In the fire-maintained longleaf pine ecosystem, we are quantifying the long-term recovery of native ground cover vegetation and fine fuels from silvicultural treatments representing a gradient of canopy retention. Overall study objectives are 1) compare the extent and patterns of disturbance to vegetation at small- and large-scales; 2) quantify vegetation recovery periods across a disturbance gradient of skidder traffic; 3) determine the impact of canopy retention on fine fuels and fire behavior; and 4) compare recovery patterns from silvicultural disturbance with that of natural disturbances of fossorial animals. Preliminary results focus on relationships between small- and large-scale vegetation patterns. This study is being conducted in second-growth longleaf pine stands ranging in age from 80 to 95 years. All plots are burned on a 2-year rotation with prescribed fire management. The experiment is an incomplete randomized block design with six blocks and three treatments within each block. Silvicultural treatments included: 1) an uncut control, 2) single-tree selection, 3) group selection, and 4) group selection with retention in the gaps. Timber was harvested in December 2009 and the skidder was equipped with a GPS to estimate the number of skidder passes. Understory vegetation was characterized at large- and small-scales using a 25 m x 25 m grid that covered each 4-ha plot. For the stand level assessment, we categorized native ground cover vegetation at each grid point sample into one of the following categories: 1) dominated by wiregrass, 2) dominated by grasses (sparse wiregrass), 3) dominated by herbaceous species (sparse wiregrass), 4) dominated by hardwoods (sparse wiregrass), 5) dominated by grasses (no wiregrass), 6) dominated by herbaceous species (no wiregrass), 7) dominated by hardwoods (no wiregrass), 8) old logging road with a bare ground component, and 9) recently disturbed dominated by ruderal species. We quantified species richness on a small-scale by recording species presence in 1m2 subplots.
Results/Conclusions
Prior to treatment , total species richness per 4-ha plot ranged from 86 to 124 species. Species richness differed among pre-treatment vegetation categories, suggesting legacies of past landuse disturbances. Plots containing wiregrass and dominated by herbaceous species had the highest species richness while wiregrass was not detected on plots containing the fewest number of species. Skidder traffic created a disturbance gradient ranging from compression of existing vegetation (minor disturbance) to a significant reduction in ground cover (major disturbance) with the number of skidder passes ranging from 1 to 49.
