Increased probability of fire during late Holocene droughts in northern New England
Understanding the role of fire in the Earth system, and particularly regional controls on its frequency and severity, is critical to risk assessment. Charcoal records from lake sediment and fire-scar networks from long-lived tree species have improved our understanding of long-term relationships between fire events and climate. This work has primarily focused on historically fire-prone ecosystems and regions. In the northeastern USA, where wildfire has been relatively infrequent in historical times, fire-risk assessments have incorporated little-to-no pre-historical data and little is known about long-term fire-climate relationships. We developed coupled, high-resolution records of moisture variability and fire from three ombrotrophic peatlands in Maine using testate amoebae and analysis of microscopic charcoal. Water-table depth reconstructions among the three sites were generally coherent, with high-magnitude dry and wet events corresponding within the uncertainty of age-depth models. At all sites, there was a significantly higher probability of fire events during high-magnitude droughts. However, although prolonged droughts were widespread and associated with higher probability of fire, the fire events were rarely synchronous among sites, with the exception of ~550 years before present (yr BP) when all three sites experienced both drought and fire. While fire has been relatively uncommon in the northeastern USA during the past century, our records clearly highlight the potential vulnerability of the region to future drought and fire impacts. Results also demonstrate the utility of coupled records of fire and climate in understanding regional fire-climate dynamics.