Abstract
Characterization of scale dependence of fire intervals could inform interpretations of fire history and improve fire prescriptions that aim to mimic historical fire regime conditions. We quantified the temporal variability in fire regimes and described the spatial dependence of fire intervals through the analysis of multi-century fire scar records (8 study sites, 332 trees, 843 fire scars) derived from two historically post oak (Quercus stellata Wangenh.) woodland landscapes. Despite large differences in fire environment conditions, study sites (∼1 km2) burned frequently (mean fire interval [MFI] ≤10 yr) before Euro-American settlement (pre-EAS), with sites in Tennessee showing higher overall fire frequency than sites in Oklahoma, USA. Pre-EAS MFIs decreased exponentially with increasing spatial extent from individual trees (∼1 m2) to landscapes (∼100 km2). The relationship between MFI and spatial extent may help to explain how historical observations of annual burning could be recorded in woodlands, when experimental studies suggest that this is too frequent for tree recruitment. Further investigations of spatial dependence of fire intervals would improve our ability to relate historical and experimental fire data to present day fire prescriptions, and vice versa.
Highlights
Fire scar history data were collected from four sites across an approximately 100 km2 area historically dominated by post oak woodlands
A total of 423 fire scars and 205 fire intervals were identified from the four study sites (Table 2)
The trend of longer site Mean fire intervals (MFIs) during the Prior to Euro-American settlement (pre-EAS) period, to shortened MFIs following EAS, to longer MFIs in the latter twentieth century was shared by sites at both Arnold Air Force Base (AAFB) and Wichita Mountains Wildlife Refuge (WMWR) (Tables 1 and 2)
Summary
L.) woodland communities in the eastern US overwhelmingly show transition to more closed-canopy conditions and fire-intolerant tree species (Dyer 2001, Nowacki and Abrams 2008, Hanberry et al 2014). Detailed and spatially explicit information is needed about the fire ecology of woodlands, including how species and ecosystem function respond to specific fire regime conditions, and how or if tree recruitment can be sustained through repeated, long-term burning. Understanding the scale dependencies of fire intervals would improve the ability to crosswalk between sources that characterize woodlands such as historical data, experimental data, and present day fire monitoring. Quantifying the variability in fire intervals across spatial and temporal scales may inform us about their relative importance as related to oak woodland development
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