WALSH, M. (1), WHITLOCK, C. (2), HEYERDAHL, E. (3), KERTIS, J. (4).

(1) Department of Geography, University of Oregon, Eugene, OR 97403, (2) Department of Earth Sciences, Montana State University, Bozeman, MT 59717, (3) USDA Forest Service Rocky Mountain Research Station, Fire Sciences Laboratory, P.O. Box 8089, Missoula, MT 59807, (4) USDA Forest Service Siuslaw National Forest, P.O. Box 1148, Corvallis, OR 97339.

The role that fire played in creating and maintaining the vegetation patterns of the Willamette Valley prior to Euro-American settlement (ca. 1850 AD) is unclear. In an ongoing research project, we are reconstructing the Holocene fire and vegetation history of the Willamette Valley based on a combination of lake-sediment and tree-ring records. High-resolution macroscopic charcoal and pollen analysis of lake-sediments provides information on decadal- to centennial-scale changes in local fire and vegetation history. Tree-ring records provide data on fire activity along the Valley fringe for the last ~100 years. The lake-sediment sites in this project are located within the Valley from north to south and encompass a range of environmental settings (i.e., riparian forest, prairie, prairie/forest border, Douglas-fir forest). Two records from Beaver Lake, OR, and Battle Ground Lake, WA, span the Holocene period and provide an opportunity to examine changes in fire frequency associated with millennial-scale climate variations, including the early-Holocene warm/dry period. A network of four additional records span the last ~2000 years and will be used to examine the relationship between fire frequency, decadal- and centennial-scale climate variability (e.g., the Medieval Climate Anomaly and the Little Ice Age), and known changes in anthropogenic activity. The comparison of lake-sediment and tree-ring records will highlight the timing and extent of changes in fire activity in the Valley associated with recent changes in human land use, including the cessation of Native American burning and Euro-American settlement/development of the Valley.