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Ecological site R024XY113OR

SODIC FAN
6-10 PZ

Accessed: 04/20/2026

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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.

Ecological site concept

This ecological site occurs on lake plains and basin floor remnants. Soil are very deep, well drained and formed in a thin layer of loess and alluvium derived from mixed parent material influenced by volcanic ash over lacustrine sediments. Soils are characterized by a very low infiltration, an ochric epipedon, moderate to very strong alkalinity, and SAR greater than 45 in the upper profile. The soil temperature regime is mesic and the soil moisture regime is typic aridic.
The plant community is characterized by the mixing of shadscale and black greasewood and approximate canopy cover is less than 15%. Approximate vegetative composition is 85% shrubs, 10% grasses, and 5% forbs.
This ESC will be field checked for correlation to similar concepts. This site has similar species composition and does not compete based on soil characteristic or abiotic factors with Sodic Terrace 6-8"PZ R024XY003NV, Sodic Terrace 8-10"PZ R024XY022NV and Sodic Terrace 6-10"PZ R024XY014OR.

Associated sites

R024XY013OR	LOW SODIC TERRACE 6-10 PZ Low Sodic Terrace 6-10 PZ (low terrace, higher salts and carbonates, lower production, different composition – SAVE4 dominant in salt desert shrub association, ARTR minor to absent)
R024XY014OR	SODIC TERRACE 6-10 PZ Sodic Terrace 6-10 PZ (terrace position, higher salts and carbonates, lower production, different composition – ARTRT, GRSP & SAVE4 near co-dominant)
R024XY030OR	LOAMY SLOPES 6-10 PZ Loamy Slopes 6-10 PZ (upland slope position, shallower soil, lower salts and carbonates, different composition – ARTRW8 dominant shrub, SAVE4 and LECI4 absent to minor)

R024XY013OR

LOW SODIC TERRACE 6-10 PZ

Low Sodic Terrace 6-10 PZ (low terrace, higher salts and carbonates, lower production, different composition – SAVE4 dominant in salt desert shrub association, ARTR minor to absent)

R024XY014OR

SODIC TERRACE 6-10 PZ

Sodic Terrace 6-10 PZ (terrace position, higher salts and carbonates, lower production, different composition – ARTRT, GRSP & SAVE4 near co-dominant)

R024XY030OR

LOAMY SLOPES 6-10 PZ

Loamy Slopes 6-10 PZ (upland slope position, shallower soil, lower salts and carbonates, different composition – ARTRW8 dominant shrub, SAVE4 and LECI4 absent to minor)

Similar sites

R024XY014OR	SODIC TERRACE 6-10 PZ Sodic Terrace 6-10 PZ (terrace position, higher salts and carbonates, lower production, different composition – ARTRT, GRSP & SAVE4 near co-dominant)

R024XY014OR

SODIC TERRACE 6-10 PZ

Sodic Terrace 6-10 PZ (terrace position, higher salts and carbonates, lower production, different composition – ARTRT, GRSP & SAVE4 near co-dominant)

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Artemisia tridentata subsp. tridentata (2) Sarcobatus vermiculatus
Herbaceous	(1) Achnatherum hymenoides (2) Leymus cinereus

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Physiographic features

This site typically occurs on alluvial fans adjacent to sodic lake basins and drainages. Slopes typically range from 1 to 6%. Elevations vary from 4,000 to 4,500 feet.

Table 2. Representative physiographic features

Landforms	(1) Alluvial fan (2) Fan remnant (3) Drainageway
Flooding duration	Very brief (4 to 48 hours)
Flooding frequency	None to occasional
Ponding duration	Very brief (4 to 48 hours) to brief (2 to 7 days)
Ponding frequency	Rare to occasional
Elevation	4000 – 4500 ft
Slope	1 – 6 %
Water table depth	60 – 0 in
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 during the months of December through April. The soil temperature regime is mesic with a mean air temperature of 48 degrees F. Temperature extremes range from 100 to -20 degrees F. The frost-free period ranges from 90 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

Bar

Line

Figure 2. Monthly precipitation range

Bar

Line

Figure 3. Monthly average minimum and maximum temperature

Soil features

The soils associated with this site are very deep, well drained and formed in a thin layer of loess and alluvium derived from mixed rocks influenced by volcanic ash over lacustrine sediments. The soil profile is characterized by a surface horizon with a platy soil structure, moderate to strong alkalinity and a SAR greater than 45.
Soil texture is a silt loam throughout. Many of these soils were formed under more poorly drained conditions than exist curently and relict redox concentrations can be found below 30cm. The surface horizon is violently effervescent and will normally crust and bake upon drying inhibiting water infiltration and seedling emergence.

Table 4. Representative soil features

Parent material	(1) Alluvium – rhyolite
Surface texture	(1) Gravelly sandy loam (2) Loam
Family particle size	(1) Loamy
Permeability class	Moderately slow
Soil depth	60 – 0 in
Available water capacity (0-40in)	6 – 8 in

Ecological dynamics

The potential native plant community is dominated by basin big sagebrush, Indian ricegrass and basin wildrye. Greasewood is prominent. Bottlebrush squirreltail and beardless wildrye (creeping) are common. Spiny hopsage, Sandberg bluegrass, needle and thread and a variety of forbs are present. Vegetative composition of the community is approximately 65 percent grasses, 30 percent shrubs and 5 percent forbs. The approximate ground cover is 50 to 60 percent (basal and crown).

Range in Characteristics:
Production increases at the upper end of the precipitation zone and in areas with increasing available subsurface moisture. Basin wildrye increases in areas with deep subsurface moisture. Greasewood increases in sodic areas with deep subsurface moisture. Spiny hopsage increases in droughty areas. Shadscale saltbush and bud sagebrush increases in drier calcareous soil areas. Indian ricegrass increases on coarser soils. Bottlebrush squirreltail and other bunchgrasses increase with precipitation and reduced sodic conditions. With an increase in fire frequency big sagebrush will decrease and basin wildrye wil increase.

Response to Disturbance - States:
When the condition of the site deteriorates as a result of over grazing Indian ricegrass, basin wildrye and bud sagebrush will decrease. Big sagebrush, greasewood, shadscale and spiny hopsage will increase. With further deterioration, spiny hopsage, shadscale, squirreltail and Sandberg bluegrass will decrease. Greasewood and big sagebrush are impacted to a lesser extent. Minor amounts of annuals will invade and bare ground increases. Soil surface conditions become increasingly sodic and site deterioration continues to occur in a cyclic pattern.

States: ARTRT-SAVE4/ELEL5-POSE-bare ground (ACHY&LECI4 absent); SAVE4/annuals-bare ground (with fire)

State and transition model

Custom diagram

Standard diagram

More interactive model formats are also available. View Interactive Models

More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective text

Ecosystem states

1. Reference State

State 1 submodel, plant communities

1.1. Reference Plant Community

State 1
Reference State

Community 1.1
Reference Plant Community

The reference native plant community is dominated by basin big sagebrush, Indian ricegrass and basin wildrye. Greasewood is prominent. Bottlebrush squirreltail and beardless wildrye (creeping) are common. Spiny hopsage, Sandberg bluegrass, needle and thread and a variety of forbs are present. Vegetative composition of the community is approximately 65 percent grasses, 30 percent shrubs and 5 percent forbs. The approximate ground cover is 50 to 60 percent (basal and crown).

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	260	390	520
Shrub/Vine	120	180	240
Forb	20	30	40
Total	400	600	800

Additional community tables

Table 6. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production ()	Foliar cover (%)
Grass/Grasslike
1	Dominant, moderate rooted bunchgrass			180–300
	Indian ricegrass	ACHY	Achnatherum hymenoides	180–300	–
2	Sub-dominant, deep-rooted bunchgrass			60–180
	basin wildrye	LECI4	Leymus cinereus	60–180	–
3	Common, perennial grasses			20–60
	squirreltail	ELEL5	Elymus elymoides	10–30	–
	beardless wildrye	LETR5	Leymus triticoides	10–30	–
4	Other perennial grasses			20–30
	saltgrass	DISP	Distichlis spicata	180–300	–
	needle and thread	HECO26	Hesperostipa comata	5–20	–
	Sandberg bluegrass	POSE	Poa secunda	5–10	–
Forb
5	Perennial forbs			10–30
	milkvetch	ASTRA	Astragalus	5–10	–
	lupine	LUPIN	Lupinus	5–10	–
	evening primrose	OENOT	Oenothera	2–5	–
	scarlet globemallow	SPCO	Sphaeralcea coccinea	2–5	–
	thelypody	THELY	Thelypodium	0–3	–
Shrub/Vine
10	Dominant, evergreen, non-sprouting shrub			70–120
	basin big sagebrush	ARTRT	Artemisia tridentata ssp. tridentata	60–90	–
	Wyoming big sagebrush	ARTRW8	Artemisia tridentata ssp. wyomingensis	12–30	–
11	Sub-dominant, deciduous, non-sprouting shrub			30–60
	greasewood	SAVE4	Sarcobatus vermiculatus	30–60	–
12	Common, evergreen, non-sprouting shrub			36–90
	shadscale saltbush	ATCO	Atriplex confertifolia	12–30	–
	spiny hopsage	GRSP	Grayia spinosa	12–30	–
	bud sagebrush	PIDE4	Picrothamnus desertorum	12–30	–
13	Other shrubs			6–36
	rubber rabbitbrush	ERNA10	Ericameria nauseosa	0–6	–
	winterfat	KRLA2	Krascheninnikovia lanata	0–6	–
	littleleaf horsebrush	TEGL	Tetradymia glabrata	0–6	–
	shortspine horsebrush	TESP2	Tetradymia spinosa	0–6	–

Interpretations

Animal community

Livestock Grazing
This site is suitable for livestock grazing use in the fall, winter and spring 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 Indian ricegrass, basin wildrye and bud sagebrush. Heavy late winter/early spring grazing during periods of "bark slippage" can severely damage bud sagebrush, spiny hopsage and shadscale. Indian ricegrass, basin wildrye and squirreltail can be severely damaged if heavily grazed during periods of grass seed formation before root reserves have accumulated and soil moisture is low. 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 winter and spring forage for mule deer and antelope.

Hydrological functions

The soils of this site are typically located on a basin fan topographic position and receive seasonal off-site surface flows in defined channel. Runoff potential is slight to moderate depending on location. Infiltration rates are moderate when the vegetation cover is high. Hydrologic cover is high when the composition of shrubs and the dominant understory grasses, Indian ricegrass, and basin wildrye are greater than 70 percent of potential. The soils are in hydrologic group C.

Other information

This site has low potential for reseeding. The droughty nature of the site and potential salt concentrations reduce the germination and establishment of currently available species. 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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