Great Plains Closed Depressional Wetland
Provisional State Rank
This system includes a variety of depressional wetlands generally found in complexes in central and eastern Montana. This type of wetland differs from Western Great Plains Open Depressional Wetlands and Great Plains Prairie Potholes by being completely isolated from both the regional groundwater system and inter-wetland surface drainage systems. They occur in depressional basins found in flat, enclosed upland areas or on level shallow lake basins. The major sources of input water are precipitation and snow melt, and water loss occurs through evapotranspiration. The basins are typified by the presence of an impermeable layer, such as dense clay formed in alluvium that is poorly drained. Subsurface soil layers are restrictive to water movement and root penetration. Ponds and lakes associated with this system can experience periodic drawdowns during dry years, but are replenished by spring rains. Closed depressions experience irregular hydroperiods, most filling with water only occasionally and drying quickly, influencing the plant communities that are present. The drawdown zone is typically dominated by western wheatgrass (Pascopyrum smithii) and foxtail barley (Hordeum jubatum). Povertyweed (Iva axillaris) and willow dock (Rumex salicifolius) occupy the broad, low gradient basins which are shallowly inundated in the spring and draw down every year to reveal bottoms of gray bentonite. Common spikerush (Eleocharis palustris) occurs within the drawdown area where there is more organic matter in the substrate. Hardstem bulrush (Schoenoplectus acutus) typifies closed depressions sufficiently deep to remain permanently inundated during most years. Species richness can vary considerably among individual examples of this system and it is especially influenced by adjacent land use like agriculture and grazing.
lowland, herbaceous, depression, depressional, playa, clay subsoil, impermeable layer, saturated, isolated wetland, strictly isolated wetland
This system can be found throughout the eastern portion of the Western Great Plains; however, it is most prevalent in the central states of Nebraska, Kansas and Oklahoma. In Montana, closed depressions are most concentrated to the north of the HiLine and Route 2, from the Blackfeet Reservation to the North Dakota border. Individual depressions can also be found across the Northwestern Glaciated Plains north of the Missouri River.
Ecological System Distribution
Approximately 161 square kilometers are classified as Great Plains Closed Depressional Wetland in the 2016 Montana Land Cover layers.
Grid on map is based on USGS 7.5 minute quadrangle map boundaries.
Montana Counties of Occurrence
BIG HORN, BLAINE, CARBON, CARTER, CASCADE, CHOUTEAU, CUSTER, DANIELS, DAWSON, FALLON, FERGUS, GARFIELD, GLACIER, GOLDEN VALLEY, HILL, JUDITH BASIN, LEWIS AND CLARK, LIBERTY, MCCONE, MEAGHER, MUSSELSHELL, PARK, PETROLEUM, PHILLIPS, PONDERA, PRAIRIE, RICHLAND, ROOSEVELT, ROSEBUD, SHERIDAN, STILLWATER, SWEET GRASS, TETON, TOOLE, TREASURE, VALLEY, WHEATLAND, WIBAUX, YELLOWSTONE
This system is typified by depressional basins found in flat enclosed upland areas and level shallow lake basins, with an impermeable layer such as dense clay isolating the wetland from the regional groundwater system. It differs from Western Great Plains Open Depression Wetlands and Great Plains Prairie Potholes by being completely isolated from both the regional groundwater system and inter-wetland surface drainage systems. These wetlands occur in depressional basins found in flat enclosed upland areas or on level shallow lake basins. The major sources of input water are precipitation and snow melt; water loss occurs through evapotranspiration. The basins are typified by the presence of an impermeable layer, such as dense clay formed in alluvium that is poorly drained. Subsurface soil layers are restrictive to water movement and root penetration (Cook and Hauer, 2007). Ponds and lakes associated with this system can experience periodic drawdowns during dry years, but are replenished by spring rains. Closed depressions experience irregular hydroperiods, filling water only occasionally and drying quickly, which influences the plant communities that are present.
Vegetation within this system is highly influenced by hydrology, salinity, fire and adjacent land uses. The drawdown zone is typically dominated by western wheatgrass (Pascopyrum smithii) and foxtail barley (Hordeum jubatum), the most common wet meadow component of this landscape. Needle spikerush (Eleocharis acicularis) and the small annual forbs slender plantain (Plantago elongata) and purslane speedwell (Veronica peregrina) are common in most stands. Povertyweed (Iva axillaris) and willow dock (Rumex salicifolius) occupy the broad, low gradient basins which are shallowly inundated in the spring and draw down every year to reveal bottoms of gray bentonite. The common spikerush (Eleocharis palustris) association is also within the drawdown zone but occurs at sites where there is more organic matter in the substrate. Foxtail barley (Hordeum jubatum) and needle spikerush (Eleocharis acicularis) are typically well represented in drier stands, while water knotweed (Polygonum amphibium) stands are found at wetter sites. Marsh vegetation, dominated by hardstem bulrush (Schoenoplectus acutus), typifies depressions sufficiently deep to remain permanently inundated during most years. Forbs commonly associated with these marsh communities include water knotweed (Polygonum amphibium), common spikerush (Eleocharis palustris) and two headed water-starwort (Callitriche heterophylla).
Alliances and Associations
- (A.1422) (Common Spikerush, Page Spikerush) Seasonally Flooded Herbaceous Alliance
- (A.1358) Foxtail Barley Temporarily Flooded Herbaceous Alliance
- (A.1046) Greasewood Intermittently Flooded Shrubland Alliance
- (A.1347) Prairie Cordgrass Temporarily Flooded Herbaceous Alliance
- (A.1232) Western Wheatgrass Herbaceous Alliance
- (A.1328) Western Wheatgrass Intermittently Flooded Herbaceous Alliance
- (A.1354) Western Wheatgrass Temporarily Flooded Herbaceous Alliance
These systems developed under Northern Great Plains climatic conditions, which included natural disturbances by large herbivores, periodic flooding events and occasional fire. Wet-drought year climatic cycles in Montana, often in 10 to 20 year intervals, influence the ecological communities in these systems (Hansen et al., 1995). Each year seeds from annuals and perennials germinate and cover exposed mud flats, but when precipitation floods the depressions, the annuals drown and the perennials survive. Over a series of years the perennials dominate. The drawdown to mudflats is necessary so that emergent vegetation can become reestablished. This flooding, drawdown and the eventual exposure of mud flats drive the water-level vegetation cycle.
Changes will occur in the plant communities due to climatic conditions and/or management actions. Due to the nature of the soils, these sites are considered moderately resilient. With continued adverse impacts, a moderate decline in vegetative vigor and composition will occur. Heavy continuous grazing and/or continuous seasonal (spring) grazing, without adequate recovery periods, will eventually lead to loss of the Western wheatgrass-foxtail barley wetland community, and inland saltgrass will begin to increase. Western wheatgrass will increase initially, but then will begin to decrease. In time, heavy continuous grazing will cause inland saltgrass, fowl bluegrass (Poa palustris), and other pioneer perennials and annuals to increase. This replacement plant community is resistant to change, due to the grazing tolerance of inland saltgrass and increased surface salts. However, a significant amount of production and diversity has been lost compared to the Western wheatgrass -foxtail barley community, and the loss of key cool season grasses and increased bare ground will affect energy flow and nutrient cycling. Water infiltration will be reduced significantly due to the massive shallow root system “root pan” characteristic of inland saltgrass, and the increased amount of bare ground. It will take a long time to bring this plant community back with management alone (USDA NRCS, 2003).
The major barriers to restoration are isolation, infrequent flooding, impermeable soils and invasive species. These factors must be addressed during the planning and long term management of restored wetlands.
Species Associated with this Ecological System
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state 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, Foresman 2012, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system 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 ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system 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, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems 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 (this information can be requested at: http://mtnhp.org/requests/default.asp
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems 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 ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- 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.
- 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.
- Native Species Commonly Associated with this Ecological System
- Native Species Occasionally Associated with this Ecological System
Original Concept Authors
Montana Version Authors
- Classification and Map Identifiers
Cowardin Wetland Classification:
National Vegetation Classification Standard:
||Temporarily flooded, seasonally flooded, semi-permanently flooded, intermittently exposed
|Geographically Isolated Wetland
||Isolated and strictly isolated
||Shrubland and Grassland
||Temperate and Boreal Shrubland and Grassland
||Temperate and Boreal Fresh Water Wet Meadow and Marsh
||Eastern North American wet Meadow, Riparian and Marsh
||Great Plains Freshwater Wet Meadow, Riparian and Marsh
National Land Cover Dataset:
|Element Global ID
||CES303.666, Western Great Plains Closed Depressional Wetland
95: Emergent Herbaceous Wetland
9252: Western Great Plains Closed Depressional Wetland
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
- Cook, Bradley J., and F. Richard Hauer. 2007. "Effects of hydrologic connectivity on water chemistry, soils, and vegetation structure and function in an intermontane depressional wetland landscape". Wetlands. 27 (3): 719-738.
- 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.
- USDA NRCS - ND SM. 2003. R054XY022ND Section II - FOTG Closed Depression Ecological Site Description.