Woody plant species composition and structure of burned sites differs only slightly from unburned sites in a Southern Appalachian wilderness area

Background/Question/Methods

When it comes to wildfire, most information available to forest managers is derived from the results of relatively small prescribed fires intended for restoration of desirable species and promotion of species diversity. The rarity of large scale wildfires in the Southern Appalachians has provided little opportunity to research the effects of wildfire at the landscape scale. Beginning in the summer of 2000, following a long drought, wildfire burned a significant portion of the Linville Gorge Wilderness Area in western North Carolina. This initial fire was followed by a series of fires in 2007. The occurrence of successive wildfires in Linville Gorge has opened up an opportunity to measure an extensive network of North Carolina Vegetation Survey (NCVS) plots established prior to the 2000 fire. We surveyed 25 unburned plots, 47 plots that burned once, and 34 plots that burned twice using NCVS methodology.  To examine the impacts of repeated fire on woody species structure we constructed relative abundance curves, rarefaction curves, and compared several indexes of diversity.  In addition, we also used non-metric multidimensional scaling (NMS) ordination to illustrate differences in species composition among the site types (i.e., unburned, burned once, burned twice).

Results/Conclusions

Rank abundance curves were similar with all sites being dominated by red maple (Acer rubrum) and mountain laurel (Kalmia latifolia).  Although individuals in unburned sites were somewhat more evenly distributed compared to the burned sites.  Rarefied species richness was highest in plots that burned twice compared to sites that burned once or not at all. Fisher’s alpha, and Simpson’s (1/D) ranked the unburned sites as the least diverse, and sites that burned twice more diverse than sites that burned once. In contrast, Shannon’s (e^H) ranked unburned sites as most diverse, which is due to the evenness illustrated by the rank abundance curve for unburned sites.  Ordination illustrated that species composition is similar among the unburned sites and both burned site types.  Although, sites that had burned once or twice show some separation along Axis 2, which appears to be driven by the higher abundance of Kalmia latifolia in sites that were burned once.  Our research reveals that wildfire appears to have produced few changes to woody plant species composition which is likely due to the abundance of woody species that resprout following top-kill.  Future research will include sampling of a larger number of unburned plots as well as sampling and analysis of herbaceous species.