ECOLOGICAL CONTEXT OF CLIMATE IMPACTS ON FIRE: WILDLAND FIRE AREA BURNED IN TEH WESTERN U.S. 1916-2003.

LITTELL, J.S. (1,2), MCKENZIE, D. (3), PETERSON, D.L. (1,2,3), WESTERLING, A.L. (4) AND SWETNAM, T.W. (5).

(1) Fire and Mountain Ecology Lab, University of Washington College of Forest Resources, Seattle, WA, (2) JISAO CSES Climate Impacts Group, Seattle, WA, (3) Fire and Environmental Research Applications Team, USDA Forest Service PNW Research Station
Seattle, WA, (4) Climate Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, (5) Laboratory of Tree-Ring Research
University of Arizona, Tucson, AZ.

We used two wildland fire area burned datasets and historical climate data to evaluate the degree to which climate variability between 1916 and 2003 exerted an influence on the annual area burned in eco-provinces of 11 western states in the US. One of the fire datasets is 88 yr long and cumulated by state. The second is 21 yr but has greater spatial precision at 1°x 1° lat/long. We used the relationships during the common period to reconstruct area burned by eco-province for the full record. Preliminary work suggests relationships between the two fire area burned datasets are reasonable for reconstruction purposes in most eco-provinces (average R^2 = 0.55, range = 0.16 – 0.81) and that the climate relationships are often temperature- and drought- driven. Sub-regional seasonal and annual predictors for temperature and precipitation combined explain 25-52% (mean 30%) of the variability in 1916-2003 fire area burned. Increasing fire area is positively associated with lagged precipitation for many of the semi-desert steppe and grassland eco-provinces, whereas the relationship is negative for more heavily forested eco-provinces. Annual temperature, however, is the single best predictor for 9 of the 15 preliminary eco-province models.