Natural Resources
Conservation Service
Ecological site FX053A99X060
Overflow (Ov)
Last updated: 11/22/2023
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): 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, 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 – Bouteloua spp. 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 Glaciated Plains (42)
• Level 4: Glaciated Dark Brown Prairie (42i)
Glaciated Northern Grasslands (42j)
Montana Riparian and Wetland Sites (Hansen et. al, 1995)
• Artemisia cana/Agropyron smithii Habitat Type
Ecological site concept
Overflow is a common ecological site occurring on flood plains and stream terraces. The distinguishing characteristics of this site are that it is located on flood plains and that it receives additional moisture from flooding and surface water runoff. Sometimes, but not always, a seasonal water table is present at a depth of more than 40 inches below the soil surface, especially during peak runoff periods. Soils for this ecological site are typically very deep (more than 60 inches), well drained, and derived from alluvium. Characteristic vegetation is green needlegrass (Nassella viridula), western wheatgrass (Pascopyrum smithii), silver sagebrush (Artemisia cana), and, in some cases, snowberry (Symphoricarpos spp.).
Associated sites
FX053A99X061 |
Riparian Woodland (RW) The Riparian Woodland site is adjacent to the Overflow site, typically on lower terraces where flooding is more frequent and riparian woody plants are dominant. |
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FX053A99X150 |
Subirrigated (Sb) The Subirrigated site is adjacent to the Overflow site, typically on lower terraces where ground water is closer to the surface and contributes significantly to site production. |
FX053A99X084 |
Slough (Sl) The Slough site is adjacent to the Overflow site, typically in oxbows or channels where flooding is very frequent and a water table is shallow and persistant. |
FX053A99X713 |
Saline Lowland (SLL) The Saline Lowland site is adjacent to the Overflow site in similar landscape positions but in areas where salts have accumulated due to geology, hydrology, or soil properties. |
Similar sites
FX053A99X713 |
Saline Lowland (SLL) This site differs from the Overflow site in that soils are saline, sodic, or saline-sodic (EC ≥ 4 or SAR ≥ 13). It supports more sodium-tolerant vegetation and is less productive. |
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FX053A99X061 |
Riparian Woodland (RW) This site differs from the Overflow 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. |
FX053A99X062 |
Swale (Se) This site differs from the Overflow 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, is slightly less productive, and has a higher proportion of mid-statured bunchgrasses than the Overflow site. |
FX053A99X150 |
Subirrigated (Sb) This site differs from the Overflow site in that it occupies lower terraces. It receives additional moisture primarily from ground water whereas the Overflow site receives it from surface water. Depth to a water table is 24 to 40 inches. |
Table 1. Dominant plant species
Tree |
Not specified |
---|---|
Shrub |
(1) Artemisia cana |
Herbaceous |
(1) Pascopyrum smithii |
Legacy ID
R053AY709MT
Click on box and path labels to scroll to the respective text.
Ecosystem states
T1A | - | Introduction of non-native grass species, such as Kentucky bluegrass, smooth brome, and crested wheatgrass. |
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T2A | - | Displacement of native species by non-native invasive species (Kentucky bluegrass, smooth brome, noxious weeds, etc.) |
T2B | - | Conversion to cropland |
T3A | - | Conversion to cropland |
T4A | - | Cessation of annual cropping |
T5A | - | 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 |
P2.2b | - | Prolonged drought, improper grazing management, or a combination of these factors. |
P2.3a | - | Normal or above-normal spring moisture, proper grazing management. |