Ecological site R044BP808MT

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.

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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): 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 Saline or Sodic (EC>7 or SAR>12 with surface 18cm)
o Typically less than 5% stone and boulder cover (<15% max)
• Soil surface texture variable with 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, stream terrace
• Parent material is tertiary valley fill and recent alluvium
• Moisture Regime: ustic
• Temperature Regime: frigid
• Dominant Cover: rangeland-shrubland
• Elevation Range: 3800-5800
• Slope Range: 1-15%

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Sarcobatus vermiculatus (2) Artemisia tridentata ssp. wyomingensis
Herbaceous	(1) Leymus cinereus (2) Distichlis spicata

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Physiographic features

Table 2. Representative physiographic features

Landforms	(1) Valley > Fan remnant (2) Valley > Eroded fan remnant
Elevation	3,800 – 6,800 ft
Slope	10%

Climatic features

Table 3. Representative climatic features

Frost-free period (characteristic range)	23-79 days
Freeze-free period (characteristic range)	65-112 days
Precipitation total (characteristic range)	11-13 in
Frost-free period (actual range)	6-94 days
Freeze-free period (actual range)	27-130 days
Precipitation total (actual range)	11-14 in
Frost-free period (average)	54 days
Freeze-free period (average)	90 days
Precipitation total (average)	12 in

Characteristic range

Actual range

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Figure 2. Monthly precipitation range

Characteristic range

Actual range

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Figure 3. Monthly minimum temperature range

Characteristic range

Actual range

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Figure 4. Monthly maximum temperature range

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Figure 5. Monthly average minimum and maximum temperature

Figure 6. Annual precipitation pattern

Figure 7. Annual average temperature pattern

Climate stations used

(1) WHITE SULPHUR SPRNGS 2 [USC00248930], White Sulphur Springs, MT
(2) WISDOM [USC00249067], Wisdom, MT
(3) HELENA RGNL AP [USW00024144], Helena, MT
(4) DEER LODGE 3 W [USC00242275], Deer Lodge, MT
(5) DILLON AP [USW00024138], Dillon, MT
(6) LIVINGSTON MISSION FLD [USW00024150], Livingston, MT

Soil features

Table 4. Representative soil features

Parent material	(1) Alluvium (2) Valley side alluvium
Surface fragment cover >3"	5%

Ecological dynamics

1.1 Basin wildrye, western wheatgrass, and alkali sacaton dominant plants. Inland saltgrass and blue grama present as subordinate plants. Scarlet globemallow, hoods phlox, and Chenopods common forbs. Greasewood and Big sagebrush dominant shrubs. Saltbush and winterfat present Bare ground is typically naturally high.
1.1a extended drought, improper grazing, climate change
1.2 Western wheatgrass and Alakali sacaton remain dominant, Mid-statured decreaser bunchgrasses will be rare. Saltgrass and other shortgrasses increasing. Large shrub production remains similar to 1.1 however subshrubs like broom snakeweed and fringed sagewort increase while winterfat is rare. Bare ground remains high
1.2a proper grazing management, favorable growing conditions, time

2.1 Shortgrass dominated (Saltgrass, Alkali (Sandberg) bluegrass). Forbs remain a small component of community. Saltbush takes on a prostrate growing form, winterfat removed from community, pricklypear cactus common. Large gaps between sagebrush and greasewood bases. Possible salt crusting on soil surface. Waterflow patterns and pedestalling frequent.
T1A poor grazing, drought with improper grazing, multiple spring grazing events,
R1A proper grazing management, favorable growing conditions, time, tree/shrub establishment

3.1 Subshrubs and shortgrasses share dominance. Forbs particularly Chenopods (namely sumpweed) common, Cheatgrass invades. Cactus common. Black greasewood takes over dominant large shrub component.
T1B introduction of invasive plants, multiple/frequent overgrazing events, drought
T2A overgrazing, introduction of weeds, drought, heavy human disturbance, conversion to introduced species
R2A fire, range seeding, timely moisture, proper grazing management, IPM
R3A IPM, range seeding, timely moisture, grazing management, brush management, range seeding, tree/shrub establishment

State and transition model

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Rangeland health reference sheet

Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.

Author(s)/participant(s)
Contact for lead author
Date	03/08/2024
Approved by	Kirt Walstad
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
Presence of water flow patterns:
Number and height of erosional pedestals or terracettes:
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Number of gullies and erosion associated with gullies:
Extent of wind scoured, blowouts and/or depositional areas:
Amount of litter movement (describe size and distance expected to travel):
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):

Dominant:

Sub-dominant:

Other:

Additional:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Average percent litter cover (%) and depth ( in):
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
Perennial plant reproductive capability:

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Natural ResourcesConservation Service

Ecological site R044BP808MT

Saline-Sodic Sagebrush Shrubland

Last updated: 3/08/2024 Accessed: 12/21/2024

General information

Figure 1. Mapped extent

MLRA notes

Ecological site concept

Table 1. Dominant plant species

Natural Resources
Conservation Service

Last updated: 3/08/2024
Accessed: 12/21/2024