Willamette Valley forests
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The Willamette Valley forests is a temperate mixed forest ecoregion of Oregon and Washington in the western United States.
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[edit] Setting
The ecoregion covers an area of 14,900 square kilometers (5,800 square miles), lying mostly in Oregon, with a small portion lying across the Columbia River in southern Washington. The ecoregion lies in the Willamette Valley, which runs from south to north between the Oregon Coast Range to the west and the Cascades Range to the east. The ecoregion is drained mostly by the Willamette River and its tributaries, which flows into the Columbia River near Portland, Oregon. The Central Pacific forests ecoregion covers the Coast Ranges to the west, while the Central and Southern Cascades forests covers the Cascades Range to the west. The Puget lowland forests, another mixed forest ecoregion, adjoins the Willamette Valley forests to the north,
[edit] Flora
Historically the Willamette Valley forests were mostly an oak savanna, tall grasslands with scattered Garry Oaks (Quercus garryana), and groves of Coast Douglas-fir (Pseudotsuga menziesii subsp. menziesii). The river floodplains contained extensive wetlands, stands of willow, alder, and cottonwood, and gallery forests.
This landscape was maintained by the Native American inhabitants of the valley by setting frequent fires which encouraged the open grasslands and killed young trees. The American settlers of the region since the 19th century converted much of the valley to agriculture, and suppressed fires, which has caused much of the former grassland and savanna to revert to closed-canopy forest.
[edit] Conservation and threats
Less than one-tenth of 1% of the original savanna vegetation remains. The remaining enclaves include a section of Garry Oak savanna preserved at Mount Pisgah Arboretum in Eugene, Oregon.
[edit] External links
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