Natural Resources
Conservation Service
Ecological site R058AE015MT
Shale (Sh) RRU 58A-E 10-14" p.z.
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.
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
| R058AE192MT |
Coarse Clay (CC) RRU 58A-E 10-14" p.z. |
|---|---|
| R058AE199MT |
Shallow Clay (SwC) RRU 58A-E 10-14" p.z. |
Similar sites
| R058AE011MT |
Saline Upland (SU) RRU 58A-E 10-14" p.z. The Saline Upland site is dominated by salt tolerant plants. |
|---|---|
| R058AE014MT |
Dense Clay (DC) RRU 58A-E 10-14" p.z. The Dense Clay site has moderately deep to deep nongranular heavy clays that are overlain by thin ineffectual layers. |
| R058AE013MT |
Claypan (Cp) RRU 58A-E 10-14" p.z. The Claypan site is moderately deep to very deep soils that have a hard claypan layer at about 2-8 inches from the surface. These sites are all more productive and have a more diverse plant community. |
| R058AE192MT |
Coarse Clay (CC) RRU 58A-E 10-14" p.z. The Coarse Clay differs mainly by having a more diverse community of plants that are typically on a Sandy site. |
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
Not specified |
| Herbaceous |
Not specified |
Physiographic features
This ecological site occurs on hills and plains in shale uplands. Slopes range from 0 to 45 percent, but are mainly less than 8 percent. This site occurs on all exposures and aspect is not significant. This site is very barren and extremely low producing.
Table 2. Representative physiographic features
| Landforms |
(1)
Hill
(2) Plain |
|---|---|
| Flooding frequency | None |
| Ponding frequency | None |
| Elevation | 579 – 1,067 m |
| Slope | 0 – 45% |
| Water table depth | 152 cm |
| 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) | 145 days |
|---|---|
| Freeze-free period (average) | 170 days |
| Precipitation total (average) | 356 mm |
Figure 2. Monthly average minimum and maximum temperature
Influencing water features
There are no influencing water features for this site.
Soil features
The soils are formed in alluvium or residuum from semiconsolidated, often acid, shales. Shale fragments are common on the surface. These soils are mainly 10 to 40 inches deep and very drougthy. Soil colors are often dark due to the parent material (e.g., lithochromic) and not from organic matter. Textures tend to be clayey.
Table 4. Representative soil features
| Surface texture |
(1) Silty clay |
|---|---|
| Family particle size |
(1) Clayey |
| Drainage class | Well drained |
| Permeability class | Slow |
| Soil depth | 25 – 102 cm |
| Available water capacity (0-101.6cm) |
0 – 5.08 cm |
| Calcium carbonate equivalent (0-101.6cm) |
0 – 5% |
| Electrical conductivity (0-101.6cm) |
8 – 16 mmhos/cm |
| Sodium adsorption ratio (0-101.6cm) |
5 – 13 |
| Soil reaction (1:1 water) (0-101.6cm) |
3.6 – 6.5 |
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 given 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.
Due to the severe soil limitations of this site, species diversity and total annual production is very low. Soil erosion is high due to the high proportion of bare ground.
Continual adverse impacts to this site over a period of years will result in the decrease of the medium grasses and shrubs, such as western wheatgrass, greasewood, and Nuttall’s saltbush.
Continued disturbances will cause the loss of the greasewood, winterfat, and shadscale. The shrubs will be replaced by longleaf sagebrush once the ecological threshold has been crossed.
Plants that are not a part of the climax community that are most likely to invade are plains pricklypear and broom snakeweed.
State and transition model
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View Interactive Models
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State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 1
Plant Community 1: Medium Grasses/ Tall Shrubs
Community 1.1
Plant Community 1: Medium Grasses/ Tall Shrubs
This is the interpretive plant community and is considered to be the Historic Climax Plant Community (HCPC) for this site. This plant community contains a low diversity of medium cool season grasses (western and thickspike wheatgrass, Montana wheatgrass, Sandberg bluegrass, and bottlebrush squirreltail). A few forbs occur in small percentages. Shrubs that occur on this site include winterfat, shadscale, greasewood, and Nuttall's saltbush. Due to the severe soil limitations of this site, species diversity and total annual production is very low. Individual species can vary greatly in production depending on growing conditions (timing and amount of precipitation and temperature). Plant litter is very limited due to low annual productivity. This plant community provides for limited soil stability as bare ground is commonly greater than 75% cover.
Figure 3. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
| Plant type | Low (kg/hectare) |
Representative value (kg/hectare) |
High (kg/hectare) |
|---|---|---|---|
| Grass/Grasslike | 135 | 235 | 336 |
| Shrub/Vine | 78 | 137 | 196 |
| Forb | 11 | 20 | 28 |
| Total | 224 | 392 | 560 |
Table 6. Ground cover
| Tree foliar cover | 0% |
|---|---|
| Shrub/vine/liana foliar cover | 10-15% |
| Grass/grasslike foliar cover | 10-15% |
| Forb foliar cover | 1-5% |
| Non-vascular plants | 0% |
| Biological crusts | 0-1% |
| 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 | 1-2% |
| Grass/grasslike basal cover | 1-5% |
| Forb basal cover | 1-2% |
| Non-vascular plants | 0% |
| Biological crusts | 0-1% |
| Litter | 5-10% |
| Surface fragments >0.25" and <=3" | 0-1% |
| Surface fragments >3" | 0% |
| Bedrock | 0% |
| Water | 0% |
| Bare ground | 75-85% |
Table 8. Canopy structure (% cover)
| Height Above Ground (m) | Tree | Shrub/Vine | Grass/ Grasslike |
Forb |
|---|---|---|---|---|
| <0.15 | – | – | – | – |
| >0.15 <= 0.3 | – | – | – | – |
| >0.3 <= 0.6 | – | 10-15% | 10-15% | 1-5% |
| >0.6 <= 1.4 | – | – | – | – |
| >1.4 <= 4 | – | – | – | – |
| >4 <= 12 | – | – | – | – |
| >12 <= 24 | – | – | – | – |
| >24 <= 37 | – | – | – | – |
| >37 | – | – | – | – |
State 2
Plant Community 2: Medium Grasses/ Medium and Low Shrubs
Community 2.1
Plant Community 2: Medium Grasses/ Medium and Low Shrubs
Slight variations in the Historical Climax Plant Community result in a community where the diversity of shrubs is lowered. Species that tend to dominate include western wheatgrass, Nuttall's saltbush, and slenderbush eriogonum.
State 3
Plant Community 3: Low Shrubs/ Half-shrubs / Cacti
Community 3.1
Plant Community 3: Low Shrubs/ Half-shrubs / Cacti
With continual adverse impacts to Plant Community 2, the plant community tends to become dominated by species such as longleaf sagebrush, slenderbush eriogonum, and bottlebrush squirreltail. There may still be remnant amounts of some of the mid-seral species such as western or thickspike and Montana wheatgrass. Broom snakeweed often invades this site. Grass biomass production and litter become reduced on the site as the 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 extremely low soil stability. These communities will respond positively to improved grazing management, but significant economic inputs and time would be required to move them toward a higher successional stage and a more productive plant community.
Additional community tables
Table 9. Community 1.1 plant community composition
| Group | Common name | Symbol | Scientific name | Annual production (kg/hectare) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Grass/Grasslike
|
||||||
| 1 | Native grasses | 135–280 | ||||
| tufted wheatgrass | ELMA7 | Elymus macrourus | 45–168 | – | ||
| western wheatgrass | PASM | Pascopyrum smithii | 45–168 | – | ||
| prairie sandreed | CALO | Calamovilfa longifolia | 0–112 | – | ||
| Montana wheatgrass | ELAL7 | Elymus albicans | 11–84 | – | ||
| 2 | Native grasses | 2–56 | ||||
| Grass, perennial | 2GP | Grass, perennial | 2–28 | – | ||
| saltgrass | DISP | Distichlis spicata | 2–28 | – | ||
| squirreltail | ELEL5 | Elymus elymoides | 2–28 | – | ||
| Sandberg bluegrass | POSE | Poa secunda | 2–28 | – | ||
|
Forb
|
||||||
| 3 | Native forbs | 11–28 | ||||
| Forb, perennial | 2FP | Forb, perennial | 2–28 | – | ||
| buckwheat | ERIOG | Eriogonum | 2–28 | – | ||
| hairy false goldenaster | HEVI4 | Heterotheca villosa | 2–28 | – | ||
| desertparsley | LOMAT | Lomatium | 2–28 | – | ||
| American vetch | VIAM | Vicia americana | 2–28 | – | ||
|
Shrub/Vine
|
||||||
| 4 | Native shrubs and half-shrubs | 78–196 | ||||
| shadscale saltbush | ATCO | Atriplex confertifolia | 2–112 | – | ||
| Nuttall's saltbush | ATNU2 | Atriplex nuttallii | 2–112 | – | ||
| Shrub, broadleaf | 2SB | Shrub, broadleaf | 2–112 | – | ||
| winterfat | KRLA2 | Krascheninnikovia lanata | 2–112 | – | ||
| greasewood | SAVE4 | Sarcobatus vermiculatus | 2–112 | – | ||
| longleaf wormwood | ARLO7 | Artemisia longifolia | 11–56 | – | ||
| slender buckwheat | ERMI4 | Eriogonum microthecum | 11–56 | – | ||
| rubber rabbitbrush | ERNAN5 | Ericameria nauseosa ssp. nauseosa var. nauseosa | 0–28 | – | ||
| Wyoming big sagebrush | ARTRW8 | Artemisia tridentata ssp. wyomingensis | 0–28 | – | ||
| 5 | Native shrubs and half-shrubs | 1–2 | ||||
| broom snakeweed | GUSA2 | Gutierrezia sarothrae | 1–2 | – | ||
| plains pricklypear | OPPO | Opuntia polyacantha | 1–2 | – | ||
Interpretations
Animal community
Livestock Grazing Interpretations:
This plant community is not well suited to managed livestock grazing due to low forage production. The steeper slopes may also limit livestock travel and result in poor grazing distribution, especially in areas away from water. Management objectives should include maintenance or improvement of the vegetation community. Short grazing periods and adequate re-growth after grazing are recommended for plant recovery. Season long use of this site can be detrimental, causing an increase in bare ground and altering the plant community over time.
Whenever Plant Community 2 occurs (medium grasses and shrubs), grazing management strategies need to be implemented to avoid further deterioration.
It is not feasible to improve the site when the dominant community type is similar to 3. Often, when this site is in this condition, there is a significant amount of erosion pavement or bare ground present. Community 3 has lost most of the attributes of healthy rangeland, including good infiltration, minimal erosion and runoff, nutrient cycling and energy use.
WILDLIFE INTERPRETATIONS:
The following is a description of habitat values for the different plant communities that may occupy the site:
Plant Community 1: Medium Grasses/ Tall Shrubs (HCPC):
The high percentage of nutritious shrubs and half-shrubs favors browsers and mixed feeders like mule deer and pronghorn, particularly on winter range. Seed production from shadscale, greasewood and other shrubs and half-shrubs supports seed-eating small mammals such as deer mice and kangaroo rats. Ground-nesting bird habitat is limited. Common nighthawks, loggerhead shrikes and Brewer’s sparrows are potential breeding birds. A variety of raptors hunt small mammals, insects and birds in this habitat.
Plant Community 2: Medium Grasses/ Medium and Low Shrubs:
Big game habitat value declines with the loss of winterfat and other browse plants. General habitat diversity declines with a partial loss of vegetative structural diversity. If big sagebrush increases, Brewer’s sparrow may benefit.
Plant Community 3: Low Shrubs/ Half-shrubs/ Cacti:
Wildlife habitat values are quite low in this community following the loss of plant species products and structural diversity.
Hydrological functions
The soils associated with this ecological site are generally in Hydrologic Soil Group D. The infiltration rates for these soils will normally be slow. The runoff potential for this site is high to very high, depending on slope and ground cover/health. Runoff curve numbers generally range from 85 to 94.
The hydrologic condition of this site has a significant affect on runoff. The hydrologic condition considers the effects of cover, including litter, and management on infiltration. Good hydrologic condition indicates that the site usually has a lower runoff potential. (Reference: Engineering Field Manual, Chapter 2 and Montana Supplement 4).
Recreational uses
This site supports sparse vegetation and recreational access is often difficult. 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): 2
NRCS-Range/Soil Correlation Observations & Soil 232 notes: 9
Contributors
Bob Leinard
JVF, REL, RSN, MJR, SKW, SVF, POH
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) | T. DeCock; R Kilian; K Kilwine |
|---|---|
| Contact for lead author | Tammy DeCock |
| Date | 06/11/2014 |
| Approved by | Jon Siddoway |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
Number and extent of rills:
On Slopes > 15% rill may be long (>5 feet) and continuous. If rills are present on slopes < 15% they should be < 3feet long and not continuous. -
Presence of water flow patterns:
Water flow paths may be obvious, regular and continuous with debris dams occurring only on lesser slopes. -
Number and height of erosional pedestals or terracettes:
Pedestals up to 0.5 inches and terracettes at debris dams are common. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare ground is < 75%. Bare ground will occur in quite large areas. -
Number of gullies and erosion associated with gullies:
Active gullies may be present on steeper slopes. -
Extent of wind scoured, blowouts and/or depositional areas:
None. -
Amount of litter movement (describe size and distance expected to travel):
Plant litter movement is expected. -
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 3 or greater. Surface Soil Aggregate Stability not under plant canopy should typically be 2 or slightly less. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Use soil series description. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Sparse plant canopy, slow infiltration rates, and the high amount of bare ground contribute to a naturally high runoff rate even in Reference condition. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
No compaction layer would be expected but soil surface is typically crusted when dry. -
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 grasses = shrubs and half shrubsSub-dominant:
Other:
Minor Species: forbs = cool season, short-stature bunch grasses and sedges = Warm season, mid-stature, rhizomatous grasses = Warm season, tall-stature, rhizomatous grasses = Cool season, mid-stature, bunch grassesAdditional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Some plant mortality and decadence (10 to 15%) is expected on this site. -
Average percent litter cover (%) and depth ( in):
Litter cover is in contact with soil surface with little evidence of biological activity. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
425 to 500 #/acre (13 to 14 inch precip. Zone) 200 to 350 #/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, Leafy spurge, knapweeds, whitetop, Dalmatian toadflax, yellow toadflax, St. Johnswort, perennial pepperweed, Yellow sweetclover -
Perennial plant reproductive capability:
All species are capable of reproducing
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