Grasslands

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Grassland Strategy Habitat
Photo Credit: West Eugene Wetlands

Grasslands include a variety of upland grass-dominated habitats, such as upland prairies, coastal bluffs, and montane grasslands.

Ecoregions

Grasslands are a Strategy Habitat in the Blue Mountains, Coast Range, Columbia Plateau, Klamath Mountains, West Cascades, and Willamette Valley ecoregions. Additional grassland habitats, such as alkali grasslands, perennial bunchgrasses, and montane grasslands, can also be found in Specialized and Local Habitats.

Characteristics

Grasslands generally occur on dry slopes or plateaus with well-drained sandy or loamy soils. Although dominant species vary across Oregon, perennial bunchgrasses and forbs dominate native grasslands. In some areas, grasslands are similar to wet prairies and wet meadows in structure and share some of the same prairie-associated plants and animals (wet prairies and wet meadows are included within the Wetlands Strategy Habitat). In all but the shallowest rocky soils, grasslands are maintained through disturbances, such as periodic fire, soil upheaval by rodents, frost heave, wind, or salt spray.

Ecoregional Characteristics

Blue Mountains

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.

Coast Range

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.

Columbia Plateau

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.

Klamath Mountains

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.

West Cascades

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.

Willamette Valley

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.

Conservation Overview

As a whole, native grasslands are one of the most imperiled habitats in the western United States and are disappearing rapidly around the globe. In Oregon, the estimated loss of grasslands ranges from 50 percent to more than 90 percent, depending on the ecoregion. The greatest loss of grasslands has been in valley bottoms and foothills where they have been impacted by conversion to agriculture, development, and invasive plant species. In some areas, past grazing has impacted grasslands, affecting plant composition and structure. Also, non-native species were historically seeded for livestock forage in some grasslands, decreasing the abundance and diversity of native plants. However, grazing practices have become more sustainable over time, and carefully managed grazing can help to maintain grassland structure where prescribed fire is not practical or desired. Disruption of historical fire regimes has allowed for shrubs or trees to encroach, replacing grasslands with forest. In addition, some foothill grasslands have been converted to forests through tree planting.

In the Blue Mountains, less grassland habitat overall has been lost as compared to the other Strategy Habitats, but grasslands are included because they have statewide and national significance, some have been impacted by past grazing practices and need restoration, and because they face threats from invasive species. There are several important grassland sites currently being managed for wildlife and habitat conservation. High-quality grasslands remain at higher elevations and in the extensive canyons in the ecoregion. Native grasslands remain a particular concern at low elevations in this ecoregion.

In the Columbia Plateau, Palouse grasslands once dominated most uplands above 1,000 feet in elevation. Due to the moderate climate and deep soils, these grassland habitats are valuable for agriculture. Over 77 percent of the historical Palouse grasslands have been converted to dryland farming, especially wheat and other grains. Many remaining grasslands have been degraded by invasive plants and poorly controlled livestock grazing.

In the Coast Range, open, grassy habitats once occurred on the marine terrace, headlands, bluffs, higher elevation ridges, and mountain peaks. In forested ecoregions, such as the Coast Range and West Cascades, grasslands are particularly important for rare plants and invertebrates. In the Coast Range, mountaintops, such as Saddle Mountain, Onion Peak, Sugarloaf Mountain, and Blue Lake Lookout, host a number of endemic plant species, including Saddle Mountain bittercress, Chambers’ paintbrush, frigid shootingstar, queen-of-the-forest, and Saddle Mountain saxifrage.

Compared to historical grassland distributions, grassland loss has been extremely high in the Coast Range (99 percent estimated loss), West Cascades (99 percent estimated loss for montane grasslands and 93 percent for balds and bluffs), and Willamette Valley (99 percent estimated loss) ecoregions. Grasslands have been lost due to conversion to other uses, particularly development, vegetation changes following fire suppression, and invasive species. In these ecoregions, grasslands are particularly fragmented and isolated. In cooperation with landowners, remnant patches in these ecoregions should be maintained and, where feasible, restored.

Strategy Species associated with grasslands vary by ecoregion but include the: Burrowing Owl, Common Nighthawk, Grasshopper Sparrow, Long-billed Curlew, Ferruginous Hawk, Oregon Vesper Sparrow, Streaked Horned Lark, Western Bluebird, Western Meadowlark, Fender’s blue butterfly, hoary elfin butterfly, Kincaid’s lupine, Oregon silverspot butterfly, Taylor’s checkerspot butterfly, Coast Range fawn lily, Cascade Head catchfly, Lawrence’s milkvetch, Spalding’s campion, and Tygh Valley milkvetch.

In 2010, the U.S. Fish and Wildlife Service developed a recovery plan for grassland-dependent species that occur in western Oregon and southwestern Washington. It provides recovery goals and conservation strategies for several Strategy Species in the Willamette Valley. Information on conservation of grasslands and grassland birds can also be found in ODFW’s The Willamette Valley Landowner’s Guide to Creating Habitat for Grassland Birds and Partners in Flight Conservation Strategy for Landbirds in Lowlands and Valleys of Western Oregon and Washington.

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.

Recommended Approach

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.

Recommended Approach

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.

Recommended Approach

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.

Recommended Approach

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.

Recommended Approach

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.

Recommended Approach

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.

Recommended Approach

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.

Resources for more information