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Scientific Name: Northwestern Great Plains Floodplain
Unique Identifier: CES303.676
Classification Confidence: 2 - Moderate

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Summary: This ecological system is found in the floodplains of medium and large rivers of the northwestern Great Plains, ranging from the Dakotas Mixedgrass Prairie west through the Northern Great Plains Steppe and north into Canada. This system occurs in the upper Missouri River Basin and includes parts of the Niobrara, White, Cheyenne, Little Missouri, Yellowstone, Powder, Bighorn, Milk, and Musselshell rivers. Alluvial soils and periodic, intermediate flooding (every 5-25 years) typify this system. These are the perennial big rivers of the region with hydrologic dynamics largely driven by snowmelt in the mountains, rather than local precipitation events. Dominant communities within this system range from floodplain forests to wet meadows to gravel/sand flats, however, they are linked by underlying soils and flooding regime. Dominant species are Populus balsamifera ssp. trichocarpa or Populus deltoides and Salix spp. Fraxinus pennsylvanica, Salix amygdaloides, and Ulmus americana are common in some stands. If present, common shrub species include Amorpha fruticosa, Cornus drummondii, Cornus sericea, Symphoricarpos occidentalis, Salix exigua, Salix interior, and Salix planifolia. Grass cover underneath the trees is an important part of this system and is a mix of cool-season graminoid species, including Carex pellita, Elymus lanceolatus, Pascopyrum smithii, and Schoenoplectus spp., with warm-season species such as Panicum virgatum, Schizachyrium scoparium, and Spartina pectinata. This system is often subjected to heavy grazing and/or agriculture and can be heavily degraded. In Montana, most occurrences are now degraded to the point where the cottonwood overstory is the only remaining natural component; undergrowth is dominated by Bromus inermis, or a complex of pasture grasses. Another factor is that groundwater depletion and lack of fire have created additional species changes. In most cases, the majority of the wet meadow and prairie communities may be extremely degraded or extirpated from the system.

Classification Approach: International Terrestrial Ecological Systems Classification (ITESC)

Classification Comments: This system needs to be more clearly delineated from Northwestern Great Plains Riparian (CES303.677). The component plant association list is incomplete. All the riparian/floodplain/alluvial systems of the Great Plains region need to be revisited for naming conventions, along with better definitions of conceptual boundaries. There is much apparent overlap in their concepts and distribution, and the names add to the confusion. In particular, the difference between "riparian" and "floodplain" usage in the names needs revisiting and possible changing. These systems include Northwestern Great Plains Floodplain (CES303.676), Northwestern Great Plains Riparian (CES303.677), Western Great Plains Floodplain (CES303.678), and Western Great Plains Riparian (CES303.956).

Similar Ecological Systems
Unique Identifier Name
CES303.678 Western Great Plains Floodplain

Component Associations
Association Unique ID Association Name
CEGL000657 Populus deltoides / Cornus sericea Floodplain Forest
CEGL000658 Populus deltoides - Fraxinus pennsylvanica Floodplain Forest
CEGL000659 Populus deltoides - (Salix amygdaloides) / Salix (exigua, interior) Floodplain Woodland
CEGL001131 Symphoricarpos occidentalis Shrubland
CEGL001197 Salix exigua Riparian Wet Shrubland
CEGL001224 Salix planifolia Wet Shrubland
CEGL001476 Spartina pectinata Western Wet Meadow
CEGL001477 Spartina pectinata - Carex spp. Wet Meadow
CEGL001813 Carex nebrascensis Wet Meadow
CEGL002026 Schoenoplectus tabernaemontani - Typha spp. - (Sparganium spp., Juncus spp.) Marsh
CEGL002028 Calamagrostis canadensis - Juncus spp. - Carex spp. Sandhills Wet Meadow
CEGL002030 Schoenoplectus acutus - Typha latifolia - (Schoenoplectus tabernaemontani) Sandhills Marsh
CEGL002049 Riverine Sand Flats - Bars Sparse Vegetation
CEGL002088 Fraxinus pennsylvanica - (Ulmus americana) / Symphoricarpos occidentalis Floodplain Forest
CEGL002152 Populus deltoides / Juniperus scopulorum Floodplain Woodland
CEGL002228 Typha spp. - Schoenoplectus spp. - Mixed Herbs Great Plains Marsh
CEGL005220 Cornus drummondii - Amorpha fruticosa - Cornus sericea Wet Shrubland


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

Non-diagnostic Classifiers
Primary Classifier Secondary Classifier
Forest and Woodland (Treed)  
Riverine / Alluvial  
Long (>25 yrs) Flooding Interval  

At-Risk Species Reported for this Ecological System
Scientific Name
  (Common Name)
NatureServe Global Status U.S. Endangered Species Act Status
Anthus spragueii
  (Sprague's Pipit)
Charadrius melodus
  (Piping Plover)
G3 LE, LT: Listed endangered, listed threatened
Lasionycteris noctivagans
  (Silver-haired Bat)
Phacelia thermalis
  (Hot Springs Phacelia)

Vegetation Composition (incomplete)
Species Name Rounded Global Status Growth Form Stratum Char-
Domi-nant Con-stant
Cover Class %
Populus balsamifera ssp. trichocarpa T5 Broad-leaved deciduous tree Tree canopy    
Populus deltoides G5 Broad-leaved deciduous tree Tree canopy    
Cornus sericea G5 Broad-leaved deciduous shrub Shrub/sapling (tall & short)    
Salix exigua G5 Broad-leaved deciduous shrub Shrub/sapling (tall & short)    
Phacelia thermalis G3 Flowering forb Herb (field)      
Suckleya suckleyana G5 Flowering forb Herb (field)      
Bromus inermis G5 Graminoid Herb (field)    
Carex pellita G5 Graminoid Herb (field)    
Carex retrorsa G5 Graminoid Herb (field)      
Carex rostrata G5 Graminoid Herb (field)      
Elymus lanceolatus G5 Graminoid Herb (field)    
Muhlenbergia glomerata G5 Graminoid Herb (field)      
Panicum virgatum 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-
Aechmophorus clarkii
  (Clark's Grebe)
Anaxyrus woodhousii
  (Woodhouse's Toad)
Anthus spragueii
  (Sprague's Pipit)
Apalone spinifera
  (Spiny Softshell)
Castor canadensis
  (American Beaver)
Charadrius melodus
  (Piping Plover)
G3 LE, LT: Listed endangered, listed threatened    
Chrysemys picta
  (Northern Painted Turtle)
Empidonax traillii
  (Willow Flycatcher)
Lasionycteris noctivagans
  (Silver-haired Bat)
Lithobates pipiens
  (Northern Leopard Frog)
Melanerpes erythrocephalus
  (Red-headed Woodpecker)
Myotis ciliolabrum
  (Western Small-footed Myotis)
Opheodrys vernalis
  (Smooth Greensnake)
Spea bombifrons
  (Plains Spadefoot)
Sterna hirundo
  (Common Tern)
Sternula antillarum
  (Least Tern)
Thamnophis sirtalis
  (Common Gartersnake)

Color legend for Distribution Map
Nation: United States
United States Distribution: MT, ND, NE, SD, WYpotentially occurs
Nation: Canada
Canadian Province Distribution: AB, MB, SK
Global Range: This system is found in the northwestern Great Plains, north of the North Platte River through southern Canada. It is found in eastern Montana along the upper Missouri, Yellowstone, Bighorn, Milk, and Musselshell rivers; in northern Nebraska and the Dakotas on the Niobrara, upper Missouri, White, Cheyenne, and Little Missouri rivers; and in Canada on the Saskatchewan River.

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 Predicted or probable

MRLC 2000 Mapzones
Code Name Occurrence Status
20 Missouri River Plateau 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): 9159

West Landfire Legend: No
East Landfire Legend: No

Element Description Edition Date: 23Jan2008
Element Description Author(s): S. Menard, K. Kindscher, M.S. Reid and K.A. Schulz

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

  • Comer, P., D. Faber-Langendoen, R. Evans, S. Gawler, C. Josse, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, M. Russo, K. Schulz, K. Snow, J. Teague, and R. White. 2003-present. Ecological systems of the United States: A working classification of U.S. terrestrial systems. NatureServe, Arlington, VA.

  • Eyre, F. H., editor. 1980. Forest cover types of the United States and Canada. Society of American Foresters, Washington, DC. 148 pp.

  • Rice, P. M., E. W. Schweiger, W. Gustafson, C. Lea, D. Manier, D. Shorrock, B. Frakes, and L. O'Gan. 2012b. Vegetation classification and mapping project report: Little Bighorn Battlefield National Monument. Natural Resource Report NPS/ROMN/NRR--2012/590. National Park Service, Fort Collins, CO. 147 pp.

  • Rolfsmeier, S. B., and G. Steinauer. 2010. Terrestrial ecological systems and natural communities of Nebraska (Version IV - March 9, 2010). Nebraska Natural Heritage Program, Nebraska Game and Parks Commission. Lincoln, NE. 228 pp.

  • Shiflet, T. N., editor. 1994. Rangeland cover types of the United States. Society for Range Management. Denver, CO. 152 pp.

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Version 7.1 (2 February 2009)
Data last updated: March 2019