Vegetation cover and type varies with soil type and to greater degree soil moisture. The limiting factors with regard to moisture are altitude and aspect. This is due to the higher precipitation rates of the higher areas and the reduced rates of evaporation and sublimation of north facing slopes. Alpine tundra exists in the highest mountain areas. Intermediate elevation areas are covered by spruce, fir and aspen forests with areas of open grassland. The riparian areas support willows, red twig dogwoods, alder and birch trees. The lower, drier areas of the study area are covered with pinion pine, lodgepole pine, juniper, and gambrel oak with mountain sage, rabbitbrush, and grasses filling the gaps. Cottonwoods are found along streams and between the agricultural fields found in the valleys and on some of the mesas.