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Ecological site R024XY016OR

LOAMY 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

R024XY015OR	DESERT LOAM 6-10 PZ Desert Loam 6-10 PZ (higher salts and carbonates, droughtier conditions, different composition – ATCO-PIDE4 dominant)
R024XY017OR	SHALLOW LOAM 8-10 PZ Shallow Loam 8-10 PZ (shallower soil, lower production)
R024XY018OR	SANDY LOAM 8-10 PZ Sandy Loam 8-10 PZ (sandy loam to loamy sand surface layer greater than 10 inches thick, different composition – needle and thread dominant)
R024XY021OR	THIN SURFACE 8-14 PZ Thin Surface 8-14 PZ (very shallow soil, different composition – ARNO4 dominant)
R024XY653OR	ARID FAN 8-10 PZ Arid Fan 8-10 PZ (lithic toe slope position, lower production)

Similar sites

R024XY017OR	SHALLOW LOAM 8-10 PZ Shallow Loam 8-10 PZ (shallower soil, lower production)
R024XY653OR	ARID FAN 8-10 PZ Arid Fan 8-10 PZ (lithic toe slope position, lower production)
R024XY015OR	DESERT LOAM 6-10 PZ Desert Loam 6-10 PZ (higher salts and carbonates, droughtier conditions, different composition – ATCO-PIDE4 dominant)
R024XY018OR	SANDY LOAM 8-10 PZ Sandy Loam 8-10 PZ (sandy loam to loamy sand surface layer greater than 10 inches thick, different composition – needle and thread dominant)

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Artemisia tridentata var. wyomingensis
Herbaceous	(1) Achnatherum thurberianum (2) Pseudoroegneria spicata ssp. spicata

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Physiographic features

This site occurs on upland fan remnants, terraces, fans and rolling hills. It is found on topography with gentle slopes. Slopes typically range from 2 to 15 percent. Elevation varies from 3800 to 5000 feet.

Table 2. Representative physiographic features

Landforms	(1) Fan remnant (2) Terrace (3) Hill
Elevation	3,800 – 5,000 ft
Slope	2 – 15%
Aspect	Aspect is not a significant factor

Climatic features

The annual precipitation ranges from 8 to 10 inches, most of which occurs in the form of snow and rain during the months of December through March. The soil temperature regime is mesic to frigid near mesic. Air temperature extremes range from 110 to -20 degrees F. The frost free period ranges from 90 to 120 days. The optimum growth period for native plants is from the first of April through 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 typically moderately deep, greater than 16 inches to deep over a duripan, compacted alluvial and lacustrine sediments, or bedrock. Surface textures vary from gravelly loams to gravelly sandy loams. Subsoils typically have an increase in clay. A desert pavement is common. Stones and cobbles are often present throughout. Soils are well drained. Permeability is moderate. The available water holding capacity (AWC) is about 4 to 6 inches for the profile. The potential for water and wind erosion is moderate. See Appendix II for soils on which this site occurs.

Table 4. Representative soil features

Parent material	(1) Eolian deposits – rhyolite
Surface texture	(1) Gravelly loam (2) Cobbly silt
Family particle size	(1) Clayey
Drainage class	Well drained
Permeability class	Moderate
Soil depth	16 – 60 in
Available water capacity (0-40in)	4 – 6 in

Ecological dynamics

The reference native plant community is dominated by Wyoming big sagebrush and Thurber needlegrass. Bluebunch wheatgrass and Indian ricegrass are prominent. Bottlebrush squirreltail and Sandberg bluegrass are common. Needle and thread is variable. Spiny hopsage and a variety of forbs are present. Vegetative composition of the community is approximately 80 percent grasses, 5 percent forbs and 15 percent shrubs. The approximate ground cover is 40-60% (basal and crown).

Four states have been identified for this site: a reference state; a state with the presence of annuals; a state with a shrub/annual co-dominance; and a state with annual dominance.

Reference: Plant community phase change is driven by infrequent fire. Wyoming and basin big sagebrush decline after fire while Thurber’s needlegrass, Indian ricegrass and other grasses increase. May see a temporary increase in rabbitbrush after fire. Time facilitates the reintroduction of sagebrush. The introduction of invasive annual grasses and forbs transitions into the state 2.

State 2: Compositionally similar to the reference state with a trace of cheatgrass and weedy forbs. Ecological function has not changed, however the resiliency of the state has been reduced by the presence of invasive weeds. Prescribed grazing and infrequent fire (> 50 year return interval) maintain state dynamics. The timing and/or intensity of grazing or prolonged drought favors Wyoming and basin big sagebrush, squirreltail and Sandberg’s bluegrass. Prescribed grazing and/or release from drought may reverse the decline in needlegrass and Indian ricegrass production. Infrequent fire reduces the shrub community and promotes the bunchgrass component. Mismanaged grazing and/or prolonged drought leads to a biotic threshold and into state 3.

State 3: Wyoming and basin big sagebrush is decadent with little recruitment. The perennial grass component is significantly reduced in both density and productivity. Cheatgrass and/or annual forbs and/or Sandberg’s bluegrass along with sagebrush control site resources and drive ecological dynamics. Bare ground is abundant. Spatial and temporal energy capture and nutrient cycling has been truncated. Infiltration may be reduced due to lack of ground cover. Risk of soil erosion by both wind and water is increased. Catastrophic wildfire will lead to an abiotic threshold and into state 4.

State 4: Cheatgrass and/or annual weed dominated plant community with limited to no shrub or perennial grass component. Soil erosion and redistribution along with changes in dynamic soil properties affect the hydrologic cycle and thus the nutrient cycle. Harsh environmental factors increase state resiliency to change.

Range in Characteristics-
Production will increases at the upper end of the precipitation zone. Thurber’s needlegrass increases on loamy surfaces, Indian ricegrass increases on sandy gravelly surfaces and bluebunch wheatgrass increases on a silty surfaces. Bottlebrush squirrel tail will increase on older higher terraces with stable erosion pavement. The old erosion pavement has developed a distinctive desert varnish. The distinctive dark color is due to precipitated concentrates of manganese and lesser amounts of iron.

Response to Disturbance - States
If the condition of the site deteriorates as a result of over grazing, Thurber’s needlegrass, Indian ricegrass and bluebunch wheatgrass will decrease in the stand. Wyoming big sagebrush, Sandberg bluegrass and squirreltail will increase. With further deterioration, annuals invade, bare ground increases, vesicular crusts enlarge, erosion accelerates and site productivity decreases. Annual invasion is prevalent under deteriorated conditions following fire.

States: ARTRW8/ELEL5-POSE-bare ground; Annuals-bare ground with fire

State and transition model

Custom diagram

Standard diagram

Figure 2. Group 6, STM

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 Plant Community

State 1 submodel, plant communities

1.1. Reference Plant Community

State 1
Reference Plant Community

Community 1.1
Reference Plant Community

Figure 3. 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	320	560	720
Shrub/Vine	60	105	135
Forb	20	35	45
Total	400	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, moderate rooted bunchgrass			140–210
	Thurber's needlegrass	ACTH7	Achnatherum thurberianum	140–210	–
2	Sub-dominant, moderate-rooted bungrasses			140–350
	bluebunch wheatgrass	PSSPS	Pseudoroegneria spicata ssp. spicata	70–210	–
	Indian ricegrass	ACHY	Achnatherum hymenoides	70–140	–
3	Common moderate and deep rooted bunchgrasses			30–130
	needle and thread	HECO26	Hesperostipa comata	0–70	–
	basin wildrye	LECI4	Leymus cinereus	10–35	–
	squirreltail	ELEL5	Elymus elymoides	15–35	–
4	Other perennial grasses			30–60
	beardless wildrye	LETR5	Leymus triticoides	0–15	–
	Sandberg bluegrass	POSE	Poa secunda	5–15	–
	foxtail wheatgrass	PSSA2	×Pseudelymus saxicola	0–15	–
	sand dropseed	SPCR	Sporobolus cryptandrus	0–15	–
Forb
5	Dominant perennial forbs			20–45
	milkvetch	ASTRA	Astragalus	7–15	–
	buckwheat	ERIOG	Eriogonum	7–15	–
	lupine	LUPIN	Lupinus	7–15	–
6	Other perennial forbs			15–60
	common yarrow	ACMI2	Achillea millefolium	2–7	–
	tapertip hawksbeard	CRAC2	Crepis acuminata	2–7	–
	fleabane	ERIGE2	Erigeron	2–7	–
	granite prickly phlox	LIPU11	Linanthus pungens	0–7	–
	desertparsley	LOMAT	Lomatium	2–7	–
	phlox	PHLOX	Phlox	2–7	–
	scarlet globemallow	SPCO	Sphaeralcea coccinea	0–7	–
	deathcamas	ZIGAD	Zigadenus	2–5	–
	silverpuffs	MICRO6	Microseris	0–5	–
	pussytoes	ANTEN	Antennaria	2–5	–
	Douglas' dustymaiden	CHDO	Chaenactis douglasii	0–5	–
Shrub/Vine
7	Dominant, evergreen, non-sprouting shrubs			50–105
	Wyoming big sagebrush	ARTRW8	Artemisia tridentata ssp. wyomingensis	35–70	–
	basin big sagebrush	ARTRT	Artemisia tridentata ssp. tridentata	14–35	–
8	Sub-dominant, evergreen, non-sprouting shrub			7–20
	spiny hopsage	GRSP	Grayia spinosa	7–20	–
9	Other perennial shrubs			20–70
	shadscale saltbush	ATCO	Atriplex confertifolia	0–15	–
	yellow rabbitbrush	CHVI8	Chrysothamnus viscidiflorus	5–15	–
	winterfat	KRLA2	Krascheninnikovia lanata	0–15	–
	bud sagebrush	PIDE4	Picrothamnus desertorum	0–15	–
	littleleaf horsebrush	TEGL	Tetradymia glabrata	5–15	–
	shortspine horsebrush	TESP2	Tetradymia spinosa	0–10	–
	mormon tea	EPVI	Ephedra viridis	0–10	–

Interpretations

Animal community

Livestock-
This site is suitable for livestock grazing use in spring, fall and early winter 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 Thurber’s needlegrass, Indian ricegrass and bluebunch wheatgrass. These bunchgrasses can be severely damaged if heavily grazed during periods of flowering and 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 offers food and cover for antelope, mule deer, sage grouse and a variety of other birds, rodents and their associated predators. It is an important spring, fall and winter use area for sage grouse, antelope and mule deer.

Hydrological functions

Watershed-
The soils of this site have a moderate runoff potential. The hydrologic cover condition is good when the deep rooted bunchgrass component is greater than 70 percent of potential. The soils are in hydrologic group C.

Other information

This site has moderately low potential for range seeding because it is very droughty.

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)	Lars Santana and Bob Gillaspy
Contact for lead author	State Rangeland Management Specialist for OR NRCS
Date	11/08/2016
Approved by	Bob Gillaspy
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
None, moderate sheet & rill erosion hazard.
Presence of water flow patterns:
None, except following extremely high intensity storms when short (less than 1 meter) flow patterns may appear on steeper slopes. Minimal evidence of past or current soil deposition or erosion.
Number and height of erosional pedestals or terracettes:
None, except few pedestals or terracettes on steeper slopes.
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
10-25% bare ground, typically bare patches are associated with shrubs. Larger bare patches maybe associated with ant mounds, rodent, and/or other natural disturbances.
Number of gullies and erosion associated with gullies:
None.
Extent of wind scoured, blowouts and/or depositional areas:
None. Wind erosion hazard is moderate.
Amount of litter movement (describe size and distance expected to travel):
Litter size is Small/Fine. Litter movement is limited, minimal, and short, associated with water flow patterns following extremely high intensity storms. Litter also may be moved during intense wind storms.
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Site is Slightly to Moderately resistant to erosion. Stability class (Herrick et al. 2001) anticipated to be 3-6 at surface under perennial vegetation. Stability class at surface in the interspaces is anticipated to be less than or equal to that under perennial vegetation.
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Surface layer structure is single grain to massive. The A horizon has a dry color of 5 - 6 and is 1 - 10 inches thick. The Soil Organic Matter (SOM) content is low (0.2 to 2.0%).
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Plant foliar cover and basal cover with small gaps between plants should reduce raindrop impact and slow overland flow, providing increased time for infiltration to occur. High herbaceous vegetation on this site will retain more water from precipitation. Moderate ground cover (40-60%) and gentle slopes (2-15%) moderately limit rainfall impact and overland flow.
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
None.
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 Deep Rooted Perennial Bunchgrass [Thurber's Needlegrass = Indian Ricegrass > Bluebunch Wheatgrass] > Evergreen Shrubs [sagebrush]

Sub-dominant:
other grasses > other shrubs

Other:
forbs

Additional:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Grasses will nearly always show some mortality and decadence. Normal decadence and mortality expected on other plants.
Average percent litter cover (%) and depth ( in):
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
Annual production: Low 400 lbs/acre, Representative Value 700 lbs/acre, High 900 lbs/acre
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:
Annuals (Cheatgrass, Medusahead, and forbs) invade sites that have lost deep rooted perennial grass functional groups.
Perennial plant reproductive capability:
All species should be capable of reproducing annually.

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