Natural Resources
Conservation Service
Ecological site R052XY705MT
Discharge Closed Depression (Cdr)
Last updated: 7/01/2019
Accessed: 11/13/2024
General information
Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
MLRA notes
Major Land Resource Area (MLRA): 052X–Brown Glaciated Plains
The Brown Glaciated Plains, MLRA 52, is an expansive and agriculturally and ecologically significant area. It consists of approximately 14.5 million acres and stretches across 350 miles from east to west, encompassing portions of 15 counties in north-central Montana. This region represents the southwestern limit of the Laurentide Ice Sheet and is considered to be the driest and westernmost area within the vast network of glacially derived prairie pothole landforms of the northern Great Plains. Elevation ranges from 2,000 feet (610 meters) to 4,600 feet (1,400 meters).
Soils are primarily Mollisols, but Entisols, Inceptisols, Alfisols, and Vertisols are also common. Till from continental glaciation is the predominant parent material, but alluvium and bedrock are also common. Till deposits are typically less than 50 feet thick, and in some areas glacially deformed bedrock occurs at or near the soil surface (Soller, 2001). Underlying the till is sedimentary bedrock largely consisting of Cretaceous shale, sandstone, and mudstone (Vuke et al., 2007). It is commonly exposed on hillslopes, particularly along drainageways. Significant alluvial deposits occur along glacial outwash channels and major drainages, including portions of the Missouri, Teton, Marias, Milk, and Frenchman Rivers. Large glacial lakes, particularly in the western half of the MLRA, deposited clayey and silty lacustrine sediments (Fullerton et al., 2013).
Much of the western portion of this MLRA was glaciated towards the end of the Wisconsin age, and the maximum glacial extent occurred approximately 20,000 years ago (Fullerton et al., 2004). The result is a geologically young landscape that is predominantly a level till plain interspersed with lake plains and dominated by soils in the Mollisol and Vertisol orders. These soils are very productive and generally are well-suited to dryland farming. Much of this area is aridic-ustic. Crop-fallow dryland wheat farming is the predominant land use. Areas of rangeland typically are on steep hillslopes along drainages.
The rangeland, much of which is native mixedgrass prairie, increases in abundance in the eastern half of the MLRA. The Wisconsin-age till in the north-central part of this area typically formed large disintegration moraines with steep slopes and numerous poorly drained potholes. A large portion of Wisconsin-age till occuring on the type of the level terrain that would typically be optimal for farming has large amounts of less-suitable sodium-affected Natrustalfs. Significant portions of Blaine, Phillips, and Valley Counties were glaciated approximately 150,000 years ago during the Illinoisan age. Due to erosion and dissection of the landscape, many of these areas have steeper slopes and more exposed bedrock than areas glaciated during the Wisconsin age (Fullerton and Colton, 1986).
While much of the rangeland in the aridic-ustic portion of MLRA 52 is classified as belonging to the “dry grassland” climatic zone, sites in portions of southern MLRA 52 may belong to the “dry shrubland” climatic zone. The dry shrubland zone represents the northern-most extent of the big sagebrush (Artemisia tridentata) steppe on the Great Plains. Because similar soils occur in both southern and northern portions of the MLRA, it is currently hypothesized that climate is the primary driving factor affecting big sagebrush distribution in this area. However the precise factors are not fully understood at this time.
Sizeable tracts of largely unbroken rangeland in the eastern half of the MLRA and adjacent southern Saskatchewan are home to the northern Montana population of greater sage-grouse (Centrocercus urophasianus), and large portions of this area are considered to be a Priority Area for Conservation (PAC) by the U.S. Fish and Wildlife Service (U.S. Fish and Wildlife Service, 2013). This population is unique among sage grouse populations because many individuals overwinter in the big sagebrush steppe (dry shrubland) in the southern portion of the MLRA and then migrate to the northern portion of the MLRA, which lacks big sagebrush (dry grassland), to live the rest of the year (Smith, 2013).
Areas of the till plain near the Bearpaw and Highwood Mountains as well as the Sweetgrass Hills and Rocky Mountain foothills are at higher elevations, receive higher amounts of precipitation, and have a typic-ustic moisture regime. These areas have significantly more rangeland production than the drier aridic-ustic portions of the MLRA and have enough moisture to produce crops annually rather than just bi-annually, as in the drier areas. Ecological sites in this higher precipitation area are classified as the moist grassland climatic zone.
Classification relationships
NRCS Soil Geography Hierarchy
• Land Resource Region: Northern Great Plains
• Major Land Resource Area (MLRA): 052 Brown Glaciated Plains
• Climate Zone: N/A
National Hierarchical Framework of Ecological Units (Cleland et al., 1997; McNab et al., 2007)
• Domain: Dry
• Division: Temperate Steppe
• Province: Great Plains-Palouse Dry Steppe Province 331
• Section: Northwestern Glaciated Plains 331D
• Subsection: Montana Glaciated Plains 331Dh
• Landtype association/Landtype phase: N/A
National Vegetation Classification Standard (Federal Geographic Data Committee, 2008)
• Class: Mesomorphic Shrub and Herb Vegetation Class (2)
• Subclass: Shrub and Herb Wetland Subclass (2.C)
• Formation: Salt Marsh Formation (2.C.5)
• Division: Distichlis spicata - Hordeum jubatum Great Plains Saline Marsh Division (2.C.5.Na)
• Macrogroup: Great Plains Saline Wet Meadow and Marsh Macrogroup (2.C.5.Na.1)
• Group: Distichlis spicata - Hordeum jubatum - Pascopyrum smithii Great Plains Saline Wet Meadow and Marsh Group (2.C.5.Na.1.a)
• Alliance: Distichlis spicata - Hordeum jubatum Wet Meadow Alliance
• Association: Distichlis spicata - Hordeum jubatum - Puccinellia nuttalliana - Suaeda calceoliformis Wet Meadow
USFWS (Cowardin et al., 1979)
• Palustrine Emergent Temporarily Flooded and Palustrine Emergent Seasonally Flooded
Classification of natural ponds and lakes in the Glaciated Prairie Region (Stewart and Kantrud, 1971)
• Ephemeral Pond, Temporary Pond, and Seasonal Pond
Ecological site concept
This provisional ecological site occurs in all climatic zones of MLRA 52. Figure 1 illustrates the distribution of closed depression ecological sites based on current data. Current mapping does not consistently differentiate between discharge and recharge closed depressions, therefore this map will require future revision. Discharge Closed Depression is an extensive ecological site occurring throughout MLRA 52. It occurs in depressions on till plains and moraines. The ponding duration is typically temporary or seasonal, however, it is highly variable depending on catchment size and annual precipitation. The Discharge Closed Depression ecological site is typically saline.
The distinguishing characteristics of this ecological site are that it is located in closed depression landforms, receives groundwater discharge as well as surface runoff from adjacent uplands, and contains hydric soils. Soils for this ecological site are typically very deep (more than 60 inches) and are derived from alluvium. Soil textures in the upper 4 inches are typically silt loam, clay loam, or clay. Soils are primarily endosaturated, have slow permeability rates, and exhibit ponding following runoff events (USDA-NRCS, 2016). Characteristic vegetation is western wheatgrass (Pascopyrum smithii), inland saltgrass (Distichlis spicata), and foxtail barley (Hordeum jubatum).
Associated sites
R052XY062MT |
Swale (Se) Dry Grassland The Swale ecological site is in upland coulees and swales. It is typically upslope from the Discharge Closed Depression ecological site on till plains and moraines. It contributes surface water to the Discharge Closed Depression ecological site. |
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R052XY730MT |
Swale (Se) Dry Shrubland The Swale ecological site is in upland coulees and swales. It is typically upslope from the Discharge Closed Depression ecological site on till plains and moraines. It contributes surface water to the Discharge Closed Depression ecological site. |
R052XY754MT |
Swale (Se) Moist Grassland The Swale ecological site is in upland coulees and swales. It is typically upslope from the Discharge Closed Depression ecological site on till plains and moraines. It contributes surface water to the Discharge Closed Depression ecological site. |
R052XY740MT |
Loamy (Lo) Moist Grassland The Loamy ecological site is in uplands surrounding the Discharge Closed Depression ecological site on till plains and moraines. It contributes surface water to the Discharge Closed Depression ecological site. |
R052XY032MT |
Loamy (Lo) Dry Grassland The Loamy ecological site is in uplands surrounding the Discharge Closed Depression ecological site on till plains and moraines. It contributes surface water to the Discharge Closed Depression ecological site. |
R052XY712MT |
Loamy (Lo) Dry Shrubland The Loamy ecological site is in uplands surrounding the Discharge Closed Depression ecological site on till plains and moraines. It contributes surface water to the Discharge Closed Depression ecological site. |
R052XY741MT |
Loamy-Steep (Lostp) Moist Grassland The Loamy Steep ecological site is on slopes greater than 15 percent surrounding the Discharge Closed Depression ecological site on till plains and moraines. It contributes surface water to the Discharge Closed Depression ecological site. |
R052XY040MT |
Loamy-Steep (Lostp) Dry Grassland The Loamy Steep ecological site is on slopes greater than 15 percent surrounding the Discharge Closed Depression ecological site on till plains and moraines. It contributes surface water to the Discharge Closed Depression ecological site. |
R052XY714MT |
Loamy-Steep (Lostp) Dry Shrubland The Loamy Steep ecological site is on slopes greater than 15 percent surrounding the Discharge Closed Depression ecological site on till plains and moraines. It contributes surface water to the Discharge Closed Depression ecological site. |
R052XY071MT |
Recharge Closed Depression (Cdr) The Recharge Closed Depression ecological site is on similar landforms as the Discharge Closed Depression ecological site. It typically is found in higher topographic positions and is the primary source of groundwater for the Discharge Closed Depression ecological site. |
Similar sites
R052XY084MT |
Slough (Sl) The Slough ecological site is on flood plains, usually in oxbows or channels where flooding is very frequent and a water table is shallow and persistant. Its hydroperiod is typically much longer than that of the Discharge Closed Depression ecological site. This site typically contains deep marsh vegetation. |
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R052XY060MT |
Overflow (Ov) The Overflow ecological site is on flood plains, usually on higher terraces that receive additional moisture from runoff and stream overflow. Vegetation is dominated by facultative upland species. |
R052XY071MT |
Recharge Closed Depression (Cdr) The Recharge Closed Depression ecological site differs from the Discharge Closed Depression ecological site in that it receives its moisture primarily from surface runoff rather than groundwater discharge. Water and soils are typically non-saline and vegetation is more diverse. A wide variety of sedges, spikerushes, and grasses are present. |
Table 1. Dominant plant species
Tree |
Not specified |
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Shrub |
Not specified |
Herbaceous |
Not specified |
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