Despite a long history of human influence in the southern Appalachian Mountains, greater than 100,000 hectares of old-growth forests remain across complex landscape gradients and now represent, in aggregate, one of the largest totals for old-growth acreage in eastern North America. However, recognition of these remnant old-growth forests based on a standard definition of canopy age structure and absence of direct human disturbance can be difficult because of patterns of natural disturbance, variation in forest structure and composition across environmental gradients, and, increasingly, the effects of indirect human disturbances, such as exotic pest introductions and pollutant deposition. In this presentation, we describe the natural and human disturbances that have shaped old-growth forests in this region; compare historical and recent structural variation of old-growth forests in Great Smoky Mountains National Park (GRSM) using datasets from the 1930s and 1990s-2000s; and present a framework for evaluating, delineating, and conserving these forests.
Results/Conclusions
The 1930s dataset represents GRSM forests at the start of chestnut blight and just prior to the advent of fire suppression. The 1990s-2000s dataset represents these forests after introduction of the balsam woolly adelgid, beech bark disease, and other exotic pests, but before arrival of the hemlock woolly adelgid. The combined 1930s distribution of five important tree species targeted by exotic pests illustrates that few to no portions of GRSM’s dominant environmental gradients remain free of indirect human disturbance. Changes in average stand structure reflect these indirect effects, including lower basal area, higher density, and lower tree size.
To address ongoing disturbance in southern Appalachian forests while still recognizing the value of forests with no recent history of major human disturbance to the canopy or soil, we present a framework for identifying and evaluating old-growth forest on three site axes – age structure of the tree canopy, degree of human disturbance, and forest continuity through time – and one landscape axis that incorporates size (area) as well as spatial and temporal heterogeneity. In the context of this framework, we discuss future research and inventory needs to delineate and conserve old-growth forests in the southern Appalachians.