Disturbed Vegetation/Invasive Species

Prior to alteration of the shrub-steppe of eastern Washington in the 1800's, big sagebrush/bluebunch wheatgrass was the dominant vegetation type over much of the Columbia Basin (Daubenmire 1970). Although the Monument area has documented large, relatively undisturbed shrub-steppe plant communities as described above, many previously disturbed areas have altered vegetative communities. One of the primary significant changes to the vegetative communities is the invasion of non-native plant species. Once introduced, these species can proliferate because of the lack of natural predators or because they can out-compete native plant species in disturbed habitats. Moreover, some species are aggressive enough to be successful in invading even intact native plant communities. Disturbed areas of the Monument units usually are dominated by cheatgrass and other exotic species cover with or without big sagebrush. Cheatgrass is a particularly competitive plant that favors disturbed areas, and has several characteristics that enhance its ability to establish and persist, including the ability to germinate in the spring or fall, high seed production, greater germinability than native grasses, and tolerance to grazing. Within several areas the native vegetation has likely been permanently replaced by cheatgrass and other non-native plants, particularly in areas where historic disturbances were the most intense (especially on historically farmed and grazed locations). Vegetation within these areas have highly variable shrub cover, high cover of cheatgrass, frequently a significant cover of Sandberg’s bluegrass, and usually a low cover of microbiotic crust. It is unlikely that native bunchgrasses will become established without extensive restoration. Additionally, noxious weeds, and other aggressive non-native plants tend to invade, and become established more readily within previously disturbed habitats. The invasion of non-native plants represents a threat to the integrity of the Monument and the preservation of its unique biodiversity.

• FWS Home
• Pacific Region Home
• USGS Hydrograph Station: Columbia River Below Priest Rapids Dam

For best printing results, set your printer to landscape.