Floristic Province Descriptions

Excerpts from: Miller, R. F. and L. L. Eddleman.2001. Spatial and Temporal Changes of Sage Grouse Habitat in the Sagebrush Biome. Oregon State University Agricultural Experiment Station. Technical Bulletin 151. Corvallis,OR. 39 pp.

Colorado Plateau The southern Great Basin and Colorado Plateau subdivisions lie south of the sagebrush steppe and north of the creosote (Larrea tridentat) and blackbrush (Coleogyne ramosissima) deserts. Predominant sagebrush species in these two subdivisions are Wyoming big sagebrush (Artemisia tridentata var. wyomingensis), mountain big sagebrush (A. tridentata var. vaseyana), low sagebrush (A. arbuscula), and black sagebrush (A. nova). Plant communities in this region are often more arid than sagebrush communities located to the north. Recovery from fire, grazing, or other disturbances is usually slower and attempts at land restoration less successful than in the sagebrush steppe (West 1983). Season of precipitation varies from minimal summer rainfall in the north-west corner of the southern Great Basin to near 40% summer rainfall in southern Utah, northern Arizona, and northern New Mexico. The majority of the Colorado Plateau receives more moisture than the southern Great Basin; however, sagebrush distribution is greatly limited by marine shale outcroppings which forms halomorphic (saline) soils. In the southern Great Basin, sagebrush communities are typically on uplands between the salt deserts occupying the lower elevation Great Basin valley floors and the semi-arid woodlands and forests occupying the mid to upper mountain slopes. However, sagebrush communities extend to nearly 3,300 m on many mountain ranges (Cronquist et al. 1994).    Go to Map

Columbia Basin The Columbia Basin contains the lowest elevation sagebrush communities in the sagebrush biome. Predominant sagebrush in this region are Wyoming big sagebrush (Artemisia tridentata var. wyomingensis) and basin big sagebrush (A. tridentata var. tridentata). The Columbia Basin sagebrush-steppe is bordered by the Palouse Prairie and coniferous forests. Precipitation primarily occurs in the winter and spring. The basin is underlain by vast lava flows however, soils have been greatly influenced by glacial loess and Pleistocene outwash (Rickard and Vaughn 1988). Soils commonly range from sandy loams to silt loams.   Go to Map

Northern Great Basin The northern Great Basin sagebrush-steppe occurs between salt deserts occupying valley floors and woodlands, conifer forests, and alpine meadows. Predominant sagebrush are Wyoming big sagebrush (Artemisia tridentata var. wyomingensis), mountain big sagebrush (A. tridentata var. vaseyana), and low sagebrush (A. arbuscula). Precipitation primarily occurs in the winter and spring. Soils are typically derived from volcanic materials (West 1983), with some outcropping of sedimentary materials (Walker and MacLeod 1991).   Go to Map

Silver Sagebrush Subdivision The Silver Sagebrush Subdivision marks the northeastern edge of the Great Plains, covering portions of Alberta, Saskatchewan, Montana, Wyoming, North Dakota, and South Dakota. The boundary for the Silver Sagebrush Subdivision was not originally included in Miller and Eddleman’s map of floristic provinces (2001), but was identified in the Range-wide Sage-grouse Conservation Assessment (Connelly et al. 2004) as an important component of sage-grouse habitat in those areas. Miller and Eddleman (2001) describe plains silver sagebrush (Artemisia cana var. cana) as a sagebrush community type that is widespread over the northern Great Plains at elevations of 1200 to 2100 m that occupy well-drained alluvial flats, terraces valley bottoms, and drainage ways (Hazlett and Hoffman 1975, Morris et al. 1976, and Beetle and Johnson 1982). Achillea, Allium, Antennaria, Aster, Eriogonum, Lomatium, and Potentilla are common forb genera associated with plains silver sagebrush stands.   Go to Map

Snake River Plain Sagebrush communities in the Snake River Plain lie between the salt deserts occupying the low valleys and the coniferous forests at the upper elevation. The sagebrush component is dominated by Wyoming big sagebrush (Artemisia tridentata var. wyomingensis) and basin big sagebrush (A. tridentata var. tridentata). Mountain big sagebrush (A. tridentata var. vaseyana) primarily occurs at the higher elevations in the mountains. Summer precipitation events increase from west to east. The Snake River Plain is built on numerous lava flows overlapped by alluvial fans from the massive granite Idaho batholith to the north and the largely sedimentary mountains to the east and south (Hironaka 1979, West 1983).    Go to Map

Southern Great Basin The southern Great Basin and Colorado Plateau subdivisions lie south of the sagebrush steppe and north of the creosote (Larrea tridentat) and blackbrush (Coleogyne ramosissima) deserts. Predominant sagebrush species in these two subdivisions are Wyoming big sagebrush (Artemisia tridentata var. wyomingensis), mountain big sagebrush (A. tridentata var. vaseyana), low sagebrush (A. arbuscula), and black sagebrush (A. nova). Plant communities in this region are often more arid than sagebrush communities located to the north. Recovery from fire, grazing, or other disturbances is usually slower and attempts at land restoration less successful than in the sagebrush-steppe (West 1983). Season of precipitation varies from minimal summer rainfall in the north-west corner of the southern Great Basin to near 40% summer rainfall in southern Utah, northern Arizona, and northern New Mexico. The majority of the Colorado Plateau receives more moisture than the southern Great Basin; however, sagebrush distribution is greatly limited by marine shale outcroppings which forms halomorphic (saline) soils. In the southern Great Basin, sagebrush communities are typically on uplands between the salt deserts occupying the lower elevation Great Basin valley floors and the semi-arid woodlands and forests occupying the mid to upper mountain slopes. However, sagebrush communities extend to nearly 3,300 m on many mountain ranges (Cronquist et al. 1994).   Go to Map

Wyoming Basin The Wyoming Basin, the eastern extension of the sagebrush-steppe and sage-grouse distribution, extends into the northern Great Plains (Johnson 1979). This eastern extension of the sagebrush steppe is primarily the result of climate. A low area of the continental divide allows air masses to flow into this area from the Great Basin during the fall and winter increasing the influence of winter precipitation. The vegetation includes many Great Basin plants with a strong component of Wyoming big sagebrush (Artemisia tridentata var. wyomingensis) often associated with silver sagebrush (A. cana). The sagebrush-steppe lies between the mixed grass prairie to the east and north, salt desert communities in the lower basins, and coniferous forests at the higher elevations. Soils are primarily loosely consolidated rock composed on shales and marlstones from ancient Eocene lakes, and alluvium from the high mountains (West 1983).   Go to Map