Print Report

A4148 Agropyron cristatum Western Ruderal Perennial Grassland Alliance

Type Concept Sentence: This semi-arid interior western U.S. ruderal perennial grassland alliance is strongly dominated (>90% relative canopy cover) by invasive, exotic perennial grasses, especially Agropyron cristatum, which can occur as a near-monoculture or mixed grassland with other exotic perennial grasses such as Poa pratensis and exotic perennial forbs and annuals.

Common (Translated Scientific) Name: Crested Wheatgrass Western Ruderal Perennial Grassland Alliance

Colloquial Name: Western Ruderal Crested Wheatgrass Grassland

Hierarchy Level:  Alliance

Type Concept: This ruderal perennial grassland alliance occurs in the interior western U.S. The vegetation is strongly dominated (>90% relative canopy cover) by invasive, exotic perennial grasses, especially Agropyron cristatum, which can occur as a near-monoculture or mixed grassland with other exotic perennial species such as Poa pratensis, and exotic perennial forbs and annuals. Agropyron cristatum has been purposefully seeded to prevent soil erosion and provide livestock forage in many areas and has naturalized outside these plantings. Scattered shrubs may be present but have low cover (<10% absolute cover). Native perennial graminoid species may be present but cover is low (<10% relative cover). Highly invasive and wind- and animal-distributed exotic forb and annual grass species may be present, including Sisymbrium altissimum, Descurainia sophia, Halogeton glomeratus, and Salsola tragus. Although exotic forbs and annual grasses may be abundant in the herbaceous layer and contribute to its ruderal nature, exotic perennial graminoids characterize the site. Stands occur in disturbed dry to mesic basins, alluvial fans, and foothills at elevations up to 2200 m throughout the cool, semi-arid interior western U.S. Vegetation dominated by relatively mesic, invasive perennial hay grasses such as Bromus inermis, Dactylis glomerata, Phleum pratense, and Poa pratensis generally occurs at higher elevations, higher latitudes or mesic microsites such as north slopes and generally has a more temperate climate and relatively mesic site conditions.

Diagnostic Characteristics: Dominant diagnostic species for this alliance are invasive, perennial grass species such as Agropyron cristatum. There are relatively few cool, semi-arid perennial exotic grasses, but there are usually abundant annual exotic species present, seasonally.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: Agropyron cristatum is an Old World introduction that grows in many alliances, especially on disturbed sites. Ranchers have planted thousands of hectares in the arid and semi-arid West to improve forage for use by livestock; it is palatable to wildlife, including antelope, deer, elk, birds, and small rodents. It naturalizes and dominates large areas, especially from northern parts of transmontane California east to the northwestern Great Plains (Ogle 2001, Kittel et al. 2012a). In conjunction with plantings, grazing pressures and changes in fire regime have caused shifts in native sagebrush stands with native understories of Achnatherum hymenoides, Elymus elymoides, Festuca idahoensis, Leymus cinereus, and Poa secunda into non-native understories or stands of Agropyron cristatum and/or Bromus tectorum.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This ruderal alliance is characterized by sparse to dense herbaceous layer dominated by perennial grasses with low cover of shrubs or annual graminoids and forbs (<5% absolute cover).

Floristics: The vegetation is strongly dominated (>90% relative canopy cover) by invasive, exotic perennial grasses, especially Agropyron cristatum, which can occur as a near-monoculture or mixed grassland with other exotic perennial species such as Poa pratensis, and exotic perennial forbs and annuals. Agropyron cristatum has been purposefully seeded to prevent soil erosion and provide livestock forage in many areas and has naturalized outside these plantings. Scattered shrubs may be present but have low cover (<10% absolute cover). Native perennial graminoid species such as Hesperostipa comata may be present but cover is low (<10% relative cover). Highly invasive and wind- and animal-distributed exotic forb and annual grass species may be present, including Sisymbrium altissimum, Descurainia sophia, Halogeton glomeratus, and Salsola tragus. Although exotic forbs and annual grasses may abundant in the herbaceous layer and contribute to its ruderal nature, exotic perennial graminoids characterize the site. Relatively mesic, invasive perennial hay grasses such as Bromus inermis, Dactylis glomerata, and Phleum pratense are absent or have low cover as they are more common in at higher elevations, higher latitudes or mesic microsites and generally occur in more temperate climates or relatively mesic sites.

Dynamics:  Agropyron cristatum burns quickly and is less susceptible to fire damage than native bunchgrasses. Its heat transfer is minimal into the soil, so the tillers and root system are usually undamaged. Tracks of Agropyron cristatum carry fires easily; they may promote the expansion and persistence of the type (Johnson 1986c). Managers plant Agropyron cristatum extensively in the Great Basin after burns and for erosion control. Its persistence following plantings involves shifts in the ecological function. Established plants replace natives; some plantings have resulted in pure stands (Johnson 1986c). Bakker et al. (2003) found that the control of Agropyron cristatum was possible without suppressing native bunchgrasses by both annual and early spring spraying with a generalist herbicide (glyphosate). This herbicide selectively killed the cool-season Agropyron cristatum. Bakker et al. (2003) found Agropyron cristatum persisting over 4 years in spite of annual herbicide application, and cover in control plots particularly increased with increased summer precipitation. They suggested that management focus on controlling Agropyron cristatum during dry years and on establishing native species during wet years.
Environmental Description:  This ruderal perennial grassland alliance occurs in the interior western U.S. Stands occur in disturbed dry to mesic basins, alluvial fans, and foothills at elevations up to approximately 2200 m throughout the cool, semi-arid interior western U.S. Vegetation dominated by relatively mesic, invasive perennial hay grasses generally occurs at higher elevations, higher latitudes or mesic microsites such as north slopes and generally has a more temperate climate and relatively mesic site conditions. Stands can occur in a wide variety of human-disturbed habitats, including highway rights-of-way, revegetation projects, etc.
Geographic Range: This alliance occurs at plains, basins, and foothill elevations (up to 2200 m) throughout the cool, semi-arid interior western U.S.

Nations: US

States/Provinces:  AZ, CA, CO, ID, MT, NM, NV, OR, UT, WA, WY


Confidence Level: Low

Confidence Level Comments: No Data Available
Grank: GNA

Greasons: No Data Available
Type Name Database Code Classification Code
Class 3 Desert & Semi-Desert Class C03 3
Subclass 3.B Cool Semi-Desert Scrub & Grassland Subclass S11 3.B
Formation 3.B.1 Cool Semi-Desert Scrub & Grassland Formation F033 3.B.1
Division 3.B.1.Ne Western North American Cool Semi-Desert Scrub & Grassland Division D040 3.B.1.Ne
Macrogroup 3.B.1.Ne.90 Crested Wheatgrass - Cheatgrass - Tall Tumblemustard Western North American Ruderal Semi-Desert Scrub & Grassland Macrogroup M499 3.B.1.Ne.90
Group 3.B.1.Ne.90.a Great Basin-Intermountain Ruderal Dry Shrubland & Grassland Group G600 3.B.1.Ne.90.a
Alliance A4148 Crested Wheatgrass Western Ruderal Perennial Grassland Alliance A4148 3.B.1.Ne.90.a
Concept Lineage: No Data Available

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: = Agropyron cristatum (Crested wheatgrass rangelands) Semi-natural Stands (Sawyer et al. 2009) [42.030.00]
= Agropyron cristatum Herbaceous Semi-Natural Alliance (CNPS 2017) [42.030.00]
< Crested wheatgrass series (Sawyer and Keeler-Wolf 1995)
< Great Basin Grassland (#43000) (Holland 1986b)
Concept Author(s): K.A. Schulz, in Faber-Langendoen et al. (2014)

Author of Description: K.A. Schulz

Acknowledgements: No Data Available

Version Date: 12-18-14
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