Composition and Structure of Replacement Forest Stands following Southern Pine Beetle Infestations as related to selected site variables in the Great Smoky Mountains

Kuykendall, Nathaniel

Forty-nine sites where the southern pine beetle had killed the pines were surveyed to determine the composition of replacement species. The elevation of each site largely determined succession species. Red maple and dogwood, red maple and sourwood, blackgum and mixed pine, scarlet oak and mixed pine, and table mountain and pitch pine were the sequences from low to high elevation at the time of the study. The author predicts the forest types that will eventually succeed as the trees reach maturity. Stand composition and eleven site factors were sampled in 49 stands in the Great Smoky Mountains in which the pine overstory had been killed by the southern pine beetle. Replacement community types were determined using cluster analysis of relative densities for 21 common species. Absolute densities for total stems, total pine, total oak, and eight individual species in the overstory, understory, and reproduction strata were related to selected site and vegetation variables by correlation and stepwise multiple regression. Infestations greatly reduced the importance of pine in all replacement stands, converting most pine dominated stands to mixed pine-hardwood. Pine reproduction was minimal in all cases. All stands appeared to be in early stages of recovery, and canopy closure was very low. Six replacement types were derived. The red maple-dogwood type occupied low elevation, lower slope, old field sites. The red maple-sourwood type occurred on mid elevation broad ridgetops and protected upper slopes. The blackgum-mixed pine type occurred on mid elevation, mid to upper slope, exposed sites. The mixed pine-scarlet oak and the Virginia pine-blackgum types occupied exposed ridgetops and upper slopes at mid to low elevations. The table mountain pine-pitch pine type occupied high elevation kills on steep, exposed, upper slope positions. Important environmental factors influencing replacement stand composition and dynamics appeared to be elevation, incident solar radiation, topographic position, and soil nutrient availability. Future composition of replacement types was projected based on present composition and site conditions. The red maple-dogwood type will succeed to stands dominated by mixed hardwoods and white pine. In the red maple-sourwood type, the blackgum-mixed pine type, and the Virginia pine-blackgum type, chestnut oak will eventually dominate with scarlet oak and scattered pines in the canopy. The mixed pine-scarlet oak type will succeed to stands dominated by scarlet oak with residual pines as associates. Canopy closure will remain very open in the table mountain pine-pitch pine type due to the suppression of regeneration by dense mountain laurel, and the overstory will consist of widely spaced scarlet oaks and residual pines.