Age Structure and Disturbance History of a Southern Appalachian Virgin Forest

Abstract

The frequency and intensity of natural disturbances in a montane old—growth forest of coniferous (Tsuga) and broad—leaved deciduous trees (Liriodendron, Betula, Costanea, Fagus, Acer) were investigated by means of diameter frequency distributions, diameter—age regressions, and analysis of radial growth patterns. The seven species investigated are represented by all—aged populations regardless of the degree of shade tolerance. The age distributions of most species, however, are irregular with several prominent peaks. Apparent coincidence of these peaks among some species suggests a common underlying influence. Radial growth patterns reveal higher than average numbers of abrupt and sustained increases in growth rate in most decades of peak recruitment which, along with other evidence, suggest that disturbance was the principal causal factor. There is evidence for eight partial disturbances in the past 250 yr, each of which generally removed <10% of the overstory trees. These fairly light disturbances appear to be sufficient to cause major deviations from the theoretical equilibrium diameter distribution of the forest.