Reconstructing pre-European fire regimes, forests and wildlife habitats in the eastern United States: Mammoth Cave National Park, Kentucky

Central Kentucky and Tennessee once supported vast areas of grasslands the first settlers called“the Barrens”.  These included post oak savanna, blackjack-black oak-post oak woodland, other forests, and canebrake as well as true eastern tallgrass and midgrass prairie.  Richness of prairie species in the two states exceeded that of all 17 states and provinces of the Great Plains, combined.  Mapping historical witness trees and landscape factors related to fire spread on GIS, we found an unexpectedly extreme range of original fire regimes, with nearly annual fires accounting for true prairies in the large barrens to the north and south of Mammoth Cave National Park, but also with fire-refugial beech forest occupying deep bowls and hollows in the rugged karst topography overlying the cave systems and in the gorge of the deeply limestone-entrenched Green River.  On parts of the uplands having only gently rolling topography there existed fire compartments of up to 300 square miles, with fifty-mile fire runs possible in flashy prairie and oak savanna grass fuels.  Several lines of evidence indicate that the original fire regime was driven by a combination of lighting plus flashy fuels in large fire compartments, with only minor supplementation byNative Americans.  First, the Desoto expedition of 1540 passing not far to the south of the study area, is thought to have introduced European diseases as they went, and plagues were being introduced along the mid-Atlantic coast by 1583.  The two original cultures of Kentucky died out quickly after the DeSoto passage; the Mississippian Culture, which dominated the Mammoth Cave region, was extirpated by 1600, only 60 years after DeSoto, while the Fort Ancient culture in northeastern Kentucky persisted a few decades longer.  This left Kentucky largely depopulated of Indians except for transient hunting parties from peripheral states.  And yet, the fire regime that supported the barrens rolled on for 180 years, until the state was opened to colonization in 1780.  Second, the calculated rate of 6-12 fires per year ignited by lightning in the barrens to the south of the park would be sufficient to maintain a nearly annual fire frequency from lightning alone.  The natural fire regime died by 1830 within 50 years of extirpation of bison and introduction of livestock which, upon saturation of the landscape, consumed the grass fuels.  Succession in the absence of fire was so far advanced by 1847 that one contemporary traveler commented "…the Barrens, formerly an extensive prairie,[are] now overgrown with a scrubby oak called Black Jack."  This wave of succession after the death of the original fire regime appears here and there in the literature all across the South.  Drastic reversals include decimation of post oak—a fire dependent species—once the most abundant tree on historical surveys, and ascendancy of red cedar.  Cedar is dominant today in much of the park, but of 2,681 witness trees, only a single red cedar was reported on early surveys.

by Dr. Cecil C. Frost; Adjunct Faculty at The University of North Carolina at Chapel Hill

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