Print Report

CEGL001583 Pascopyrum smithii - Nassella viridula Grassland

Type Concept Sentence: No Data Available

Common (Translated Scientific) Name: Western Wheatgrass - Green Needlegrass Grassland

Colloquial Name: Western Wheatgrass - Green Needlegrass Mixedgrass Prairie

Hierarchy Level:  Association

Type Concept: This western wheatgrass - needlegrass community is common across much of the northern Great Plains of the United States and possibly Canada. Stands occur in narrow valleys, on stream terraces, and on rolling uplands. The soils are usually loams with well-developed profiles. It is dominated by mid grasses with a moderate to high vegetation cover. The dominant species are Pascopyrum smithii and Nassella viridula. Other mid grasses in this community are Elymus lanceolatus, Hesperostipa comata, Koeleria macrantha, Poa spp., Sporobolus cryptandrus, and, on sandier soils, Calamovilfa longifolia. Shorter graminoids are common, including Bouteloua gracilis, Carex duriuscula, Carex filifolia, and Carex inops ssp. heliophila. Where it is present within the range of this community, Carex pensylvanica may be abundant. The forbs Astragalus spp., Achillea millefolium, Sphaeralcea coccinea, Artemisia ludoviciana, and Lepidium densiflorum are also typical of this community.

Diagnostic Characteristics: No Data Available

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This association includes stands growing on mesic sites and containing substantial cover of plants characteristic of such sites, including Nassella viridula, Poa secunda (= Poa juncifolia, = Poa nevadensis), Poa pratensis, and Achillea millefolium. The amount of these species that is diagnostic of this association is unknown (pending further analysis of stand data), but they contribute at least 5% of the herbaceous canopy cover. Some of these species (especially Nassella viridula) may be present in upland vegetation such as ~Pascopyrum smithii - Bouteloua gracilis - Carex filifolia Grassland (CEGL001579)$$, but they contribute only trace amounts to the vegetation. In Nebraska this type is recognizable, but forms a close association with other mixedgrass types, and thus is lumped with them. Nassella viridula does often strongly dominate with Pascopyrum smithii in mesic bottoms, but if grazing pressures were removed from upland slopes dominated by Pascopyrum smithii and Bouteloua gracilis, it is thought that Nassella viridula would recover its dominance on those slopes (G. Steinauer pers. comm. 2000). In Colorado, Nasella viridula occurs as a species on the Palmer divide, but not as part of type (K. Decker pers. Comm. 2019).

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: No Data Available

Floristics: This community is dominated by mid grasses, generally between 0.6 and 1 m tall. The vegetation cover tends to be moderate to high, with almost all of the canopy provided by graminoids (Redmann 1975, USFS 1992). The dominant species are Pascopyrum smithii and Nassella viridula, although Elymus lanceolatus (another rhizomatous wheatgrass that is similar in morphology and ecology to Pascopyrum smithii) is the dominant species in some stands. At least 5% canopy cover of Nassella viridula may be diagnostic for this association. Other common grasses are Hesperostipa comata (= Stipa comata), Koeleria macrantha, Poa secunda (= Poa juncifolia), Poa pratensis, Sporobolus cryptandrus, and, on sandier soils, Calamovilfa longifolia. Shorter graminoids are less common, but may include Bouteloua gracilis, Carex duriuscula (= Carex eleocharis), Carex filifolia, Carex inops ssp. heliophila, and Carex pensylvanica. These species are present in many stands, but they usually contribute little cover. The wheatgrass basin association of Nebraska (Steinauer and Rolfsmeier 2003), which may belong to this association, also contains Schizachyrium scoparium. Cheatgrasses (Bromus racemosus (= Bromus commutatus), Bromus arvensis (= Bromus japonicus), Bromus tectorum) are present in many stands and contribute substantial cover in some. The forbs Symphyotrichum falcatum (= Aster falcatus), Astragalus spp., Achillea millefolium, Sphaeralcea coccinea, Artemisia ludoviciana, Lepidium densiflorum, and Vicia americana are also typical of this community. Artemisia cana ssp. cana or Artemisia tridentata ssp. wyomingensis may be present, often as scattered shrubs contributing little cover. Stands with denser shrubs are transitional to shrub-herbaceous vegetation.

Dynamics:  Heavy livestock grazing reduces the cover of Pascopyrum smithii and allows unpalatable or grazing-resistant species such as Bouteloua gracilis, Vulpia octoflora, and Bromus spp. to increase (Hansen and Hoffman 1988). Observations by Vanderhorst et al. (1998) suggest that grazing causes Nassella viridula, a species highly palatable to all classes of livestock and to wildlife, especially in the spring (Weaver and Albertson 1956, Soil Conservation Service 1988), to decrease as well.
Environmental Description:  This community is found at the bottom of narrow valleys, on stream terraces, and on rolling uplands (Jones 1992b, USFS 1992). Soils are fine-textured (clays, silty clays, clay loams, or rarely loams) and well-drained. The soil profile is typically well-developed. The parent material is siltstone and mixed sedimentary rock (USFS 1992). This community usually occurs on level or nearly level ground but sometimes may be on moderate slopes of any aspect.
Geographic Range: This western wheatgrass - needlegrass community is common across much of the northern Great Plains of the United States and possibly Canada, ranging from Wyoming and possibly Nebraska, north to Montana and North Dakota, and possibly Saskatchewan.

Nations: CA?,US

States/Provinces:  CO, MT, ND, NE, SD, SK?, WY


Confidence Level: Moderate

Confidence Level Comments: No Data Available
Grank: G3G4

Greasons: No Data Available
Type Name Database Code Classification Code
Class 2 Shrub & Herb Vegetation Class C02 2
Subclass 2.B Temperate & Boreal Grassland & Shrubland Subclass S18 2.B
Formation 2.B.2 Temperate Grassland & Shrubland Formation F012 2.B.2
Division 2.B.2.Nb Central North American Grassland & Shrubland Division D023 2.B.2.Nb
Macrogroup 2.B.2.Nb.2 Needle-and-Thread - Western Wheatgrass - Plains Rough Fescue Grassland Macrogroup M051 2.B.2.Nb.2
Group 2.B.2.Nb.2.c Western Wheatgrass - Needle-and-Thread - Little Bluestem Mixedgrass Prairie Group G141 2.B.2.Nb.2.c
Alliance A4031 Western Wheatgrass - Green Needlegrass Northwestern Great Plains Grassland Alliance A4031 2.B.2.Nb.2.c
Association CEGL001583 Western Wheatgrass - Green Needlegrass Grassland CEGL001583 2.B.2.Nb.2.c
Concept Lineage: No Data Available

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: = Agropyron smithii - Stipa viridula Habitat Type (Hirsch 1985)
= Agropyron smithii / Stipa viridula Habitat Type (USFS 1992)
? Elytrigia smithii / Stipa viridula Plant Association (Johnston 1987)
= Pascopyrum smithii - Nassella viridula Herbaceous Vegetation (Cooper et al. 2001)
= Pascopyrum smithii - Nassella viridula Herbaceous Vegetation (Faber-Langendoen 2001)
= Stipa viridula Community (Redmann 1975)
Concept Author(s): K.J. Hirsch (1985)

Author of Description: K.J. Hirsch, J. Drake and D. Faber-Langendoen

Acknowledgements: No Data Available

Version Date: 12-21-95
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