These are partially glaciated, high, rugged mountains with glacial features including moraines, cirques, and tarn (lake)s. Perennial or intermittent, high gradient, cold streams are fed by snowmelt and springs, supporting federally threatened bull trout and Lahontan cutthroat trout in Nevada. Riffle segments have cobble or boulder substrates. Annual precipitation is sufficient to support a Great Basin pine forest community of Douglas-fir, subalpine fir, ponderosa pine, and limber pine, with whitebark pine near the tree line, and aspen stands in riparian meadows, moist draws, and wet depressions. The understory features low juniper, mountain big sagebrush, mountain brush, serviceberry, snowberry, mountain-mahogany, Idaho fescue, sheep fescue, rough fescue, bottlebrush squirreltail, prairie lupine, mountain brome, bluebunch wheatgrass, and Sandberg bluegrass. Small areas of tundra and alpine meadows are found at the highest elevations. On Steens Mountain, above the juniper woodland zone of the Semirarid Uplands, the landscape is almost treeless; broad areas of mountain big sagebrush alternate with scattered groves of aspen. Alpine areas on Steens Mountain were seriously eroded following intense grazing by domestic sheep in the late 19th century. The region covers in Nevada, in Oregon, and in Idaho, and contains the Jarbidge Wilderness in the Humboldt-Toiyabe National Forest. The Salt Shrub Valleys ecoregion is composed of arid basins formerly inundated by Pleistocene lakes. Elevation varies from 3,500 to 5,200 feet (1,067 to 1,585 m) The nearly flat to gently sloping basins and playas are poorly drained, have a high water table, and retain water seasonally. They are flanked by bajadas and alluvial fans. The region also contains wetlands, hot springs, terraces, dunes, and a few hills. Soils, climate, and vegetation are transitional to the Central Basin and Range to the south. Characteristically, the basin floors have strongly saline and very alkaline soils that support black greasewood, inland saltgrass, bud sagebrush, shadscale, alkali sacaton, rushes, basin wildrye, bottlebrush squirreltail, and cheatgrass.