Great Plains Saline Depression Wetland
Provisional State Rank
This ecological system is very similar to both the Western Great Plains Open Freshwater Depression Wetland and the Western Great Plains Closed Depression Wetland found in wetland complexes in the central and northeastern portion of Montana. However, this system differs due to increased soil salinity, which causes these systems to become brackish. This high salinity is attributed to high evaporation and the accumulation of minerals dissolved in the water. Wetlands in this system are discharge wetlands, where water high in dissolved salts has moved from the regional groundwater system into the depression. Hydroperiods vary depending on precipitation and snowmelt, the primary source of water. Water is prevented from percolating out of the depression due to impermeable dense clay, and salt encrustations can occur on the surface with drying. Species that typify this system are salt-tolerant and halophytic graminoids such as alkali bulrush (Schoenoplectus maritimus), common three square (Schoenoplectus pungens), inland saltgrass (Distichlis spicata), Nuttall’s alkali grass (Puccinellia nuttalliana), foxtail barley (Hordeum jubatum), red swampfire (Salicornia rubra) and freshwater cordgrass (Spartina pectinata), and shrubs such as black greasewood (Sarcobatus vermiculatus). During exceptionally wet years, an increase in precipitation can dilute the salt concentration in the soils in some cases, allowing for less salt-tolerant species to occur. The distribution of this system extends into central Montana, where it occurs in the matrix of the Northwestern Great Plains Mixed Grass Prairie. However, these depressions are most concentrated to the north of the HiLine and Route 2, from the Blackfeet Reservation to the North Dakota Border. Individual occurrences can also be found across the Northwest Glaciated Plains north of the Missouri River.
Isolated to partially isolated wetland, depression, saline conditions
This system can occur throughout the western Great Plains but is more prevalent in the south-central portions of the division. Its distribution extends into central Montana where it occurs in the matrix of the Northwestern Great Plains Mixed Grass Prairie. These saline 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 464 square kilometers are classified as Great Plains Saline Depression 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
BEAVERHEAD, BIG HORN, BLAINE, CARBON, CARTER, CASCADE, CHOUTEAU, CUSTER, DANIELS, DAWSON, FALLON, FERGUS, FLATHEAD, GALLATIN, GARFIELD, GLACIER, GOLDEN VALLEY, HILL, JUDITH BASIN, LAKE, LEWIS AND CLARK, LIBERTY, MCCONE, MEAGHER, MISSOULA, MUSSELSHELL, PARK, PETROLEUM, PHILLIPS, PONDERA, POWDER RIVER, RICHLAND, ROOSEVELT, ROSEBUD, SHERIDAN, STILLWATER, SWEET GRASS, TETON, TOOLE, TREASURE, VALLEY, WHEATLAND, WIBAUX, YELLOWSTONE
This system is distinguished from the freshwater depression systems by brackish water caused by strongly saline and alkaline soils. This high salinity is attributed to excessive evaporation and the accumulation of minerals dissolved in groundwater discharge. Water is prevented from percolating out of the depression due to an impermeable dense clay soil. Salt encrustations can occur on the surface due to slow water movement (Hansen et al, 1995). On the Blackfeet Indian reservation, water samples collected from saline depressions had conductivity values that ranged from 1,550-40,000 uhmos/cm (Lesica and Shelley, 1988).
Vegetation within this system is highly influenced by soil salinity and soil moisture. Salt-tolerant and halophytic species that typify this system include alkali bulrush (Schoenoplectus maritimus), common three square (Schoenoplectus pungens), inland saltgrass (Distichlis spicata), Nuttall’s alkali grass (Puccinellia nuttalliana), foxtail barley (Hordeum jubatum), red swampfire (Salicornia rubra) and freshwater cordgrass (Spartina pectinata), and shrubs such as black greasewood (Sarcobatus vermiculatus). Other species include western wheatgrass (Pascopyrum smithii) and foxtail barley (Hordeum jubatum). Plant zonation related to soil salinity is often apparent in these systems. with distinct rings occurring around the fringe of the depression. In deeper, more depressed halophytic habitats, red swampfire or prairie cordgrass will dominate with Nuttall’s alkali grass found directly upslope, followed by inland saltgrass. Shrubs such as greasewood and winterfat (Krascheninnikovia lanata) are common around the outer margins of this system. Pursh seepweed (Suaeda calceoliformis), annual goosefoot (Chenopodium species) and seaside arrowgrass (Triglochin maritima) are common forbs.
In northeastern Montana, the alkali bulrush association occurs as an emergent band around open water or as zonal vegetation around other plant associations. Water tables are often high, often remaining above the soil surface at least through late summer. Soils are poorly drained, alkaline Entisols. Alkali bulrush forms dense, monotypic stands with up to 91% cover. In some areas along the wetland edge, very minor amounts of common spikerush (Eleocharis palustris) may be present. Alkali bulrush can survive periods of total inundation up to 1 meter (3.3 feet) deep, as well as drought periods where the water table remains less than 1 meter below the soil surface. It is a vigorously rhizomatous species that colonizes and spreads when the water table is within 10 centimeters (4 inches) of the surface. Cover of alkali bulrush may be replaced by red swampfire and other associated species during drought years.
Red swampfire occurs in the drawdown zone that is flooded during the early part of the growing season but where the water table drops below soil surface by late spring or early summer. Soils in this zone usually have silty-clay to clay texture, and the soil surface is covered with salt crusts. Principle salts are sulfates and chlorides of sodium and magnesium. It is one of a very few species that can persist in these hyper-saline conditions when the water table drops below the soil surface (Dodd and Coupland,1966).
Alliances and Associations
- (A.1436) (Narrowleaf Cattail, Broadleaf Cattail) - (Clubrush species) Semipermanently Flooded Herbaceous Alliance
- (A.1267) Alkali Sacaton Herbaceous Alliance
- (A.1433) Common Threesquare Semipermanently Flooded Herbaceous Alliance
- (A.1358) Foxtail Barley Temporarily Flooded Herbaceous Alliance
- (A.1554) Greasewood Intermittently Flooded Shrub Herbaceous Alliance
- (A.1341) Inland Saltgrass - (Foxtail Barley) Temporarily Flooded Herbaceous Alliance
- (A.1332) Inland Saltgrass Intermittently Flooded Herbaceous Alliance
- (A.1335) Nuttall's Alkali Grass Intermittently Flooded Herbaceous Alliance
- (A.1818) Red Saltwort Seasonally Flooded Herbaceous Alliance
- (A.1764) Sago Pondweed Permanently Flooded Herbaceous Alliance
- (A.1764) Sago Pondweed Permanently Flooded Herbaceous Alliance
- (A.1444) Saltmarsh Clubrush Semipermanently Flooded Herbaceous Alliance
- (A.1401) Sprangletop Seasonally Flooded Herbaceous Alliance
- (A.1354) Western Wheatgrass Temporarily Flooded Herbaceous Alliance
These systems developed under Northern Great Plains climatic conditions that include natural influence of periodic flooding events and occasional fire. Climate has an important effect on saline areas because precipitation and snowmelt transport salts to the depressions and can dilute the soil solution while temperature and wind influence the rate of evapotranspiration. Increased precipitation and/or runoff can dilute the salt concentration and allow for less salt-tolerant species to occur while increased evapotranspiration increases soil salinity leading to a more brackish habitat type.
Changes will occur in the plant communities due to climatic conditions and/or management activities.
In saline depression wetland systems where water has been drained or altered, the original hydrology of the system must be restored. If hydrology is restored, re-growth and re-colonization from dormant rhizomatous root systems of common emergent species can occur during periods of flooding. Cattle grazing should be deferred or controlled to allow regrowth, recolonization and resprouting from existing root systems. Annuals such as red swampfire and annual goosefoots require periods of inundation and drawdown to initiate germination and to complete their life cycles at the end of the growing season.
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:
|Geographically Isolated Wetland
||Isolated to partially isolated
||Temperate and Boreal Freshwater Wet Meadow and Marsh
||Western North American Freshwater Marsh
||North American Brackish and Saline Marsh
||North American Brackish and Saline Marsh
|Element Global ID
||CES303.669, Western Great Plains Saline Depression Wetland
9256: Western Great Plains Saline Depression Wetland
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
- Dodd, J. D., and R. T. Coupland. 1966. Vegetation of saline areas in Saskatchewan. Ecology 47(6):958-968.
- 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. 1989. The vegetation and flora of glaciated prairie potholes on the Blackfeet Indian Reservation, Montana. Unpublished report to Big Sky Field Office, The Nature Conservancy, Helena, MT, 26 pp.