Pacific Northwest Research Station

Title: Holocene fire and vegetation dynamics in a montane forest, North Cascade Range, Washington, USA

Author: Prichard, Susan J.; Gedalof, Ze'ev; Oswald, W. Wyatt; Peterson, David L.

Date: 2009

Source: Quaternary Research DOI: 10.1016/j.yqres.2009.03.008

Description: 

We reconstructed a 10,500-yr fire and vegetation history of a montane site in the North Cascade Range, Washington State based on lake sediment charcoal, macrofossil, and pollen records. High-resolution sampling and abundant macrofossils made it possible to analyze relationships between fire and vegetation. During the early Holocene (> 10,500 to ca. 8000 cal yr BP) forests were subalpine woodlands dominated by Pinus contorta. Around 8000 cal yr BP, P.contorta sharply declined in the macrofossil record. Shade tolerant, mesic species first appeared ca. 4500 cal yr BP. Cupressus nootkatensis appeared most recently at 2000 cal yr BP. Fire frequency varies throughout the record, with significantly shorter mean fire return intervals in the early Holocene than the mid and late Holocene. Charcoal peaks are significantly correlated with an initial increase in macrofossil accumulation rates followed by a decrease, likely corresponding to tree mortality following fire. Climate appears to be a key driver in vegetation and fire regimes over millennial time scales. Fire and other disturbances altered forest vegetation at shorter time scales, and vegetation may have mediated local fire regimes. For example, dominance of P. contorta in the early Holocene forests may have been reinforced by its susceptibility to frequent, stand-replacing fire events.

Keywords: Pacific Northwest, North Cascades Range, vegetation history, fire history, lake sediment charcoal, holocene

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Citation

Prichard, Susan J.; Gedalof, Ze'ev; Oswald, W. Wyatt; Peterson, David L.  2009.  Holocene fire and vegetation dynamics in a montane forest, North Cascade Range, Washington, USA.   Quaternary Research DOI: 10.1016/j.yqres.2009.03.008.