Level IV: (4d) Cascades: Alpine/Subalpine
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.