Regional frequencies of tree species associated with anthropogenic disturbances in three forest types

Abstract We used a probability-based sampling scheme to survey the forested lands of Georgia and Alabama, two adjacent states in southeastern USA. Using a nationally consistent plot design and field methods, we evaluated the presence/absence of tree species at 123 1/15 ha plots for individuals having a diameter at breast height >2.5 cm. Three forest cover types were considered: loblolly-shortleaf pine, oak-hickory, and oak-pine. Visually evident anthropogenic disturbances (e.g. artificial regeneration, logging, and prescribed burning), if any, were recorded on each plot. We classified plots with visually evident anthropogenic disturbance as `disturbed'. The remaining plots were classified as `undisturbed'. For each of the three forest types considered, mean species richness of trees was significantly greater in undisturbed plots. Of 61 species forest type combinations, eight (13.1%) had significantly different frequencies in undisturbed than in disturbed areas. In the loblolly-shortleaf pine type, five of the 18 species (27.8%) considered occurred significantly more frequently on undisturbed plots. In the oak-hickory type, two of the 21 species considered (9.5%) occurred more frequently on undisturbed plots and one species, loblolly pine, occurred more frequently on disturbed plots. Species occurring more frequently on undisturbed areas in these forest types included occupants of both the mid and upper canopy. Loblolly pine is not a common associate in the undisturbed oak-hickory forest. These results and those from other studies strongly suggest that anthropogenic disturbance, particularly clearcutting and subsequent planting of pine plantations, is having profound effect on the structure and composition of the forested area of the region. Because the three forest cover types we considered account for approximately 71% of the total forested area of the region, these results should be useful for forest management and conservation planning in the states. Management implications of mixed pine-hardwood stands vs. pine plantations in the south-east are discussed.