Multi-scale synthesis of historical fire regimes along the south-central US prairie\u2013forest border

Molly V Rooney,Michael C Stambaugh

doi:10.1186/s42408-019-0043-y

Abstract

BackgroundAlong the prairie–forest border in the south-central USA exists one of the most extensive areas of uncut forest in the nation (>323 750 hectares), providing unique potential for developing multi-century records of environmental changes through dendrochronological analyses. Twentieth century changes in vegetation, increased prescribed fire management, and recent years of elevated wildfire activity have increased interest in understanding the region’s long-term fire regime characteristics. To address this need, we analyzed and compared fire intervals, seasonality, severity, and extent based on fire-scar history datasets from three new and ten existing study sites.ResultsAt the study sites, mean fire intervals ranged from 3 to 10 years prior to Euro-American settlement and generally became more frequent after. The majority of fires occurred in the dormant season and resulted in low percentages of trees scarred. Coinciding with Euro-American settlement (EAS), fire frequencies appear to have varied by geography. At the regional scale, fire regimes have trended towards decreased fire severity and slightly decreased fire intervals over the past 300 years. Further, fires appear to have increased in extent from circa 1770 to the mid to late 1800s, after which it began to decline, circa 1920.ConclusionsAlthough frequent, descriptions of fire regimes since the eighteenth century should be characterized as time-dependent and spatially variable, likely depending on local socio-ecological influences. Similar influences may explain fire frequency increases following EAS, while fire severity trended lower.

Highlights

Along the prairie–forest border in the south-central USA exists one of the most extensive areas of uncut forest in the nation (>323 750 hectares), providing unique potential for developing multi-century records of environmental changes through dendrochronological analyses
During the last two centuries, fire suppression has resulted in vegetation alterations at a continental scale, including extensive areas of open-canopy oak savannas and woodlands transitioning to more closed-canopy conditions (DeSantis et al 2011; Hanberry et al 2014; Stambaugh et al 2014)
Diseases introduced by Europeans caused Native American populations to collapse and likely further altered fire regimes through reduced anthropogenic ignitions (Waldman 1985)

Summary

Introduction

Along the prairie–forest border in the south-central USA exists one of the most extensive areas of uncut forest in the nation (>323 750 hectares), providing unique potential for developing multi-century records of environmental changes through dendrochronological analyses. Twentieth century changes in vegetation, increased prescribed fire management, and recent years of elevated wildfire activity have increased interest in understanding the region’s long-term fire regime characteristics. To address this need, we analyzed and compared fire intervals, seasonality, severity, and extent based on fire-scar history datasets from three new and ten existing study sites. Slow growing, and of poor form due to site and environmental factors, have limited economic value and, the region holds one of the most extensive areas of uncut forest in the US (>323 750 hectares; Therrell and Stahle 1998), providing unique potential for documenting long-term environmental changes through dendrochronological analyses. Diseases introduced by Europeans caused Native American populations to collapse and likely further altered fire regimes through reduced anthropogenic ignitions (Waldman 1985)

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