A 9000-YEAR FIRE HISTORY FROM THE OREGON COAST RANGE, BASED ON A HIGH-RESOLUTION CHARCOAL STUDY

High-resolution analysis of macroscopic charcoal in sediment cores fro m Little Lake was used to reconstruct the fire history of the last 900 0 years. Variations in sediment magnetism were examined to detect chan ges in allochthonous sedimentation associated with past fire occurrenc e. Fire intervals from ca. 9000 to 6850 calendar years BP averaged 110 +/- 20 years, when the climate was warmer and drier than today and xe rophytic vegetation dominated. From ca. 6850 to 2750 calendar years BP the mean fire interval lengthened to 160 +/- 20 years in conjunction with the onset of cool humid conditions. Fire-sensitive species, such as Thuja plicata Donn ex D. Don, Tsuga heterophylla (Raf.) Sarg., and Picea sitchensis (Bong.) Carr., increased in abundance. At ca. 4000 ca lendar years BP, increases in allochthonous sedimentation increased th e delivery of secondary charcoal to the site. From ca. 2750 calendar y ears BP to present, the mean fire interval increased to 230 +/- 30 yea rs as cool humid conditions and mesophytic taxa prevailed. The Little Lake record suggests that fire frequency has varied continuously on mi llennial time scales as a result of climate change and the present-day fire regime has been present for no more than 1000 years.