Patterns of seedling and overstory composition along a gradient of hurricane disturbance in an old-growth bottomland hardwood community

Abstract

Disturbance patterns and species composition in the seedling and canopy layers were examined across the range of post-hurricane damage in an old-growth bottomland hardwood forest. Canopy coverage, tip-up number and area, snags, and coarse woody debris were quantified in plots along randomly oriented transects established in bottomland hardwood stands and mixed Pinus taeda L. - bottomland hardwood stands. Wilcoxon rank sum tests of these individual disturbance features indicated greater disturbance in plots containing the early successional species, Pinus taeda, than in mixed bottomland plots without it. Principal components analysis (PCA) using these features illustrated much overlap between the two assemblages and suggested a continuum of canopy and soil disturbance conditions from windthrows along axis I and a continuum of canopy disturbance due to snag formation along axis II. Woody seedlings and trees were inventoried in 30 plots spanning the range of disturbance. Seedling species richness exhibited a rank order increase along axis I. Floristic trends in both seedling and tree layers were significantly correlated with disturbance represented by PCA axis I scores. Removal from the canopy and lack of successful recruitment of Pinus taeda, a former canopy dominant, suggest that the hurricane has shifted this old-growth floodplain forest to a different successional state.