Vegetation response to large scale disturbance in a southern Appalachian forest: Hurricane Opal and salvage logging
Disturbance such as catastrophic windthrow can play a major role in the structure and composition of southern Appalachian forests. We report effects of Hurricane Opal followed by salvage logging on vegetation dynamics (regeneration, composition, and diversity) the first three years after disturbance at the Coweeta Hydrologic Laboratory in western North Carolina. The objective of this study was to compare species composition and diversity of understory and groundlayer species in a hurricane + salvage logged (H+S) forest to an adjacent undisturbed forest. Abundance of groundlayer species was much higher in the H+S forest than in the undisturbed forest, and abundance increased over time. Percent cover, density, and species richness were significantly higher in the H+S forest than in the undisturbed forest. In addition, percent cover increased by approximately 85% between 1997 and 1999 in the H+S plots.
Shannon's index of diversity (H') based on percent cover was significantly higher in the H+S forest than the undisturbed forest by the third year after disturbance. However, there was no significant difference in H' based on density between H+S forest and the undisturbed forest in either year. In the undisturbed forest, 59 species and 50 genera represented 30 families. By 1999 (the third year after disturbance), the H+S forest retained 93 species. 72 genera and 42 families. The Asteraceae and Liliaceae had the highest number of species in both sampled forests, with more species of Liliaceae in the H+S plots. Micro-relief created from pit and mound topography from uprooting of windthrown trees, shade from the slash-debris left on site from the salvage logging, and shade from the remaining overstory trees created a mosaic of environmental conditions. This environmental heterogeneity could be responsible for the mix of early (shade intolerant) and late (shade tolerant) successional herbaceous species, and a higher species richness and diversity than the undisturbed forest.