A 35,000 yr fire history from the Oregon Coast Range, USA

Abstract

ABSTRACT We extend a published 9000 yr fire history record from Little Lake, in the Oregon Coast Range, to 35,000 yr and compare it with the established pollen record from the site. The fire history is based on a high-resolution analysis of charcoal preserved in lake sediments, providing a fire history record that spans the Last Glacial Maximum in North America. The data enabled us to address questions regarding the interactions between large-scale climate changes associated with the shift from glacial to interglacial conditions and the accompanying changes in forest vegetation and fire regimes. The vegetation history indicates a change from open subalpine forests to closed western hemlock and Douglas fir forests as climate moved from cold and dry full glacial to warm and wet Holocene conditions. The fire history indicates that although there was more biomass burned in the Holocene, the frequency of fires between glacial and interglacial conditions was not significantly different, and the fire frequency did not change in concert with regional shifts in vegetation. This suggests that fire is a product of seasonal or multiyear variations in climate that may not cause significant shifts in vegetation. Also, as this short-term climate variability becomes more common in the near future, conditions for fires in these mesic forests may become more common as well.