Natural Resources
Conservation Service
Ecological site R043BY428WY
Lowland (LL) 15-19” Northern Plains Precipitation Zone
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.
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
| R043BY404WY |
Clayey (Cy) 15-19” Northern Plains Precipitation Zone |
|---|---|
| R043BY430WY |
Overflow (Ov) 15-19” Northern Plains Precipitation Zone |
| R043BY450WY |
Sandy (Sy) 15-19” Northern Plains Precipitation Zone |
Similar sites
| R058BY128WY |
Lowland (LL) 10-14” PZ Lowland 10-14” Northern Plains P.Z., has lower production. |
|---|
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
Not specified |
| Herbaceous |
Not specified |
Physiographic features
This site is located on nearly level land adjacent to streams that run water at least during the major part of the growing season.
Table 2. Representative physiographic features
| Landforms |
(1)
Hill
(2) Alluvial fan (3) Ridge |
|---|---|
| Flooding duration | Brief (2 to 7 days) to long (7 to 30 days) |
| Flooding frequency | Occasional to frequent |
| Ponding frequency | None |
| Elevation | 3,700 – 7,500 ft |
| Slope | 6% |
| Ponding depth |
Not specified |
| Water table depth | 12 – 60 in |
| Aspect | Aspect is not a significant factor |
Climatic features
Annual precipitation ranges from 15" to 19" per year. May is generally the wettest month. July, August and September are somewhat drier with daily amounts rarely exceeding one inch. Snowfall is quite heavy in the mountainous area. Annual snowfall averages close to 70 inches.
Sunshine is abundant in the latter part of the summer, the greatest amount being in July and August. Sunshine possibility during these two months averages 70 to 75% possibility with only a 65% possibility for June and September. Winter averages about 40% sunshine.
Because of the varied topography, the wind will vary considerably for different parts of the area. The wind is usually much lighter at the lower elevations and in the valleys as compared with the higher terrain. The average winter wind velocity is 8.5 mph, while the summer wind velocity averages 7.5 mph. Winds during storms and on ridges may exceed 45 mph.
Temperatures show a wide range between summer and winter, and between daily maximums and minimums. Summer nights are cool and temperatures drop into the forties at most places before sunrise. Summer daytime temperatures are usually in the seventies and occasionally reach eighty, but rarely reach the mid nineties. Winters are cold with daily lows below freezing most of the time. January has the coldest temperatures with a range of near 10 deg. F at night to the mid thirties in the afternoon. Temperatures of well below zero to –30 deg. F are not uncommon in the winter months.
The growing season for the cool season plants will generally start about April 15 to May 1 and continue to about October 10.
The following information is from the “Sheridan Airport” climate station:
Frost-free period (32 °F): 95-156 days; (5 yrs. out of 10, these days will occur between May 21 – September 19)
Freeze-free period 28 °F): 116-187 days; (5 yrs. out of 10, these days will occur between May 4 – September 29)
Mean annual precipitation: 14.7 inches
Mean annual air temperature: 45.0 °F (31.2 °F Avg. Min. – 58.8 °F Avg. Max.)
For detailed information visit the Natural Resources Conservation Service National Water and Climate Center at http://www.wcc.nrcs.usda.gov/ website. Other climate station(s) representative of this precipitation zone include: “Parkman 5 WNW”
Table 3. Representative climatic features
| Frost-free period (average) | 156 days |
|---|---|
| Freeze-free period (average) | 187 days |
| Precipitation total (average) | 19 in |
Influencing water features
Stream type: None
Soil features
The soils of this site are deep (greater than 40” to bedrock), well drained and moderately permeable. A fluctuating water table occurs in these areas, but is usually deeper than 3 feet.
Table 4. Representative soil features
| Surface texture |
(1) Loam (2) Clay loam (3) Fine sandy loam |
|---|---|
| Family particle size |
(1) Loamy |
| Drainage class | Poorly drained to well drained |
| Permeability class | Moderately slow to rapid |
| Soil depth | 20 – 60 in |
| Surface fragment cover <=3" | Not specified |
| Surface fragment cover >3" | 10% |
| Available water capacity (0-40in) |
1 – 6.2 in |
| Calcium carbonate equivalent (0-40in) |
5% |
| Electrical conductivity (0-40in) |
8 mmhos/cm |
| Sodium adsorption ratio (0-40in) |
10 |
| Soil reaction (1:1 water) (0-40in) |
6.6 – 8.4 |
| Subsurface fragment volume <=3" (Depth not specified) |
15% |
| Subsurface fragment volume >3" (Depth not specified) |
10% |
Ecological dynamics
As this site deteriorates from improper grazing management, species such as Kentucky bluegrass and cheatgrass invade as snowberry and silver sagebrush increase. Cool season grasses such as green needlegrass and western wheatgrass will decrease in frequency and production. Mature cottonwoods do not reproduce.
The Historic Climax Plant Community (description follows the plant community diagram) has been determined by study of rangeland relic areas, or areas protected from excessive disturbance. Trends in plant communities going from heavily grazed areas to lightly grazed areas, seasonal use pastures, and historical accounts have also been used.
The following is a State and Transition Model Diagram that illustrates the common plant communities (states) that can occur on the site and the transitions between these communities. The ecological processes will be discussed in more detail in the plant community narratives following the diagram.
State and transition model
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View Interactive Models
Click on state and transition labels to scroll to the respective text
State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 4 submodel, plant communities
State 1
Rhizomatous Wheatgrasses, Green Needlegrass, Cottonwoods Plant Community
Community 1.1
Rhizomatous Wheatgrasses, Green Needlegrass, Cottonwoods Plant Community
The interpretive plant community for this site is the Historic Climax Plant Community. This state evolved with grazing by large herbivores and is well suited for grazing by domestic livestock. Potential vegetation is about 70% grasses or grass-like plants, 10% forbs and 20% woody plants. The understory of this state is dominated by cool season midgrasses. The major grasses include rhizomatous wheatgrass, needleandthread, green needlegrass and slender wheatgrass. Other grasses occurring on the site include Sandberg bluegrass, Canada wildrye, needleleaf sedge, and prairie junegrass. Cottonwoods of various age classes dominate the overstory. Woody plants such as green ash, chokecherry, boxelder, silver sagebrush, wild plums and snowberry may make up to 20% of the production on this state. This state produces between 2000 and 4000 pounds annually, depending on the growing conditions. The state is extremely resilient and well adapted to the Northern Great Plains climatic conditions. The diversity in plant species allow for high drought resistance. This is a healthy and sustainable plant community (site/soil stability, watershed function, and biologic integrity). Transitions or pathways leading to other plant communities are as follows: • Moderate, continuous season-long grazing and lack of flooding will convert this plant community to the Mature cottonwoods/Grass Vegetation State. • Heavy, continuous, improper grazing and lack of flooding will convert this plant community to the Mature cottonwoods/Cheatgrass Vegetation State. • Haying will convert this state to the Rhizomatous Wheatgrass Vegetation State.
Figure 2. Annual production by plant type (representative values) or group (midpoint values)
Figure 3. Plant community growth curve (percent production by month). WY1302, 15-19NP Extra water sites - LL, Ov, CyO, SL.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
| 0 | 0 | 0 | 5 | 15 | 35 | 25 | 10 | 10 | 0 | 0 | 0 |
State 2
Mature Cottonwoods/Cool-Season Grasses Plant Community
Community 2.1
Mature Cottonwoods/Cool-Season Grasses Plant Community
This plant community evolved under moderate grazing by domestic livestock. Cool-season grasses make up the majority of the understory with the balance made up of short warm-season grasses, annual cool-season grass, and miscellaneous forbs. Mature cottonwoods make up the overstory. Dominant grasses include rhizomatous wheatgrasses, Kentucky bluegrass, needleandthread, and green needlegrass. Grasses of secondary importance include prairie junegrass, blue grama, Sandberg bluegrass,and slender wheatgrass. Forbs, commonly found in this plant community, include Louisiana sagewort (cudweed), plains wallflower, hairy goldaster, slimflower scurfpea, and scarlet globemallow. Silver sagebrush, green ash, boxelder, chokecherry, and snowberrry canopy cover may be 20-40%. This state produces between 1200 and 3000 pounds annually, depending on the growing conditions. When compared to the Historical Climax Plant Community, rhizomatous wheatgrasses and green needlegrass have decreased. Needleandthread and Sandberg bluegrass have increased. Silver sagebrush has increased. Reproduction of cottonwoods is limited. The overstory of cottonwoods and understory of grass and forbs provide a diverse plant community which will support domestic livestock and wildlife such as birds, mule deer and antelope. The site is stable and protected from excessive erosion. The biotic integrity of this plant community is usually intact. However, the lack of cottonwood reproduction will reduce the wildlife habitat. The watershed is usually functioning. Transitions or pathways leading to other plant communities are as follows: • Prescribed grazing and flooding will result in a plant community very similar to the Historic Climax Plant Community. • Heavy, continuous, improper grazing and lack of flooding will convert this plant community to the Mature cottonwoods/Cheatgrass Vegetation State
Figure 4. Plant community growth curve (percent production by month). WY1302, 15-19NP Extra water sites - LL, Ov, CyO, SL.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
| 0 | 0 | 0 | 5 | 15 | 35 | 25 | 10 | 10 | 0 | 0 | 0 |
State 3
Mature Cottonwoods/Cheatgrass Plant Community
Community 3.1
Mature Cottonwoods/Cheatgrass Plant Community
This plant community is the result of long-term improper grazing use. This state is dominated by perennial short-grasses and cheatgrass. Silver sagebrush and snowberry have increased. Mature cottonwoods make up the overstory. Weeds such as American licorice, and noxious weeds, such as Canada thistle and leafy spurge may invade it. The total annual production (air-dry weight) of this state is about 900 pounds per acre, but it can range from about 600 lbs./acre in unfavorable years to about 1200 lbs./acre in above average years. The soil of this state is protected. The watershed is functioning but may produce excessive runoff. The biotic integrity is threatened by invasive species. Transitional pathways leading to other plant communities are as follows • Prescribed Grazing and flooding over the long-term will return this state to near Historic Climax Plant Community, except that silver sagebrush and mature cottonwoods will persist.
Figure 5. Plant community growth curve (percent production by month). WY1302, 15-19NP Extra water sites - LL, Ov, CyO, SL.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
| 0 | 0 | 0 | 5 | 15 | 35 | 25 | 10 | 10 | 0 | 0 | 0 |
State 4
Rhizomatous Wheatgrass Plant Community
Community 4.1
Rhizomatous Wheatgrass Plant Community
This plant community is the result of haying. The state is dominated by western wheatgrass with some green needlegrass. The overstory is sparse mature cottonwoods. Production ranges from 1200 to 3000 pounds, depending on climatic conditions. When compared to the Historic Climax Plant Community this state has lost much of its diversity. Woody vegetation is mainly mature cottonwoods. There are few forbs. The soil is protected by rhizomatous wheatgrass sod. The biotic community is restricted by the lack of diversity. Watershed values are protected due to the lack of steep slopes on this site. This plant community is not resistant to change and is more vulnerable to severe disturbance than the HCPC. The introduction of grazing or fire quickly changes the plant community. Soil erosion is accelerated because of increased bare ground. Water flow patterns and pedestaling are obvious. Infiltration is reduced and runoff is increased. Transitions or pathways leading to other plant communities are as follows: • Proper grazing use and flooding may return this state to the Historic climax plant community over the long term.
Figure 6. Plant community growth curve (percent production by month). WY1302, 15-19NP Extra water sites - LL, Ov, CyO, SL.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
| 0 | 0 | 0 | 5 | 15 | 35 | 25 | 10 | 10 | 0 | 0 | 0 |
Additional community tables
Table 5. Community 1.1 plant community composition
| Group | Common name | Symbol | Scientific name | Annual production (lb/acre) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Grass/Grasslike
|
||||||
| 1 | 300–750 | |||||
| green needlegrass | NAVI4 | Nassella viridula | 300–750 | – | ||
| 2 | 300–750 | |||||
| western wheatgrass | PASM | Pascopyrum smithii | 300–750 | – | ||
| 3 | 300–750 | |||||
| basin wildrye | LECI4 | Leymus cinereus | 300–750 | – | ||
| 4 | 150–300 | |||||
| Columbia needlegrass | ACNE9 | Achnatherum nelsonii | 150–300 | – | ||
| 5 | 150–300 | |||||
| Canada wildrye | ELCA4 | Elymus canadensis | 150–300 | – | ||
| 6 | 150–300 | |||||
| slender wheatgrass | ELTR7 | Elymus trachycaulus | 150–300 | – | ||
| 7 | 150–450 | |||||
| Grass, perennial | 2GP | Grass, perennial | 0–150 | – | ||
| Pumpelly's brome | BRINP5 | Bromus inermis ssp. pumpellianus var. pumpellianus | 0–150 | – | ||
| Idaho fescue | FEID | Festuca idahoensis | 0–150 | – | ||
| needle and thread | HECO26 | Hesperostipa comata | 0–150 | – | ||
| prairie Junegrass | KOMA | Koeleria macrantha | 0–150 | – | ||
| Sandberg bluegrass | POSE | Poa secunda | 0–150 | – | ||
| 8 | 150–300 | |||||
| Forb, perennial | 2FP | Forb, perennial | 0–150 | – | ||
| yarrow | ACHIL | Achillea | 0–150 | – | ||
| tarragon | ARDR4 | Artemisia dracunculus | 0–150 | – | ||
| white sagebrush | ARLU | Artemisia ludoviciana | 0–150 | – | ||
| prairie clover | DALEA | Dalea | 0–150 | – | ||
| fleabane | ERIGE2 | Erigeron | 0–150 | – | ||
| American licorice | GLLE3 | Glycyrrhiza lepidota | 0–150 | – | ||
| dock | RUMEX | Rumex | 0–150 | – | ||
| groundsel | TEPHR3 | Tephroseris | 0–150 | – | ||
| American vetch | VIAM | Vicia americana | 0–150 | – | ||
| violet | VIOLA | Viola | 0–150 | – | ||
|
Tree
|
||||||
| 9 | 150–300 | |||||
| narrowleaf cottonwood | POAN3 | Populus angustifolia | 150–300 | – | ||
|
Shrub/Vine
|
||||||
| 10 | 150–600 | |||||
| Shrub (>.5m) | 2SHRUB | Shrub (>.5m) | 0–150 | – | ||
| boxelder | ACNEI2 | Acer negundo var. interius | 0–150 | – | ||
| silver sagebrush | ARCA13 | Artemisia cana | 0–150 | – | ||
| hawthorn | CRATA | Crataegus | 0–150 | – | ||
| green ash | FRPE | Fraxinus pennsylvanica | 0–150 | – | ||
| American plum | PRAM | Prunus americana | 0–150 | – | ||
| chokecherry | PRVIV | Prunus virginiana var. virginiana | 0–150 | – | ||
| western snowberry | SYOC | Symphoricarpos occidentalis | 0–150 | – | ||
Interpretations
Animal community
Animal Community – Wildlife Interpretations
Rhizomatous Wheatgrasses, Green Needlegrass, Cottonwoods Plant Community (HCPC): The predominance of grasses in this plant community favors grazers and mixed-feeders, such as bison, elk, and antelope. Woody vegetation provides thermal cover and habitat for migratory birds. However, topographical variations could provide some escape cover. When found adjacent to sagebrush dominated states, this plant community may provide brood rearing/foraging areas for sage grouse, as well as lek sites. Other birds that would frequent this plant community include western meadowlarks, horned larks, migratory song birds, and golden eagles. Many grassland obligate small mammals would occur here.
Mature Cottonwoods/Grass Plant Community: The combination of an overstory of cottonwoods and an understory of grasses and forbs provide a very diverse plant community for wildlife.
It may provide some foraging opportunities for sage grouse when it occurs proximal to woody cover. Good grasshopper habitat equals good foraging for birds.
Mature Cottonwoods/ Cheatgrass Plant Community: The plant community composition is less diverse, and thus, less apt to meet the seasonal needs of large herbivores such as deer and antelope. It may provide some foraging opportunities for sage grouse when it occurs proximal to woody cover. The overstory of large cottonwoods provides habitat for a variety of birds ranging from raptors to neo-tropical migrants.
Rhizomatous Wheatgrass Plant Community: This plant community may be useful for the same large grazers that would use the Historic Climax Plant Community. However, the plant community composition is less diverse, and thus, less apt to meet the seasonal needs of these animals. It may provide some foraging opportunities for sage grouse when it occurs proximal to woody cover. Good grasshopper habitat equals good foraging for birds.
Animal Community – Grazing Interpretations
The following table lists suggested stocking rates for cattle under continuous season-long grazing under normal growing conditions. These are conservative estimates that should be used only as guidelines in the initial stages of the conservation planning process. Often, the current plant composition does not entirely match any particular plant community (as described in this ecological site description). Because of this, a field visit is recommended, in all cases, to document plant composition and production. More precise carrying capacity estimates should eventually be calculated using this information along with animal preference data, particularly when grazers other than cattle are involved. Under more intensive grazing management, improved harvest efficiencies can result in an increased carrying capacity. If distribution problems occur, stocking rates must be reduced to maintain plant health and vigor.
Plant Community Production Carrying Capacity*
(Lb./ac) (AUM/ac)
Rhizomatous WG, Green Needlegrass,Cottonwoods 2000-4000 .8
Mature Cottonwoods/Grass 1200-3000 .7
Mature Cottonwoods/Cheatgrass 600-1200 .25
Rhizomatous Wheatgrass 1200-3000 .4
* - Continuous, season-long grazing by cattle under average growing conditions.
Grazing by domestic livestock is one of the major income-producing industries in the area. Rangeland in this area may provide yearlong forage for cattle, sheep, or horses. During the dormant period, the forage for livestock use needs to be supplemented with protein because the quality does not meet minimum livestock requirements.
Hydrological functions
Water is the principal factor limiting forage production on this site. This site is dominated by soils in hydrologic group B and C, with localized areas in hydrologic group D. Infiltration ranges from moderately slow to rapid. Runoff potential for this site varies from low to moderate depending on soil hydrologic group and ground cover. In many cases, areas with greater than 75% ground cover have the greatest potential for high infiltration and lower runoff. An example of an exception would be where short-grasses form a strong sod and dominate the site. Areas where ground cover is less than 50% have the greatest potential to have reduced infiltration and higher runoff (refer to Part 630, NRCS National Engineering Handbook for detailed hydrology information).
Rills and gullies should not typically be present. Water flow patterns should be barely distinguishable if at all present. Pedestals are only slightly present in association with bunchgrasses. Litter typically falls in place, and signs of movement are not common. Chemical and physical crusts are rare to non-existent. Cryptogamic crusts are present, but only cover 1-2% of the soil surface.
Recreational uses
This site provides hunting opportunities for upland game species. The wide variety of plants which bloom from spring until fall have an esthetic value that appeals to visitors.
Wood products
No appreciable wood products are present on the site.
Other products
None noted
Supporting information
Inventory data references
Inventory Data References (narrative)
Information presented here has been derived from NRCS clipping data and other inventory data. Field observations from range trained personnel was also used. Other sources used as references include USDA NRCS Water and Climate Center, USDA NRCS National Range and Pasture Handbook, and USDA NRCS Soil Surveys from various counties.
Inventory Data References
Data Source Number of Records Sample Period State County
SCS-RANGE-417 1971-1994 WY
Ocular estimates 5 1990-1999 WY
Contributors
G. Mitchell
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 | 04/01/2005 |
| Approved by | E. Bainter |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
Number and extent of rills:
Rills should not be present -
Presence of water flow patterns:
Barely observable -
Number and height of erosional pedestals or terracettes:
Essentially non-existent -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare ground is 10-20% occurring in small areas throughout site -
Number of gullies and erosion associated with gullies:
Active gullies should not be present -
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. Plant litter remains in place and is not moved by erosional forces. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Plant cover and litter is at 80% or greater of soil surface and maintains soil surface integrity. Soil Stability class is anticipated to be 5 or greater. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Use Soil Series description for depth and color of A-horizon -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Grass canopy and basal cover should reduce raindrop impact and slow overland flow providing increased time for infiltration to occur. Healthy deep rooted native grasses enhance infiltration and reduce runoff. Infiltration is moderately slow to moderate. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
No compaction layer or soil surface crusting should be present. -
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:
Mid stature Cool Season Grasses >> Shrubs > Trees = Short Grasses = Forbs -
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Some decadence and mortality among tree species -
Average percent litter cover (%) and depth ( in):
Average litter cover is 35-45% with depths of 0.25 to 1.0 inches -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
3000 lbs/ac -
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:
Kentucky bluegrass, Cheatgrass, Silver sagebrush, Snowberry and Species found on Noxious Weed List -
Perennial plant reproductive capability:
All species are capable of reproducing
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