Natural Resources
Conservation Service
Ecological site R052XC210MT
Saline Upland (SU) 10-14" p.z.
Last updated: 1/24/2024
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). The bedrock 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 mixed-grass 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 occurring on the type of 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 climatic zone represents the northernmost 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.
Ecological site concept
Saline Upland is an ecological site of limited extent occurring on fans, fan aprons, and terraces in MLRA 52. The distinguishing characteristic of this site is that saline, sodic, or saline-sodic conditions are evident in the upper 20 inches of soil. Soils for this ecological site are typically very deep (more than 60 inches), well drained, and derived from clayey alluvium or outwash deposits. Characteristic vegetation is western wheatgrass (Pascopyrum smithii), alkali sacaton (Sporobolus airoides), Nuttall’s saltbush (Atriplex nuttallii).
Associated sites
R052XC205MT |
Clayey (Cy) 10-14" p.z. soils >20 inches in depth, higher production, and no hardpan, different species composition |
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R052XC216MT |
Shallow to Gravel (SwGr) 10-14" p.z. similar position in landscape, soils with depth restriction that limits available moisture, soils 10-20” deep to sands or loamy sands |
R052XC215MT |
Shallow Clay (SwC) 10-14" p.z. soils 10-20” deep to bedrock’ soils are clayey over clayey shale |
R052XC204MT |
Claypan (Cp) 10-14" p.z. has 2-8” of soil over the hard argillic layer, less bare ground, and higher production |
R052XC206MT |
Dense Clay (DC) 10-14" p.z. has a hard restrictive layer in the soil at or near the surface, salt tolerant plants may be present but are rarely dominant |
Similar sites
R052XN170MT |
Saline Upland (SU) 10-14" p.z. R053AE071MT, same concept different climate and potential. |
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Table 1. Dominant plant species
Tree |
Not specified |
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Shrub |
(1) Atriplex nuttallii |
Herbaceous |
(1) Pascopyrum smithii |
Click on box and path labels to scroll to the respective text.
Ecosystem states
T1A | - | Extended drought (>7 years), non-prescribed grazing, no fire |
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R2A | - | Prescribed grazing, fire, favorable precipitation |
T2A | - | Prolonged drought (5-7 years), non-prescribed grazing, no fire |
R3A | - | Fire, prescribed grazing |
State 1 submodel, plant communities
1.1a | - | No fire, non-prescribed grazing, drought (3-5 years) |
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1.2a | - | Fire, prescribed grazing |