Diagnostic Classifiers: Montane; Forest and Woodland (Treed); Needle-Leaved Tree
Concept Summary: This system consists of forests in the highest elevation zone of the Southern Blue Ridge and parts of the central Appalachians, generally dominated by Picea rubens, Abies fraseri, or Abies balsamea, or by a mixture of spruce and one of the firs.. Abies fraseri is the constituent fir from Mount Rogers in Virginia southward and is replaced northward by Abies balsamea. Examples occur above 1676 m (5500 feet) in the Southern Blue Ridge but as low as 975 m (3200 feet) at the northern range in West Virginia and may range up to the highest peaks. Elevation and orographic effects make the climate cool and wet, with heavy moisture input from fog as well as high rainfall. Strong winds, extreme cold, rime ice, and other extreme weather are periodically important.
Comments: The border of this system with adjacent systems is often gradational. The non-forested systems that occur in the same elevation zone may have transition zones of open woody vegetation, though some have sharp borders. The transition to Southern Appalachian Northern Hardwood Forest (CES202.029) or other systems that adjoin at lower elevation is marked by a gradual shift in canopy dominance from conifers to hardwoods. In relatively undisturbed stands, the canopy composition and structure are the best way to determine the boundary of this system.
This system is similar to the spruce-fir systems of the northern Appalachians and the boreal forests but differs in having less frequent natural fire, having southern seasonal dynamics (shorter winters, less extreme cold temperatures, lack of long summer days), lacking a history of glaciation, and in a flora and fauna that has southern Appalachian endemics and lacks some characteristic northern species. High-elevation spruce-fir in West Virginia is placed in this system because its location well below the glacial boundary and presence of species of more southern affinity (e.g., Rhododendron maximum and Vaccinium erythrocarpum) differentiate it from the northern Appalachian system, despite having Abies balsamea rather than Abies fraseri. Abies balsamea appears to be infrequent in this system, for example being restricted to wet areas in West Virginia.
Range: This system ranges from the Balsam Mountains and Great Smoky Mountains of North Carolina and Tennessee northward to the mountains of Virginia and West Virginia.
TNC Ecoregions: 51:C, 59:C
Subnations: NC, TN, VA, WV
Federal Lands: NPS (Blue Ridge Parkway, Great Smoky Mountains); USFS (Cherokee, George Washington, Jefferson, Nantahala, Pisgah)
Environment: This system occurs at elevations typically above 1676 m (5500 feet), up to the highest peaks. It occurs on most of the landforms that are present in this elevational range; most sites are strongly exposed and convex in shape. Elevation and orographic effects make the climate cool and wet, with heavy moisture input from fog as well as high rainfall. Strong winds, extreme cold, rime ice, and other extreme weather are periodically important. Concentration of air pollutants has been implicated as an important anthropogenic stress in recent years. Soils are generally very rocky, with the matrix ranging from well-weathered parent material to organic deposits over boulders. Soils may be saturated for long periods from a combination of precipitation and seepage. Any kind of bedrock may be present, but most sites have erosion-resistant felsic igneous or metamorphic rocks.
Vegetation: Vegetation consists primarily of forests dominated by Picea rubens, Abies fraseri, or Abies balsamea, occasionally by Sorbus americana. Betula alleghaniensis, Tsuga canadensis, and Quercus rubra are the only other locally common canopy species. Lower strata are most typically dominated by mosses, ferns or forbs, but a few associations have dense shrub layers of Rhododendron catawbiense, Rhododendron maximum, or Vaccinium erythrocarpum.
Dynamics: This system is naturally dominated by stable, uneven-aged forests, with canopy dynamics dominated by gap-phase regeneration on a fine scale. Despite the extreme climate, Picea rubens is long-lived (300-400 years). Both Picea and Abies seedlings are shade-tolerant, and advanced regeneration is important in stand dynamics. Natural disturbances include lightning fire, debris avalanches, wind events, and ice storms (White and Pickett 1985, Nicholas and Zedaker 1989). Occasional extreme wind events disturb larger patches on the most exposed slopes. There are hints of fir wave activity in the uncommon forests strongly dominated by Abies fraseri, but this is not well-developed. Fire is a very rare event under natural conditions, due to the wetness and limited flammability of the undergrowth, and return intervals have been estimated between 500-1000 years. If fires occur, they are likely to be catastrophic, because few of the species are at all fire-tolerant. Anthropogenic disturbances and stresses, beyond the effects of logging, have had major effects on dynamics in these systems in recent decades. An introduced insect, the balsam woolly adelgid (Adelges piceae), has killed almost all of the mature Abies fraseri. Saplings are not susceptible, resulting in many dense stands of young trees. It is unclear if these stands will establish seedlings before they too are killed. Stress caused by concentrated air pollutants on the mountain tops has been suggested as a cause of observed growth declines in Picea rubens. Earlier, unnatural fires fueled by logging slash turned large expanses of this system into grass-shrub-hardwood scrub that has not recovered to conifer dominance after 90 years. Climatic changes may affect this systems severely. Global warming can be expected to raise the lower elevational limit and greatly reduce the land area available to this system.
Spatial Summary: Large-patch to matrix system, dominating the highest mountain areas. Small-patch systems may be embedded.
Size: Generally covers most of the landscape in the limited areas at the tops of the highest mountain ranges. Natural patches range from hundreds to thousands of acres. A couple remnant patches of thousands of acres remain, while other intact patches are dozens of acres embedded in landscapes of degraded spruce-fir systems.
Heterogeneity: Most natural occurrences are contiguous over their extent, with only small patches of other systems embedded. Within the system, most occurrences contain one or two dominant associations, and may have two to four additional associations present.
Adjacent Ecological System Comments:Bordered by Southern Appalachian Northern Hardwood Forest (CES202.029) or Appalachian (Hemlock)-Northern Hardwood Forest (CES202.593) at lower elevation. It may contain embedded small patches of Southern Appalachian Rocky Summit (CES202.327) and Southern Appalachian Grass and Shrub Bald (CES202.294).
References: Comer et al. 2003, Lohman and Watson 1943, Nicholas and Zedaker 1989, White and Pickett 1985
Version: 11 Oct 2004 Stakeholders: East, Southeast
Concept Author: M. Schafale and R. Evans LeadResp: Southeast