Spruce-Fir Forests
Forests dominated by two conifer species, red spruce and Fraser fir, cap the tallest peaks of the Southern Appalachians. Bordered by northern hardwood forest below, spruce-fir forests begin at elevations above 4600-5500 ft (1400-1680 m). The lowest elevations for this forest type occur on north-facing slopes (Brown 1941). Within the spruce-fir zone, red spruce is the dominant species at lower elevations then gives way to Fraser fir above (Whittaker 1956).
Spruce-fir forests have a coniferous overstory. Fraser fir is endemic to the Southern Appalachians and can form almost pure stands on the highest peaks. Yellow birch and American beech provide a deciduous component to these forests, especially in the ecotone with northern hardwood forests where they intermix with red spruce and eastern hemlock. Yellow birch is the least shade tolerant species of this forest type and grows best on sites that have experienced natural or anthropogenic disturbance. Dry, rocky sites often have an evergreen understory of Catawba rhododendron (Rhododendron catawbiensis). The most exposed locations may give way to shrub-dominated heath balds. More mesic sites have a dense canopy, a sparse understory, and a heavy ground cover of mosses, lichens, and shade-tolerant wildflowers.
This community type is a Pleistocene relic that is now confined to a limited number of high mountains in southwestern Virginia, eastern Tennessee, and western North Carolina. Southern Appalachian spruce-fir forests are similar in species richness and physiognomy to the boreal conifer forests of New England and Canada. Needle-leaved, evergreen trees dominate and an understory component of mosses and lichens (White and others 1993). Bird species that breed in spruce-fir forests include northern saw-whet owls (Aegolius acadicus), winter wrens (Troglodytes troglodytes), golden-crowned kinglets (Regulus satrapa), red-breasted nuthatches (Sitta canadensis) and common ravens (Corvus corax). These ecological similaries between the seperated southern and boreal and spruce-fir forests are remarkable. This separation is made because elevations in the Central Appalachians of Pennsylvania, West Virginia, and Virginia are not high enough to support this forest type.
Spruce-fir is the least abundant forest community type in the Southern Appalachians and is separated into disjunct patches. These spruce-fir forests are regarded as high-elevation "habitat islands" and have become the subject of conservation concern both because of their natural biogeography and because of anthropogenic impacts on these communites. Populations of species having limited dispersal capabilities and specialized habitat needs may be effectively isolated from habitat patches on distant peaks. Limited habitat area means species populations are small and vulnerable to extinction. There is concern about the persistence of some endemic species such as the northern flying squirrel (Glaucomys sabrinus) and the spruce-fir moss spider (Microhexura montivaga). These forests were impacted around 1900 by logging and in the latter half of the 20th century by air pollution and the balsam wooly adelgid (Adelges piceae), an exotic insect that attacks Fraser firs. Logging and associated impacts may have reduced the extent of these forest by 50 percent, and mortality rates of fir due the air pollution and the adelgid range from 45 to 90 percent (White and others 1993). Most spruce-fir sites are now in public ownership and protected and managed by U.S. Forest Service or National Park Service. However, the prognosis for the future health of this ecosystem is not positive.
Representative tree species of Spruce-fir Forests
- Red spruce (Picea rubens)
- Fraser fir (Abies fraseri)
- Yellow birch (Betula allegheniensis)
- American beech (Fagus grandifolia)
- Mountain ash (Sorbus americana)
- Mountain maple (Acer spicatum)
- Fire cherry (Prunus pensylvanica)
Encyclopedia ID: p1594
