Environmental Description:  This alliance occurs in the alpine and upper subalpine zones of the southern and central Rocky Mountains and the high plateaus and mountain ranges in the Colorado Plateau and Great Basin. It also occurs at higher latitudes at Glacier National Park in northwestern Montana and in Waterton Lakes National Park, Alberta (Reid et al. 2004). The climate regime is continental, with long, cold winters and short summers with frequent afternoon thunderstorms. Strong southerly to westerly winds are common in the winter and spring, and sites are nearly blown free of snow in the winter. This patterned to heterogeneous vegetation type is characteristic of fell-fields, large expanses of steeply sloped (to 70%), unstable colluvium. Stands occur in high subalpine at 1940 m to mid-alpine at 2620 m. In the Colorado Front Range, stands are found on gentle to steep, rocky or gravelly slopes and ridges and outcrops in the lower alpine tundra close to the krummholz between 3350-3450 m elevation (Komarkova 1976). Sites are on warm, dry microsites on low-gradient, stable scree slopes and on moraines (Komarkova 1976). The defining rocky surface is composed of coarse-textured debris, cobbles, talus, and small-sized scree; regardless of fragment size, the amount of exposed rock cover is high(>70%). Soils are young and poorly developed due to low soil temperature, low soil moisture during the summer, and a short growing season, and are classified as Entisols (Cryorthents). Occasionally soils have a partially decomposed leaf litter layer and are classified as Histosols (Cryofibrists). The soil profile has only one horizon. Parent materials are variable. In the northern extent the physiognomy of this type is not so much that of an alpine-vegetated slope but of sparsely distributed shrubs on a rocky substrate (Reid et al. 2004).