SAGEBRUSH STEPPE (91)

Geographic Distribution. The predominant cover type of the Owyhee Uplands ecoregion of southeastern Oregon. Sagebrush steppe is a common vegetation element in the watersheds of the Malheur, Powder, and Burnt Rivers. Sagebrush steppe is also commonly found in the non-cultivated portions of the Columbia River basin.

Structure and Appearance. Complicated mosaic of grasses (mostly introduced) and shrubs (mostly the differing varieties of big sagebrush). Historically, this type contained a predominance of bunchgrasses with scattered shrubs. Overgrazing has shifted the composition to favor sagebrush.

Composition. Shrub layer always contains some mixture of sagebrush and sagebrush-like vegetation. The three common subspecies of big sagebrush, Wyoming (Artemisia tridentata var. wyomingensis), basin (A. tridentata var. tridentata), and mountain (A. tridentata var. vaseyana) will grow with shorter varieties of sagebrush (rigid (Artemisia rigida), low (A. arbuscula), silver (A. cana) and three-tip [A. tripartata]) along with rabbitbrush (Chrysothamnus viscidiflorus and C. nausosus), based on local environment and site history.

A variety of bunchgrasses are associated with this type although they rarely comprise much of the stand due to grazing pressure. Some of the characteristic native grasses of this type are Great Basin wildrye (Elymus cinereus), Thurber needlegrass (Stipa thurberiana), Indian ricegrass (Oryzopsis hymenoides), blue bunch wheatgrass (Agropyron spicatum), Idaho fescue (Festuca idahoensis), bluegrass (Poa secunda), and sand dropseed (Sporobolus cryptandrus). In many areas, these have given way to cheatgrass (Bromus tectorum), and crested wheatgrass (Agropyron cristatum).

Landscape Setting. The sagebrush steppe primarily is adjacent to the big sagebrush type. These two types may, in fact, weave together in complicated mosaics at the edges of the Basin and Range ecoregion and in the interior uplands. Distinction between the two types is complicated and therefore somewhat crude and inexact in its depiction on the map.

References. Johnson and Simon 1986, Johnson and Clausnitzer 1987, Crawford et al. 1999, Franklin and Dyrness 1973.