Cascades

The Cascade Mountains in Oregon are divided into two distinct Ecoregions, a West and an East Cascades. Read about how one geological feature has rich ecological diversity.

West Cascades

The West Cascades ecoregion extends from just east of the Cascade Mountains summit to the foothills of the Willamette, Umpqua and Rogue Valleys, and spans the entire length of the state of Oregon, from the Columbia River to the California border.

The topography and soils of the West Cascades ecoregion has been shaped dramatically by its volcanic past. Geologically, the West Cascades has two distinct areas: the younger volcanic crest (approximately three million years old) and the “old Cascades” to the west of the crest (at least 30 million years old). The volcanic crest includes the highest peaks in Oregon: Mt. Hood, Mt. Jefferson, and North, Middle, and South Sisters, all more than 10,000 feet. The older western Cascade Mountain Range is characterized by long, steep ridges and wide, glaciated valleys.

This ecoregion is almost entirely forested by conifers, although the dominant tree species vary by elevation, site characteristics, and stand history. Douglas-fir is the most common tree below 4,000 feet, often with western hemlock as a co-dominant. At higher elevations, dominant tree species include Pacific silver fir, mountain hemlock, or subalpine fir. Other common conifers include western redcedar, grand fir, and noble fir. Above approximately 7000 feet, the conditions are too severe for tree growth, and alpine parklands and dwarf shrubs predominate, including some wetlands and barren expanses of rock and ice. The climate and resulting fire regime varies with latitude and elevation. Fire regimes in the forests vary across the ecoregion, with the northern portion of the ecoregion seeing less frequent but more severe fires, whereas the southern portion is typically drier with frequent, lightning-caused fires. In the southern areas with higher fire frequency, Ponderosa pine, sugar pine, and incense cedar often are found with Douglas-fir at the lower elevations. The climate varies with elevation. At the lower elevations, winter conditions are mild with high rainfall. Above 4,000 feet, much of the precipitation occurs as snowfall.

The West Cascades ecoregion houses just over one percent of Oregon’s population, mostly in towns including Cascade Locks, Butte Falls, Detroit, Gates, Idanha, McKenzie Bridge, Blue River, Oakridge, Westfir, and part of Sweet Home (the remainder of which lies in the Willamette Valley ecoregion). Local economies were once entirely dependent on timber harvest, but have been greatly affected as market conditions, long-term and broad-scale changes in the forest products marketplace, and shifts in public forest management priorities have shaped Oregon’s timber industry. Many towns are increasingly promoting recreational opportunities - including hiking, camping, fishing, hunting, birding, mountain biking and skiing - to supplement timber harvest revenue. However, timber harvest is expected to remain important to local West Cascades economies in the future.

East Cascades

The East Cascades ecoregion extends from just east of the Cascade Mountains summit to the warmer, drier high desert to the east. Stretching the full north-to-south length of the state, the East Cascades is narrow at the Columbia River but becomes wider toward the California border.

This ecoregion varies dramatically from its cool, moist border with the West Cascades ecoregion to its dry eastern border, where it meets sagebrush country in some regions. The climate is generally dry, with wide variations in temperature. The East Cascades includes several peaks and ridges in the 6,000-7,000 foot range, but, overall, the slopes on the east side of the Cascade Mountain range are less steep and cut by fewer streams than the Western Cascade Ecoregion. The East Cascades’ volcanic history is evident through numerous buttes, lava flows, craters, and lava caves, and in the extensive deep ash deposits created by the explosion of historical Mt. Mazama during the creation of Crater Lake.

Terrain ranges from forested uplands to marshes and agricultural fields at lower elevations. The northern two-thirds of the East Cascades ecoregion is drained by the Deschutes River, ultimately flowing into the Columbia. Most of the southern portion of the East Cascades ecoregion is drained by the Klamath River, with a small portion draining into Goose Lake, a closed basin. In general, the East Cascades is drier than the West Cascades, with fewer rivers flowing over the mountain slopes. However, the East Cascades is characterized by many lakes, reservoirs and marshes, providing exceptional habitat for aquatic species and wildlife closely associated with water, including waterbirds, amphibians, fish, aquatic plants and aquatic invertebrates. In fact, the East Cascades ecoregion supports some of the most remarkable aquatic biological diversity in the United States.

When compared to Oregon’s other ecoregions, the East Cascades has the second-highest average income (the Willamette ecoregion supports the highest per-capita income). Much of this income is related to tourism and recreation, with forestry and agriculture also important components. Towns include Bend, Klamath Falls, Lakeview, and Hood River; many of these towns are experiencing rapid population growth. Most of the Warm Springs Indian Reservation is found in the East Cascades ecoregion.

text taken from the Oregon Conservation Strategy, 2006, Oregon Department of Fish and Wildlife

Update

The Oregon Master Naturalist Program is currently developing a statewide curriculum. In time, the West Cascades ecoregion will have a specific regional supplement that will give participants a more in depth look at the region. Continue to check this web site for an update as regionally specific supplements are added.