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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.
Associated sites
R058AE002MT Clayey (Cy) RRU 58A-E 10-14" p.z.
R058AE011MT Saline Upland (SU) RRU 58A-E 10-14" p.z.
R058AE013MT Claypan (Cp) RRU 58A-E 10-14" p.z.
Similar sites
R058AE015MT Shale (Sh) RRU 58A-E 10-14" p.z.
The Shale site differs by having soils that are usually shallow with very little soil profile evident.
R058AE013MT Claypan (Cp) RRU 58A-E 10-14" p.z.
The ClayPan site differs by generally having 2-8 inches of soil over the hard argillic layer, less bare ground, and higher production.
R058AE011MT Saline Upland (SU) RRU 58A-E 10-14" p.z.
The Saline Upland site differs by not having the very hard layer near the surface and by having a plant community of mainly salt tolerant species. In addition, the electroconductivities significantly limit, if not prohibit, the potential for any form of mechanical treatment or reseeding on the Saline Upland. Soils in the Saline Upland site generally are given a Capability Class rating of 7. (Soils in the Dense Clay site are generally Capability Class 6.)
Table 1. Dominant plant species
Tree Not specified
Shrub Not specified
Herbaceous Not specified
Physiographic features
This site occurs on old lake plains, sedimentary plains, terraces, and fans. Slopes range from 0 to 15 percent, but are mainly less than 8. This site occurs on all exposures and aspect is not significant. Alkali accumulations are apparent and salt tolerant plants are a major component of the vegetative community.
Table 2. Representative physiographic features
Landforms (1) Lake plain
(2) Plain
(3) Terrace
Flooding frequency None Ponding frequency None Elevation 1900 – 3500 ft Slope 0 – 15 % Water table depth 60 in Aspect Aspect is not a significant factor Climatic features
MLRAs 58A and 60B are considered to have a continental climate characterized by cold winters, hot summers, low humidity, light rainfall, and much sunshine. Extremes in temperature are typical. The climate is the result of this MLRA’s location in the geographic center of North America. There are few natural barriers on the northern Great Plains and the winds move freely across the plains and account for rapid changes in temperature. Seasonal precipitation is often limiting for plant growth. Annual fluctuations in species composition and total production are typical depending on the amount and timing of rainfall.
Temperatures can be very extreme in this part of Montana. Summer daytime temperatures are typically quite warm, generally averaging in the mid to upper 80º’s F for July and August. Summertime temperatures will typically reach in the 100º’s F at some point during the summer, and can reach 90º F any month between May and September. Conversely, winter temperatures can be cold, averaging in the mid teens to mid 20º’s F for December and January. There will typically be several days of below zero temperatures each winter. It is not uncommon for temperatures to reach 30–40º F below zero, or even colder, most any winter.
Spring can be windy throughout these MLRA’s, with winds averaging over 10 mph about 15 percent of the time. Speeds of 50 mph or stronger can occasionally occur as a weather system crosses this part of Montana.
MLRAs 58AE and 60BE have been divided into two distinct precipitation zones for the purpose of developing ecological site descriptions: 10–14” Mean Annual Precipitation (MAP) and 15–19” MAP.
10–14 inch zone:
The majority of the rangeland in these areas falls within the 11 to 13 inch range. During an average year, 70 to 75 percent of the annual precipitation falls between April and September, which are the primary growing season months.
Snowfall is not heavy in the area, averaging 28 total inches in the 10-14 inch MAP (Yellowstone Valley). Heavy snowfall occurs infrequently, usually late in the winter or early spring. Snow cover is typically 1 to 3 inches.
The frost free (32º F.) season averages about 105 to 145 days each year in the uplands, to nearly 170 days along the Yellowstone River Valley.
For local climate station information, refer to http://www.wcc.nrcs.usda.gov/cgibin/state.pl?state=mt.
Table 3 Representative climatic features
Frost-free period (average) 150 days Freeze-free period (average) 170 days Precipitation total (average) 10 in BarLineFigure 2. Monthly precipitation range
BarLineFigure 3. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
These are moderately deep to very deep nongranular clay soils that are strongly to very strongly alkaline. They are hard to very hard when dry and very sticky when wet. They typically have a thin vesicular crust on the surface. The subsoil is mainly massive, or has very strong columnar structure. Permeability and root development are severely limited by the surface crust, hard subsoil, and alkalinity.
Table 4. Representative soil features
Surface texture (1) Clay
(2) Silty clay
(3) Silty clay loam
Family particle size (1) Clayey
Drainage class Well drained Permeability class Very slow Soil depth 40 – 60 in Available water capacity
(0-40in)5 – 10 in Calcium carbonate equivalent
(0-40in)0 – 5 % Electrical conductivity
(0-40in)2 – 8 mmhos/cm Sodium adsorption ratio
(0-40in)13 – 30 Soil reaction (1:1 water)
(0-40in)7.8 – 9.6 Ecological dynamics
This site developed under Northern Great Plains climatic conditions, which included the natural influence of large herbivores and occasional fire. The plant community
upon which interpretations are primarily based is the Historic Climax Plant Community (HCPC). This community is described as a reference to understand the original potential of this site, and is not always considered to be the management goal for every acre of rangeland. The following descriptions should enable the landowner or manager to better understand which plant communities occupy their land, and assist with setting goals for vegetation management. It can also be useful to understand the environmental and economic values of each plant community.
This site is considered moderately resilient to disturbance as it has moderate to high soil limitations for plant growth. Changes may occur to the Historic Climax Plant Community due to management actions and/or climatic conditions. Under continued adverse impacts, a moderate decline in vegetative vigor and composition will occur. Under favorable vegetative management treatments, this site can more readily return to a community that resembles the Historic Climax Plant Community.
Continual adverse impacts to the site over a period of years results in a departure from the HCPC, with a decrease of the taller, more palatable species such as western and thickspike wheatgrasses, green needlegrass, and Nuttall's saltbush. These plants will begin to be replaced by short grasses such as Sandberg bluegrass and blue grama. Continued deterioration results in a community dominated by Wyoming big sagebrush, plains pricklypear, bottlebrush squirreltail, blue grama, and Sandberg bluegrass with a corresponding increase in the amount of bare ground.
Plants that are not a part of the climax community that are most likely to invade are annual bromes, annual forbs, and broom snakeweed.
State and transition model
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Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 1
Plant Community 1: Tall and Medium Grasses/ Forbs/ ShrubsCommunity 1.1
Plant Community 1: Tall and Medium Grasses/ Forbs/ ShrubsThis is the interpretive plant community and is considered to be the Historic Climax Plant Community (HCPC) for this site. This plant community contains a simple mix of tall and medium height cool season grasses (western and thickspike wheatgrass and green needlegrass). A few forbs occur in small percentages. Shrubs that occur on this site include Nuttall's saltbush and Wyoming big sagebrush.
This site is not highly productive. Large areas of bare ground between the plants are common. This site also occurs as a "pan" when in complex with better sites, usually Clayey or ClayPan.
This plant community is well adapted to the Northern Great Plains climatic conditions. The diversity in plant species and the presence of tall, deep rooted perennial grasses allows for high drought tolerance, considering the limitations of the site. Individual species can vary greatly in production depending on growing conditions (timing and amount of precipitation and temperature). Plants on this site have strong, healthy root systems that allow production to increase significantly with favorable precipitation. Abundant plant litter is available
for soil building and moisture retention. Plant litter is properly distributed with very little movement off-site
and natural plant mortality is very low. This plant community provides for high soil stability and a functioning hydrologic cycle.
Figure 4. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
Plant type Low
(lb/acre)Representative value
(lb/acre)High
(lb/acre)Grass/Grasslike 210 420 540 Shrub/Vine 122 245 315 Forb 18 35 45 Total 350 700 900 Table 6. Ground cover
Tree foliar cover 0% Shrub/vine/liana foliar cover 20-30% Grass/grasslike foliar cover 20-30% Forb foliar cover 0-0% Non-vascular plants 0% Biological crusts 0-0% Litter 0% Surface fragments >0.25" and <=3" 0% Surface fragments >3" 0% Bedrock 0% Water 0% Bare ground 0% Table 7. Soil surface cover
Tree basal cover 0% Shrub/vine/liana basal cover 0-10% Grass/grasslike basal cover 10-10% Forb basal cover 0-0% Non-vascular plants 0% Biological crusts 0-0% Litter 20-20% Surface fragments >0.25" and <=3" 0-0% Surface fragments >3" 0% Bedrock 0% Water 0% Bare ground 40-60% Table 8. Canopy structure (% cover)
Height Above Ground (ft) Tree Shrub/Vine Grass/
GrasslikeForb <0.5 – – – – >0.5 <= 1 – – – – >1 <= 2 – 20-25% 20-30% 1-2% >2 <= 4.5 – – – – >4.5 <= 13 – – – – >13 <= 40 – – – – >40 <= 80 – – – – >80 <= 120 – – – – >120 – – – – State 2
Plant Community 2: Medium Shrubs/ Medium and Short GrassesCommunity 2.1
Plant Community 2: Medium Shrubs/ Medium and Short GrassesSlight variations in the historical climax plant community result in a community where the western wheatgrass, green needlegrass and
Nuttall's saltbush decreases in composition. Species that tend to dominate include Wyoming big sagebrush and short grasses such as Sandberg bluegrass and blue grama.
Grass biomass production and litter become reduced on the site as the taller grasses disappear, increasing evaporation and reducing moisture retention. Additional open space in the community can result in undesirable invader species. This plant community provides for moderate soil stability.
State 3
Plant Community 3: Shrubs/ Cacti/ Annual Grasses and ForbsCommunity 3.1
Plant Community 3: Shrubs/ Cacti/ Annual Grasses and ForbsWith continual heavy disturbance over several years, this site will experience a loss of topsoil and an increase of bare ground. Continued degradation in the plant community usually results in a community dominated by Wyoming big sagebrush, plains pricklypear, and annual grasses and forbs. Bottlebrush squirreltail is often a component of this community.
Additional community tables
Table 9. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Native grasses 205–450 western wheatgrass PASM Pascopyrum smithii 105–360 – tufted wheatgrass ELMA7 Elymus macrourus 105–360 – green needlegrass NAVI4 Nassella viridula 4–90 – Montana wheatgrass ELAL7 Elymus albicans 0–90 – Sandberg bluegrass POSE Poa secunda 4–45 – 2 Native grasses and sedges 4–90 Grass, perennial 2GP Grass, perennial 4–45 – blue grama BOGR2 Bouteloua gracilis 4–45 – needleleaf sedge CADU6 Carex duriuscula 4–45 – threadleaf sedge CAFI Carex filifolia 4–45 – plains reedgrass CAMO Calamagrostis montanensis 4–45 – saltgrass DISP Distichlis spicata 4–45 – squirreltail ELEL5 Elymus elymoides 4–45 – prairie Junegrass KOMA Koeleria macrantha 4–45 – Sandberg bluegrass POSE Poa secunda 4–45 – alkali sacaton SPAI Sporobolus airoides 4–45 – Forb3 Native forbs 18–45 Forb, perennial 2FP Forb, perennial 4–45 – common yarrow ACMI2 Achillea millefolium 4–45 – onion ALLIU Allium 4–45 – aster ASTER Aster 4–45 – milkvetch ASTRA Astragalus 4–45 – buckwheat ERIOG Eriogonum 4–45 – scarlet beeblossom GACO5 Gaura coccinea 4–45 – desertparsley LOMAT Lomatium 4–45 – prairie thermopsis THRH Thermopsis rhombifolia 4–45 – Shrub/Vine4 Native shrubs and half-shrubs 122–315 Wyoming big sagebrush ARTRW8 Artemisia tridentata ssp. wyomingensis 35–225 – Nuttall's saltbush ATNU2 Atriplex nuttallii 35–225 – winterfat KRLA2 Krascheninnikovia lanata 4–90 – greasewood SAVE4 Sarcobatus vermiculatus 4–90 – Shrub, broadleaf 2SB Shrub, broadleaf 4–90 – prairie sagewort ARFR4 Artemisia frigida 4–45 – 5 Native shrubs and half-shrubs 1–2 broom snakeweed GUSA2 Gutierrezia sarothrae 1–2 – plains pricklypear OPPO Opuntia polyacantha 1–2 – Table 10. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 11. Community 3.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
Livestock Grazing Interpretations:
Managed livestock grazing is suitable on this site as it has the potential to produce a moderate amount of high quality forage. Management objectives should include maintenance or improvement of the plant community. Shorter grazing periods and adequate re-growth after grazing are recommended for plant maintenance and recovery. Heavy stocking and season long use of this site can be detrimental and will alter the plant community composition and production over time.
Whenever Plant Community 2 occurs (shrubs and medium grasses), grazing management strategies need to be implemented to avoid further deterioration. This community is still stable, productive, and healthy provided it receives proper management. This community will respond fairly quickly to improved grazing management including increased growing season rest of key forage plants. Grazing management alone can usually move this community back to one more similar to potential if a good seed source of the taller grasses still exists.
Plant Community 3 has severely reduced forage production (< 225 pounds per acre) and is comprised mostly of non-palatable species for livestock. Once this site is occupied by Plant Community 3, it will be more difficult to restore it to a community that resembles the potential with grazing management alone. Additional growing season rest in conjunction with mechanical treatment are often necessary for re-establishment of the desired species and to restore the stability and health of the site. The presence of sodium severely limits the potential for response to any treatments.
Wildlife Interpretations:
The following is a description of habitat values for the different plant communities that may occupy the site:
Plant Community 1: Tall and Medium Grasses/ Forbs/ Shrubs (HCPC):
The prevalence of Nuttall’s saltbush, winterfat and Wyoming big sagebrush favors mixed feeders like the pronghorn. Nutritious early to mid-season forage is also available for grass feeders, including bison and elk. Sage grouse may use this open habitat for lek sites and feeding on sagebrush. Small mammal species composition will be dominated by seed-eaters, particularly deer mice. Brewer’s sparrows and mountain plovers are examples
of breeding bird species potentially using this community spring-fall. Relatively low amounts of litter and residual grass cover limit use by a number of ground-nesting bird species.
Plant Community 2: Medium Shrubs/ Medium and Short Grasses:
The reduction in tall grasses, Nuttall's saltbush and winterfat reduces habitat value for pronghorn and other ungulates, as well as
seed-eating small mammals. An increase in big sagebrush cover may improve winter and nesting habitat for sage grouse and spring-fall habitat for Brewer’s sparrows and sage thrashers, but the decrease in litter and residual grass cover generally reduces nesting habitat quality for ground-nesting birds.
Plant Community 3: Shrubs/ Cacti/ Annual Grasses and Forbs:
Sagebrush specialists, including pronghorn, sage grouse and Brewer’s sparrow may use this community seasonally; pronghorn during
winter, sage grouse during winter and the nesting season, and Brewer’s sparrow spring through fall migration. Seed-eating small mammals, especially deer mice, may thrive on annual forb seed production. The community has relatively low value for most wildlife species considering the lack of vegetative structural diversity, residual grass carry-over and litter cover.
Hydrological functions
The runoff potential for this site is very high depending on slope and ground cover/health. Runoff curve numbers generally range from 84 to 93. The soils associated with this ecological site are generally in Hydrologic Soil Group D. The infiltration rates for these soils will normally be very slow.
Good hydrologic conditions exist on rangelands if plant cover (grass, litter, and brush canopy) is greater than 70%. Fair conditions exist when cover is between 30 and 70%, and poor conditions exist when cover is less than 30%. Sites in high similarity to HCPC (Plant Communities 1 and 2) generally have enough plant cover and litter to optimize infiltration, minimize runoff and erosion, and have a good hydrologic condition. The
deep root systems of the potential vegetation help maintain or increase infiltration rates and reduce runoff.
Sites in low similarity (Plant Community 3) are generally considered to be in poor hydrologic condition as the majority of plant cover is from shallow-rooted species and shrubs.
Erosion is minor for sites in high similarity. Rills and gullies should not be present. 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 erosion. Soil surfaces should not be compacted or crusted. Plant cover and litter helps
retain soil moisture for use by the plants. Maintaining a healthy stand of perennial vegetation will optimize the amount of precipitation that is received. (Reference: Engineering Field Manual, Chapter 2 and Montana Supplement 4).
Recreational uses
This site provides recreational opportunities for big game and upland bird hunting, and hiking. The forbs have flowers that appeal to photographers. This site provides valuable open space and visual aesthetics.
Other information
The following is an example of how to calculate the recommended stocking rate. This example does not use production estimates from this specific ecological site. You will need to adjust the annual production values and run the calculations using total annual production values from the ecological sites encountered on each individual ranch/pasture. Before making specific recommendations, an on-site evaluation must be made.
Example of total annual production amounts by type of year:
Favorable years = 2200 lbs/acre
Normal years = 1480 lbs/acre
Unfavorable years = 1200 lbs/acre
It is recommended that on slopes of 30% or less, stocking rate should be derived from the total annual production pounds minus 500 pounds for residual dry matter and 25% harvest efficiency. On slopes over 30%, stocking rate is derived from total annual production pounds minus 800 pounds for residual dry matter and 25% harvest efficiency. Refer to the NRCS National Range and Pasture Handbook for a list of Animal Unit Equivalents.
Sample Calculations using Favorable Year production amounts:
< 30% slopes: AUM/AC = [(2200-500)(0.25)]/915 lbs/month for one AU = 0.46 AUM/AC
AC/AUM = (1.0 AU)/(0.46AUM/AC) = 2.2 AC/AUM
> 30% slopes: AUM/AC = [(2200-800)(0.25)]/915 lbs/month for one AU = 0.38 AUM/AC
AC/AUM = (1.0 AU)/(0.38 AUM/AC) = 2.6 AC/AUM
NOTE: 915 lbs/month for one Animal Unit is used as the baseline for maintenance requirements. This equates to 30 lbs/day of air-dry forage (1200 lb cow at 2.5% of body weight).
Supporting information
Inventory data references
NRCS-Production & Composition Record for Native Grazing Lands (Range-417): 3 BLM-Soil & Vegetation Inventory Method (SVIM) Data: 6 NRCS-Range Condition Record (ECS-2): NRCS-Range/Soil Correlation Observations & Soil 232 notes: 38
Contributors
Bob Leinard
JVF, REL, RSN, MJR, SKW, SVF, POHRangeland 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) T. DeCock; R Kilian Contact for lead author Tammy DeCock Date 06/11/2014 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
Rills should not be present. -
Presence of water flow patterns:
Water flow patterns are obvious and numerous and may reach up to 10 inches wide and 2 feet long. -
Number and height of erosional pedestals or terracettes:
Erosional pedestals up to ½ inch may be present. Terracettes should be minor. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare ground is < 60%. Bare ground will occur in quit large areas. -
Number of gullies and erosion associated with gullies:
Active gullies should not be present. Existing gullies should be “healed” with a good vegetative cover. -
Extent of wind scoured, blowouts and/or depositional areas:
None. -
Amount of litter movement (describe size and distance expected to travel):
Little to no plant litter movement. If litter movement occurs, it is only for a short distance. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Surface Soil Aggregate Stability under plant canopy should typically be 5 or greater. Surface Soil Aggregate Stability not under plant canopy should typically be 3 or slightly less. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Use soil survey series description. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Sparse plant canopy (20% maximum), very slow to slow infiltration rates, and the high amount of bare ground contribute to a naturally high runoff rate even in HCPC. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
No compaction layer should be evident. This site is often typified by a vesicular surface (less than 2 inches) over a very hard subsoil. -
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:
Cool season, mid-stature, rhizomatous grassesSub-dominant:
Shrubs and half shrubs >> Cool season, Mid-stature, Bunch grasses = Cool season, short-stature, bunch grasses and sedges = Warm season, mid-stature, bunch grassesOther:
Minor components: Cool season, short-stature, rhizomatous grasses and sedges = forbs = Warm season, mid-stature, rhizomatous grassesAdditional:
(Blue grama should be grouped with warm season, short-stature, rhizomatous grasses due to its growth form) -
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Some plant mortality and decadence (5 to 10%) is expected on this site. -
Average percent litter cover (%) and depth ( in):
Litter cover is in contact with soil surface. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
800 to 900 #/acre (13 to 14 inch precip. Zone) 350 to 700 #/ac (10 to 12 inch precip. Zone). -
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:
Halogeton,knapweeds,whitetop,perennial pepperweed. -
Perennial plant reproductive capability:
All species are capable of reproducing.
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