Natural Resources
Conservation Service

Ecological site R043BP815MT

Subirrigated Grassland Group

Last updated: 3/01/2024
Accessed: 11/21/2024

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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): 043B–Central Rocky Mountains

The Central Rocky Mountains (MLRA 43B) of Montana occupy some 28,850 square miles and exist primarily in Central and SW portions of the state. The climate is extremely variable with precipitation lows of 9 to 100 inches per year and frost free days of less than 30 to over 110 days. The geology of the region is also highly variable. The combination of variable climate and geology create a complex relationship of plant communities. MLRA 43B elevations typically exist between 6000 and 12,799ft at Granite Peak (the highest point in Montana).

The Continental Divide runs through this MLRA effectively splitting its watershed to contribute to either the Missouri River to the East and the Columbia River to the West.

Ecological site concept

• Site receives additional water
• This site occurs on low terraces adjacent to flood plains of perennial or intermittent streams (though not in the floodplain), near springs and seeps, or other areas having a permanent or perched water table.
• Moisture Regime: ustic to udic
• Temperature Regime: frigid to cryic
• Elevation Range: 3900-7200ft
• Soils are
o Not saline or saline-sodic
o Moderately deep, deep, or very deep
o Typically less than 5% stone and boulder cover (<10% max)
• Seasonal high water table within 40” (approx. 100cm) of soil surface.
• Area of rugged mountain, hills, plateaus, and valleys of the Central Rocky Mountains in Southwest Montana.
• Dominant Cover: rangeland (grass dominated)
• Slope: 0-8% (typically less than 4%)

Site Development and Testing Plan
This Provisional Ecological Site Description was developed to meet the criteria as defined in Soil Survey National Instruction part 306 (430-306-NI, April 2015) as interpreted by Regional Ecological Site Specialist. Information in this description are first approximations based on broad groupings of soil properties and vegetation characteristics associated with those groupings. Although this description has been through the quality control and quality assurance review process it has not been certified for use in conservation planning.

Associated sites

R043BP801MT	Bottomland Group Bottomland site is often a neighboring site which is closest to a stream or river. The Subirrigated Grassland will be the slightly drier site however still have a water table.
R043BP817MT	Subirrigated Shrubland Group Subirrigated Shrubland is a neighboring site and occupies the same landscape position. These two sites are often intermixed in a complex that can be hard to map separately.

R043BP801MT

Bottomland Group

Bottomland site is often a neighboring site which is closest to a stream or river. The Subirrigated Grassland will be the slightly drier site however still have a water table.

R043BP817MT

Subirrigated Shrubland Group

Subirrigated Shrubland is a neighboring site and occupies the same landscape position. These two sites are often intermixed in a complex that can be hard to map separately.

Similar sites

R043BP801MT	Bottomland Group Bottomland site is often a neighboring site which is closest to a stream or river. The Subirrigated Grassland will be the slightly drier site however still have a water table. The Bottomland site will express a canopy of deciduous trees and will have less soil development
R043BP817MT	Subirrigated Shrubland Group Subirrigated Shrubland is a neighboring site and occupies the same landscape position. These two sites are often intermixed in a complex that can be hard to map separately. The Subirrigated Shrubland expresses a high deciduous shrub component made primarily of willow species.

R043BP801MT

Bottomland Group

Bottomland site is often a neighboring site which is closest to a stream or river. The Subirrigated Grassland will be the slightly drier site however still have a water table. The Bottomland site will express a canopy of deciduous trees and will have less soil development

R043BP817MT

Subirrigated Shrubland Group

Subirrigated Shrubland is a neighboring site and occupies the same landscape position. These two sites are often intermixed in a complex that can be hard to map separately. The Subirrigated Shrubland expresses a high deciduous shrub component made primarily of willow species.

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Salix (2) Physocarpus malvaceus
Herbaceous	(1) Leymus cinereus (2) Deschampsia cespitosa

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Physiographic features

This site occurs on low terraces adjacent to flood plains of perennial or intermittent streams (though not in the floodplain), near springs and seeps, or other areas having a permanent or perched water table. Slopes are nearly level to 8 percent, but rarely exceed 4 percent.

Table 2. Representative physiographic features

Landforms	(1) Mountain valleys or canyons > Terrace
Flooding duration	Extremely brief (0.1 to 4 hours) to brief (2 to 7 days)
Flooding frequency	None to rare
Elevation	3,900 – 7,200 ft
Slope	8%
Water table depth	40 in
Aspect	Aspect is not a significant factor

Climatic features

This site has a variable climate that encompasses both ustic and udic soil moisture regimes as well as frigid to cryic soil temperature regimes. Relative Effective Annual Precipitation (REAP) is 10 to 40 inches with 20 to 90 frost-free days.

Table 3. Representative climatic features

Frost-free period (characteristic range)	19-68 days
Freeze-free period (characteristic range)	85-109 days
Precipitation total (characteristic range)	16-23 in
Frost-free period (actual range)	4-79 days
Freeze-free period (actual range)	51-116 days
Precipitation total (actual range)	13-27 in
Frost-free period (average)	42 days
Freeze-free period (average)	93 days
Precipitation total (average)	20 in

Characteristic range

Actual range

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Figure 1. Monthly precipitation range

Characteristic range

Actual range

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Figure 2. Monthly minimum temperature range

Characteristic range

Actual range

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Figure 3. Monthly maximum temperature range

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Figure 4. Monthly average minimum and maximum temperature

Figure 5. Annual precipitation pattern

Figure 6. Annual average temperature pattern

Climate stations used

(1) GIBSON DAM [USC00243489], Augusta, MT
(2) SEELEY LAKE RS [USC00247448], Bonner, MT
(3) POTOMAC [USC00246685], Bonner, MT
(4) SULA 14 NE [USC00247967], Sula, MT
(5) WISE RIVER 3 WNW [USC00249082], Wise River, MT
(6) HEBGEN DAM [USC00244038], West Yellowstone, MT
(7) RED LODGE [USC00246918], Red Lodge, MT
(8) MYSTIC LAKE [USC00245961], Fishtail, MT
(9) NEIHART 8 NNW [USC00246008], Monarch, MT
(10) MILLEGAN 14 SE [USC00245712], White Sulphur Springs, MT

Influencing water features

Site receives water from overflow as well as has a water table within 40 inches of the surface due to its location adjacent to streams, springs, and seeps.

Wetland description

Soils may or may not exhibit signs of redoximorphic processes due to soil texture as well as timing and duration of inundation

Soil features

Soils are moderately deep to deep with varying texture (stratified) due to occasional flooding events. Soil may exhibit classic redoximorphic features of reduction and oxidation; however, in sandier soils these features may not be evident. Parent material is recent alluvium. Geology may be mixed particularly in southwest Montana.

Table 4. Representative soil features

Parent material	(1) Alluvium – igneous, metamorphic and sedimentary rock
Surface texture	(1) Gravelly, cobbly loam
Drainage class	Excessively drained to poorly drained
Soil depth	20 – 100 in
Surface fragment cover <=3"	15%
Surface fragment cover >3"	10%
Available water capacity (0-40in)	3.8 – 8.2 in
Soil reaction (1:1 water) (0-10in)	6.6 – 734
Subsurface fragment volume <=3" (10-20in)	45%
Subsurface fragment volume >3" (10-20in)	22%

Ecological dynamics

1 - Reference State
1.1 Mixed bunchgrass community of basin wildrye, tufted hairgrass, reedgrass, mannagrass, and thickspike wheatgrass. Shrubs rare (willow, ninebark, dogwood). Bare ground low

1.1a extended drought, improper grazing, climate change

1.2 Tufted hairgrass and basin wildrye share dominance. Shrubs such as shrubby cinquefoil, dogwood, and rose increasing. Minor tree component may be present (black cottonwood, spruce, and limited lodgepole pine)

1.2a proper grazing management, favorable growing conditions, time
T1A poor grazing, drought with improper grazing, multiple spring grazing
T1B sod-busting, introduction of tame pasture species and other invasive plants, overgrazing, drought, heavy

2 - Grass-like State
2.1 Basin wildrye rare with tufted hairgrass, reedgrass, and thickspike dominant. Shrubby cinquefoil common. Possible hummocking from livestock. Bare ground high.

T2A overgrazing, introduction of weeds, drought, heavy human disturbance, conversion to introduced species
R1A proper grazing management, favorable growing conditions, time, range seeding

3 - Invaded State
3.1 Site generally devoid of most native plants. Kentucky bluegrass and smooth brome common.

R2A fire, range seeding, timely moisture, proper grazing management, IPM
R3A IPM, range seeding, timely moisture, grazing management, brush management, range seeding

State and transition model

Custom diagram

Standard diagram

More interactive model formats are also available. View Interactive Models

Interpretations

Animal community

The Subirrigated Grassland ecological site grouping provides wildlife habitat for an array of species. Prior to the settlement of this area, large herds of antelope, elk and bison roamed. Though the bison that once utilized this landscape have been replaced with domestic livestock, wildlife still utilize this largely intact landscape for habitat.

The relatively high grass component of the Reference Community provides excellent nesting cover for multiple neotropical migratory birds as well as provide hiding habitat for larger animals.

Managed livestock grazing is suitable on this site due to the potential to produce an abundance of high quality forage. This is often a preferred site for grazing by livestock, and animals tend to congregate in these areas. In order to maintain the productivity of this site, grazing on adjoining sites with less production must be managed carefully to be sure utilization is not excessive. Management objectives should include maintenance or improvement of the native plant community. Careful management of timing and duration of grazing is important. Shorter grazing periods and adequate deferment during the growing season are recommended for plant maintenance, health, and recovery.

Continual non-prescribed grazing of this site will be injurious, will alter the plant composition and production over time, and will result in transition to the Shortgrass State. Transition to other states will depend on duration of poorly managed grazing as well as other circumstances such as weather conditions and fire frequency.

Further degradation will result in transition to the Invaded State. Management should focus on grazing management strategies that will prevent further degradation, such as seasonal grazing deferment or winter grazing where feasible. Communities within this state are still stable and healthy under proper management. Forage quantity and quality may be substantially decreased from the Reference State.

Grazing is possible in the Invaded State. Invasive species are generally less palatable than native grasses. Forage production is typically greatly reduced in this state. Due to the aggressive nature of invasive species, sites in the Invaded State face increased risk for further degradation. Grazing has to be carefully managed to avoid further soil loss and degradation and possible livestock health issues.

Prescriptive grazing can be used to manage invasive species. In some instances, carefully targeted grazing (sometimes in combination with other treatments) can reduce or maintain species composition of invasive species.

Hydrological functions

The hydrologic cycle functions best in the Reference State (1) with good infiltration and deep percolation of rainfall; however, the cycle degrades as the vegetation community declines. Rapid rainfall infiltration, high soil organic matter, good soil structure, and good porosity accompany high bunchgrass canopy cover. High ground cover reduces rain drop impact on the soil surface, which keeps erosion and sedimentation transport low. Water leaving the site will have minimal sediment load, which allows for high water quality in associated streams. High rates of infiltration will allow water to move below the rooting zone during periods of heavy rainfall. The Reference Community (1.1) should have no rills or gullies present and drainage ways should be vegetated and stable. Water flow patterns, if present, will be barely observable. Plant pedestals are essentially non-existent. Plant litter remains in place and is not moved by wind or water.

Improper grazing management results in a community shift to the Bunchgrass Community (1.2). This plant community has a similar canopy cover, but only slightly higher bare ground. Therefore, the hydrologic cycle is functioning at a level similar to the water cycle in the Reference Community (1.1).

In the Invaded State (3) canopy and ground cover are greatly reduced compared to the Reference State (1), which impedes the hydrologic cycle. Infiltration will decrease and runoff will increase due to reduced ground cover, presence of shallow-rooted species, rainfall splash, soil capping, reduced organic matter, and poor structure. Sparse ground cover and decreased infiltration can combine to increase frequency and severity of flooding within a watershed. Soil erosion is accelerated, quality of surface runoff is poor, and sedimentation increases.

Recreational uses

This site provides some limited recreational opportunities for hiking, horseback riding, big game and upland bird hunting. The forbs have flowers that appeal to photographers. This site provides valuable open space.

Wood products

n/a

Supporting information

Inventory data references

Information presented was derived from NRCS inventory data, literature, field observations, and personal contacts with range-trained personnel (i.e., used professional opinion of agency specialists, observations of land managers, and outside scientists).

Other references

• Barrett, H. 2007. Western Juniper Management: A Field Guide.
• Bestelmeyer, B., J.R. Brown, J.E. Herrick, D.A. Trujillo, and K.M. Havstad. 2004. Land Management in the American Southwest: a state-and-transition approach to ecosystem complexity. Environmental Management 34:38–51.
• Bestelmeyer, B. and J. Brown. 2005. State-and-Transition Models 101: A Fresh look at vegetation change.
• Blaisdell, J.P. 1958. Seasonal development and yield of native plants on the Upper Snake River Plains and their relation to certain climate factors.
• Colberg, T.J. and J.T. Romo. 2003. Clubmoss effects on plant water status and standing crop. Journal of Range Management 56:489–495.
• DiTomaso, J.M. 2000. Invasive weeds in Rangelands: Species, Impacts, and Management. Weed Science 48:255–265.
• Dormaar, J.F., B.W. Adams, and W.D. Willms. 1997. Impacts of rotational grazing on mixed prairie soils and vegetation. Journal of Range Management 50:647–651.
• Hobbs, J.R. and S.E. Humphries. 1995. An integrated approach to the ecology and management of plant invasions. Conservation Biology 9:761–770.
• Humphrey, L. David. 1984. Patterns and mechanisms of plant succession after fire on Artemisia-grass sites in southeastern Idaho Vegetation. 57: 91-101.
• Masters, R. and R. Sheley. 2001. Principles and practices for managing rangeland invasive plants. Journal of Range Management 38:21–26.
• McLean, A. and S. Wikeem. 1985. Influence of season and intensity of defoliation on bluebunch wheatgrass survival and vigor in southern British Columbia. Journal of Range Management 38:21–26.
• Miller, R.F., T.J. Svejcar, and J.A. Rose. 2000. Impacts of western juniper on plant community composition and structure. Journal of Range Management 53:574–585.
• Ross, R.L., E.P. Murray, and J.G. Haigh. July 1973. Soil and Vegetation of Near-pristine sites in Montana.
• Smoliak, S., R.L. Ditterlin, J.D. Scheetz, L.K. Holzworth, J.R. Sims, L.E. Wiesner, D.E. Baldridge, and G.L. Tibke. 2006. Montana Interagency Plant Materials Handbook.
• Stavi, I. 2012. The potential use of biochar in reclaiming degraded rangelands. Journal of Environmental Planning and Management 55:1–9.
• Stringham, T.K., W.C. Kreuger, and P.L. Shaver. 2003. State and Transition Modeling: an ecological process approach. Journal of Range Management 56:106–113.
• Stringham, T.K. and W.C. Krueger. 2001. States, Transitions, and Thresholds: Further refinement for rangeland applications.
• Tirmenstein, D. 1999. Gutierrezia sarothrae. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). https://www.fs.fed.us/database/feis/plants/shrub/gutsar/all.html [2022, March 30].
• Walker, L.R. and S.D. Smith. 1997. Impacts of invasive plants on community and ecosystem properties. Pages 69–86 in Assessment and management of plant invasions. Springer, New York, NY.
• Whitford, W.G., E.F. Aldon, D.W. Freckman, Y. Steinberger, and L.W. Parker. 1989. Effects of Organic Amendments on Soil Biota on a Degraded Rangeland. Journal of Range Management 41:56–60.
• Wilson, A.M., G.A. Harris, and D.H. Gates. 1966. Cumulative Effects of Clipping on Yield of Bluebunch wheatgrass. Journal of Range Management 19:90–91.

Contributors

Petersen, Grant

Approval

Kirt Walstad, 3/01/2024

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	03/02/2024
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 R043BP815MT

Subirrigated Grassland Group

Last updated: 3/01/2024 Accessed: 11/21/2024

General information

MLRA notes

Ecological site concept

Associated sites

Similar sites

Table 1. Dominant plant species

Natural Resources
Conservation Service

Last updated: 3/01/2024
Accessed: 11/21/2024