PARENT SESSION
Poster Session #64: Long Term Ecological Research.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Twenty years of landscape-level change in canopy species dominance in an old-growth mixed mesophytic forest.

McEwan, Ryan^*,1, Muller, Robert¹, ¹ University of Kentucky, Lexington, Kentucky

ABSTRACT- Our grasp on the long-term stability of topographic patterns of canopy dominance in old-growth forests remains tenuous, yet these systems are often pointed to as successional endpoints and reference systems. We examined twenty years of vegetation data, and analyzed current patterns of regeneration in an old-growth forest in order to: (1) document topographic shifts in canopy dominance, (2) examine patterns of regeneration, and (3) explore the implications of these findings for future forest composition. This study is part of a long-term ecological monitoring project in a 52 ha old-growth forest on the Cumberland Plateau in southeastern Kentucky. From 1979 to 1999 Fagus grandifolia (5.8 m²/ha in 1979) was supplanted by Quercus montana (6.1 m²/ ha in 1999) as the most important canopy species and Acer rubrum (0.9 to 1.7 m²/ha) and Quercus alba (1.3 to 1.9 m²/ha) increased in importance. Twenty-year shifts in mid-story dominance patterns reveal an increasing importance of A. rubrum (1.4 to 2.0 m²/ha) and A. saccharum (1.2 to 1.8 m²/ha). In the current stand, regeneration in the shrub- and ground-layer is dominated by A. saccharum (903.1 stems/ha) and A. rubrum (0.02 m²/m² cover) respectively. Size-class distributions indicate adequate regeneration for A. rubrum, A. saccharum and F. grandifolia, while failing recruitment is evident for Q. alba and Q. montana. Topographically, regeneration patterns of A. rubrum, A. saccharum and F. grandifolia reveal the potential for expanding canopy dominance. In contrast, regeneration patterns of Q. montana and Q. alba indicate the potential for loss of canopy dominance on all but the most xeric sites in the watershed. The long-term shifts in canopy dominance and regeneration patterns in the current stand indicate that this old-growth mixed mesophytic forest system is not in equilibrium with regard to species compositional dominance or topographic distributions. Diffuse human impacts such as fire suppression and chestnut blight may be driving these quasi-allogenic processes in this undisturbed system.

KEY WORDS: old-growth forest, long-term dynamics, topographic distributions , regeneration patterns