Date of this Version
Final Report to Joint Fire Science Program, Project Number 06-3-1-05
Information about historic fire regimes and the departure of current fire regimes from historic conditions is essential for guiding and justifying management actions, such as prescribed burning programs for ecosystem process restoration and fuel reduction. Such information is noticeably lacking for the southern Appalachian Mountains, where human populations are encroaching onto wildland areas, and where decades of fire exclusion have contributed to the decline of fire-associated communities and also to altered fuel loads. We address this knowledge gap via a multi-scale investigation of the variability in fire regimes over time and space using tree-ring reconstructions of fire history and stand dynamics in pine and mixed hardwood-pine forests. The tree-ring analyses are augmented by soil charcoal analyses and by statistical and GIS analyses of fire records from federal agencies. We used a multi-spatial scale approach to determine locations for tree-ring reconstructions of fire history. First, we established a network of four sites across the lowelevation pine-hardwood ecosystems in the western Great Smoky Mountains National Park (GSMNP), where we also set up plots for examining vegetation dynamics via age structure and species composition. We established a second network for reconstructing fire history and vegetation dynamics in middle-elevation forests of GSMNP spanning xeric to mesic sites. Together these low- and middle-elevation reconstructions portray patterns of fire and vegetation response across a broad landscape. Finally, we established two additional fire history sites, one in the Ridge and Valley terrain west of the GSMNP, and the other along the eastern escarpment of the Blue Ridge Mountains to the northeast of GSMNP. These sites combine with the GSMNP sites to characterize region-scale patterns and variations in fire history. Analyses of the tree-ring data reveal that fires burned frequently (at about 2–14 year intervals) in the southern Appalachian Mountains from the late 1700s/early 1800s until the early to middle 1900s, when burning declined coincident with fire protection. The density of trees, especially fire-intolerant species, increased in the 1900s as fire frequency declined. The soil charcoal study was conducted within the low-elevation tree-ring study sites in GSMNP. Charcoal fragments range in age from modern to about 3000 years old. About 75% of the hundreds of charcoal fragments identified in the cores are of pine. These results suggest that fire was a component of the forests long before the beginning of the tree-ring fire chronologies. They also emphasize the association of pine with fire in these humid environments where vegetation succession tends toward the replacement of pines by hardwoods. The GIS and statistical analyses of recent burning patterns clarify relationships among fire, climate, and terrain. Fire occurs most commonly in drier climates within the region, and during dry years. At the scale of local terrain, dry sites (e.g., ridgetops) burn more commonly than moist sites (e.g., valleys). Such topographic patterns are influenced by broader climatic conditions, however. Topographic patterning is more pronounced under wet climatic conditions than under dry conditions, which permit fires to spread into mesic topographic positions.
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