Natural Resources
Conservation Service
Ecological site R053AY722MT
Thin Claypan (TCp)
Last updated: 11/22/2023
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): 053A–Northern Dark Brown Glaciated Plains
The Northern Dark Brown Glaciated Plains, MLRA 53A, is a large, agriculturally and ecologically significant area. It consists of approximately 6.1 million acres and stretches 140 miles from east to west and 120 miles from north to south, encompassing portions of 8 counties in northeastern Montana and northwestern North Dakota. This region represents part of the southern edge of the Laurentide Ice Sheet during maximum glaciation. It is one of the driest and westernmost areas within the vast network of glacially derived prairie pothole landforms of the Northern Great Plains and falls roughly between the Missouri Coteau to the east and the Brown Glaciated Plains to the west. Elevation ranges from 1,800 feet (550 meters) to 3,300 feet (1,005 meters).
Soils are primarily Mollisols, but Inceptisols and Entisols 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 (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 in glacial outwash channels and along major drainages, including portions of the Missouri, Poplar, and Big Muddy Rivers. Large eolian deposits of sand occur in the vicinity of the ancestral Missouri River channel east of Medicine Lake (Fullerton et al., 2004). The northwestern portion of the MLRA contains a large unglaciated area containing paleoterraces and large deposits of sand and gravel known as the Flaxville gravel.
Much of this MLRA was glaciated towards the end of the Wisconsin age, and the maximum glacial extent occurred approximately 20,000 years ago (Fullerton and Colton, 1986; Fullerton et al., 2004). Subsequent erosion from major stream and river systems has created numerous drainageways throughout much of the MLRA. The result is a geologically young landscape that is predominantly a dissected till plain interspersed with alluvial deposits and dominated by soils in the Mollisol and Inceptisol orders. Much of this area is typic ustic, making these soils very productive and generally well suited to production agriculture.
Dryland farming is the predominant land use, and approximately 50 percent of the land area is used for cultivated crops. Winter, spring, and durum varieties of wheat are the major crops, with over 48 million bushels produced annually (USDA-NASS, 2017). Areas of rangeland typically are on steep hillslopes along drainages. The rangeland is mostly native mixed-grass prairie similar to the Stipa-Agropyron, Stipa-Bouteloua-Agropyron, and Stipa-Bouteloua faciations (Coupland, 1950, 1961). Cool-season grasses dominate and include rhizomatous wheatgrasses, needle and thread, western porcupine grass, and green needlegrass. Woody species are generally rare; however, many of the steeper drainages support stands of trees and shrubs, such as green ash and chokecherry. Seasonally ponded, prairie pothole wetlands may occur throughout the MLRA, but the greatest concentrations are in the east and northeast where receding glaciers stagnated and formed disintegration moraines with hummocky topography and numerous areas of poorly drained soils.
Classification relationships
NRCS Soil Geography Hierarchy
• Land Resource Region: Northern Great Plains
• Major Land Resource Area (MLRA): 053A Northern Dark Brown Glaciated Plains
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: Glaciated Northern Grasslands Section 331L
• Subsection: Glaciated Northern Grasslands Subsection 331La
• Landtype association/Landtype phase: N/A
National Vegetation Classification Standard (Federal Geographic Data Committee, 2008)
• Class: Mesomorphic Shrub and Herb Vegetation Class (2)
• Subclass: Temperate and Boreal Grassland and Shrubland Subclass (2.B)
• Formation: Temperate Grassland and Shrubland Formation (2.B.2)
• Division: Central North American and Shrubland Division (2.B.2.Nb)
• Macrogroup: Hesperostipa comata - Pascopyrum smithii - Festuca hallii Grassland Macrogroup (2.B.2.Nb.2)
o Group: Hesperostipa comata - Bouteloua gracilis Dry Mixedgrass Prairie Group (2.B.2.Nb.2.b)
EPA Ecoregions
• Level 1: Great Plains (9)
• Level 2: West-Central Semi-Arid Prairies (9.3)
• Level 3: Northwestern Glaciated Plains (42)
• Level 4: Glaciated Dark Brown Prairie (42i)
Glaciated Northern Grasslands (42j
Ecological site concept
Thin Claypan is an ecological site of limited extent site occurring on till plains, moraines, and fans in MLRA 53A. The distinguishing characteristic of this site is the presence of a dense, sodium-affected (natric) horizon 1 to 4 inches below the soil surface. The natric horizon exhibits columnar structure, is very hard, and severely limits both root penetration and infiltration. Soils for this ecological site are typically moderately deep to very deep (more than 20 inches to bedrock), well drained, and derived from till or glaciofluvial deposits. Characteristic vegetation is rhizomatous wheatgrasses and blue grama (Bouteloua gracilis).
Associated sites
R053AY706MT |
Loamy (Lo) This site occupies similar landscapes to the Thin Claypan ecological site. In the natric soils catena, Loamy is typically found on the highest microtopographic position; whereas, the Thin Claypan ecological site occupies mid or lower positions. |
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R053AY702MT |
Claypan (Cp) This site occupies similar landscapes to the Thin Claypan ecological site. In the natric soils catena, the Claypan ecological site is typically found in mid or upper level microtopographic positions; typically higher than Thin Claypan, but lower than Loamy. |
R053AY710MT |
Panspot (Pn) This site occupies similar landscapes to the Thin Claypan ecological site. In the natric soils catena, the Panspot ecological site is found on the lowest microtopographic position in the complex. |
Similar sites
R053AY706MT |
Loamy (Lo) This site differs from the Thin Claypan ecological site in that the root restricting layer (evidenced by columnar structure) is either absent or greater than 10 inches below the soil surface. Deep rooted bunchgrasses are a major component of the plant community. |
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R053AY702MT |
Claypan (Cp) This site differs from the Thin Claypan ecological site in that the root restricting layer (evidenced by columnar structure) is between 4 to 10 inches below the soil surface. Bunchgrasses occur but are not a major plant constituent of the plant community. |
R053AY710MT |
Panspot (Pn) This site differs from the Thin Claypan ecological site in that the root restricting layer (evidenced by columnar structure) is 1 inch or less below the soil surface. Commonly occurs in small depressions or pits on the landscape. |
Figure 1. Diagram of similar and associated sites
Table 1. Dominant plant species
Tree |
Not specified |
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Shrub |
Not specified |
Herbaceous |
(1) Pascopyrum smithii |
Click on box and path labels to scroll to the respective text.
Ecosystem states
States 2 and 5 (additional transitions)
T1A | - | Introduction of non-native grass species, such as crested wheatgrass and Kentucky bluegrass. |
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T2A | - | Prolonged drought, improper grazing management, or a combination of these factors |
T2B | - | Displacement of native species by non-native invasive species (crested wheatgrass, noxious weeds, etc.) |
T2C | - | Conversion to cropland |
R3A | - | Range seeding, grazing land mechanical treatment, timely moisture, proper grazing management (management intensive and costly) |
T3B | - | Conversion to cropland |
T4A | - | Conversion to cropland |
T5A | - | Cessation of annual cropping |
T6A | - | Conversion to cropland |
State 1 submodel, plant communities
State 2 submodel, plant communities
P2.1a | - | Drought, improper grazing management |
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P2.2a | - | Return to normal or above average precipitation, proper grazing management |