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Ecological site R024XY644OR

SILTY DUNES

Accessed: 11/21/2024

Home / Esd catalog / MLRA 024X / Ecological site R024XY644OR

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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.

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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

R024XY006OR	LAKE TERRACE Lake Terrace (mildly sodic, different composition - LETR5 strongly dominant, SAVE4 absent)
R024XY120OR	SILTY LOW SODIC TERRACE 6-10 PZ Silty Low Sodic Terrace 6-10 PZ (loam over silty clay loam subsoil, different composition - ATCO & GRSP prominent)
R024XY625OR	ALKALINE BASIN 8-10 PZ Alkaline Basin 8-10 PZ (loam over a heavier subsoil, different composition - SAVE4 & LECI4 dominant, DISP prominent)
R024XY645OR	SILTY ALKALINE BOTTOM 8-10 PZ Silty Alkaline Bottom 8-10 PZ (lower sodic condition, deep ashy fine loamy often over diatomaceous earth, different composition – ARTRT dominant, LECI4 prominent)

Similar sites

R024XY645OR	SILTY ALKALINE BOTTOM 8-10 PZ Silty Alkaline Bottom 8-10 PZ (lower sodic condition, deep ashy fine loamy often over diatomaceous earth, different composition – ARTRT dominant, LECI4 prominent)
R024XY121OR	SILTY SODIC TERRACE 6-10 PZ Silty Sodic Terrace 6-10 PZ (lower sodic conditions, loam over silty clay loam subsoil, different composition –ARTRT dominant, GRSP prominent)
R024XY112OR	DRY SODIC FLOODPLAIN Dry Sodic Floodplain (higher sodic conditions, gravelly loamy surface over stratified heavier subsoil, different composition - SAVE4 & DISP dominant)
R024XY632OR	DRY LAKE TERRACE 6-10 PZ Dry Lake Terrace (lower sodic conditions, silt loam over clayey subsoil, different composition – ARTRT dominant)
R024XY625OR	ALKALINE BASIN 8-10 PZ Alkaline Basin 8-10 PZ (loam over a heavier subsoil, different composition - SAVE4 & LECI4 dominant, DISP prominent)
R024XY120OR	SILTY LOW SODIC TERRACE 6-10 PZ Silty Low Sodic Terrace 6-10 PZ (loam over silty clay loam subsoil, different composition - ATCO & GRSP prominent)
R024XY009OR	DRY BASIN Dry Basin (fine sandy loam over silt loam, longer available seasonal water table, higher production, different composition – ARTRT & LECI4 dominant)

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Sarcobatus vermiculatus
Herbaceous	(1) Leymus triticoides

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Physiographic features

This site typically occurs as dunes on low elevation dry lake basins. They occur on the north and east edges of old lake shores and flats where windblown silts have accumulated. Slopes typically range from 2 to 15% with short reaches up to 30 percent on leeward dune faces. Elevations vary from 4,000 to 4,800 feet.

Table 2. Representative physiographic features

Landforms	(1) Dune (2) Basin floor
Elevation	4,000 – 4,800 ft
Slope	2 – 15%
Aspect	Aspect is not a significant factor

Climatic features

The annual precipitation ranges from 6 to 10 inches, most of which occurs in the form of rain and snow during the months of December through April. The soil temperature regime is mesic to frigid near mesis with a mean air temperature of 48 degrees F. Temperature extremes range from 100 to -20 degrees F. The frost-free period ranges from 70 to 120 days. The optimum growth period for plant growth is from April to early June.

Table 3. Representative climatic features

Frost-free period (average)	120 days
Freeze-free period (average)	130 days
Precipitation total (average)	10 in

Soil features

The soils of this site are typically silty to loamy textured, very deep and well drained. The surface layer is a silt loam to ashy loamy fine sand. Subsoils are ashy fine sandy loams to silty clay loams over lacustrine sediments. Soils are sodic with pH’s increasing in the subsoil. Permeability is moderately slow to slow. The available water holding capacity (AWC) is about 6 to 8 inches for the profile. A seasonal water table is present at 30 to greater than 72 inches. The water erosion potential is slight to moderate depending on slope. The potential for wind erosion is high.

Table 4. Representative soil features

Parent material	(1) Eolian deposits – rhyolite
Surface texture	(1) Ashy silt loam (2) Loamy fine sand
Family particle size	(1) Loamy
Drainage class	Well drained to moderately well drained
Permeability class	Moderately slow to slow
Soil depth	60 in
Available water capacity (0-40in)	6 – 8 in
Calcium carbonate equivalent (0-40in)	Not specified
Electrical conductivity (0-40in)	Not specified
Sodium adsorption ratio (0-40in)	Not specified
Soil reaction (1:1 water) (0-40in)	Not specified

Ecological dynamics

The potential native plant community is dominated by beardless wildrye (creeping). Greasewood is subdominant. Spiny hopsage, basin big sagebrush and a variety of other grasses and forbs are present. Vegetative composition of the community is approximately 55 percent grasses, 5 percent forbs and 40 percent shrubs. The approximate ground cover is 50 to 60 percent (basal and crown).

Range in Characteristics:
Production and beardless wildrye will increases in areas with additional available subsurface moisture and on north facing dune aspects. Greesewood increases in areas of higher salinity. Basin big sagebrush increases in areas of lower salinity. Higher salt concentrations reduce plant growth and inhibits seedling emergence.

Response to Disturbance - States:
When the condition of the site deteriorates as a result of over grazing beardless wildrye will decrease and areas of bare ground will increase. Greasewood, basin big sagebrush, rabbitbrush and unpalatable salt tolerant forbs increase. With further deterioration shrubs continue to increase, beardless wild rye continues to decrease and areas of bare ground enlarge. Exposed areas of silty soils are subject to water erosion on dune slopes. Soil surface conditions become increasingly sodic. Production decreases and site deterioration continues to occur in a cyclic pattern.

States - SAVE4/Bare ground

State and transition model

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Ecosystem states

1. Reference Plant Community

State 1 submodel, plant communities

1.1. Reference Plant Community

State 1
Reference Plant Community

Community 1.1
Reference Plant Community

The reference native plant community is dominated by beardless wildrye (creeping). Greasewood is subdominant. Spiny hopsage, basin big sagebrush and a variety of other grasses and forbs are present. Vegetative composition of the community is approximately 55 percent grasses, 5 percent forbs and 40 percent shrubs. The approximate ground cover is 50 to 60 percent (basal and crown).

Figure 2. 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	330	385	440
Shrub/Vine	240	280	320
Forb	30	35	40
Total	600	700	800

Additional community tables

Table 6. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production (lb/acre)	Foliar cover (%)
Grass/Grasslike
1	Dominant, moderate rooted, rhizomatous grass			280–350
	beardless wildrye	LETR5	Leymus triticoides	280–350	–
2	Other perennial grasses			5–70
	Indian ricegrass	ACHY	Achnatherum hymenoides	0–21	–
	basin wildrye	LECI4	Leymus cinereus	0–21	–
	saltgrass	DISP	Distichlis spicata	0–14	–
	squirreltail	ELEL5	Elymus elymoides	5–14	–
Forb
3	Perennial forbs			28–42
	milkvetch	ASTRA	Astragalus	14–21	–
	salt heliotrope	HECU3	Heliotropium curassavicum	14–21	–
Shrub/Vine
4	Dominant, evergreen, sprouting shrub			140–210
	greasewood	SAVE4	Sarcobatus vermiculatus	140–210	–
5	Other shrubs			33–147
	spiny hopsage	GRSP	Grayia spinosa	14–70	–
	basin big sagebrush	ARTRT	Artemisia tridentata ssp. tridentata	14–35	–
	yellow rabbitbrush	CHVI8	Chrysothamnus viscidiflorus	5–14	–
	rubber rabbitbrush	ERNA10	Ericameria nauseosa	0–14	–
	shortspine horsebrush	TESP2	Tetradymia spinosa	0–14	–

Interpretations

Animal community

Livestock grazing:
This site is suitable for livestock grazing use in the late spring and fall under a planned grazing system. Use should be postponed until the soils are firm enough to prevent trampling damage and soil compaction. Grazing management should be keyed for beardless wildrye. Deferred grazing or rest is recommended at least once every three years.

Wildlife:
This site is used by pronghorn antelope, mule deer, rabbits, rodents, upland birds and various predators. It provides cover and good spring forage for numerous species.

Hydrological functions

The soils of this site are typically in or near the lowest topographic position. As dunes, slopes are quite variable over short distances and subject to wind erosion when disturbed. They have medium infiltration rates when vegetation cover is high. Hydrologic cover is high when the beardless wildrye component is greater than 70 percent of potential. The soils are in hydrologic group B.

Other information

This site has limited suitability for reseeding. As dunes, slopes are quite variable over short distances and difficult to reseed. They are subject to severe wind erosion when disturbed. Salt concentrations can reduce the germination and establishment of beardless wildrye. Seed availability of beardless wildrye is limited. Soils are corrosive to steel.

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
Approved by
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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