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Fire History in the Pacific Northwest
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There are two stories to the frequency of naturally caused fires in
the Pacific Northwest: the "west side story and the "east side story".
Forests of Mt. Rainier, Olympic, and the western portion of North
Cascades National Parks are generally moist, fir-dominated regions. The
fire cycle at any one point is infrequent here, occuring at intervals of
150 to 700 years.
East of the Cascades, the fire story is quite different. Much of
the fire history here at Crater Lake National Park has been documented
through the research of James Agee, professor of Forest Ecology at the
University of Washington, and other researchers since the mid-70's. For
example, the drier, ponderosa pine-dominated region encompassing lower
elevations at Crater Lake National Park has a much shorter interval
between fire. Here natural fires occurred every 2 to 17 years.
Research indicates that historical fire regimes varied according to the
forest type in terms of fire frequency and severity. Mountain
hemlock/Shasta red fir forest regions have a 42 year mean fire return
interval while Lodgepole pine forest areas experience natural fires
every 60 to 80 years on average.
Prior to fire suppression activities, these small but frequent fires
served to decrease the amount of fuel on the forest floor. In the
absence of fire, ground fuels and understory vegetation began to
accumulate to unnaturally high levels. This accumulation of fuels
presented a serious fire hazard. To lessen this hazard and restore
natural forest conditions, resource managers at Crater Lake are
prescribing low intensity fires. These burns are set in pre-determined
areas usually in the spring and fall so that low levels of fire
intensity are assured.
Fire is a natural process - a part of each park's ecosystem of
plants, animals, soil, water, and air - and is as much as a part of the
forests as avalanches, windstorms, native insect and disease outbreaks,
and, certainly evident at Crater Lake National Park, volcanoes. All of
these naturally occurring forces have played an important role in
shaping the forest landscape we all enjoy today.
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