Grasslands include a variety of upland grass-dominated habitats, such as upland prairies, coastal bluffs, and montane grasslands.
Bunchgrass grasslands occur primarily in the northeastern portion of the ecoregion, although other grassy habitats occur throughout the ecoregion. At low elevations, semi-desert grasslands are dominated by drought-resistant perennial bunchgrasses, such as needle-and-thread, dropseed, threeawn, and muhly, and may have scattered shrubs. Mid-elevation plateau grasslands include extensive bunchgrass prairies of Idaho fescue, junegrass, and bluebunch wheatgrass. At high elevations, ridgetop balds and alpine parks are dominated by green or mountain fescue, needlegrass, and/or bluegrass species. High-elevation grasslands often are on south-facing slopes surrounded by subalpine conifer woodlands.
Coastal bluff and montane grasslands are dominated by low-growing vegetation, such as perennial bunchgrasses, forbs, mosses, and dwarf shrubs. They occur within a matrix of conifer forests. Outer coastal bluffs and headlands are influenced by wind and salt spray, which limit the growth of woody vegetation. Montane grasslands include dry meadows and balds and occur on dry, south- or west-facing slopes with shallow sandy or gravelly soils. They are primarily influenced by periodic fire, soil upheaval by rodents, and drought conditions.
Grasslands include river terrace grasslands, prairies, canyon slopes, and rocky ridges. At low and mid elevations, semi-desert grasslands are dominated by drought-resistant perennial bunchgrasses, such as needle-and-thread, dropseed, threeawn, and muhly, and may have scattered shrubs. Palouse grasslands occur in flat areas with deep soils and are dominated by bluebunch wheatgrass, Idaho fescue, and other grasses and forbs. Canyon and foothill grasslands are found on the steeper, rocky slopes surrounding the major rivers in this region and are dominated by bluebunch wheatgrass, Idaho fescue, Sandberg’s bluegrass, balsamroot, and other forbs.
Grasslands are found in valley bottoms, often in a mosaic with chaparral and savanna, on open serpentine barrens, and high mountain meadows. Historically, grasslands in this ecoregion were maintained by frequent burning and included scattered deciduous and conifer trees. Oak savannas are grasslands with scattered trees that are usually large with well-developed limbs and canopies.
Montane grasslands include open dry meadows, grasslands, and balds. Montane grassland habitats occur in a matrix of mixed conifer forests and woodlands. Mid- and high-elevation dry meadows tend to have deeper and better-drained soils than the surrounding forests and are dominated by grasses and wildflowers, such as green, Roemer's, alpine, or western fescue, California brome, timber oatgrass, broadleaf lupine, and beargrass. Balds and bluffs generally occur on south- to west-facing slopes on shallow, well-drained soils and are dominated by bunchgrasses, forbs, and mosses.
Grasslands, also called upland prairies, are dominated by grasses, forbs, and wildflowers. Grasslands have well-drained soils and often occur on dry slopes. They are similar to wet prairies in structure and share some of the same prairie-associated plants and animals (wet prairies are included within the Wetlands Strategy Habitat). Oak savannas are grasslands with scattered Oregon white oak trees, generally only one or two trees per acre (denser oak stands are included in the Oak Woodlands Strategy Habitat). Oak trees in savannas are usually large with well-developed limbs and canopies.
Limiting Factors and Recommended Approaches
Limiting Factor: Altered Fire Regimes
At sites with deep soils, maintenance of grasslands is dependent, in part, on periodic fire. Fire suppression has led to encroachment by shrubs and conifer trees in some areas. In the Columbia Plateau, the introduction of cheatgrass can increase the frequency, intensity, and spread of fires. In the Coast Range, prescribed fire is difficult due to high precipitation and wet conditions. When conditions are dry enough to use prescribed fire, there are usually concerns with risk to surrounding forests. In the Klamath Mountains and Willamette Valley, prescribed fire poses challenges, such as conflicts with surrounding land use, smoke management and air quality, and safety.
Maintain open grassland structure by using multiple site-appropriate tools, such as prescribed burns, mowing, controlled grazing, hand-removal of encroaching shrubs and trees, or thinning. Re-introduce fire at locations and at times where conflicts, such as smoke and safety concerns, can be minimized. For all tools, minimize ground disturbance and impacts to native species. Minimize the spread of cheatgrass. Carefully manage livestock grazing to maintain native plants and soil crust (cryptogrammic crust) in low cheatgrass areas. Control fires in cheatgrass-dominated areas. (KCI: Disruption of Disturbance Regimes)
Limiting Factor: Invasive Species
Invasive plants are degrading grassland habitats, displacing native plants and animals. Depending on the area, invasive species include cheatgrass, medusahead, ventenata, rush skeleton weed, spikeweed, Hungarian brome, yellow star-thistle, knapweeds (diffuse, spotted, and purple), leafy spurge, Canada thistle, St. John’s wort, tansy ragwort, Armenian (Himalayan) blackberry, evergreen blackberry, Scotch broom, false-brome, Harding grass, and tall oatgrass. Most low-elevation grasslands are almost entirely dominated by invasive grasses, forbs, and shrubs. At higher elevations, such as montane grasslands in the West Cascades, invasive plants are less common. However, these habitats need to be monitored to detect new invasive species as livestock (e.g., cows, pack horses, riding horses) can introduce invasive plants.
Identify the best remaining native grasslands and work with landowners to maintain quality and limit the spread of invasive species. Emphasize prevention, risk assessment, early detection, and quick control to prevent new invasive species from becoming fully established. Prioritize control efforts and use site-appropriate methods to control newly-established invasive plant species for which management can be most effective. Re-seed with site-appropriate native grasses and forbs after control efforts. Conduct research to determine methods to manage established species, such as cheatgrass, medusahead rye, and Hungarian brome. Where appropriate, manage livestock grazing and recreational use to minimize new introductions in montane grasslands. Support current prevention programs, such as weed-free hay certification. (KCI: Invasive Species)
Limiting Factor: Land Use Conversion
Remnant low-elevation grasslands in valleys, foothills, and coastal headlands are subject to conversion to agricultural, residential, or urban uses.
Because many of these areas are privately-owned, voluntary cooperative approaches are the key to long-term conservation. Important tools include financial incentives, technical assistance, regulatory assurance agreements, and conservation easements. Use and extend existing incentive programs, such as the Conservation Reserve Program and Grassland Reserve Program, to conserve, manage, and restore grasslands and to encourage no-till and other compatible farming practices. Support and implement existing land use regulations to preserve forest land, open spaces, recreation areas, and natural habitats.
Limiting Factor: Land Management Conflicts
Resource conflicts can arise because high quality grasslands are often high quality grazing resources. Although grazing can be compatible with conservation goals, it needs to be managed carefully because Oregon’s bunchgrass habitats are more sensitive to grazing than the sod-forming grasses of the mid-western prairies. Overgrazing can lead to soil erosion, changes in plant species composition and structure, and degradation by invasive plants. Grassland management practices, such as mowing, haying, burning, and herbicide/insecticide application during the nesting season, can be detrimental to species.
Use incentive programs and other voluntary approaches to manage and restore grasslands on private lands. Manage public land grazing to maintain grasslands in good condition. Conduct research and develop incentives to determine grazing regimes that are compatible with a variety of conservation goals. Promote operation of grassland management practices (e.g., mowing, haying, burning, herbicide application) outside of the primary breeding season (roughly April-August). Restore native grassland habitat when possible, removing woody growth and invasive weeds to create a mosaic of clumped vegetation, bare ground, and a mixture of grasses and forbs with a variety of heights. Promote use of native plants and seed sources in conservation and restoration programs.
Limiting Factor: Reduction of Habitat Patch Size and Connectivity
In the Columbia Plateau and Willamette Valley ecoregions, grassland habitats often occur in small patches, such as roadsides and field edges. These patches are valuable habitat for some species, especially some plants and invertebrates. However, many grassland-obligate species (e.g., grassland birds) require large patch sizes for nesting. These species tend to avoid edge habitat and areas of dense woody vegetation, which can harbor predators. Small grassland patches also increase the potential for negative impacts from adjacent lands (e.g., herbicide and pesticide drift). Poor connectivity between remnant patches can limit dispersal capabilities for some species.
Maintain or restore grassland habitat considering patch size, shape, vegetation structure, and plant composition that best benefits Strategy Species. Maintain high priority patches and improve connectivity between similar habitat types. Use a landscape approach in conservation plans and incentive programs to create large, contiguous blocks of grassland habitat by expanding buffers around key grassland sites. Connect grassland habitats, such as fallow fields, pastures, and natural meadows, to create contiguous grassland habitat and improve connectivity between patches.
Limiting Factor: Loss of Habitat Complexity in Oak Savannas
In the Klamath Mountains and Willamette Valley ecoregions, large-diameter oak trees with lateral limb structure and cavities continue to be lost. Oak woodlands and savannas complement grassland habitat and should be maintained. Many native wildlife utilize large-diameter oaks for nesting, feeding, and shelter.
Maintain large oaks, remove competing conifers or densely-stocked small oaks, and create snags to provide cavity habitat.
Limiting Factor: Recreational Impacts
In some grasslands in the Coast Range, Klamath Mountains, Willamette Valley, and West Cascades ecoregions, recreational use impacts grassland species and vegetation. Some grassland-obligate species are highly sensitive to disturbance during the breeding season from people, pets, and recreational activities.
Work with land managers to direct recreational use away from highly sensitive areas. Provide recreational users with information on grassland issues and low-impact uses.