The Cascades Subalpine/Alpine (4d) ecoregion contains the prominent volcanic peaks of the high Cascades. Pleistocene glaciation reshaped the mountains above 6500 feet, leaving moraines, glacial lakes, and U-shaped glacial canyons. Glaciers and permanent snowfields still occur on the highest peaks. The vegetation is adapted to high elevations, cold winter temperatures, short growing season, and deep winter snow pack. Herbaceous subalpine meadow vegetation and scattered patches of mountain hemlock, subalpine fir, and whitebark pine occur near timberline.

The High Southern Cascades Montane Forest (4e) ecoregion is an undulating, glaciated, volcanic plateau containing isolated buttes, cones, and peaks. The terrain is less dissected than the Southern Cascades (4f). At 4,000 to 8,200 feet, maximum elevations are intermediate to those in the Southern Cascades (4f) and the Cascades Subalpine/Alpine ecoregion (4d). 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 (4f). Grand fir, white fir, and Shasta red fir also occur and become more common toward the south and east. The High Southern Cascades Montane Forest (4e) has a longer summer drought and more intermittent streams than the Cascade Crest Montane Forest (4c).

Ecoregion 9. Eastern Cascades Slopes and Foothills

Ecoregion 9 is in the rainshadow of the Cascade Range. It experiences greater temperature extremes and receives less precipitation than ecoregions to the west. Open forests of ponderosa pine and some lodgepole pine distinguish this region from the higher ecoregions to the west where hemlock and fir forests are common, and the lower, drier ecoregions to the east where shrubs and grasslands are predominant. The vegetation is adapted to the prevailing dry, continental climate and frequent fire. Historically, creeping ground fires consumed accumulated fuel and devastating crown fires were less common in dry forests.

The Pumice Plateau (9e) ecoregion is a high volcanic plateau. Ecoregion 9e is characteristically covered by thick deposits of pumice and volcanic ash. Soils are very deep, highly permeable, and droughty. Spring-fed creeks and marshes occur. Ponderosa pine forests are common on slopes; colder depressions and flats are dominated by lodgepole pine and higher elevations have white fir. Freezing temperatures are possible any time of year.

Information source: The descriptions above were provided by the website of the Western Ecology Division of the Environmental Protection Agency.