Spatial variability of historical fires across a red pine–oak landscape, Pennsylvania, USA

Long‐term, ecosystem‐specific fire regime information improves natural community restoration and management by providing a basis for scientifically reasoned fire management prescriptions. Historical fire regimes can be reconstructed to sub‐annual resolution using fire‐scarred trees, and while such reconstructions have become increasingly prevalent across the eastern USA, little information regarding how they vary at landscape scale is available. Most studies report fire regime characteristics (i.e., frequency, seasonality) at site‐composite levels, commonly at ≤1 km2 spatial resolution. In this study, we analyzed the historical spatial variation of fire regime characteristics over the past four centuries (1620 CE to present) in a red pine/oak landscape (30.75 km2) in north‐central Pennsylvania, USA. Fire event data were reconstructed based on fire scars and locations of 192 living and dead red pines. The spatial and temporal distributions of fire scars revealed a historical fire regime dominated by frequent, dormant season fires most often detected at relatively small spatial extents and by relatively few trees. There was, however, evidence of less frequent, relatively large fires that scarred high percentages of trees. These fire regime characteristics likely resulted in a spatially and temporally transient patchwork of varying vegetation age and structures resulting in a heterogeneous landscape. At the landscape scale, fire frequency changed with human cultures, while fire spatial extent and scarring patterns appeared to be modulated by drought conditions. Results from this study show historical precedence for landscape‐scale burning across a broad range of drought conditions and spatial extents, which should be considered when designing fire‐management and ecosystem restoration objectives. The understanding of fire's importance in the ecology and management of natural communities in the eastern USA has seen continual advancement, based largely on the development of new tree‐ring and fire‐scar derived fire history datasets (Guyette et al. 2006, Stambaugh et al. 2006, 2011, 2018, Flatley et al. 2013, Aldrich et al. 2014, Kipfmueller et al. 2017, Abadir et al. 2019, Meunier et al. 2019). Tree‐ring and fire‐scar records allow for increased understanding of prehistoric ecological processes that, through time, resulted in the ecological conditions (Batek et al. 1999) later reported in documentary archives (Ruffner 2006, Hanberry et al. 2014a). The temporal perspective offered by these natural archives has identified variability in historical fire regimes