The Uncompahgre Plateau supports a wide variety of plant communities (Map D). Landsat Satellite Imagery (2002) for vegetation has been used to determine acreages and locations of vegetation.  Plant community identification was done using ground truthing. The species composition and productivity of the Plateau’s plant communities are dependent on soil types, precipitation levels, elevation, slope, and aspect. The more productive soils and higher precipitation rates found at the higher elevations correlate with the richer variety of vegetative types and abundance. Annual precipitation on the Plateau varies from less than 10” at the lowest elevations to more than 30” along the summit. Winter snowfall accounts for the majority of the precipitation at the higher elevations. Monsoon precipitation between July and September is also an important source of moisture at all elevations.

Plant communities on the Plateau change with elevation gradient. Below approximately 6000’ near the Dolores, San Miguel, Uncompahgre and Gunnison Rivers, a salt-tolerant, desert plant community is the predominant, extant vegetation type. Important species in this community include four-wing saltbush, shadscale saltbush, black sagebrush, winterfat, rabbitbrush, cacti, snakeweed, greasewood, and in the Gateway area, blackbrush. In the Uncompahgre Valley and in the area surrounding Nucla, irrigated agricultural areas dominate this zone where land clearing, leveling, water redistribution, and cultivation have dramatically changed the landscape and vegetation. Noxious weeds in these lower elevation areas include Russian knapweed, Canada thistle, halogeton, Russian thistle, cheatgrass, tamarisk, and whitetop.

Riparian areas on the Plateau are limited and therefore are of primary importance. In lowland riparian and wetland areas the dominant native plant species include coyote willow, narrowleaf cottonwood, boxelder, chokecherry, sumac, silver buffaloberry, hawthorn, cattails, rushes, and a variety of grasses, sedges, and forbs. Willows, birches, thinleaf alder, and blue spruce are characteristic of higher elevation riparian areas.

Between 6,000’-7,500’, pinyon pine and Utah juniper are generally the dominate vegetation types. Pinyon-juniper (PJ) forests cover approximately 40% of the project area. Other species associated with the PJ zone include big basin sagebrush, mountain big sagebrush, Wyoming big sagebrush, black sagebrush, cacti, saltbushes, western wheatgrass, and Indian ricegrass. At the higher end of the PJ zone, mountain shrubs such as mountain mahogany, serviceberry and Gambel oak and a variety of grasses and forbs become increasingly abundant.

Above approximately 7,500’, the PJ community gives way to mountain shrub, Gambel oak, and ponderosa pine. Vegetation types associated with this zone include serviceberry, mountain mahogany, mountain big sagebrush, and snowberry. On the northwest side of the Plateau, manzanita is also a common component of the mountain shrub type.

Above approximately 8,000’, the mountain shrub/Gambel oak and pine oak communities transition into aspen and spruce/fir forests and open meadows. Important species include quaking aspen, Douglas fir, sub-alpine fir, Engelmann spruce, blue spruce, snowberry, cinquefoil, mountain big sagebrush, and silver sagebrush. Grasses and forbs expand in diversity and number particularly in areas with relatively open canopies such as the aspen stands.

The only federally listed threatened and endangered plant species known to occur on the Plateau is the Unita Basin hookless cactus (Sclerocactus glaucus). Its status is threatened. The Uinta Basin hookless cactus is found on Salt-Desert/Grassland sites west and northwest of Delta in the vicinity of Cactus Park, lower Roubideau, lower Escalante Canyon and McCarty Bench. These populations appear to be in good condition.