The impact of historic logging on woody debris distribution and stream morphology in the Great Smoky Mountains National Park, North Carolina-Tennessee
Date of Award
Master of Science
Kenneth H. Orvis, Liem Tran
In the early 1900s, large sections of the Great Smoky Mountains were intensively logged. Since then, most locations have been allowed to naturally become forest-covered again, resulting in areas of secondary growth and old growth forest. To determine whether differences in large woody debris (LWD) loading and channel morphology persist today, I measured LWD, channel widths and depths, and channel bed sediments of streams in old and secondary growth forest in the Great Smoky Mountains National Park.
LWD pieces in streams in old growth had larger mean diameters and lengths compared to LWD in streams in secondary growth forest. Streams in old growth had 5.6 times more LWD volume than those in secondary growth. More LWD pieces were in debris dams in old growth than in secondary growth forest.
Channel bed sediment size did not differ significantly between streams in old and secondary growth forest. Channel widths and depths were signifiantly larger in streams in old growth forest. LWD pieces affected channel depth primarily by creating pools and causing deposition of sediment. LWD affected width by directing stream flow toward banks and by protecting banks from erosion. I observed that the orientation of LWD was important in determining its geomorphic role.
Although I found no relationship between LWD loading and watershed area, I found a relationship between watershed area and the importance of LWD in impacting channel morphology. Despite differences in LWD frequency and total volume, streams in old and secondary growth forest differed little in width and depth in the largest watersheds in this study. However, in smaller watersheds, streams in old growth were not as narrow or as shallow as streams in secondary growth.
LWD loading can vary substantially between streams, even those with sim- ilar surrounding forest types, climate, and disturbance histories; therefore, caution should be exercised when using LWD loading rates from other studies in environmental management.
Despite nearly 80 years of forest regrowth, LWD loading and channel mor- phologies of streams still show the impacts of logging.
Morris, Christopher M., "The impact of historic logging on woody debris distribution and stream morphology in the Great Smoky Mountains National Park, North Carolina-Tennessee. " Master's Thesis, University of Tennessee, 2008.