Cascades (ecoregion)

This article is about the ecoregion designated by the EPA. For the mountains, see Cascade Range.

Cascades
Scattered patches of subalpine fir grow below glaciers and permanent snowfields on the south slope of Mount Rainier in ecoregion 4d.
Level III ecoregions of the Pacific Northwest. The Cascades ecoregion is marked with (4).
Ecology
Borders	Puget Lowland (2) Willamette Valley (3) Eastern Cascades Slopes and Foothills (9) North Cascades (77) Klamath Mountains (78)
Geography
Area	44,952 km² (17,356 sq mi)
Country	United States
States	Washington, Oregon and California
Coordinates	45°N 122°W / 45°N 122°W / 45; -122Coordinates: 45°N 122°W / 45°N 122°W / 45; -122

The Cascades ecoregion is a Level III ecoregion designated by the United States Environmental Protection Agency (EPA) in the U.S. states of Washington, Oregon, and California. Somewhat smaller than the Cascade mountain range for which it is named, the ecoregion extends north to Snoqualmie Pass, near Seattle, and south to Hayden Pass, near the Oregon-California border, including the peaks and western slopes of most of the High Cascades. A discontiguous section is located on Mount Shasta in California.

The mountainous region is underlain by Cenozoic volcanic rock that has been affected by alpine glaciations. The eastern part of the region contains active and dormant volcanoes in the Cascades Volcanic Arc, with elevations of up to 11,239 feet (3,426 m). The western Cascades are older, lower, and dissected by numerous, steep-sided stream valleys. The region has a moist, temperate climate, which supports an extensive and highly productive coniferous forest that is intensively managed for logging, as well as recreational use. Subalpine meadows occur at higher elevations.

Much of the region consists of public lands managed by the federal government, including the Mount Baker-Snoqualmie, Wenatchee, Gifford Pinchot, Mount Hood, Columbia River Gorge National Scenic Area, Willamette, Umpqua, and Rogue River National Forests; the Clearwater, Norse Peak, Tatoosh, William O. Douglas, Goat Rocks, Mount Adams, Indian Heaven, Trapper Creek, Salmon–Huckleberry, Mount Hood, Table Rock, Bull of the Woods, Opal Creek, Middle Santiam, Menagerie, Mount Jefferson, Mount Washington, Three Sisters, Diamond Peak, Boulder Creek, Mount Thielsen, Rogue–Umpqua Divide, Sky Lakes, and Mountain Lakes Wilderness Areas; Mount Rainier and Crater Lake National Parks; and the Mount St. Helens National Volcanic Monument.^[1]^[2]

The Cascades is bordered on the north by the North Cascades ecoregion, on the south by the Klamath Mountains ecoregion, on the east by the Eastern Cascades Slopes and Foothills, and on the west by the Willamette Valley and Puget Lowland ecoregions. It been subdivided into six Level IV ecoregions in Washington and Oregon, as described below. Level IV mapping is not yet complete in California.^[1]^[2]

Animals include black bears, deer, elk, bobcats, cougars, coyotes, skunks, raccoons, and chipmunks.

Level IV ecoregions

Level IV ecoregions in the Cascades in Oregon and Washington. A separate section on California's Mt. Shasta has not been mapped yet. (Full map).

Western Cascades Lowlands and Valleys (4a)

The Western Cascades Lowlands and Valleys ecoregion comprises a network of steep ridges and narrow valleys on the lower slopes of the Cascade Mountains. Elevation varies from 600 to 4000 feet (183 to 1219 m). Its mild, wet climate promotes lush forests dominated by western hemlock and Douglas-fir, with western redcedar, bigleaf maple, red alder, vine maple, salal, rhododendron, Oregon grape, huckleberry, thimbleberry, swordfern, oxalis, hazel, and blackberry. Soils are warmer here than in higher elevation ecoregions, and it is one of the most important timber producing areas in the Pacific Northwest. The steep valleys trending to the west contain high and medium gradient rivers and streams that support cold water salmonids, including the threatened Chinook salmon, steelhead, and bull trout. Notable river drainages in Oregon include the North Umpqua, North and Middle Forks of the Willamette, McKenzie, North Santiam, South Santiam, Clackamas, Salmon and Bull Run River watersheds; and in Washington, the Lewis, Cowlitz, Nisqually, Puyallup, White, and Green River watersheds. Reservoirs store winter snowmelt for irrigation and municipal water supply in the Willamette Valley. The Westerns Cascades Lowlands and Valleys is the largest of the Cascades subregions, covering 3,905 square miles (10,114 km²) in Oregon and 2,397 square miles (6,208 km²) in Washington.^[1]^[2]

Western Cascades Montane Highlands (4b)

The Western Cascades Montane Highlands ecoregion is characterized by steeply sloping, dissected mountains with high to medium gradient streams and glacial rock-basin lakes. Elevation varies from 3,000 and 6,500 feet (914 to 1,981 m). The western Cascades are older and more eroded than the lava plateau and prominent snow-covered cones of the High Cascades to the east. They are underlain by dark basalt in contrast to the gray andesite of the High Cascades. The region has lower temperatures and receives more winter snow than the lowlands and valleys to the west. Soils have a frigid or cryic temperature regimes. Abundant precipitation supports forests dominated by Douglas-fir and western hemlock, with mountain hemlock, noble fir, subalpine fir, grand fir, Pacific silver fir, red alder, and Pacific yew, and an understory of vine maple, rhododendron, Oregon grape, huckleberry, and thimbleberry. Today, the region is heavily managed for logging and recreation, and it is an important water source for lower elevation urban, suburban, and agricultural areas. It is the second largest of the Cascades subregions, covering 2,729 square miles (7,068 km²) in Oregon and 1,828 square miles (4,734 km²) in Washington.^[1]^[2]

Cascade Crest Montane Forest (4c)

The Cascade Crest Montane Forest ecoregion consists of an undulating plateau punctuated by volcanic buttes and cones that reach a maximum elevation of about 6,500 feet (1,981 m). Volcanism in the Pliocene epoch overtopped the existing Miocene volcanics of the Western Cascades Montane Highlands. Later, Pleistocene glaciation left numerous rock-basin lakes throughout the plateau. Sinuous, medium gradient streams cross the subdued, glaciated terrain. The region is extensively forested with mountain hemlock, Pacific silver fir, and subalpine fir, with some grand fir, noble fir, Douglas-fir, Engelmann spruce, and lodgepole pine, and an understory of vine maple, huckleberry, rhododendron, beargrass, twinflower, and wintergreen. Mountain meadows support sedges, dwarf willows, and tufted hairgrass. The region covers 1,909 square miles (4,944 km²) in Oregon and 310 square miles (803 km²) in Washington, running along the spine of the Cascades; an isolated pocket of this ecoregion can be found on Newberry Volcano southeast of Bend.^[1]^[2]

Cascades Subalpine/Alpine (4d)

The Cascades Subalpine/Alpine ecoregion is an area of high, glaciated, volcanic peaks rising above subalpine meadows, with cascading streams, glacial cirques, and tarns. Pleistocene glaciation reshaped the mountains above 6,500 feet (1,981 m), leaving moraines, glacial lakes, and U-shaped glacial canyons. Glaciers and permanent snowfields still occur on the highest peaks, decreasing from north to south. The vegetation is adapted to high elevations, cold winter temperatures, a short growing season, and a deep winter snow pack. Herbaceous and shrubby subalpine meadow vegetation and scattered patches of mountain hemlock, subalpine fir, and whitebark pine occur near the timberline. Wet meadows support Brewer's sedge, Holm's sedge, black alpine sedge, tufted hairgrass, and alpine aster. Elsewhere, there is bare rock. The region covers 388 square miles (1,005 km²) in Washington and 331 square miles (857 km²) in Oregon and contains many of the prominent volcanic peaks of the high Cascades, including Mount Rainier, Mount Adams, Mount Hood, Mount Jefferson, Three Sisters, Mount Bachelor, Diamond Peak, Mount Scott, and Mount McLoughlin.^[1]^[2]

High Southern Cascades Montane Forest (4e)

The High Southern Cascades Montane Forest ecoregion is an undulating, glaciated, volcanic plateau punctuated by isolated buttes and cones. Many tarns occur. With an elevation that varies from 4,000 to 8,200 feet (1220 to 2500 m), it is an intermediate zone between the Southern Cascades and the Subalpine/Alpine zone. Cryic soils support mixed coniferous forests dominated by mountain hemlock, lodgepole pine, and Pacific silver fir; they are colder than the mesic and frigid soils of the Southern Cascades. Grand fir, white fir, and Shasta red fir also occur and become more common toward the south and east. Whitebark pine is found at high elevations. Understory plants include woodrush, Prince’s pine, lupine, and sidebells shinleaf. At the highest elevations, open meadows support Shasta buckwheat, Newberry knotweed, and Brewer's sedge. The region tends to be drier than the Cascade Crest Montane Forest, with a longer summer drought and more intermittent streams. The region covers 915 square miles (2,370 km²) in Southern Oregon and includes the lower elevations of Crater Lake National Park.^[1]^[2]

Southern Cascades (4f)

The Southern Cascades ecoregion is lower in elevation and less rugged than the surrounding regions and is characterized by gently sloping mountains and broad valleys. Elevation varies from 1400 to 5300 feet (427 to 1615 m). The climate is drier than other parts of the Cascades, and the vegetation reflects the long summer drought. River and stream discharge are also significantly lower than in systems to the north. Western hemlock and western red cedar, which are indicator species in the Western Cascades ecoregions, decline southward in the Southern Cascades, and are replaced by Sierra Nevada species such as California incense-cedar, white fir, Shasta red fir, and sugar pine, with an understory of snowberry, twinflower, Oregon grape, serviceberry, golden chinkapin, and oceanspray. At lower elevations, Douglas-fir and ponderosa pine are prevalent. The region covers 1,414 square miles (3,662 km²) in Southern Oregon, in the South Umpqua and Rogue River watersheds, separated from the Western Cascades by the Calapooya Divide.^[1]^[2]

Ecoregions defined by the EPA and the Commission for Environmental Cooperation:
- List of ecoregions in North America (CEC)
- List of ecoregions in the United States (EPA)
- List of ecoregions in Oregon
- List of ecoregions in Washington
- List of ecoregions in California
The conservation group World Wildlife Fund maintains an alternate classification system:
- List of ecoregions (WWF)
- List of ecoregions in the United States (WWF)

Level III Ecoregions in Oregon

Marine West Coast Forest	1 Coast Range 3 Willamette Valley

Northwestern Forested Mountains	4 Cascades 9 Eastern Cascades Slopes and Foothills 11 Blue Mountains 78 Klamath Mountains

North American Deserts	10 Columbia Plateau 12 Snake River Plain 80 Northern Basin and Range

as defined by the United States Environmental Protection Agency

Level III Ecoregions in the United States

Marine West Coast Forest	1 Coast Range 2 Puget Lowland 3 Willamette Valley 111 Ahklun and Kilbuck Mountains 113 Alaska Peninsula Mountains 115 Cook Inlet 119 Pacific Coastal Mountains 120 Coastal Western Hemlock-Sitka Spruce Forests

Northwestern Forested Mountains	4 Cascades 5 Sierra Nevada 9 Eastern Cascades Slopes and Foothills 11 Blue Mountains 15 Northern Rockies 16 Idaho Batholith 17 Middle Rockies 19 Wasatch and Uinta Mountains 21 Southern Rockies 41 Canadian Rockies 77 North Cascades 78 Klamath Mountains 105 Interior Highlands 116 Alaska Range 117 Copper Plateau 118 Wrangell Mountains

Mediterranean California	6 Southern and Central California Chaparral and Oak Woodlands 7 Central California Valley 8 Southern California Mountains

North American Deserts	10 Columbia Plateau 12 Snake River Plain 13 Central Basin and Range 14 Mojave Basin and Range 18 Wyoming Basin 20 Colorado Plateaus 22 Arizona/New Mexico Plateau 24 Chihuahuan Deserts 80 Northern Basin and Range 81 Sonoran Basin and Range

Temperate Sierras	23 Arizona/New Mexico Mountains

Great Plains	25 Western High Plains 26 Southwestern Tablelands 27 Central Great Plains 28 Flint Hills 29 Central Oklahoma/Texas Plains 30 Edwards Plateau 31 Southern Texas Plains 34 Western Gulf Coastal Plain 40 Central Irregular Plains 42 Northwestern Glaciated Plains 43 Northwestern Great Plains 44 Nebraska Sand Hills 45 Piedmont 46 Northern Glaciated Plains 47 Western Corn Belt Plains 48 Lake Agassiz Plain

Eastern Temperate Forest	32 Texas Blackland Prairies 33 East Central Texas Plains 35 South Central Plains 36 Ouachita Mountains 37 Arkansas Valley 38 Boston Mountains 39 Ozark Highlands 51 North Central Hardwood Forests 52 Driftless Area 53 Southeastern Wisconsin Till Plains 54 Central Corn Belt Plains 55 Eastern Corn Belt Plains 56 Southern Michigan/Northern Indiana Drift Plains 57 Huron/Erie Lake Plains 59 Northeastern Coastal Zone 60 Northern Appalachian Plateau and Uplands 61 Erie Drift Plain 63 Middle Atlantic Coastal Plain 64 Northern Piedmont 65 Southeastern Plains 66 Blue Ridge 67 Ridge and Valley 68 Southwestern Appalachians 69 Central Appalachians 70 Western Allegheny Plateau 71 Interior Plateau 72 Interior River Valleys and Hills 73 Mississippi Alluvial Plain 74 Mississippi Valley Loess Plains 75 Southern Coastal Plain 82 Laurentian Plains and Hills 83 Eastern Great Lakes and Hudson Lowlands 84 Atlantic Coastal Pine Barrens

Northern Forests	49 Northern Minnesota Wetlands 50 Northern Lakes and Forests 58 Northeastern Highlands 62 North Central Appalachians

Tropical Wet Forests	76 Southern Florida Coastal Plain

Southern Semi-Arid Highlands	79 Madrean Archipelago

Taiga	101 Arctic Coastal Plain 102 Arctic Foothills 103 Brooks Range 104 Interior Forested Lowlands and Uplands 106 Interior Bottomlands 107 Yukon Flats 108 Ogilvie Mountains

Tundra	109 Subarctic Coastal Plains 110 Seward Peninsula 112 Bristol Bay-Nushagak Lowlands 114 Aleutian Islands

as defined by the United States Environmental Protection Agency

References

1 2 3 4 5 6 7 8 This article incorporates public domain material from the United States Geological Survey document: Thorson, T.D., Bryce, S.A., Lammers, D.A. et al. "Ecoregions of Oregon" (PDF). (color poster with map, descriptive text, summary tables, and photographs; with a Reverse side).
1 2 3 4 5 6 7 8 This article incorporates public domain material from the United States Geological Survey document: Pater, D., Bryce, S.A., Kagan, J. et al. "Ecoregions of Western Washington and Oregon" (PDF). (color poster with map, descriptive text, summary tables, and photographs; with a Reverse side).

External links

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