FOREST DEVELOPMENT, PATTERNS AND PROCESSES FOLLOWING SUCCESSIVE CLEARCUTS IN THE SOUTHERN APPALACHIANS (DISTURBANCE, SUCCESSION, ECOLOGY)

Four watersheds at Coweeta Hydrologic Laboratory were studied to elucidate forest development, patterns and processes in the Southern Appalachians following disturbance. Forest composition (density, basal area, Importance Values, etc.) and structure (size-class distribution of stems and canopy structure) of Watershed 13 from 1934 to 1984 is described based on seven inventories made during this period. Analyses of environmental variables among three community types confirm a gradient in soil moisture and nutrients over the watershed (Cove Hardwoods type, highest resource level; Oak-Pine, lowest). Species distributions likewise are generally related to this topo-edaphic gradient. Past disturbances (selective logging in early 1900\u27s, chestnut blight, clearcuts in 1939-1940 and 1962) have favored the expansion of opportunistic mesic species such as Liriodendron tulipifera and Betula lenta onto sites historically believed to be too xeric. It was hypothesized that these mesic species would not survive on such sites due to a hydrologic shift, as streamflow and presumably soil moisture returned to predisturbance levels. Growth data for the major species during the past 21 years after the second clearcut do not support the hypothesis, nor do growth and population structure data from Watersheds 1, 3, and 17. For example, growth of Liriodendron over an elevational gradient on Watershed 3 does not uniformly decrease with increasing elevation. Basal area and mortality rate of Pinus strobus does not differ significantly over the resource gradient, represented by former community types, on Watersheds 1 and 17 which were planted entirely to this species in the late 1950\u27s. The size-class distribution of P. strobus stems suggests that there is no clear trend in intraspecific competition among former community types although competition should have been greatest in the Cove type where resources were thought to be highest. Results indicate a general trend in forest development in the Southern Appalachians following disturbance. Tree species which first colonize a site appear able to mature there regardless of predisturbance spatial patterns. Species which establish are a function of the disturbance imposed over site characteristics