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Distinguishing between desirable and undesirable old-growth overstory systems as goals of conservation and management.
Gilliam, Frank*,1, Platt, William2, 1 Marshall University, Huntington, WV2 Louisiana State University, Baton Rouge, LA
ABSTRACT- Knowledge of the structure and composition of old-growth longleaf pine stands is imperative in the conservation and management of longleaf ecosystems. Among the challenges to our understanding of the ecology of old-growth longleaf sites, however, is the great degree of variability among sites, something that arises out of spatial variation in several factors, the most important of which is disturbance regime. Although once viewed as early-successional forests of low diversity, longleaf pine ecosystems are now seen as high-diversity, persistent savannas maintained by disturbance and pyrogenic vegetation, containing numerous endemic species. We distinguish between desirable versus undesirable characteristics of old-growth longleaf pine systems by comparing two sites that differ in disturbance regime: the Boyd Tract (NC) and the Wade Tract (GA). The Boyd Tract has undergone chronic fire suppression and occurs in the Sandhills, a region that experiences hurricanes infrequently. The Wade Tract has undergone annual prescribed burning and has historically experienced relatively frequent hurricanes. Differences between sites were seen more in stand structure than in overstory composition. Basal area of the Boyd Tract was over three times that of the Wade Tract. Relative dominance of longleaf pine also varied between sites, approximately 50 and 95% at the Boyd and Wade Tracts, respectively. These sharp contrasts in stand structure and longleaf pine dominance between the Boyd and Wade Tracts demonstrate the importance of large-scale disturbance, especially hurricanes and fire, in shaping the structure and function of longleaf pine ecosystems of the southeastern United States. In particular, long-term fire exclusion the Boyd Tract has altered stand structure substantially by decreasing longleaf pine regeneration. Reintroduction of fire accompanied by physical removal of dense turkey oak stems at the Boyd Tract resulted in only transient increases in longleaf seedling density. Thus, chronic fire exclusion can bring about long-term changes in longleaf pine stand structure.
Key words: old-growth, longleaf pine, conservation, management