Jennifer R. Marlon, Yale School of Forestry and Environmental Studies
Large wildfires are relatively rare today across the northeastern U.S., but small fires continue to be an important ecological process in a variety of settings. The North Atlantic pine-oak forests and barrens are adapted to periodic fire, for example, and fire has also long influenced forests with mixed red spruce, balsam fir, and hardwoods in northern New England. In some areas where fire has long been absent, land-use changes have altered fuels to increase fire hazard, threatening rare plants and biodiversity conservation efforts. Understanding the fire history of a place requires records spanning beyond the historical era because the patchy and infrequent nature of fires by definition makes them difficult to observe over short time periods.
Charcoal accumulation in the sediments of lakes and wetlands, when undisturbed, can serve as a natural archive of fire history for an individual watershed. Networks of local sediment records across a broader area can show how levels of burning have fluctuated over centuries and millennia. To better understand the baseline variability of fire regimes in New England, a paleoecological study of 13 sites is in progress. Analyses of paleoecological, paleoclimate, and archaeological data are underway to better understand the interactions between fire, forest composition, climate change, and human activities during the past 2000 years. Preliminary results indicate that charcoal abundances (biomass burning) was highest in pine forests and lowest in beech forests. The lakes surrounded by oak-dominated forests had intermediate levels of charcoal. Biomass burning has generally declined during the past 2000 years at all sites until the arrival and settlement of Europeans, after which it increased. The new research suggest that the long-term decline in burning can be attributed to a gradual cooling and wetting trend, with shorter-term variations likely reflecting drought events and human activities. Further analyses will examine the extent to which biomass burning trends differ from those in the broader Northeastern US, and whether patterns of fire history reveal can reveal any insights into the importance of Native American burning throughout the region.