NOAA/WDS Paleoclimatology - Bakker fire data from Kellett Bluff, Northwest Washington - IMPD USWKB001

Fire is a common disturbance in many forests. We conducted a fire history study on 40 Douglas-fir (Pseudotsuga menziesii) trees from two sites, Kellett Bluff and Turn Point, in the San Juan Islands of Washington state, USA. In total, 146 fire scars were identified and dated, representing 34-35 fires per site. Fires occurred between 1565 and 1964. Individual trees recorded up to 10 fires. The composite mean fire interval (MFI) was 11-13 years over the entire study period and 6 years in the historical period (1780-1895). These sites were structured by frequent, low-severity fires, yet supported a tree component for centuries - the oldest tree in this study was more than 500 years old. A program of frequent, low-severity fire may be critical for their long-term persistence. Comparisons of fire history data among these and five other local sites indicate frequent fires but little synchronicity; the MFI was 4 years but most fires were only recorded at single sites. Although forests west of the Cascade Mountains are often described as subject to infrequent, high-severity fires, these results highlight the need for a more refined understanding of historical fire regimes in this region.