Natural Resources
Conservation Service
Ecological site R058AY711MT
Overflow 10-14
Last updated: 8/29/2024
Accessed: 11/21/2024
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: Mesomorphic Shrub and Herb Vegetation Class (2)
• Subclass: Temperate and Boreal Grassland and Shrubland Subclass (2.B)
• Formation: Temperate Grassland, Meadow, and Shrubland Formation (2.B.2)
• Division: Great Plains Grassland and Shrubland Division (2.b.2.Nb)
• Macrogroup: Hesperostipa comata – Pascopyrum smithii – Festuca hallii Grassland Macrogroup (2.B.2.Nb.2)
• Group: Pascopyrum smithii – Hesperostipa comata – Schizachyrium scoparium Mixedgrass Prairie Group (2.B.2.Nb.2.c)
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 on terraces or alluvial fans on floodplains and receives additional moisture from flooding or run-in, at elevations ranging from 1,900 to 3,500 feet, and on slopes ranging from 0 to 5 percent. The streams associated with this site are generally intermittent or perennial. This site occurs on all aspects, although aspect is not a significant factor. The soils of this ecological site are deep to very deep and are well drained. The soil textures on this site typically range from fine sandy loam to silty clay loam but can have a wide variation since these soils typically result from water deposition.
Associated sites
R058AY738MT |
Subirrigated 10-19 The Subirrigated ecological site is adjacent to the Overflow ecological site, typically on lower terraces where ground water is closer to the surface and contributes significantly to site production. |
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R058AY713MT |
Saline Overflow 10-14 The Saline Overflow ecological site is adjacent to the Overflow ecological site in similar landscape positions but in areas where salts have accumulated due to geology, hydrology, or soil properties. |
R058AY736MT |
Riparian Woodland 10-19 The Riparian Woodland ecological site is adjacent to the Overflow ecological site, typically on lower terraces where flooding is more frequent and riparian woody plants are dominant. |
Similar sites
R058AY720MT |
Swale 10-14 This site differs from the Overflow ecological site in that it does not receive additional moisture from stream overflow but gets run-in from above. It is located in upland swales rather than on floodplains. |
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R058AY736MT |
Riparian Woodland 10-19 This site differs from the Overflow ecological site in that it occupies lower terraces and is dominated by riparian woody species. Shrubs and trees dominate the site in terms of cover and production. |
R058AY738MT |
Subirrigated 10-19 This site differs from the Overflow ecological site in that it occupies lower terraces. It receives additional moisture primarily from ground water whereas the Overflow ecological site receives it from surface water. Depth to a water table is 24 to 40 inches. |
R058AY713MT |
Saline Overflow 10-14 This site differs from the Overflow ecological site in that soils are saline, sodic, or saline-sodic (EC ≥ 4 or SAR ≥ 13). |
Table 1. Dominant plant species
Tree |
Not specified |
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Shrub |
(1) Artemisia cana |
Herbaceous |
(1) Pascopyrum smithii |
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 or non-native hayland (frequently combined with irrigation practices) |
T2A | - | Tillage or herbicide application and seeding of annual crops or non-native hayland (frequently combined with irrigation practices) |
T3A | - | Cessation of cultivation |
T4A | - | Tillage or herbicide application and seeding of annual crops or non-native hayland (frequently combined with irrigation practices) |
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 |