Natural Resources
Conservation Service
Ecological site R058AY720MT
Swale 10-14
Last updated: 8/29/2024
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): 058A–Northern Rolling High Plains, Northern Part
MLRA 058A, Northern Rolling High Plains (Northern Part), is an expansive and agriculturally and ecologically significant area encompassing 26 counties in southeast Montana (99 percent) and northeast Wyoming (1 percent). It stretches approximately 290 miles from east to west and 220 miles from north to south and comprises approximately 42,350 square miles (26,875,928 acres). The area is within the Missouri Plateau, Unglaciated, Section of the Great Plains Province of the Interior Plains. It is an area of old plateaus and terraces that have been eroded. Slopes generally are gently rolling to steep, and wide belts of steeply sloping badlands border a few of the larger river valleys. In some areas flat-topped, steep-sided buttes rise sharply above the general level of the plains. Elevations generally range from 1,950 to 3,280 feet, increasing from east to west and from north to south.
Tertiary continental shale, siltstone, and sandstone of the Fort Union Formation underlie the eastern one-third to one-half of this area. Marine and continental sediments of the Cretaceous Montana Group underlie the rest of the MLRA, generally at the higher elevations. There are also younger Cretaceous sediments of the Livingston Group occurring between the higher elevation Montana Group sediments and the lower elevation Tertiary sediments. The dominant soil orders in MLRA 058A are Entisols and Inceptisols. The soils in the area dominantly have a frigid soil temperature regime, an ustic soil moisture regime, and mixed or smectitic mineralogy. They range from shallow to very deep and are generally well drained and clayey or loamy.
The area primarily supports native prairie vegetation characterized by a variety of cool-season and warm-season graminoids, forbs, and shrubs. In the western portion of the area, cool-season grasses such as western wheatgrass and bluebunch wheatgrass are dominant but, in the eastern portion of the area, warm-season grasses such as little bluestem and sideoats grama become dominant. Wyoming big sagebrush, silver sagebrush, and fringed sagewort are common shrub species throughout the area. Forested areas occur in rough hilly areas and river breaks, particularly in areas with higher precipitation. Common tree species are ponderosa pine and Rocky Mountain juniper with scattered pockets of Douglas fir.
More than 75 percent of this MLRA is native rangeland utilized for livestock production and more than 50 percent of the MLRA consists of privately-owned ranches. Approximately 15 percent of the MLRA is used as cropland. Other land uses including forestland, urban development, water, and other uses combine for less than 10 percent of the total land use.
Classification relationships
NRCS Soil Geography Hierarchy
• Land Resource Region: Western Great Plains
• Major Land Resource Area (MLRA): 058A Northern Rolling High Plains, Northern Part
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: North Central Highlands (331K) and Powder River Basin (331G)
National Vegetation Classification Standard (Federal Geographic Data Committee, 2008)
• Class: Xeromorphic Woodland, Scrub and Herb Vegetation Class (3)
• Subclass: Cool Semi-Desert Scrub and Grassland Subclass (3.B)
• Formation: Cool Semi-Desert Scrub and Grassland Formation (3.B.1)
• Division: Cool Semi-Desert Scrub and Grassland Division (3.B.1.Ne)
• Macrogroup: Artemisia tridentata - Artemisia tripartita ssp. tripartita - Purshia tridentata Steppe and Shrubland Macrogroup (3.B.1.Ne.3)
• Group: Artemisia tridentata ssp. wyomingensis - Artemisia tridentata ssp. tridentata Steppe and Shrubland Group (3.B.1.Ne.3.a)
EPA Ecoregions
• Level 1: Great Plains (9)
• Level 2: West-Central Semi-Arid Prairies (9.3)
• Level 3: Northwestern Great Plains (9.3.3)
• Level 4: Montana Central Grasslands (43n), River Breaks (43c), and Pine Scoria Hills (43p)
Ecological site concept
This ecological site occurs in concave positions such as swales where it receives extra moisture through run off from adjacent areas. The slopes typically range from 0 to 5 percent. This site occurs on all aspects, although aspect is not a significant factor. The soils of this ecological site are moderately deep to very deep and are well drained. The soil textures are typically loam, sandy loam, or fine sandy loam.
Associated sites
R058AY710MT |
Loamy Steep 10-14 This site occurs on moderate to steeply sloping hillslopes adjacent to and upslope from the Swale ecological site. It occurs in lower backslope positions where slopes are 15 percent or greater and depth to bedrock is greater than 20 inches. |
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R058AY708MT |
Loamy 10-14 This site occurs on nearly level to gently sloping uplands that are adjacent to and surrounding from the Swale ecological site. It occurs on footslope, or summit positions and on higher microtopography than the Swale ecological site. |
Similar sites
R058AY708MT |
Loamy 10-14 This site differs from the Swale ecological site in that this site does not receive additional moisture from surface water run in. Plant community is far less productive and contains fewer forbs and shrubs. |
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R058AY715MT |
Sandy 10-14 This site differs from the Swale ecological site in that this site does not receive additional moisture from surface water run in. Plant community is far less productive and contains fewer forbs and shrubs. |
R058AY711MT |
Overflow 10-14 This site differs from the Swale ecological site in that it is on flood plains rather than upland swales. It generally is on stream terraces adjacent to a perennial stream and in some areas has a water table greater than 40 inches below the soil surface. |
Figure 1. Similar and Associated Sites Diagram
Table 1. Dominant plant species
Tree |
Not specified |
---|---|
Shrub |
(1) Artemisia cana |
Herbaceous |
(1) Nassella viridula |
Click on box and path labels to scroll to the respective text.
Ecosystem states
T1A | - | Introduction of invasive species (non-native perennial grasses, noxious weeds, etc.) |
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T1B | - | Tillage or herbicide application and seeding of annual crops. |
T2A | - | Tillage or herbicide application and seeding of annual crops. |
T3A | - | Cessation of cultivation (frequently in conjunction with earthmoving or land smoothing). |
T4A | - | Tillage or herbicide application and seeding of annual crops |
State 1 submodel, plant communities
1.1A | - | Drought, improper grazing management |
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1.2A | - | Normal or above-normal spring moisture, proper grazing management |
1.2B | - | Prolonged drought, continued improper grazing, or a combination of these factors |
1.3A | - | Normal or above-normal spring moisture, proper grazing management |