Great Plains Floodplain Forest
Global Name:
Great Plains Cottonwood - Willow Floodplain Forest
Global Rank:
G3?
State Rank:
S2
(see reason below)
External Links
State Rank Reason
These habitats have been severely impacted by hydrologic changes and invasive species, resulting in a large decrease in condition and extent.
General Description
This National Vegetation Classification Group occurs along rivers and larger streams across the Great Plains region in Montana. It is most prevalent along the major prairie rivers in the eastern third of the state. Riparian forest and woodland communities in this groups are typically dominated or co-dominated by Eastern Cottonwood (Populus deltoides), Green Ash (Fraxinus pennsylvanica), Boxelder (Acer negundo), American Elm (Ulmus americana), and/or Peachleaf Willow (Salix amygdaloides). Communities dominated or co-dominated by Eastern Cottonwood are most common while those dominated or co-dominated by American Elm (Ulmus americana) are the least abundant. The tree canopy can be open to closed and is generally >25% and can range from about 30-50ft in height. The shrub and herbaceous strata can range from nearly absent to dense. Periodic flooding is important in establishing and maintaining stands of this group. Flooding regime (frequency, severity, duration) is also important in shaping the understory composition and structure. Scouring and deposition during flooding create areas of new bare mineral soil necessary for Eastern Cottonwood regeneration.
This group is similar to the Great Plains Floodplain and the Great Plains Riparian Ecological Systems.
Diagnostic Characteristics
Riparian & Wetland Forest; Great Plains Region; Floodplains
Typical Dominants: Green Ash (Fraxinus pennsylvanica), American Elm (Ulmus americana), Eastern Cottonwood (Populus deltoides), Boxelder (Acer negundo), Peachleaf Willow (Salix amygdaloides)
Similar Systems
Range
In Montana, this group occurs east of the Continental Divide throughout the Great Plains Region along major River drainages and floodplains. It is most abundant in the eastern third of the state.
In Montana, G147 occurs in Level III Ecoregions 42 (Northwestern Glaciated Plains) and 43 (Northwestern Great Plains).
In Montana, G147 occurs within these Major Land Resource Areas: 52 - Brown Glaciated Plains, 53A - Northern Dark Brown Glaciated Plains, 53B - Central Dark Brown Glaciated Plains, 58A,B,C,D - Northern Rolling High Plains, and 60A,B - Pierre Shale Plains.
Density and Distribution
Based on 2025 land cover layer. Grid on map is based on USGS 7.5 minute quadrangle map boundaries.
Mapped Distribution by County
Big Horn, Blaine, Carbon, Carter, Cascade, Chouteau, Custer, Daniels, Dawson, Fallon, Fergus, Gallatin, Garfield, Glacier, Golden Valley, Hill, Judith Basin, Lewis and Clark, Liberty, Mccone, Meagher, Musselshell, Park, Petroleum, Phillips, Pondera, Powder River, Prairie, Richland, Roosevelt, Rosebud, Sheridan, Stillwater, Sweet Grass, Teton, Toole, Treasure, Valley, Wheatland, Wibaux, Yellowstone
Based on 2025 land cover layer.
Spatial Pattern
Small Patch and Large Patch
Environment
This group occurs along rivers and larger streams across the Great Plains region in Montana. Communities in this group may occur as relatively broad and extensive forests, as seen along the lower stretches of the Missouri and Yellowstone Rivers, or more narrow bands, as seen along the Milk, Little Missouri, Tongue and Powder Rivers. The elevational range of this group is from 1,900-4,300 feet (Hansen et al. 1995). These are the big perennial rivers of the region, with hydrologic dynamics largely driven by snowmelt and rainfall originating in their headwater watersheds, rather than by local precipitation events. In an undisturbed state, periodic flooding of the fluvial and alluvial soils and channel migration will create alluvial bars, depressions and backwaters supporting zones or mosaics of wetland and riparian vegetation, whose composition and structure is sustained, altered and redistributed by hydrology. Periodic flooding is important in establishing and maintaining stands of this group. Flooding regime (frequency, severity, duration) is also important in shaping the understory composition and structure. Scouring and deposition during flooding create new areas of bare mineral soil necessary for Eastern Cottonwood regeneration. Soils in these communities can be Entisols, Inceptisols and Mollisols on older stabilized sites. Often there is up to 1 meter of soil overlying river gravels and cobble. Water tables can drop to within 1 meter of the soil surface in summer months.
Vegetation
Riparian forest and woodland communities in this group are typically dominated or co-dominated by Eastern Cottonwood (Populus deltoides), Green Ash (Fraxinus pennsylvanica), Boxelder (Acer negundo), American Elm (Ulmus americana), and/or Peachleaf Willow (Salix amygdaloides). Communities dominated or co-dominated by Eastern Cottonwood are most common while those dominated or co-dominated by American Elm (Ulmus americana) are the least abundant. The tree canopy can be open to closed and is generally >25% and can range from about 30-50ft in height. The shrub and herbaceous strata can range from nearly absent to dense. Common shrubs include Western Snowberry (Symphoricarpos occidentalis), Rose (Rosa spp), Red-osier Dogwood (Cornus sericea), Currants and Gooseberries (Ribes spp), Serviceberry (Amelanchier alnifolia) and Chokecherry (Prunus virginiana). Common graminoids associated with these floodplain habitats include Big Bluestem (Andropogon gerardii), Woolly Sedge (Carex pellita), Thickspike Wheatgrass (Elymus lanceolatus), Switchgrass (Panicum virgatum), Western Wheatgrass (Pascopyrum smithii), and Little Bluestem (Schizachyrium scoparium).
Non-native grasses and forbs are common in many of these floodplain environments and may outcompete the native species leading to a conversion of the herbaceous undergrowth. Smooth Brome (Bromus inermis), Common Timothy (Phleum pratense), Redtop (Agrostis stolonifera) Kentucky Bluegrass (Poa pratensis), Quackgrass (Elymus repens), Sweetclover (Melilotus species), Clovers (Trifolium species), Canada Thistle (Cirsium arvense) Leafy Spurge (Euphorbia virgata) and Common Dandelion (Taraxacum officinale) are often present or abundant.
This group is represented by 2 Alliances and 6 associations in Montana within the National Vegetation Classification, which may encompass the range of communities found in the state. A Populus deltoides/Pascopyrum (Elymus) smithii Riparian Woodland Association is described for SD and WY and may occur in MT as well.
National Vegetation Classification
Download the complete NVC hierarchy for Montana
TP1 B08 Palustrine Wetland
TP1.a S69 Forested Wetland
TP1.a2 F136 Temperate-Boreal Forested Wetland
TP1.a2.Nb D011 Eastern North American Flooded and Swamp Forest
TP1.a2.Nb.4 M028 Great Plains Flooded and Swamp Forest
TP1.a2.Nb.4.a G147 Great Plains Cottonwood - Willow Floodplain Forest
A2233 Populus deltoides Northern Plains Floodplain Forest Alliance
CEGL000657 Populus deltoides / Cornus sericea Floodplain Forest
CEGL000660 Populus deltoides / Symphoricarpos occidentalis Floodplain Woodland
CEGL000947 Salix amygdaloides Riparian Woodland
CEGL008967 Populus deltoides - Salix amygdaloides / Salix interior Floodplain Woodland
A4131 Fraxinus pennsylvanica - Ulmus americana - Populus deltoides Floodplain Forest Alliance
CEGL000628 Acer negundo / Prunus virginiana Floodplain Forest
CEGL000658 Populus deltoides - Fraxinus pennsylvanica Floodplain Forest
CEGL002680 Populus deltoides / Pascopyrum smithii Riparian Woodland
*Disclaimer: Some Alliances and Associations are considered provisional. Some require further documentation to verify their occurrence in the state
and some may be modified or deleted in future revisions after collection of additional data and information.
Dynamic Processes
Periodic flooding is important in establishing and maintaining stands of this group. Flooding regime (frequency, severity, duration) is also important in shaping the understory composition and structure. Scouring and deposition during flooding create areas of new bare mineral soil necessary for Eastern Cottonwood regeneration. In Montana, many occurrences are now degraded to the point where the cottonwood overstory is the only remaining natural component. The hydrology of these floodplain systems has been affected by dams, highways, railroads and agricultural ditches. As a result, they have lost their characteristic wetland /riparian mosaic structure. This has resulted in a highly altered community consisting of relict cottonwood stands with little regeneration. In the groups’s disturbed/altered hydrological state and/or under heavy grazing pressure, there will be an increase in shrub species such as Western Snowberry (Symphoricarpos occidentalis) and Rose (Rosa spp) and a corresponding decrease in willow species, Red-osier Dogwood (Cornus sericea), Currant (Ribes spp), Serviceberry (Amelanchier alnifolia) and Chokecherry (Prunus virginiana).
Successional processes create a community resembling adjacent upland communities; Western Snowberry and Rose may persist but will be joined by other native shrubs from adjacent upland communities, such as Silver Sagebrush (Artemisia cana) and Wyoming Big Sagebrush (Artemisia tridentata ssp. wyomingensis). In addition, exotic shrub species such as Salt-cedar (Tamarix spp) can invade disturbed floodplain habitats. Russian Olive (Elaeagnus angustifolia) has become a dominant overstory tree in many areas, shading out native species. In these disturbed floodplains, the understory vegetation is dominated by a mixture of pasture grasses such as Smooth Brome (Bromus inermis), Common Timothy (Phleum pratense), Redtop (Agrostis stolonifera) and Kentucky Bluegrass (Poa pratensis), as well as non-native forbs such as Sweetclover (Melilotus species), Clovers (Trifolium species), Canada Thistle (Cirsium arvense) and Common Dandelion (Taraxacum officinale). Once exotic grasses become dominant, especially in the absence of episodic flooding, these habitats cannot return to their original state without substantial management intervention.
Management
Cottonwoods and willows are the dominant species in these Great Plains floodplain habitats, creating a highly productive and important communities. They are specifically adapted to large flooding events that promote dispersion and colonization of newly formed alluvial bars, as such, maintaining the frequency and duration of the flows necessary for colonization to succeed is vital for their persistence on the landscape (Scott et al 1997). Great Plains floodplain habitats have been substantially impacted by the development of both groundwater and surface water for irrigation, isolating rivers from their adjacent floodplains. Unless water management can restore periodic flooding, floodplains and riparian areas may become dominated by late-seral communities, and nutrient cycles may be disrupted without floodwaters depositing organic material (Decker 2007). In addition, management efforts need to target aggressive non-native shrubs like Salt-cedar (Tamarix spp) and Russian Olive that can drastically alter ecological processes. Salt-cedar is an early successional species with dispersal strategies and habitat requirements similar to native cottonwoods and willows (Lesica and Miles 2004). It can replace the native cottonwoods and willows where natural flow regimes have been altered. Early detection and rapid response are necessary to prevent its spread. Prescribed spring grazing by sheep has been effective in controlling leafy spurge along some rivers, particularly the upper Powder River (Rinella and Hileman 2009).
Restoration Considerations
Restoration strategies are dependent on the degree and type of disturbance event. Restoration efforts must first concentrate on restoring hydrologic processes or simulating large flood events. Vigor, health and degree of vegetative regeneration of existing trees and shrubs must be evaluated to determine if these components of the community are capable of recovery in an acceptable time frame. Because all major shrub species within this floodplain system are capable of re-sprouting and typically possess extensive, spreading root systems, modified land management practices in areas of low to moderate impact can minimize additional restoration needs.
Removing or limiting grazing will allow the understory vegetation to recover if there are existing populations of herbaceous native species (Carex, Juncus, and native grasses) with rhizomatous root systems capable of re-colonizing bare soils. Presence of rhizomatous, highly adaptable exotic grasses such as Kentucky Bluegrass (Poa pratensis), Common Timothy (Phleum pratense) and Smooth Brome (Bromus inermis) as well as non-native forbs such as Sweetclover (Melilotus species), Clovers (Trifolium species), Canada Thistle (Cirsium arvense) and Common Dandelion (Taraxacum officinale) however, will persist on the site and may compete with existing populations of native graminoids and forbs.
Species Associated with this Community
- How Lists Were Created and Suggested Uses and Limitations
Animal Species Associations
Please note that while all vertebrate species have been systematically associated with vegetation communities, only a handful of invertebrate species have been associated with vegetation communities and invertebrates lists for each vegetation community should be regarded as incomplete. Animal species associations with natural vegetation communities that they regularly breed or overwinter in or migrate through were made by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Werner et al. 2004, Adams 2003, and Foresman 2012);
- Evaluating structural characteristics and distribution of each vegetation community relative to the species' range and habitat requirements;
- Examining the observation records for each species in the state-wide point observation database associated with each vegetation community;
- Calculating the percentage of observations associated with each vegetation community relative to the percent of Montana covered by each vegetation community to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use. Species that only overwinter in Montana were only evaluated for overwintering habitat use. Species that only migrate through Montana were only evaluated for migratory habitat use. In general, species are listed as associated with a vegetation community if it contains structural characteristics known to be used by the species. However, species are not listed as associated with a vegetation community if we found no support in the literature for the species’ use of structural characteristics of the community even if point observations were associated with it. If you have any questions or comments on animal species associations with vegetation communities, please contact the Montana Natural Heritage Program's Senior Zoologist.
Plant Species Associations
Please note that while diagnostic, dominant, or codominant vascular plant species for a vegetation community have been systematically assigned to those communities and vascular plant Species of Concern were systematically evaluated for their associations with vegetation communities, the majority of Montana’s vascular plant species have not been evaluated for their associations with vegetation communities and no attempt has been made to associate non-vascular plants, fungi, or lichens with vegetation communities. Plant species associations with natural vegetation communities were made in a manner similar to that described above for animals, but with review of Lesica et al. (2022) and specimen collection data from the Consortium of Pacific Northwest Herbaria. If you have any questions or comments on plant species associations with vegetation communities, please contact the Montana Natural Heritage Program's Program Botanist.
Suggested Uses and Limitations
Species associations with vegetation communities should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning. These potential lists of species should not be used in place of documented occurrences of species or predicted habitat suitability models (this information can be requested at: https://mtnhp.mt.gov/requests/), or systematic surveys for species and onsite evaluations of habitat by trained biologists. Users of this information should be aware that the land cover data used to generate species associations is based on satellite imagery from 2016 and was only intended to be used at broader landscape scales. Land cover mapping accuracy is particularly problematic when the vegetation communities occur as small patches or where the land cover types have been altered over the past decade. Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections). Finally, although a species may be associated with a particular vegetation community within its known geographic range, portions of that vegetation community may occur outside of the species' known geographic range.
Literature Cited
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Consortium of Pacific Northwest Herbaria. https://www.pnwherbaria.org/ Last accessed May 30, 2025.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Lesica P., M. Lavin, and P.F. Stickney. 2022. Manual of vascular plants, 2nd Edition. Brit Press. 779 p.
- Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
- Species of Concern Associated with this Community
Vascular Plants
Mammals
Birds
Reptiles
Amphibians
Invertebrates
- Diagnostic, Dominant, or Codominant Plant Species for this Community
Vascular Plants
- Other Native Species Commonly Associated with this Community
Vascular Plants
Amphibians
Original Concept Authors
J. Drake (2015)
Montana Version Authors
S. Mincemoyer, L. Vance, C. McIntyre, T. Luna
Version Date
12/6/2024
References
- Literature Cited AboveLegend:
View Online PublicationDecker, Karin. 2007. Western Great Plains riparian woodland and shrubland ecological system ecological integrity assessment. Ft. Collins, Colo: Colorado State University, Colorado Natural Heritage Program.
Hansen, P. L., R. D. Pfister, K. Boggs, B. J. Cook, J. Joy, and D. K. Hinckley. 1995. Classification and management of Montana's riparian and wetland sites. Montana Forest and Conservation Experiment Station, School of Forestry, University of Montana, Miscellaneous Publication No. 54. 646 pp. + posters.- Lesica, P., and S. Miles. 2004. "Ecological strategies for managing tamarisk on the C.M. Russell National Wildlife Refuge, Montana, USA". Biological Conservation. 119 (4): 535-543.
- Rinella, M.J. and B.J. Hileman. 2009. Efficacy of prescribed grazing depends on timing intensity and frequency. Journal of Applied Ecology. 46, pp 796–803
- Scott, M. L., G. T. Auble, and J. M. Friedman. 1997. Flood dependency of cottonwood establishment along the Missouri River, Montana, USA. Ecological Applications7:677-690.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?- Friedman, J. M., M. L. Scott, and G. T. Auble. 1997. Water management and cottonwood dynamics along prairie streams. Pages 49-71 in: F. L. Knopf and F. B. Samson. Ecology and Conservation of Great Plains Vertebrates. Springer-Verlag, New York, NY.
- Friedman, J. M., W. R. Osterkamp, M. L. Scott, and G. T. Auble. 1998. Downstream effects of dams on channel geometry and bottomland vegetation: regional patterns in the Great Plains. Wetlands 18:619-633.
- Hauer, F Richard, and Mark S Lorang. 2004. "River regulation, decline of ecological resources, and potential for restoration in a semi-arid lands river in the western USA". Aquatic Sciences. 66 (4): 388.
- Junk WJ, Welcomme RL. 1990. Floodplains. p 491-524 in: Patten BC, editor. Wetlands and Shallow Continental Water Bodies. The Hague, The Netherlands: SPB Academic Pub.
- Ward, J V, and J A Stanford. 1995. 'Ecological Connectivity in Alluvial River Ecosystems and its Disruption by Flow Regulation'. Regulated Rivers. 11 (1): 105.
- Web Search Engines for Articles on "Great Plains Cottonwood - Willow Floodplain Forest"
