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CEGL001670 Pseudoroegneria spicata - Festuca idahoensis Palouse Grassland

Type Concept Sentence: No Data Available


Common (Translated Scientific) Name: Bluebunch Wheatgrass - Idaho Fescue Palouse Grassland

Colloquial Name: Bluebunch Wheatgrass - Idaho Fescue Palouse Grassland

Hierarchy Level:  Association

Type Concept: This perennial bunchgrass association grows between 1580-1935 m elevation in the Palouse Prairie of southeastern Washington, Oregon and Idaho. Stands occur on ridgetops or on flat to concave surfaces on the middle or upper third of the slope. Slopes range from 0%-110%, and stands can be found on all aspects. Temperatures are very warm during the growing season and precipitation is low. Soils are moderate to deep, permitting the establishment of Festuca idahoensis and Pseudoroegneria spicata. These codominants combine for approximately 40% cover. Poa secunda is also usually present with a mean cover of 12%. On gentle slopes the cover of Poa secunda increases to about 18%. Forbs are many and varied including Achillea millefolium var. occidentalis, Eriogonum heracleoides, and Lomatium sp.

Diagnostic Characteristics: No Data Available

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: Johnson and Simon (1987) differentiated similar stands of Pseudoroegneria spicata - Festuca idahoensis into three associations. This is not the same association as ~Festuca idahoensis - Pseudoroegneria spicata Grassland (CEGL001624)$$ found in canyons of the same region.

Similar NVC Types: No Data Available
note: No Data Available

Physiognomy and Structure: No Data Available

Floristics: This grassland association is dominated by the perennial bunchgrasses Pseudoroegneria spicata and Festuca idahoensis, with cover together from 30% to over 100%. These bunchgrasses are typically from 0.5-1.0 m tall. Poa secunda is a frequent component, with lower stature than the dominant grasses and cover ranging from less than 10% to over 45%. Richness of perennial forbs is high (46 species), but their cover is generally less than 20%. Some of the more common and constant forbs include Achillea millefolium, Lithophragma glabrum, Lomatium triternatum, and Calochortus macrocarpus. Annual species are also diverse, but many of them are exotics. Shrubs are very infrequent. A cryptogamic layer is well-developed on undisturbed sites. The annual grass Bromus tectorum may permanently displace the perennial native grasses where cattle grazing has been heavy. In most stands, Bromus is codominant. Additionally, most stands have a significant component of introduced annual forbs, including Draba verna, Holosteum umbellatum, and Sisymbrium altissimum.

Dynamics:  This community is apparently unaffected by fire as most dominant species resprout readily following fires. Extremely hot fires during the dry season may be more damaging to the native perennial grasses.

Environmental Description:  This association is found in the Columbia Basin region, in the Pseudoroegneria - Festuca zone of Daubenmire (1970). The region is shrub-steppe, in the rainshadow of the Cascade Ranges, and too dry to support forest vegetation. The climate is characterized by moderately cold winters and warm to hot summers. Precipitation occurs primarily in the winter as rains and occasional snows. Overall, the climate is cooler in winter than that found in the canyons of the Snake River, which bisects the region. The climate is warmer and wetter than what occurs to the west of this region. This association generally does not occur in deep, hot canyons.

Elevations where this association is found range from roughly 250-1000 m, on northerly, flat to steep slopes. Soils are deep loams and silt loams derived from loess, over basalt bedrock. Calcareous deposits are found in the C horizon or coating the fractured bedrock. A cryptogam layer is well-developed on undisturbed sites.

Geographic Range: This association is restricted to a few subsections in the east-central Columbia Basin of Washington and Oregon on the rolling loess topography above the deep Snake River and its tributary canyons.

Nations: US

States/Provinces:  ID, OR, WA




Confidence Level: Moderate

Confidence Level Comments: No Data Available

Grank: G1

Greasons: No Data Available


Concept Lineage: No Data Available

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available

Synonomy: = Agropyron spicatum - Festuca idahoensis Habitat Type (Daubenmire 1970)
= Festuca idahoensis - Agropyron spicatum / Phlox colubrina Plant Association (Johnson and Simon 1987)
= Festuca idahoensis - Agropyron spicatum Plant Association (Johnson and Clausnitzer 1992)
= Festuca idahoensis - Agropyron spicatum Plant Association (Johnson and Simon 1987)
= Festuca idahoensis / Agropyron spicatum Habitat Type (Tisdale 1986)
= Festuca Phase of Agropyron-Poa Association (Poulton 1955)
< Bunchgrass on deep soil, gentle slopes (Hall 1973)

Concept Author(s): M.S. Reid

Author of Description: M.S. Reid, M. Schindel and R. Crawford

Acknowledgements: No Data Available

Version Date: 06-16-93

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  • Bourgeron, P. S., and L. D. Engelking, editors. 1994. A preliminary vegetation classification of the western United States. Unpublished report. The Nature Conservancy, Western Heritage Task Force, Boulder, CO. 175 pp. plus appendix.
  • Daubenmire, R. F. 1970. Steppe vegetation of Washington. Washington State University Agricultural Experiment Station Technical Bulletin No. 62. 131 pp.
  • Hall, F. C. 1973. Plant communities of the Blue Mountains in eastern Oregon and southeastern Washington. R6 Area Guide 3-1. USDA Forest Service, Pacific Northwest Region, Portland, OR. 62 pp.
  • Johnson, C. G., Jr., and S. A. Simon. 1987. Plant associations of the Wallowa-Snake Province Wallowa-Whitman National Forest. Technical Paper R6-ECOL-TP-255A-86. USDA Forest Service, Pacific Northwest Region, Wallowa-Whitman National Forest. 399 pp. plus appendices.
  • Johnson, C. G., and R. R. Clausnitzer. 1992. Plant associations of the Blue and Ochoco mountains. R6-ERW-TP-036-92. USDA Forest Service, Pacific Northwest Region, Wallowa-Whitman National Forest. 163 pp. plus appendices.
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  • WNHP [Washington Natural Heritage Program]. 2018. Unpublished data files. Washington Natural Heritage Program, Department of Natural Resources, Olympia, WA.
  • Western Ecology Working Group of NatureServe. No date. International Ecological Classification Standard: International Vegetation Classification. Terrestrial Vegetation. NatureServe, Boulder, CO.