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Purshia tridentata / Pseudoroegneria spicata - Leymus cinereus Shrub Herbaceous Vegetation | Western Ecology Working Group of...
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Name: Purshia tridentata / Pseudoroegneria spicata - Leymus cinereus Shrub Herbaceous Vegetation
Reference: Western Ecology Working Group of...
Description: This association is reported from sites located on recent, relatively unweathered mafic lava flows of the Great Rift System, within the Snake River Basalt ecoregional section. The plant association occurs in a semi-arid climatic region, on relatively recent mafic volcanic flow substrates. The area has an average annual precipitation of 17 inches, with a peak in winter. Most precipitation occurs as snow. A secondary peak occurs in May. Temperatures are typically hot in summer and cold in winter. The association occurs on slopes of medium-aged and older cinder cones. Sufficient weathering has occurred on these sites so that soil water-holding capacity is great enough to support Purshia tridentata. By comparison, adjacent younger cinder deposits are occupied by Eriogonum ovalifolium var. depressum Dwarf-shrubland (CEGL001401). Purshia tridentata forms a low and relatively open layer in this shrub herbaceous type. Cover varies from 15-25%. Several other shrub species are commonly present as scattered individuals, including the deciduous Symphoricarpos oreophilus and Ribes cereum, and the evergreen Ericameria nauseosa (= Chrysothamnus nauseosus), Artemisia tridentata ssp. vaseyana, and Eriogonum heracleoides. Total shrub cover rarely exceeds 30%. The perennial bunchgrass Leymus cinereus dominates the visual aspect of the herbaceous layer, with a growth form of large clumps up to 1 m across. The smaller bunchgrass Pseudoroegneria spicata occurs in higher densities than Leymus cinereus in many areas of this vegetation type. Other grasses usually present include Elymus elymoides, Achnatherum thurberianum (= Stipa thurberiana), and Poa secunda. The perennial forb Pteryxia terebinthina forms a relatively dense understory, especially where grass density is lower. Other common forbs include Balsamorhiza sagittata, Arabis holboellii, Delphinium andersonii, Lithospermum ruderale, Phacelia hastata, and the suffrutescent species Eriogonum umbellatum and Eriogonum ovalifolium. Total cover of the herbaceous layer is not available, but may be as high as 50%. 
Accession Code: VB.CC.21124.PURSHIATRIDENTA
Plot-observations of this Community Concept: 0
      Party Perspective according to: NatureServe (organization)
Perspective from: 26-Nov-1997 to: 17-Nov-2014
      Names:   Translated: Bitterbrush / Bluebunch Wheatgrass - Great Basin Lyme Grass Shrub Herbaceous Vegetation
  UID: ELEMENT_GLOBAL.2.685323 NatureServe ExplorerNatureServe Explorer logo
  Code: CEGL001497
  Scientific: Purshia tridentata / Pseudoroegneria spicata - Leymus cinereus Shrub Herbaceous Vegetation
  Common: Antelope Bitterbrush / Bluebunch Wheatgrass - Basin Wildrye
(convergence) and Synonyms:
(undetermined) Purshia tridentata / Pseudoroegneria spicata - Leymus cinereus Shrub Herbaceous Vegetation