Natural Resources
Conservation Service
Ecological site R060BE570MT
Overflow 10-14
Last updated: 8/27/2024
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.
Figure 1. Mapped extent
Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.
MLRA notes
Major Land Resource Area (MLRA): 060B–Pierre Shale Plains, Northern Part
MLRA 060B, Pierre Shale Plains (Northern Part), is almost entirely in Montana (94 percent) and Wyoming (6 percent). The area makes up about 2,160,000 acres and occurs in the uplands between most of the major rivers in southeastern Montana and northeastern Wyoming. 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 deeply eroded.
The shale plains have long, smooth, gentle to strong slopes. Slopes along drainageways and streams are moderately steep or steep. Elevation ranges from 1,900 to 3,500 feet on uplands. Marine and continental sediments of the Cretaceous Montana Group underlie most of this MLRA.
The average annual precipitation in the area is 14 inches and ranges from 11 to 17 inches. Most of the annual precipitation occurs as high-intensity, convective thunderstorms during the growing season. Precipitation in winter occurs mainly as snow, which usually is accompanied by high winds that cause much drifting.
The average annual temperature is 43 to 46 degrees Fahrenheit. The freeze-free period averages 142 days and ranges from 130 to 160 days. The frost-free period averages 120 days and ranges from 110 to 135 days.
The dominant soil orders in this MLRA are Alfisols, Entisols, and Vertisols. The soils in the area dominantly have a frigid soil temperature regime, an ustic soil moisture regime, and smectitic mineralogy. The soils are shallow to very deep, generally well drained, and clayey.
The area supports native prairie vegetation characterized by a diversity of cool-season and warm-season grasses, sedges, forbs, and shrubs. A majority of this area is in farms or ranches and comprised of rangeland used for livestock grazing. Some small areas of nearly level to moderately sloping soils are used for winter wheat or for livestock feed crops.
Classification relationships
NRCS Soil Geography Hierarchy
• Land Resource Region: Western Great Plains
• Major Land Resource Area (MLRA): 060B Pierre Shale 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 Missouri Plateau Section (331M)
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 & 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: Sagebrush Steppe (43e)
Ecological site concept
This ecological site occurs in swales and drainageways and on stream terraces where it receives additional moisture from flooding or run-in from adjacent areas. The streams associated with this site are ephemeral, meaning they flow only in direct response to a precipitation event or snow melt. This site occurs at elevations ranging from 1,900 to 3,500 feet and on slopes ranging 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 deep to very deep and are well drained. The soil surface 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
R060BE566MT |
Clayey 10-14 The Clayey ecological site occurs on slopes of 0 to 15 percent, has soils with greater than 35 percent clay content, and has lower total annual production. The Clayey ecological site is positioned above the Overflow ecological site. The Clayey ecological site does not receive additional moisture from flooding or run-in from adjacent areas. |
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R060BE579MT |
Loamy 10-14 The Loamy ecological site occurs on slopes of 0 to 15 percent and has lower total annual production. The Loamy ecological site is positioned above the Overflow ecological site. The Loamy ecological site does not receive additional moisture from flooding or run-in from adjacent areas. |
R060BE583MT |
Clayey Steep 10-14 The Clayey Steep ecological site occurs on slopes of 15 to 45 percent, has greater than 35 percent clay content, and has lower total annual production. The Clayey Steep ecological site is positioned above the Overflow ecological site. The Clayey Steep ecological site does not receive additional moisture from flooding or run-in from adjacent areas. |
Similar sites
R060BE571MT |
Saline Lowland 10-14 The Saline Lowland ecological site occurs on similar slopes and landform positions and has similar total annual production as the Overflow ecological site, but the Saline Lowland ecological site is dominated by salt tolerant species. The Saline Lowland ecological site does not receive additional moisture from flooding or run-in from adjacent areas. |
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Table 1. Dominant plant species
Tree |
Not specified |
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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 non-native invasive species (annual bromes, non-native perennial grasses, noxious weeds) |
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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 |