Upland Hardwood Silviculture Techniques in North Alabama
Callie Jo Schweitzer, Research Forester, USDA Forest Service
Have you ever wondered how the upland hardwood forests of north Alabama came to be? Have you ever wondered why we often favor certain tree species in our cultural preferences (oak cabinets, walnut tables, cherry anything)? Do you really know what the term clearcutting means?
A new USDA Forest Service research laboratory, developed as a subunit of the Ecology and Management of Southern Appalachian Hardwood Forests research work unit, is addressing some of the questions concerning sustainable management of the upland hardwood forests of the Cumberland Plateau and associated highlands. Knowledge about the silvics and site requirements of tree species and their complex relationships within forest communities is continually refined through research and the experience of forest managers. Initial scientific activities in this new program have focused on understanding vegetation distribution and productivity in relation to environmental gradients and understanding structural and compositional dynamics in response to disturbance.
Five disturbance treatments are being tested in three replicated sites located in northern Jackson County, Alabama. The five disturbance regimes implemented were chosen to elucidate the effects of the level of tree retention on key elements of forest structure and composition. The treatments consisted of leaving a percentage of the trees occupying a particular site, often referred to as a shelterwood method of regeneration for hardwood sites. For this study, sites retained 100, 75, 50, 25 and 0 percent of their trees. One major objective on these sites was to regenerate oaks, which can be difficult due to competition with other species, such as yellow poplar. We are currently developing a model that will allow us to predict post-harvest performance of oaks and other species both in terms of height growth and in terms of the probability of attaining a favorable competitive position in a new stand that develops. This study is one that will assist us in calibrating our model and testing our predictions.
What if there are no suitable species for which to manage? This is a common scenario on many sites that have been continuously high-graded, removing the best trees and leaving the rest. We are addressing these concerns by artificially introducing northern red oak seedlings to our study sites. We are testing the conditions under which the oaks will most favorably respond. For example, we hope to demonstrate that planted oak seedlings grow better under partially shaded conditions compared to full sun, and, if this is indeed the case, we will attempt to explain why by studying seedling physiology along with microclimate characteristics.
Finally, there is a lack of information on how these disturbances affect other inhabitants and users of the forests. We have implemented a study to examine songbird response to these treatments, as habitat alterations and its consequences is an invaluable aspect of the field of avian ecology and understanding these processes is essential to the conservation of birds. Another study is addressing the effects these treatments have on the abundance, species diversity, species richness and population structure of reptile and amphibian communities. Some innovative field sampling techniques are being employed to quantify these individuals. We hope to achieve a better understanding of the relationships of silvicultural practices and populations of forest biota.