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Scientific Name: Northern Rocky Mountain Lower Montane, Foothill and Valley Grassland
Unique Identifier: CES306.040
Classification Confidence: 3 - Weak

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Summary: This ecological system of the northern Rocky Mountains is found at lower montane to foothill elevations in the mountains and large valleys of northeastern Wyoming and western Montana, west through Idaho into the Blue Mountains of Oregon, and north into the Okanagan and Fraser plateaus of British Columbia and the Canadian Rockies. They also occur to the east in the central Montana mountain "islands," foothills, as well as the Rocky Mountain Front and Big and Little Belt ranges. These grasslands are floristically similar to Inter-Mountain Basins Big Sagebrush Steppe (CES304.778), Columbia Basin Foothill and Canyon Dry Grassland (CES304.993), and Columbia Basin Palouse Prairie (CES304.792), but are defined by shorter summers, colder winters, and young soils derived from recent glacial and alluvial material. These grasslands reflect a shift in the precipitation regime from summer monsoons and cold snowy winters found in the Southern Rockies to predominantly dry summers and winter precipitation. In the eastern portion of its range in Montana, winter precipitation is replaced by a spring peak in precipitation. They are found at elevations from 300 to 1650 m, ranging from small meadows to large open parks surrounded by conifers in the lower montane, to extensive foothill and valley grasslands below the lower treeline. In the southern extent, some of these valleys may have been primarily sage-steppe with patches of grassland in the past, but because of land-use history post-settlement (herbicide, grazing, fire, pasturing, etc.), they have been converted to grassland-dominated areas. Soils are relatively deep, fine-textured, often with coarse fragments, and non-saline, often with a microphytic crust. The most important species are cool-season perennial bunchgrasses and forbs (>25% cover), sometimes with a sparse (<10% cover) shrub layer. Pseudoroegneria spicata, Festuca campestris, Festuca idahoensis, or Hesperostipa comata commonly dominate sites on all aspects of level to moderate slopes and on certain steep slopes with a variety of other grasses, such as Achnatherum hymenoides, Achnatherum richardsonii, Hesperostipa curtiseta, Koeleria macrantha, Leymus cinereus, Elymus trachycaulus, Bromus inermis var. pumpellianus, Achnatherum occidentale, Pascopyrum smithii, and other graminoids such as Carex filifolia and Danthonia intermedia. Other grassland species include Opuntia fragilis, Artemisia frigida, Carex petasata, Antennaria spp., and Selaginella densa. Important exotic grasses include Phleum pratense, Bromus inermis, and Poa pratensis. Shrub species may be scattered, including Amelanchier alnifolia, Rosa spp., Symphoricarpos spp., Juniperus communis, Artemisia tridentata, and in Wyoming Artemisia tripartita ssp. rupicola. Common associated forbs include Geum triflorum, Galium boreale, Campanula rotundifolia, Antennaria microphylla, Geranium viscosissimum, and Potentilla gracilis. A soil crust of lichen covers almost all open soil between clumps of grasses; Cladonia and Peltigera are the most common lichens. Unvegetated mineral soil is commonly found between clumps of grass and the lichen cover. The fire regime of this ecological system maintains a grassland due to rapid fire return that retards shrub invasion or landscape isolation and fragmentation that limits seed dispersal of native shrub species. Fire frequency is variable but is presumed to be generally less than 20 years to reduce shrub cover and maintain grassland. These are extensive grasslands, not grass-dominated patches within the sagebrush shrub-steppe ecological system. Festuca campestris is easily eliminated by grazing and does not occur in all areas of this system.

Classification Approach: International Terrestrial Ecological Systems Classification (ITESC)

Classification Comments: This is the same as the Interior Plateau Grassland also called "Northern Plateau Grassland" of the Okanagan Ecoregional Plan. In Wyoming, this is distinguished from Northwestern Great Plains Mixedgrass Prairie (CES303.674) by the presence of Festuca idahoensis or Carex rossii, the lack of Bouteloua gracilis (which is common in CES303.674), or the presence of Artemisia nova or Artemisia tripartita ssp. rupicola, neither of which occur in CES303.674.

Similar Ecological Systems
Unique Identifier Name
CES304.778 Inter-Mountain Basins Big Sagebrush Steppe
CES304.787 Inter-Mountain Basins Semi-Desert Grassland
CES304.792 Columbia Basin Palouse Prairie
CES304.993 Columbia Basin Foothill and Canyon Dry Grassland
CES306.806 Northern Rocky Mountain Subalpine-Upper Montane Grassland

Component Associations
Association Unique ID Association Name
CEGL001609 Festuca idahoensis - Carex hoodii Grassland
CEGL001616 Festuca idahoensis - Eriogonum heracleoides Grassland
CEGL001620 Festuca idahoensis - Koeleria macrantha Grassland
CEGL001621 Festuca idahoensis - Pascopyrum smithii Grassland
CEGL001624 Festuca idahoensis - Pseudoroegneria spicata Grassland
CEGL001625 Festuca idahoensis - Achnatherum richardsonii Grassland
CEGL001629 Festuca campestris - Pseudoroegneria spicata Grassland
CEGL001642 Leymus salinus ssp. salmonis - Enceliopsis nudicaulis Sparse Vegetation
CEGL001643 Leymus salinus ssp. salmonis - Lupinus argenteus Sparse Vegetation
CEGL001665 Pseudoroegneria spicata - Carex filifolia Grassland
CEGL001668 Pseudoroegneria spicata - Eriogonum heracleoides Grassland
CEGL001897 Festuca idahoensis Grassland
CEGL001898 Festuca idahoensis - Carex filifolia Grassland
CEGL001901 Festuca idahoensis - Leucopoa kingii Grassland
CEGL005469 Achnatherum nelsonii - Lupinus argenteus Grassland
CEGL005860 Achnatherum nelsonii - Lupinus sericeus Grassland
CEGL005862 Calamagrostis rubescens Grassland
CEGL005868 Elymus repens Ruderal Grassland
CEGL005869 Festuca campestris - (Festuca idahoensis) - Achnatherum richardsonii Grassland
CEGL005870 Festuca campestris - Festuca idahoensis - Geranium viscosissimum Grassland
CEGL005874 Phleum pratense - Poa pratensis - Bromus inermis Ruderal Grassland
CEGL005875 Festuca campestris - Festuca idahoensis Grassland


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

Diagnostic Classifiers
Primary Classifier Secondary Classifier
Lowland Foothill
Lowland Lowland
Very Shallow Soil  
Loam Soil Texture  
Silt Soil Texture  
Cool-season bunch grasses  

At-Risk Species Reported for this Ecological System
Scientific Name
  (Common Name)
NatureServe Global Status U.S. Endangered Species Act Status
Artemisia tripartita ssp. rupicola
  (Wyoming Threetip Sagebrush)
Botrychium ascendens
  (Upward-lobed Moonwort)
Rana pretiosa
  (Oregon Spotted Frog)
G2 LT: Listed threatened
Ranunculus glaberrimus var. reconditus
  (Obscure Buttercup)

Vegetation Composition (incomplete)
Species Name Rounded Global Status Growth Form Stratum Char-
Domi-nant Con-stant
Cover Class %
Balsamorhiza sagittata G5 Flowering forb Herb (field)    
Ranunculus glaberrimus var. reconditus T2 Flowering forb Herb (field)      
Botrychium ascendens G3 Fern (Spore-bearing forb) Herb (field)      
Achnatherum occidentale G5 Graminoid Herb (field)    
Achnatherum richardsonii G5 Graminoid Herb (field)    
Bromus inermis ssp. pumpellianus T5 Graminoid Herb (field)    
Carex filifolia G5 Graminoid Herb (field)    
Carex petasata G5 Graminoid Herb (field)    
Danthonia intermedia G5 Graminoid Herb (field)    
Festuca campestris G5 Graminoid Herb (field)    
Festuca idahoensis G5 Graminoid Herb (field)    
Hesperostipa comata G5 Graminoid Herb (field)    
Hesperostipa curtiseta G5 Graminoid Herb (field)    
Poa secunda G5 Graminoid Herb (field)    
Pseudoroegneria spicata G5 Graminoid Herb (field)    

Animal Species Reported for this Ecological System
Scientific Name
  (Common Name)
Global Status U.S. Endangered Species Act Status Charact-
Coluber constrictor
  (North American Racer)
Microtus pennsylvanicus
  (Meadow Vole)
Pituophis catenifer
Rana pretiosa
  (Oregon Spotted Frog)
G2 LT: Listed threatened    

Color legend for Distribution Map
Nation: United States
United States Distribution: ID, MT, OR, WA, WY
Nation: Canada
Canadian Province Distribution: AB, BC
Global Range: This lower montane, foothill and valley grassland system occurs throughout the southern interior and southern portion of the Fraser Plateau, as well as the valleys around the Fraser River in the Pavilion Ranges, the Nicola River and the Similkameen River in British Columbia. It also occurs in the mountains and large valleys of northwestern Wyoming and western Montana, east to the central Montana Rocky Mountain Front and mountain "island" ranges, west through Idaho into the Blue Mountains of Oregon.

Biogeographic Divisions
Division Code and Name Primary Occurrence Status
207-North American Pacific Warm Continental C: Confident or certain
306-Rocky Mountain C: Confident or certain

The Nature Conservancy's Conservation Ecoregions
Code Name Occurrence Status
26 Northern Great Plains Steppe Confident or certain
6 Columbia Plateau Predicted or probable
68 Okanagan Confident or certain
7 Canadian Rocky Mountains Confident or certain
8 Middle Rockies - Blue Mountains Confident or certain
9 Utah-Wyoming Rocky Mountains Predicted or probable

MRLC 2000 Mapzones
Code Name Occurrence Status
1 Northern Cascades Confident or certain
8 Grande Coulee Basin of the Columbia Plateau Confident or certain
9 Blue Mountain Region Confident or certain
10 Northwestern Rocky Mountains Confident or certain
18 Snake River Plain Confident or certain
19 Northern Rocky Mountains Confident or certain
20 Missouri River Plateau Confident or certain
21 Middle Rocky Mountains Confident or certain
22 Wyoming Basin Confident or certain
29 Wyoming Highlands Confident or certain

National Mapping
ESLF Code (Ecological System Lifeform): 7112
ESP Code (Environmental Site Potential): 1139
EVT Code (Existing Vegetation Type): 2139

West Landfire Legend: Yes
East Landfire Legend: No

Element Description Edition Date: 24May2018
Element Description Author(s): R. Crawford, M.S. Reid, G. Kittel, K.A. Schulz

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