Date of Award
Master of Science
Niki Stephanie Nicholas
Wayne Clatterbuck, G. Hopper, Arnold Saxton
Since the early 1900s the southern Appalachian red spruce (Picea rubens Sarg.)-Fraser fir (Abies piceae (Pursh) Poir.) forests have been subjected to numerous destructive influences. Historical logging practices, fire, exotic insect infestations, acidic deposition, and global climate change have demonstratively altered the structure and composition of this fragile ecosystem. Most profound was the discovery in 1957 of the balsam woolly adelgid (Adelges piceae Ratz. Homoptera: Adelgidae ), an exotic sap-sucking aphid. A study was initiated in the Great Smoky Mountains National Park, which contains 74% of the red spruce-Fraser ecosystem. Thirty-six 20x20 m permanent plots untouched by logging were established in 1990 on five high elevation mountain peaks to monitor the changes in the forest and were re-sampled in 2000-01. From the late 1940s to 1990-91, live fir basal area decreased by 6.64 m2/ha. Between 1990-91 and 2000 live fir density increased by 156 stems/ha. Despite the increase in density this second generation of Fraser fir remained sparse compared to the 1940s. All of the species in the sapling cohort (<5cm diameter at breast height (dbh), and ≥1.37m tall) increased showing a positive response to overstory deterioration. All species in the seedling cohort (<1.37m tall) decreased exhibiting the effects of inhibition from the sapling layer, voids in seed years, and germination difficulty from lack of soil moisture. Mean age of all seedling and sapling size fir decreased since 190-91 suggesting a faster growing second generation in 2000. Mortality rates of all overstory species decreased since the late 1980s. However, the future of this young cohort of understory trees in unknown. A dense even-aged forest could create the ideal habitat of the adelgid, causing another rapid outbreak. If adelgid populations do not stabilize and Fraser fir does not develop a resistance this cohort could be in jeopardy once it reaches maturity. Provided it lives long enough to produce viable seed it will become a two-aged forest never reaching the "old growth" un-even aged structure that existed prior to infestation.
Mancusi, Michael R., "Structural Changes in the Red Spruce-Fraser Fir Forest. " Master's Thesis, University of Tennessee, 2004.