountains of Tennessee; in the Mount Rogers - Whitetop Mountain area of the Virginia Blue Ridge (Grayson, Smyth and Washington counties); on Salt Pond Mountain in the Ridge and Valley of west-central Virginia (Giles County); on Allegheny Mountain in Highland County, Virginia, and adjacent Pocahontas County, West Virginia; and in Fayette County, West Virginia, along and near the New River Gorge, and along Gauley River in West Virginia. This vegetation type may be locally distributed throughout higher elevations of the Southern and Central Appalachians.
States/Provinces: NC, TN, VA, WV
|US Forest Service Ecoregions (1994/1995)|
Central Appalachian Broadleaf Forest - Coniferous Forest - Meadow Province
Confident or certain
Northern Ridge and Valley Section
Confident or certain
Confidence Level: Moderate
Confidence Level Comments:
Greasons: This community type is naturally uncommon within its range due to specific requirements for protected, mesic sites at high elevations. Most remaining examples of this community have been affected by past logging and are currently threatened with the loss of their Tsuga canadensis component due to ongoing or potential infestations by the exotic pest hemlock woolly adelgid (Adelges tsugae). This community type has a restricted but locally extensive distribution in the highest mountains of southwestern and west-central Virginia, North Carolina, West Virginia, and Tennessee. This association was originally described from Great Smoky Mountains National Park.
Synonomy: = Betula alleghaniensis - Tsuga canadensis - (Picea rubens) / Rhododendron maximum Forest (Fleming and Coulling 2001)
? Betula alleghaniensis / Oxalis montana Association: Betula alleghaniensis / Rhododendron maximum Variant (Fleming and Moorhead 1996)
= Betula alleghaniensis / Rhododendron maximum forest (Vanderhorst 2001b)
< Hemlock - Yellow Birch: 24 (Eyre 1980)
? Red Spruce Community: Hemlock - Spruce Subtype (Adams and Stephenson 1991)
Concept Author(s): G. Fleming and P. Coulling
Author of Description: G. Fleming, P. Coulling, S.C. Gawler and K.D. Patterson
Version Date: 09Apr2010
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