Print Report

A4031 Pascopyrum smithii - Nassella viridula Northwestern Great Plains Grassland Alliance

Type Concept Sentence: This alliance is found in the northern Great Plains on fine-textured soils in mesic settings where the midgrasses Pascopyrum smithii and Nassella viridula are dominant or codominant.

Common (Translated Scientific) Name: Western Wheatgrass - Green Needlegrass Northwestern Great Plains Grassland Alliance

Colloquial Name: Northwestern Great Plains Mesic Western Wheatgrass Grassland

Hierarchy Level:  Alliance

Type Concept: This alliance is found in the northern Great Plains from the southern Prairie Provinces of Canada to Colorado and western Nebraska. Midgrasses are dominant, especially Pascopyrum smithii. Other common species are Elymus lanceolatus, Nassella viridula, Koeleria macrantha, and Hesperostipa comata. The short graminoids Bouteloua gracilis, Carex filifolia, Carex inops ssp. heliophila, Carex duriuscula, and the exotics Bromus racemosus and Bromus tectorum can contribute substantial cover. Shrubs and scattered trees can often be found in the mesic settings occupied by this alliance. It usually occurs on fine-textured soils in mesic settings. Some stands can be on deep sandy soils. It is often in swales or valleys but can also be on rolling uplands.

Diagnostic Characteristics: This northern Great Plains alliance is dominated by mid grasses, especially Pascopyrum smithii but also Elymus lanceolatus and Nassella viridula. These species should contribute more cover than Hesperostipa comata.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This alliance shares some abundant species with the poorly described ~Hesperostipa curtiseta - Elymus lanceolatus Grassland Alliance (A4029)$$ which probably occurs in similar habitats and is on the margin of the range of this alliance (A4031).. Pascopyrum smithii is a common constituent in many communities in the Great Plains. Its presence in so many communities can make it difficult to distinguish communities within this alliance from other dry-mesic midgrass communities in other alliances. The dominance of Pascopyrum smithii is typically a good diagnostic feature. Stands that have other species as codominants or even dominants may be difficult to classify. This alliance is a mesic climate version of A4032 in the dry mixedgrass group. In Nebraska, this type occurs north of Pine Ridge. Nasella viridula is not that constant in Nebraska.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This is an herbaceous alliance, dominated by short to mid-height graminoids. Mid grasses are the dominant vegetation in most examples of this alliance, although short grasses and sedges can be codominant. The vegetation tends to be denser where the mid grasses are predominant and more open where shorter graminoids are abundant. The mid grasses grow to 0.5-1.0 m on favorable sites, while the short grasses and sedges are less than 0.5 m tall. Both forb and shrub species are minor in this alliance. If shrubs are present, they are typically less than 1 m in height.

Floristics: The most abundant midgrass across all sites is Pascopyrum smithii. Some sites are dominated by Nassella viridula. Common associates include Elymus trachycaulus, Hesperostipa comata (= Stipa comata), Hesperostipa spartea (= Stipa spartea), Koeleria macrantha, Poa spp., and Schizachyrium scoparium. In the drier communities of this alliance Bouteloua gracilis is the most common shortgrass. Other short graminoids typically found in the drier communities include Aristida purpurea, Bouteloua curtipendula, Carex duriuscula (= Carex eleocharis), Carex filifolia, and Carex inops ssp. heliophila; the exotics Bromus racemosus (= Bromus commutatus) and Bromus tectorum can contribute substantial cover. Forbs and shrubs are generally minor components of communities within this alliance. If shrubs are present, they are rarely taller than 1 m. Some forbs that are usually scattered about are Amorpha canescens, Astragalus spp., Gaura coccinea, Sphaeralcea coccinea, and Tragopogon dubius. Shrubs include Artemisia cana, Artemisia frigida, Opuntia spp., and Symphoricarpos occidentalis.

Dynamics:  Pascopyrum smithii is rhizomatous and is tolerant of moderate grazing. If severely overgrazed, Pascopyrum smithii will decline and may be replaced by less desirable warm-season grasses and exotic species such as Poa pratensis.
Environmental Description:  Grasslands included in this alliance occur across the Great Plains, on several different soil types (Hanson and Whitman 1938, Johnston 1987, USFS 1992). The soil is most often clay or clay loam; however, it can be loam or sandy loam. In the eastern and central part of this alliance''s range, these communities can be found on flat or rolling uplands, hillslopes, or along streams or depressions. In the western part of the range, communities are found where local conditions are wetter than the average. This includes such areas as localized depressions, the base of slopes or along rivers or streams (Weaver and Albertson 1956, Jones 1992b).
Geographic Range: This alliance is found in the northern Great Plains from the southern Prairie Provinces of Canada to western Nebraska.

Nations: CA,US

States/Provinces:  AB, MB, MT, ND, NE, SD, SK, WY


Confidence Level: Low

Confidence Level Comments: No Data Available
Grank: GNR

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 CEGL001579 Western Wheatgrass - Blue Grama - Threadleaf Sedge Grassland CEGL001579 2.B.2.Nb.2.c
Association CEGL001583 Western Wheatgrass - Green Needlegrass Grassland CEGL001583 2.B.2.Nb.2.c
Association CEGL002034 Western Wheatgrass - Needle-and-Thread Central Mixedgrass Grassland CEGL002034 2.B.2.Nb.2.c
Association CEGL002270 Blue Grama - Buffalograss Northern Plains Grassland CEGL002270 2.B.2.Nb.2.c
Concept Lineage: This alliance is composed of three associations from old A.1232, one from old A.1261, and one from old A.3521.

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: >< Elytrigia smithii Series (Johnston 1987)
Concept Author(s): J. Drake, in Faber-Langendoen et al. (2013)

Author of Description: J. Drake

Acknowledgements: No Data Available

Version Date: 12-18-14
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