Postglacial climate and fire-mediated vegetation change on the western Olympic Peninsula, Washington

The mode and tempo of forest compositional change during periods of rapid climate change, including the potential for the fire regime to produce non-linear relationships between climate and vegetation, is a long-standing theme of forest ecological research. In the old conifer forests of the coastal Pacific Northwest, fire disturbances are sufficiently rare that their relation to climate and their ecological effects are poorly understood. We used a 14,700-year high-resolution sediment record from Yahoo Lake on the Olympic Peninsula to examine vegetation (landscape vegetation from pollen and local vegetation from macrofossils) and fire (landscape fire from total charcoal and local fire from charcoal peaks) in conjunction with independent records of climate. We hypothesized that the successional stage of the local forest will exhibit alternate stable states over a range of fire activity, that species turnover will increase abruptly above a certain level of fire activity and that both respo...