A Comparison of Overstory Community Structure in Three Southern Appalachian Spruce-Fir Forests

Abstract

NICHOLAS, N. S., S. M. ZEDAKER (Department of Forestry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061), AND C. EAGAR (Northeastern Forest Experiment Station, USDA Forest Service, Durham, New Hampshire 03824). A comparison of overstory community structure in three southern Appalachian spruce-fir forests. Bull. Torrey Bot. Club 1 19: 316-332. 1992.-The southern Appalachian spruce-fir ecosystem is described in terms of stand structure and comparisons of current status to descriptions of earlier studies at three sites: Mount Rogers National Recreation Area (NRA) of Virginia, the Black Mountains of North Carolina, and the Great Smoky Mountains of Tennessee and North Carolina Community classification using two-way indicator species analysis delineated four forest types: SPRUCE, SPRUCE-BIRCH, SPRUCE-FIR, and FIR. Both the Mt. Rogers NRA and Black Mountains sites were patchworks of disturbance histories while most of the Smokies site was old-growth. At second-growth plots average dominant and codominant red spruce (Picea rubens Sargent) age ranged from 59-100 years while at the Smokies spruce mean age varied from 168-210. Distribution of basal area at the Smokies was skewed towards diameter distributions of greater than 45 cm DBH while basal area at Mt. Rogers NRA and the Black Mountains was concentrated in trees with diameters of less than 45 cm. Past studies indicated that undisturbed spruce-fir species distribution tended to follow an elevation gradient: spruce dominance changing to Fraser fir (Abiesfraseri (Pursh) Poiret) dominance as elevation increased. Current stand composition at the Black Mountains and the Great Smokies also shows a shift from spruce to fir; however, Mt. Rogers is an exception to that trend. As fir abundance increases with elevation there are increasing levels of balsam woolly adelgid-caused (Adelges piceae Ratzeburg) mortality at the Black and Smoky Mountains where there is a greater proportion of standing dead fir than live fir. Unlike the other two sites, Fraser fir on Mount Rogers still have escaped major damage from the adelgid. But advanced age structure of fir stands on top of Mount Rogers and elsewhere may result in high mortality rates in the near future.