Environmental Description:  This association occurs in the lower foothills of a mountainous region, on the eastern side of the Continental Divide. The region is characterized by a strongly continental climate, with hot summers and cold winters. In winter, cyclonic storms control the precipitation pattern, occasionally causing deep snows. These storms can occur during spring and fall months as well. In summer, convective rainshowers contribute a large amount to the total annual precipitation and generate lightning which is a significant cause of forest fire. Annual precipitation averages 33-43 cm (13-17 inches), 65% of which falls between May and September. Strong downslope winds can occur any time of the year, but are particularly prevalent in the late winter and spring.

This association is found from 1600 to 2100 m (5200-6900 feet) elevation, on topographic features including hogbacks, ridges, mesas and slopes. Slopes vary from gentle to somewhat steep (up to 45%), and aspects are often easterly, except at the higher elevations, where they are southerly. It occupies the most xeric of the forested sites in the eastern Front Range, a zone between grass- and shrub-dominated vegetation at lower elevations and more densely forested in more mesic areas. Parent materials are primarily sandstones and conglomerates. Most soils are lithic orthents, where bedrock approaches the surface. They are poorly developed, well-drained, very rocky and/or gravelly, loam or sandy loam in texture, and with much exposed surface rock. At lower elevations in the Front Range, soil texture and rocky sites are apparently the most important factors in the shift from grassland to vegetation dominated by woody species.