Natural Resources
Conservation Service
Ecological site R044BP812MT
Shallow Shrubland
Last updated: 8/26/2019
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): 044B–Central Rocky Mountain Valleys
44B Central Rocky Mountain Valleys
Major Land Resource Area (MLRA) 44B, Central Rocky Mountain Valleys, is nearly 3.7 million acres of Southwest Montana. This MLRA borders 2 MLRAs: 43B Central Rocky Mountains and Foothills, and MLRA 46 Northern and Central Rocky Mountain Foothills.
The major watersheds of this MLRA are the Missouri and Yellowstone Rivers along with their associated headwaters such as the Beaverhead, Big Hole, Jefferson, Ruby, Madison, Gallatin, and Shields Rivers. Limited portions of the MLRA are west of the Continental Divide along the Clark Fork River. These waters allow for extensive irrigation for crop production in an area that would generally be only compatible with rangeland and grazing. The Missouri River and its headwaters are contained behind several reservoirs used for irrigation water, hydroelectric power, and municipal water.
The primary land use of this MLRA is production agriculture (grazing, small grain production, and hay) with limited mining. Urban Development is also high.
MRLA 44B consists of 7 Climate based Land Resource Units (LRUs). Annual precipitation ranges from a low of 9” to a high near 24”. The driest areas tend to be in the valley bottoms of southwest Montana in the rain shadow of the mountains. The wettest areas tend to be near the edges of the MLRA where it borders with MLRA 43B. Frost Free periods also vary greatly with from less than 30 days in the Big Hole Valley to approximately 110 days in the warm valleys along the Yellowstone River and Missouri River Headwaters.
MLRA 44B’s plant communities are highly variable however are dominated by a cool season grass and shrub steppe community on the rangeland and a mixed coniferous forest in the mountains. Warm season grasses occupy an extremely limited extent in this MLRA. Most subspecies of Big Sagebrush are present, to some extent, across the MLRA.
Ecological site concept
• Site does not receive any additional water
• Soils are
o Not saline or saline-sodic
o Not strongly or violently effervescent (CaCO3 >14%) in surface mineral 18cm
o Shallow depth (less than 50cm (20 in) to bedrock, lithic, or paralithic root restrictive layer
o Less than 5% stone and boulder cover (<15% max)
• Soil surface texture ranges from sandy loam to clay loam in surface mineral 4”
• An area of dissected mountain valleys. The valleys are typically bordered by mountains trending north to south.
• Site Landform: hillslopes, buttes, escarpment
• Parent material is typically colluvium and/or residuum
• Moisture Regime: ustic
• Temperature Regime: frigid to cryic
• Dominant Cover: rangeland (grass dominated)
• Elevation Range: 3800-6850 (Representative Range 4500-6000)
• Slope range: 0-60 (often less than 45%)
Table 1. Dominant plant species
Tree |
Not specified |
---|---|
Shrub |
(1) Symphoricarpos albus |
Herbaceous |
(1) Pseudoroegneria spicata |
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