Revealing historical fire regimes of the Cumberland Plateau, USA, through remnant fire-scarred shortleaf pines (Pinus echinata Mill.)

Abstract

Background Vegetation of the Cumberland Plateau (USA) has undergone dramatic transitions since the last glaciation and particularly since the onset of widespread logging and twentieth century fire exclusion. Shortleaf pine (Pinus echinata Mill.), one of the most fire-dependent conifers in the US, occurs throughout the Cumberland Plateau, but its abundance has declined dramatically since Euro-American settlement and continues to decline. To better understand the historical ecology of fire within the natural range of shortleaf pine, we reconstructed fire regimes at three new sites throughout the central and southern Cumberland Plateau region based on fire scars on shortleaf pine trees. Results Fire event chronologies extended back to the seventeenth century and revealed historical fire regimes that were frequent and dominated by dormant-season and low-severity events. Fires occurred on average every 4.4 to 5.3 years at the study sites before widespread Euro-American settlement, and were more frequent (2.3 to 3.8 years) following settlement. Cumberland Plateau fires may be linked to adjacent ecoregions such as the Eastern Highland Rim to the west. Among all sites, we found that long-term trends in fire activity were similar and fit into a regional waveform pattern of fire activity likely driven by humans (i.e., Native American depopulation, European settlement, and twentieth century fire exclusion). Conclusions The decline in shortleaf pine and other fire-dependent ecosystems across the Cumberland Plateau is due to multiple interacting factors and, based on these data, frequent fire should be considered a historically important ecological driver of these systems.

Fire history and vegetation data reveal ecological benefits of recent mixed-severity fires in the Cumberland Mountains, West Virginia, USA

“…We documented the effects of "mesophication" (Nowacki and Abrams 2008) at Wall Fork, where there has been a near absence of fire since the 1950s. Here, the fire history is similar to that observed in other regional fire-scar records sourced from public lands where fire was excluded from the landscape by the mid-twentieth century (Lafon et al 2017;Stambaugh et al 2020). Conversely, we observed significantly more pine recruitment and herbaceous diversity (i.e., no evidence of mesophication) at Hite Fork, where multiple fires have burned since the 1980s.…”

“…Filtered MFI was approximately 7-8 years during the Boom and Bust era , which is slightly longer than the approximately 5-year MFI observed at two mixed pine-oak sites at the New River Gorge in nearby Fayette County, West Virginia during a similar time period (Maxwell and Hicks 2010;Saladyga 2017). The majority of pine or mixed pine-oak sites in the CHF have a comparable pre-fire exclusion or industrial era MFI of less than 12 years (e.g., Hessl et al 2011;Aldrich et al 2014;Howard et al 2021), with some shorter intervals (3-4 years) on the Appalachian (Hutchinson et al 2019), Cumberland (Stambaugh et al 2020), andOzark (Guyette et al 2006) Plateaus. The general correspondence of MFI among these sites as well as the preponderance of dormant season fire scars in each record suggest these fire regimes were driven primarily by human ignitions.…”

“…We assigned fire scars identified in each cross-section sample to a calendar year and, whenever possible, the season of occurrence based on the relative position within annual growth rings (Fig. 2) (e.g., Stambaugh et al 2020). Scars that occurred during the dormant season between annual growth rings were assigned to the calendar year after scarring.…”

“…In the Appalachian Mountains, from eastern Tennessee to Pennsylvania, fire-scar records extend from the seventeenth century to the present, with sample depth at most sites declining rapidly in the eighteenth century (Lafon et al 2017). These sites are concentrated in the Ridge and Valley physiographic province, the Blue Ridge Mountains, and on the western edge of the Appalachian Plateau in Ohio and Kentucky, while recent studies have addressed knowledge gaps along the Cumberland Plateau from Kentucky to Alabama (Hutchinson et al 2019;Stambaugh et al 2020). Mean fire intervals across the region range from approximately 2 to 12 years during the pre-exclusion era (pre-1930) and fire scars are completely or nearly absent from most site records after 1950.…”