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Ecological site R024XY645OR

SILTY ALKALINE BOTTOM 8-10 PZ

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.

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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, LETR5 strongly dominant)
R024XY644OR	SILTY DUNES Silty Dunes (higher sodic conditions, deep silt loam, greater slopes,different composition – SAVE4 dominant, ARTRT absent to minor)

R024XY006OR

LAKE TERRACE

Lake Terrace (mildly sodic, LETR5 strongly dominant)

R024XY644OR

SILTY DUNES

Silty Dunes (higher sodic conditions, deep silt loam, greater slopes,different composition – SAVE4 dominant, ARTRT absent to minor)

Similar sites

R024XY009OR	DRY BASIN Dry Basin (fine sandy loam over silt loam, longer available seasonal water table, higher production, different composition – ARTRT & LECI4 dominant)
R024XY120OR	SILTY LOW SODIC TERRACE 6-10 PZ Silty Low Sodic Terrace 6-10 PZ (higher sodic conditions, loam over silty clay loam subsoil, different composition – SAVE4 dominant, ATCO & GRSP prominent)
R024XY632OR	DRY LAKE TERRACE 6-10 PZ Dry Lake Terrace 6-10 PZ (silt loam over clayey subsoil, different composition – LECI4 absent to minor)
R024XY625OR	ALKALINE BASIN 8-10 PZ Alkaline Basin 8-10 PZ (higher sodic conditions, loam over a heavier subsoil, different composition - SAVE4 & LECI4 dominant, DISP prominent)
R024XY644OR	SILTY DUNES Silty Dunes (higher sodic conditions, deep silt loam, greater slopes, different composition – SAVE4 dominant, ARTRT absent to minor)
R024XY112OR	DRY SODIC FLOODPLAIN Dry Sodic Floodplain (higher sodic conditions, gravelly loamy surface over stratified heavier subsoil, different composition - SAVE4 & DISP dominant, LETR5 minor)
R024XY121OR	SILTY SODIC TERRACE 6-10 PZ Silty Sodic Terrace 6-10 PZ (loam over silty clay loam subsoil, different composition – GRSP prominent, LECI4 absent to minor)

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Sarcobatus vermiculatus (2) Artemisia tridentata ssp. tridentata
Herbaceous	(1) Leymus triticoides (2) Leymus cinereus

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Physiographic features

This site typically occurs on the floors of old dry lake beds derived from volcanic ash. Slopes typically range from 0 to 2%. Elevations vary from 4,200 to 4,500 feet.

Table 2. Representative physiographic features

Landforms	(1) Basin floor (2) Lakebed
Ponding duration	Brief (2 to 7 days) to very brief (4 to 48 hours)
Ponding frequency	Frequent to occasional
Elevation	4,200 – 4,500 ft
Slope	2%
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. An ephemeral supply of ponded and subsurface moisture augments the precipitation. The soil temperature regime is mesic to frigid near mesic with a mean air temperature of 47 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)	0 days
Precipitation total (average)	10 in

Soil features

The soils of this site are formed in lacustrine sediments derived from volcanic ash. They are typically fine-loamy in textured, very deep and well drained. The surface layer is an ashy silt loam over an ashy loam subsoil. Substratums are often paragravelly ashy silt loams with diatomaceous sediments. Soils are mildly sodic with pH’s increasing in the subsoil. Ponding in the spring is frequent. Permeability is moderately 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 60 inches. The water erosion potential is slight due to the low elevation flat position of the site. Wind erosion potential is moderate.

Table 4. Representative soil features

Parent material	(1) Lacustrine deposits – rhyolite
Surface texture	(1) Ashy silt loam
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). Basin wildrye is subdominant along with greasewood and basin big sagebrush. A variety of other grasses and forbs are present. Vegetative composition of the community is approximately 70 percent grasses, 5 percent forbs and 25 percent shrubs. The approximate ground cover is 60 to 70 percent (basal and crown).

Range in Characteristics:
Production increases with increasing available subsurface moisture and in areas with decreasing alkalinity. Beardless wildrye increases in areas with finer surface textures and lower surface alkalinity. Basin wildrye increases in areas with greater available subsurface moisture. Greasewood increases in areas with higher alkalinity and basin big sagebrush increases with decreasing alkaline conditions. Areas with greater amounts of saltgrass are transitional to other sites. 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 basin wildrye will decrease. Beardless wildrye, bottlebrush squirreltail, greasewood and basin big sagebrush will increase. With further deterioration shrubs continue to increase, creeping wild rye decreases, annuals invade sparingly and areas of bare ground increase. As bare soil increases, soil surface conditions become increasingly sodic and saltgrass increases. Production decreases and site deterioration continues to occur in a cyclic pattern.

States: SAVE4-ARTRT/LETR5-bare ground;
SAVE4/DISP-LETR5-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). Basin wildrye is subdominant along with basin greasewood and basin big sagebrush. A variety of other grasses and forbs are present. Vegetative composition of the community is approximately 70 percent grasses, 5 percent forbs and 25 percent shrubs. The approximate ground cover is 60 to 70 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	350	490	630
Shrub/Vine	125	175	225
Forb	25	35	45
Total	500	700	900

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, moderately rooted, rhizomatous grass			210–420
	beardless wildrye	LETR5	Leymus triticoides	210–420	–
2	Sub-dominant, deep rooted bunchgrass			70–210
	basin wildrye	LECI4	Leymus cinereus	70–210	–
3	Other perennial grasses			14–49
	squirreltail	ELEL5	Elymus elymoides	14–35	–
	saltgrass	DISP	Distichlis spicata	0–14	–
Forb
4	Perennial forbs			28–42
	milkvetch	ASTRA	Astragalus	14–21	–
	salt heliotrope	HECU3	Heliotropium curassavicum	14–21	–
Shrub/Vine
5	Dominant, deciduous, non-sprouting shrub			70–105
	greasewood	SAVE4	Sarcobatus vermiculatus	70–105	–
6	Co-dominant, evergreen, non-sprouting shrub			70–105
	basin big sagebrush	ARTRT	Artemisia tridentata ssp. tridentata	70–105	–
7	Other shrubs			7–35
	rubber rabbitbrush	ERNA10	Ericameria nauseosa	7–35	–

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 basin 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 good visibility and limited forage for antelope.

Hydrological functions

The soils of this site are typically in or near the lowest topographic position. It accumulates off-site surface flows and when ponded has virtually no runoff potential. The soils have medium infiltration rates when vegetation cover is high. Hydrologic cover is high when the basin wildrye and beardless wildrye component is greater than 70 percent of potential. The soils are in hydrologic group C.

Other information

This site can be difficult to reseed when in poor soil condition. Salt concentrations can reduce germination of basin wildrye and creeping wildrye. Beardless wildrye has limited seed availability. 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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