Two statewide fires in 1825 and 1947, combined to burn millions of acres across Maine, mediating vegetation changes in places such as Mount Desert Island (MDI). Due to historically infrequent fires, little is known about long term fire-climate interactions in pre-European Maine. Concerns about future warming means there is an urgent need to fill this gap in our knowledge.
We used Maine’s north-south climatic gradient to contrast changes within two paleofire records that span the Holocene to analyze trends that may have been mediated by changes in climate, as has been shown to occur within mixed hardwood and boreal forests of northeastern North America. Charcoal was extracted and counted using standard methods from two cores; Sargent Mountain Pond (SMP) on MDI cored in 2007 and Galilee Pond in northern Maine cored in 2006.
Results/Conclusions
The paleofire record at Galilee Pond generally displays low charcoal concentration values since deglaciation, 13,200 years ago cal. BP, until an abrupt increase around 6,100 years ago cal. BP. Increasing charcoal concentration values also occur between 8,100 – 9.500 years ago cal. BP. This change coincides with >50% reductions in organic content in the sediments and changes in lake level at other sites in the region. A high magnitude peak closely following the reduction in sediment organic content suggests a severe fire that occurred following a documented period of regional drought.
In contrast, fire history at SMP displays a high variability throughout, conflicting with the historical assumption that fire hasn’t play a role in northern New England landscapes. Charcoal deposition increased abruptly around the time of the Younger Dryas cold event (13,600 - 11,700 cal. yr BP), which has been shown to have a strong signal in New England paleovegetation records, suggesting a response of fire to abrupt climatic changes even in the cooler coastal climate refugium. Charocal deposition also differed during the mid-Holocene (8000 – 4000 cal. yr BP), a time of increasing insolation and warmer, drier conditions than today.
Together, these results support further investigation into the drivers of fire in Maine, such as the relative role of climate versus humans, and that wildfires may be more prevalent in the coming centuries.