Browsing by Subject "Great Smoky Mountains National Park"
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Item Fire Regimes of the Southern Appalachian Mountains: Temporal and Spatial Variability and Implications for Vegetation Dynamics(2012-08-31) Flatley, William 1977-Ecologists continue to debate the role of fire in forests of the southern Appalachian Mountains. How does climate influence fire in these humid, temperate forests? Did fire regimes change during the transition from Native American settlement to Euro-American settlement? Are fire regime changes resulting in broad vegetation changes in the forests of eastern North America? I used several approaches to address these questions. First, I used digitized fire perimeter maps from Great Smoky Mountains National Park and Shenandoah National Park for 1930-2009 to characterize spatial and temporal patterns of wildfire by aspect, elevation, and landform. Results demonstrate that fuel moisture is a primary control, with fire occurring most frequently during dry years, in dry regions, and at dry topographic positions. Climate also modifies topographic control, with weaker topographic patterns under drier conditions. Second, I used dendroecological methods to reconstruct historical fire frequency in yellow pine (Pinus, subgenus Diploxylon Koehne) stands at three field sites in the southern Appalachian Mountains. The fire history reconstructions extend from 1700 to 2009, with composite fire return intervals ranging from 2-4 years prior to the fire protection period. The two longest reconstructions record frequent fire during periods of Native American land use. Except for the recent fire protection period, temporal changes in land use did not have a significant impact on fire frequency and there was little discernible influence of climate on past fire occurrence. Third, I sampled vegetation composition in four different stand types along a topographic moisture gradient, including mesic cove, sub-mesic white pine (Pinus strobus L.) hardwood, sub-xeric oak (Quercus L.), and xeric pine forests in an unlogged watershed with a reconstructed fire history. Stand age structures demonstrate changes in establishment following fire exclusion in xeric pine stands, sub-xeric oak stands, and sub-mesic white pine-hardwood stands. Fire-tolerant yellow pines and oaks are being replaced by shade-tolerant, fire sensitive species such as red maple (Acer rubrum L.) and hemlock (Tsuga canadensis L. Carr.). Classification analysis and ordination of species composition in different age classes suggest a trend of successional convergence in the absence of fire with a shift from four to two forest communities.Item Simulating Historic Landscape Patterns of Fire in the Southern Appalachian Mountains: Implications for Fire History and Management(2014-05-21) Gass, Ellen RFire suppression policies implemented in the early 20th century led to a decrease in fire-associated species and ecosystems in the southern Appalachian Mountains. As managers work towards restoration, a greater understanding of the pre-suppression fire regime is needed. Fire frequency and seasonality can be determined from physical fire records, such as fire scars, but fire size, fire cycle, ignition density, and ignition source are more difficult to ascertain. Using FARSITE, a spatially explicit fire model, I predicted past fire spread in the western Great Smoky Mountains National Park (GSMNP). Results showed a mean pre-suppression fire size of over an order of magnitude larger than fires on current landscape conditions (567 ha vs. 45 ha). Large fire sizes would have encouraged fire-associated vegetation and continuous flammable fuelbeds. In addition, the current lightning ignition rate within the study area resulted in a 120-135 year pre-suppression lightning fire cycle, which indicates that natural fires were influential on the landscape. This fire cycle is shorter than the lightning fire cycle experienced today (approx. 25-30,000 years). Using the mean fire return interval from previous research, I determined the potential contribution of lightning and anthropogenic ignitions to the fire cycle. This contributes to the debate on the importance of lightning versus anthropogenic ignitions to the pre-suppression fire regime. Most importantly, the estimation of mean fire size, fire cycle, and ignition density for lightning and anthropogenically ignited fires may aid federal resource managers as they use lightning ignitions and prescribed burns to restore fire-associated ecosystems in the GSMNP and other areas of the southern Appalachians.