Environmental Description:  This alliance is composed of montane coniferous forests found in the interior Pacific Northwest, from southernmost interior British Columbia, eastern Washington, eastern Oregon, northern Idaho, western and northern Montana, and south along the east slope of the Cascades in Washington and Oregon. Elevations range from 460 to 2400 m (1500-7900 feet). Climate is mostly temperate, continental with maritime influences and is strongly influenced by the rainshadow effect of the Cascade Range or Coast Ranges of southern Oregon. Winter snowpacks typically melt off in early spring at lower elevations. Annual precipitation ranges from 40 cm in the Blue Mountains, up to 150-230 cm in the Cascades. Sites are typically on hot, dry, middle to upper slopes near grassy ridgetops. Slopes are moderate to steep with typically southern to western aspects, but stands may occur on northern slopes at low elevations. Substrates are typically shallow, lithic, course-textured soils derived from colluvium and residuum. Soil texture ranges from gravelly sand to sandy loam. There is often high surface cover of rock (to 50%), and coarse fragments average 40%. Parent materials may include granitic till or outwash, basalt, lava, pumice ash, tuff, granitics and sandstone. These rocky, shallow soils have so little moisture-holding capacity that these sites are effectively very dry for plant growth despite the substantial input of precipitation on most sites. These sites are exposed to high winds. Wind detracts from soil moisture status by blowing off snow, directly desiccating plants, and eroding soil.