I. Forest 10 I. A n a. Lowland tropical or subtropical seasonal evergreen forest 10




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I.A.8.N.c. Conical-crowned temperate or subpolar needle-leaved evergreen forest

A.136 Abies fraseri - Picea rubens Forest Alliance


Fraser Fir - Red Spruce Forest Alliance

Alliance Concept

Summary: This forest alliance is restricted to the highest mountain systems of the Southern Blue Ridge Province, in eastern Tennessee, western North Carolina, and southwestern Virginia, within the distributional range of Abies fraseri. Canopies can be dominated by Abies fraseri or Picea rubens, or codominated by Abies fraseri and Picea rubens. Canopy/subcanopy species of minor importance can include Acer spicatum, Acer pensylvanicum, Amelanchier laevis, Betula alleghaniensis, Prunus pensylvanica, and Sorbus americana. Forests on extreme sites may have a stunted appearance and, in some communities, standing dead stems of Abies fraseri are common, with extensive patches of Abies fraseri seedlings in canopy gaps. The density and composition of the shrub and herbaceous strata vary between associations in this alliance. Forests in this alliance typically have a well-developed bryophyte layer. Mosses, liverworts, and lichens grow densely on fallen logs, tree trunks, and the forest floor, giving these forests a distinctive carpeted appearance. This alliance contains many species endemic to the Southern Blue Ridge or that have the bulk of their worldwide range in that region. The alliance is conceptually related to more northern spruce-fir alliances and shares many northern or boreal species (often occurring in communities of this alliance as disjuncts from their main distribution), but is considered a separate alliance because of its large component of southern Appalachian endemic species. Forests of this alliance occur on all topographic positions except the steepest rocky cliffs. Elevations range from 1370-2300 m (4500-6600 feet), with pure Abies fraseri associations best developed at above 1830 m (6000 feet). The dominant soils are Inceptisols with scattered occurrences of Spodosols at the highest elevations. Generally, soils can be described as shallow and rocky, with well-developed organic and A horizons. All soils in these high-elevation forests are low in base saturation, high in organic matter, and are acid in reaction (pH 3-5), with a high aluminum content. The moisture regimes of these areas are mesic to wet due to high rainfall, abundant cloud cover, fog deposition, and low temperatures. The climate has been classified as perhumid, with the temperature varying elevationally from mesothermal to microthermal. The regional geology is dominated by complexly folded metamorphic, sedimentary, and igneous rocks of the Precambrian and early Paleozoic age, including phyllites, slates, schists, sandstones, quartzites, granites, and gneisses. These forests are affected by debris avalanches, wind disturbance and lightning fire. Because of the shallow soils and extreme wind exposure, these forests are susceptible to large blowdowns, particularly in areas damaged by Adelges piceae, the Balsam Woolly Adelgid.
Environment: Forests of this alliance occur on all topographic positions except the steepest rocky cliffs. Elevations range from 1370-2300 m (4500-6600 feet), with pure Abies fraseri associations best developed at above 1830 m (6000 feet). The dominant soils are Inceptisols with scattered occurrences of Spodosols at the highest elevations (White et al. 1993). Generally, soils can be described as shallow and rocky, with well-developed organic and A horizons. All soils in these high-elevation forests are low in base saturation, high in organic matter, and are acid in reaction (pH 3-5), with a high aluminum content. The moisture regimes of these areas are mesic to wet due to high rainfall, abundant cloud cover, fog deposition, and low temperatures. The climate has been classified as perhumid, with the temperature varying elevationally from mesothermal to microthermal. The regional geology is dominated by complexly folded metamorphic, sedimentary, and igneous rocks of the Precambrian and early Paleozoic age, including phyllites, slates, schists, sandstones, quartzites, granites, and gneisses. These forests are affected by debris avalanches, wind disturbance and lightning fire. Because of the shallow soils and extreme wind exposure, these forests are susceptible to large blowdowns, particularly in areas damaged by Adelges piceae, the Balsam Woolly Adelgid.

Vegetation: Canopies can be dominated by Abies fraseri or Picea rubens, or codominated by Abies fraseri and Picea rubens. Canopy/subcanopy species of minor importance can include Acer spicatum, Acer pensylvanicum, Amelanchier laevis, Betula alleghaniensis, Prunus pensylvanica, and Sorbus americana. Forests on extreme sites may have a stunted appearance and, in some communities, standing dead stems of Abies fraseri are common, with extensive patches of Abies fraseri seedlings in canopy gaps. The density and composition of the shrub and herbaceous strata vary between associations in this alliance. Typical shrub species include Menziesia pilosa, Rhododendron carolinianum, Rhododendron maximum, Rhododendron catawbiense, Ribes rotundifolium, Rubus idaeus ssp. strigosus, Rubus allegheniensis, Sambucus racemosa var. racemosa (= Sambucus racemosa var. pubens), Vaccinium erythrocarpum, Vaccinium simulatum, Viburnum nudum var. cassinoides, and Viburnum lantanoides. Typical herbaceous species include Ageratina altissima var. roanensis, Angelica triquinata, Eurybia chlorolepis (= Aster chlorolepis), Oclemena acuminata (= Aster acuminatus), Athyrium filix-femina ssp. asplenioides, Chelone lyonii, Circaea alpina ssp. alpina, Clintonia borealis, Dryopteris campyloptera, Geum radiatum, Houstonia serpyllifolia, Huperzia lucidula, Medeola virginiana, Oxalis montana, Rugelia nudicaulis, Solidago glomerata, Streptopus lanceolatus var. roseus (= Streptopus roseus), and Viola macloskeyi ssp. pallens. Forests in this alliance typically have a well-developed bryophyte layer. Mosses, liverworts, and lichens grow densely on fallen logs, tree trunks, and the forest floor, giving these forests a distinctive carpeted appearance. Typical nonvascular species include Bazzania trilobata, Dicranum scoparium, Dicranum fuscescens, Hylocomiastrum umbratum, Hylocomium splendens, Hypnum spp., Polytrichum ohioense, Ptilium crista-castrensis, and Rhytidiadelphus triquetrus. This alliance contains many species endemic to the Southern Blue Ridge or that have the bulk of their worldwide range in that region. The alliance is conceptually related to more northern spruce-fir alliances and shares many northern or boreal species (often occurring in communities of this alliance as disjuncts from their main distribution), but is considered a separate alliance because of its large component of southern Appalachian endemic species.

Dynamics:

Similar Alliances: Picea rubens - Abies balsamea Forest Alliance (A.150) Picea rubens Forest Alliance (A.138)

Similar Alliance Comments:

Alliance Distribution

Range: This alliance is found in North Carolina, Tennessee, and Virginia. This forest alliance is restricted to the highest mountain systems of the Southern Blue Ridge Province, in eastern Tennessee, western North Carolina, and southwestern Virginia, within the distributional range of Abies fraseri. These forests reach their northern range limit in southwestern Virginia, where they are confined to elevations above 1700 m (5400 feet) on Mount Rogers in Grayson and Smyth counties.

Nations: US

Subnations: NC, TN, VA

TNC Ecoregions: 51:C, 59:C

USFS Ecoregions: M221Aa:CCC, M221Ba:CCC, M221Bc:CCP, M221Dc:CCC, M221Dd:CCC

Federal Lands: NPS (Blue Ridge Parkway, Great Smoky Mountains); USFS (Cherokee, George Washington, Jefferson, Nantahala, Pisgah)

Alliance Sources

Author(s): K.D. Patterson

References: Allard 1990, Brown 1941, Bruck 1988, Busing et al. 1988, Cogbill and White 1991, Crandall 1958, Crandall 1960, Davis 1930, Dull et al. 1988b, Eyre 1980, Grossman and Goodin 1995, Korstian 1937, McLeod 1988, NCNHP 1993, Nicholas et al. 1992, Oosting and Billings 1951, Pyne 1994, Ramseur 1960, Rawinski 1992, Schafale and Weakley 1990, Schofield 1960, Stephenson and Adams 1984, Stephenson and Clovis 1983, Wentworth et al. 1988, White 1984a, White and Cogbill 1992, White and Pickett 1985, White et al. 1993, Whittaker 1956, Zedaker et al. 1988
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