Increasingly detailed records of long‐term fire regime characteristics are needed to test ecological concepts and inform natural resource management and policymaking. We reconstructed and analyzed twelve 350+ yr‐long fire scar records developed from 2612 tree‐ring dated fire scars on 432 living and dead pine (Pinus pungens, Pinus rigida, Pinus resinosa, Pinus echinata) trees from across central Pennsylvania. We used multiple spatial and time series analysis methods to quantify fire regime characteristics (frequency, seasonality, percentages of trees scarred, extent) and fire–climate–human associations. Prior to the 20th‐century fire suppression, fire regimes at the majority of sites consisted of frequent, low‐to‐moderate severity, dormant season fires. Fires were often regionally synchronous when preceded by significantly dry years. Using documentary archives, we provide the first description of a “wave of fire”—an anthropogenic signal in fire frequency that progressively moved across the region. This “wave of fire” reflects a changing progression of anthropogenic fire regimes from Native American occupation and depopulation, to Euro‐American settlement, to industrialization and declining fire use up to the 20th century era of fire suppression. The wave of fire provides a new perspective on historical and modern fire regime dynamics and identifies socio‐ecological impacts since North American colonization. Because the anthropogenic wave of fire exists at sites across North America, we emphasize the need for a broader determination of its geographic prevalence and variability as such determinations could influence historical ecology interpretations and perspectives on past and future roles of humans in managing ecosystems with fire.
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.
Synthesis of multiple sources of fire history information increases the power and reliability of fire regime characterization. Fire regime characterization is critical for assessing fire risk, identifying climate change impacts, understanding ecosystem processes, and developing policies and objectives for fire management. For these reasons, we conducted a literature review and spatial analysis of historical fire intervals in Texas, USA, a state with diverse fire environments and significant fire-related challenges. Limited literature describing historical fire regimes exists and few studies have quantitatively assessed the historical frequency of wildland fire. Written accounts provided anecdotal fire information that is spatially and temporally constrained. Three spatial datasets depicting historic mean fire intervals (MFIs) showed agreement in that the majority of Texas consisted of frequent fire regimes (MFIs = 1 yr to 12 yr), and that a gradient of decreasing fire return intervals existed from west to east. Much potential likely exists for acquiring fire history data in the Piney Woods region, the Oak Woods and Prairies region, and the mountain ranges of the Trans Pecos region. These data will be valuable for improving fire regime characterization to guide fire planning and budget processes, for the restoration and maintenance of fire-adapted landscapes, and for informing fire prevention and education activities.
Long-term knowledge of fire regimes aids in understanding the past, present, and future changes in Great Plains ecosystems. Dated fire scar histories and fire rate metrics in the Great Plains allow for quantitative analysis of the effects of climate on fire occurrence, frequency, forcing factors, and probability. Up to three centuries of fire scar data combined with modeling results from Great Plains sites show that spatially, fire frequency was greatly affected by annual maximum temperature from north to south, by annual precipitation east to west, by their interactions, and by precipitation thresholds. A fire-climate model, pc 2 fm (Physical Chemistry Fire Frequency Model), calibrated with rate metrics (mean fire intervals) derived from fire history data, estimates that in the Great Plains, fire intervals ranged from <4 to > 30 years. A “precipitation threshold” divides the Great Plains into eastern and western fire regime regions along an approximate 60–100 cm north-south annual precipitation isohyet. Future changes in annual wildland fire probability at 1.2 km 2 are predicted to change from –10% to 70% in the Great Plains. Midlatitude regions of the Great Plains (Wyoming, eastern Colorado, Nebraska, Kansas, and South Dakota) are expected to increase the most in annual fire probability while some areas in Texas will decrease in fire probability due to fuel limitations.
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