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Scientific Name: Northwestern Great Plains Mixedgrass Prairie
Unique Identifier: CES303.674
Classification Confidence: 2 - Moderate

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Summary: This system extends from northern Nebraska into southern Canada and westward through the Dakotas to the Rocky Mountain Front in Montana and eastern Wyoming, on both glaciated and non-glaciated substrates. Soil texture (which ultimately effects water available to plants) is the defining environmental descriptor; soils are primarily fine and medium-textured and do not include sand, loamy sand, or sandy loam soils. This system occurs on a wide variety of landforms (e.g., rolling uplands stream terraces, ridgetops) and in proximity to a diversity of other systems. Most usually it is found in association with Western Great Plains Sand Prairie (CES303.670) which occupies the coarser-textured substrates. Northwestern Great Plains Shrubland (CES303.662) is intermixed on the landscape in draws and ravines which receive more precipitation runoff and are somewhat protected from fires. In various locales generally north and east of the Missouri River, the topography where this system occurs is broken by many glacial pothole lakes, and this system may be proximate to Great Plains Prairie Pothole (CES303.661). On the eastern Montana and western Dakota plains, mixedgrass prairie is by far the predominant system. Here it occurred continuously for hundreds of square kilometers, interrupted only by riparian areas or sand prairies, which were associated with gentle rises, eroded ridges, or mesas derived from sandstone. The growing season and rainfall are intermediate to drier units to the southwest and mesic tallgrass regions to the east. Graminoids typically comprising the greatest canopy cover include Pascopyrum smithii, Nassella viridula, and Festuca spp. In Montana these include Festuca campestris and Festuca idahoensis. Other commonly dominant species in Montana are Bouteloua gracilis, Hesperostipa comata, and Carex filifolia, while Festuca campestris and Festuca idahoensis may be more abundant in the north and foothill/montane grassland transition areas. Bouteloua curtipendula, Elymus lanceolatus, Muhlenbergia cuspidata, and Pseudoroegneria spicata are common, and sometimes abundant, components of this system. Remnants of Hesperostipa curtiseta-dominated vegetation are found in northernmost Montana and North Dakota associated with the most productive sites (largely plowed to cereal grains); this species, usually in association with Pascopyrum smithii, is much more abundant in Canada. Sites with a strong component of Nassella viridula indicate a more favorable moisture balance and perhaps a favorable grazing regime as well because this is one of the most palatable of the mid-grasses. Hesperostipa comata is also an important component and becomes increasingly so as improper grazing practices favor it at the expense of (usually) Pascopyrum smithii; progressively more destructive grazing can result in the loss of Pascopyrum smithii from the system followed by drastic reduction in Hesperostipa comata and ultimately the dominance of Bouteloua gracilis (or Poa secunda and other short graminoids) and/or a lawn of Selaginella densa. Koeleria macrantha, at least in Montana and southern Canada, is the most pervasive grass; if it has high cover, past intensive grazing is the presumed reason. In the eastern portion of this system's range, tallgrass species, especially Andropogon gerardii, Panicum virgatum, and Sorghastrum nutans, are often present to common on more mesic sites. Shrub species such as Symphoricarpos spp., Artemisia frigida, and Artemisia cana occur in the western and central portions while Symphoricarpos spp. and Prunus spp. can be found in the eastern portion. Sites with slightly to moderately saline soils have small to moderate amounts of salt-tolerant species such as Distichlis spicata and Sporobolus airoides. Fire, grazing and climate constitute the primary dynamics affecting this system. Drought can also impact this system, in general favoring the shortgrass component at the expense of the mid-grasses. With intensive grazing, cool-season exotics such as Poa pratensis, Bromus inermis, and Bromus tectorum can increase in dominance; both of the rhizomatous grasses have been shown to markedly depress species diversity. Shrub species such as Juniperus virginiana can also increase in dominance with fire suppression. This system is one of the most disturbed grassland systems in Nebraska, North and South Dakota, and Canada.

Classification Approach: International Terrestrial Ecological Systems Classification (ITESC)

Classification Comments: This system is found in the western Great Plains north of the shortgrass prairie and west of the northern tallgrass prairie. Because of its proximity to other prairie types, this system contains elements from both shortgrass and tallgrass prairies, which combine to form the mixedgrass prairie throughout its range. This system was edited to expand the concept for central Montana mixedgrass prairie and to exclude specifically sandy soil grasslands, which are placed into Western Great Plains Sand Prairie (CES303.670). This system is similar to Central Mixedgrass Prairie (CES303.659) and can contain elements of Great Plains tallgrass and shortgrass systems. However, it differs from Central Mixedgrass Prairie (CES303.659) in that the cooler climate in this region allows natural cool-season grasses to be more important (greater than 50% cover). Cover of native, nongrazing-induced shrubs typically does not exceed 25% in conjunction with topographic relief (breaks); otherwise the stand would be considered part of Northwestern Great Plains Shrubland (CES303.662). Additional review and commentary by Canadian, Dakotan, and Nebraskan ecologists is needed to flesh out the compositional variation and range of distribution for this important grassland system. In Wyoming, this system transitions into Northern Rocky Mountain Lower Montane, Foothill and Valley Grassland (CES306.040) in the foothills of the northern Wyoming mountains where Pascopyrum smithii communities finger up into foothills. If Festuca idahoensis, Carex rossii, Artemisia nova, or Artemisia tripartita ssp. rupicola occur, then the example is not this system.

Similar Ecological Systems
Unique Identifier Name
CES303.451 Northern Great Plains Fescue-Mixed Grass Prairie
CES303.659 Central Mixedgrass Prairie
CES303.662 Northwestern Great Plains Shrubland
CES303.817 Western Great Plains Foothill and Piedmont Grassland

Component Associations
Association Unique ID Association Name
CEGL001065 Amelanchier alnifolia / Pseudoroegneria spicata - Bunchgrass Shrubland
CEGL001099 Elaeagnus commutata / Pascopyrum smithii Wet Shrubland
CEGL001131 Symphoricarpos occidentalis Shrubland
CEGL001394 Juniperus horizontalis / Schizachyrium scoparium Dwarf-shrubland
CEGL001502 Dasiphora fruticosa ssp. floribunda / Festuca idahoensis Shrub Grassland
CEGL001503 Dasiphora fruticosa ssp. floribunda / Festuca campestris Shrub Grassland
CEGL001530 Artemisia tridentata / Festuca idahoensis Shrub Grassland
CEGL001531 Artemisia tridentata ssp. vaseyana / Festuca campestris Shrub Grassland
CEGL001556 Artemisia cana ssp. cana / Pascopyrum smithii Shrub Wet Meadow
CEGL001579 Pascopyrum smithii - Bouteloua gracilis - Carex filifolia Grassland
CEGL001583 Pascopyrum smithii - Nassella viridula Grassland
CEGL001610 Festuca idahoensis - Carex inops ssp. heliophila Grassland
CEGL001629 Festuca campestris - Pseudoroegneria spicata Grassland
CEGL001663 Pseudoroegneria spicata - Bouteloua curtipendula Grassland
CEGL001664 Pseudoroegneria spicata - Bouteloua gracilis Grassland
CEGL001675 Pseudoroegneria spicata - Pascopyrum smithii Grassland
CEGL001682 Schizachyrium scoparium - Carex inops ssp. heliophila Grassland
CEGL001683 Schizachyrium scoparium - Muhlenbergia cuspidata Grassland
CEGL001708 Hesperostipa neomexicana Grassland
CEGL001709 Hesperostipa neomexicana - Bouteloua curtipendula Grassland
CEGL002034 Pascopyrum smithii - Hesperostipa comata Central Mixedgrass Grassland
CEGL002037 Hesperostipa comata - Bouteloua gracilis - Carex filifolia Grassland
CEGL002183 Amelanchier alnifolia Shrubland
CEGL002189 Betula pumila - Salix candida / Carex lasiocarpa - Symphyotrichum boreale Prairie Fen
CEGL002198 Dasiphora fruticosa ssp. floribunda / Schizachyrium scoparium Shrub Grassland
CEGL002237 Elymus lanceolatus - Koeleria macrantha Grassland
CEGL002253 Hesperostipa curtiseta - Elymus lanceolatus Grassland
CEGL002436 Festuca altaica - (Hesperostipa spp., Achnatherum spp.) Grassland
CEGL003789 Hesperostipa curtiseta - Pascopyrum smithii Grassland
CEGL004066 Juniperus virginiana var. virginiana / Schizachyrium scoparium - Bouteloua curtipendula Great Plains Grassland
CEGL005291 Eleocharis palustris Great Plains Marsh
CEGL005875 Festuca campestris - Festuca idahoensis Grassland


Land Cover Class: Herbaceous
Spatial Pattern: Matrix
Natural/Seminatural: No
Vegetated ( > 10% vascular cover):
Upland: Yes
Wetland: No
Isolated Wetland: No

Non-diagnostic Classifiers
Primary Classifier Secondary Classifier
Shallow Soil  
Loam Soil Texture  

At-Risk Species Reported for this Ecological System
Scientific Name
  (Common Name)
NatureServe Global Status U.S. Endangered Species Act Status
Vulpes velox
  (Swift Fox)

Vegetation Composition (incomplete)
Species Name Rounded Global Status Growth Form Stratum Char-
Domi-nant Con-stant
Cover Class %
Penstemon angustifolius G5 Flowering forb Herb (field)      
Bouteloua gracilis G5 Graminoid Herb (field)    
Carex filifolia G5 Graminoid Herb (field)    
Carex retrorsa G5 Graminoid Herb (field)      
Festuca campestris G5 Graminoid Herb (field)    
Festuca idahoensis G5 Graminoid Herb (field)    
Hesperostipa comata ssp. comata T5 Graminoid Herb (field)    
Hesperostipa curtiseta G5 Graminoid Herb (field)    
Koeleria macrantha G5 Graminoid Herb (field)    
Nassella viridula G5 Graminoid Herb (field)    
Pascopyrum smithii G5 Graminoid Herb (field)    

Animal Species Reported for this Ecological System
Scientific Name
  (Common Name)
Global Status U.S. Endangered Species Act Status Charact-
Calcarius ornatus
  (Chestnut-collared Longspur)
Coluber constrictor
  (North American Racer)
Crotalus viridis
  (Prairie Rattlesnake)
Cynomys ludovicianus
  (Black-tailed Prairie Dog)
Microtus ochrogaster
  (Prairie Vole)
Oreoscoptes montanus
  (Sage Thrasher)
Pituophis catenifer
Vulpes velox
  (Swift Fox)

Color legend for Distribution Map
Nation: United States
United States Distribution: MT, ND, NE, SD, WY
Nation: Canada
Canadian Province Distribution: AB, MB, SK
Global Range: This system is found in the western Great Plains north of the shortgrass prairie and west of the northern tallgrass prairie and extends from northern and western Nebraska into southern Canada, and west to central Montana and eastern Wyoming. The U.S. range corresponds to Bailey et al. (1994) sections 331D, 331E, 331F (mostly), 331G, 332A, 332B, 332D, and perhaps minor extensions into 251B, and in Canada to the Moist Mixed Grassland and Fescue Grassland.

Biogeographic Divisions
Division Code and Name Primary Occurrence Status
205-Eastern Great Plains P: Predicted or probable
303-Western Great Plains C: Confident or certain

The Nature Conservancy's Conservation Ecoregions
Code Name Occurrence Status
26 Northern Great Plains Steppe Confident or certain
34 Dakota Mixed-Grass Prairie Confident or certain
66 Aspen Parkland Predicted or probable
67 Fescue-Mixed Grass Prairie Confident or certain

MRLC 2000 Mapzones
Code Name Occurrence Status
20 Missouri River Plateau Confident or certain
22 Wyoming Basin Confident or certain
29 Wyoming Highlands Confident or certain
30 Northwestern Great Plains Confident or certain
31 Sandhills Confident or certain
39 Prairie Coteau Lands Confident or certain
40 Northern Great Plains Confident or certain

National Mapping
ESLF Code (Ecological System Lifeform): 7114
ESP Code (Environmental Site Potential): 1141
EVT Code (Existing Vegetation Type): 2141

West Landfire Legend: Yes
East Landfire Legend: Yes

Element Description Edition Date: 20Nov2015
Element Description Author(s): S. Menard, K. Kindscher, G. Kittel, S. Cooper, M.S. Reid, K.A. Schulz, J. Drake

Ecological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

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