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Ecological site R011XY012OR

Silty 8-11 PZ

Accessed: 11/23/2024

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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

R011XY013OR	Clayey 8-11 PZ Clayey 8-11 PZ
R011XY016OR	Sandy 8-11 PZ Sandy 8-11 PZ
R011XY018OR	Shallow Loam 8-11 PZ Shallow Loam 8-11 PZ
R011XY020OR	South Slopes 8-11 PZ South Slopes 8-11 PZ
R011XY032OR	Silty North Slopes 8-11 PZ Silty North Slopes 8-11 PZ
R011XY034OR	Sandy North Slopes 8-11 PZ Sandy North Slopes 8-11 PZ

Similar sites

R011XY013OR	Clayey 8-11 PZ Clayey 8-11 PZ (clayey surface, different composition-beardless wheatgrass dominant, Thurber's neeedlegrass minor)
R011XY018OR	Shallow Loam 8-11 PZ Shallow Loam 8-11 PZ (shallower soil, lower production)

R011XY013OR

Clayey 8-11 PZ

Clayey 8-11 PZ (clayey surface, different composition-beardless wheatgrass dominant, Thurber's neeedlegrass minor)

R011XY018OR

Shallow Loam 8-11 PZ

Shallow Loam 8-11 PZ (shallower soil, lower production)

Table 1. Dominant plant species

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

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Physiographic features

This site occurs on low elevation terraces in the Malheur, Owyhee and adjacent Snake River drainage. Slopes typically range from 0 to 12%. Elevations vary from 2,100 to 3,200 feet.

Table 2. Representative physiographic features

Landforms	(1) Terrace
Elevation	640 – 975 m
Slope	0 – 12%
Aspect	Aspect is not a significant factor

Climatic features

The annual precipitation ranges from 8 to 11 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 53 degrees F. Temperature extremes range from 110 to -10 degrees F. The frost free period ranges from 150 to 190 days. The optimum growth period for plant growth is late March through June.

Table 3. Representative climatic features

Frost-free period (average)	190 days
Freeze-free period (average)	0 days
Precipitation total (average)	279 mm

Bar

Line

Figure 2. Monthly average minimum and maximum temperature

Soil features

The soils of this site are typically moderately deep to very deep and well drained. Typically the surface layer is a silt loam to a very fine sandy loam 8 to 16 inches thick. The subsoil is a silt loam to silty clay loam 15 to 25 inches thick. Depth to lacustrine or alluvial sediments ranges from 20 to greater than 60 inches. An indurate pan may be present. Permeability is moderate. The available water holding capacity (AWC) is about 4 to 6 inches for the profile. The erosion potential is moderate.

Table 4. Representative soil features

Surface texture	(1) Silt loam (2) Very fine sandy loam
Family particle size	(1) Loamy
Drainage class	Well drained
Permeability class	Moderate to moderately slow
Soil depth	51 – 152 cm
Available water capacity (0-101.6cm)	10.16 – 15.24 cm

Ecological dynamics

The potential native plant community is dominated by Wyoming big sagebrush, spiny hopsage and beardless wheatgrass. Thurber’s needlegrass is prominent. Sandberg bluegrass is the dominant shallow rooted perennial grass. A variety of forbs and shrubs are present. Vegetative composition of the community is approximately 75 percent grasses, 10 percent forbs and 15 percent shrubs. The approximate ground cover is 60 to 70 percent (basal and crown).

Range in Characteristics:
Wyoming big sagebrush and spiny hopsage are co-dominant with Wyoming big sagebrush increasing at the upper end of the precipitation zone and spiny hopsage on droughtier sites. Beardless wheatgrass increases on silty surfaces. Thurber’s needlegrass increases on very fine sandy loam surfaces and on droughtier sites. Needle and thread is present on coarser surfaces. Sandberg bluegrass increases on silty surfaces in association with a strong microbiotic crust. Winterfat increases in lower precipitation areas on silts. Production increases at the upper end of the precipitation zone.

Response to Disturbance:
When the condition of the site deteriorates as a result of over grazing beardless wheatgrass and Thurber’s needlegrass rapidly decreases. Wyoming big sagebrush, basin big sagebrush and Sandberg bluegrass increase. Cheatgrass, other annuals, biennial weeds and bulbous bluegrass invade. With fire and continued disturbance big sagebrush is severely impacted. Rabbitbrush increases slightly and annuals and noxious biennial forbs strongly invade. Bare ground increases and excessive erosion contributes to downstream sedimentation. The excessive erosion is most pronounced in drainage areas where deep incised gulley’s form.

States:
ARTRW/POSE-BRTE (degraded without fire); POSE-POBU/biennial forbs and BRTE/biennial forbs (following fire on degraded range)

State and transition model

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. Historic Climax Plant Community

State 1 submodel, plant communities

1.1. Historic Climax Plant Community

State 1
Historic Climax Plant Community

Community 1.1
Historic Climax 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 (kg/hectare)	Representative value (kg/hectare)	High (kg/hectare)
Grass/Grasslike	420	588	841
Shrub/Vine	84	118	168
Forb	56	78	112
Total	560	784	1121

Additional community tables

Table 6. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production (kg/hectare)	Foliar cover (%)
Grass/Grasslike
1	Dominant, perennial, deep-rooted bunchgrasses			549–706
	beardless wheatgrass	PSSPI	Pseudoroegneria spicata ssp. inermis	314–392	–
	Thurber's needlegrass	ACTH7	Achnatherum thurberianum	235–314	–
4	Sub-dominant, perennial, shallow rooted grass			16–39
	Sandberg bluegrass	POSE	Poa secunda	16–39	–
5	Other perennial grasses			39–105
	bluebunch wheatgrass	PSSPS	Pseudoroegneria spicata ssp. spicata	8–31	–
	Indian ricegrass	ACHY	Achnatherum hymenoides	8–16	–
	squirreltail	ELEL5	Elymus elymoides	8–16	–
	needle and thread	HECO26	Hesperostipa comata	8–16	–
	basin wildrye	LECI4	Leymus cinereus	8–16	–
	foxtail wheatgrass	PSSA2	×Pseudelymus saxicola	0–11	–
Forb
8	Dominant, perennial forbs			55–102
	arrowleaf balsamroot	BASA3	Balsamorhiza sagittata	16–24	–
	fleabane	ERIGE2	Erigeron	8–16	–
	buckwheat	ERIOG	Eriogonum	8–16	–
	desertparsley	LOMAT	Lomatium	8–16	–
	phlox	PHLOX	Phlox	8–16	–
	common yarrow	ACMI2	Achillea millefolium	8–16	–
9	Other perennial forbs			24–94
	milkvetch	ASTRA	Astragalus	3–8	–
	hawksbeard	CREPI	Crepis	3–8	–
	plains pricklypear	OPPO	Opuntia polyacantha	3–8	–
	lupine	LUPIN	Lupinus	3–8	–
	hoary tansyaster	MACA2	Machaeranthera canescens	0–4	–
	beardtongue	PENST	Penstemon	0–4	–
	scarlet globemallow	SPCO	Sphaeralcea coccinea	0–4	–
	deathcamas	ZIGAD	Zigadenus	0–4	–
	common woolly sunflower	ERLA6	Eriophyllum lanatum	0–4	–
	haplopappus	HAPLO11	Haplopappus	0–4	–
	western stoneseed	LIRU4	Lithospermum ruderale	0–4	–
	woodland-star	LITHO2	Lithophragma	2–4	–
	mariposa lily	CALOC	Calochortus	0–4	–
	bastard toadflax	COMAN	Comandra	0–4	–
	onion	ALLIU	Allium	2–4	–
	pussytoes	ANTEN	Antennaria	2–4	–
Shrub/Vine
11	Dominant shrubs			78–157
	spiny hopsage	GRSP	Grayia spinosa	39–78	–
15	Other shrubs			9–55
	basin big sagebrush	ARTRT	Artemisia tridentata ssp. tridentata	4–8	–
	fourwing saltbush	ATCA2	Atriplex canescens	0–8	–
	rubber rabbitbrush	ERNA10	Ericameria nauseosa	4–8	–
	broom snakeweed	GUSA2	Gutierrezia sarothrae	0–8	–
	winterfat	KRLA2	Krascheninnikovia lanata	0–8	–
	granite prickly phlox	LIPU11	Linanthus pungens	0–8	–
	littleleaf horsebrush	TEGL	Tetradymia glabrata	0–8	–

Interpretations

Animal community

Livestock Grazing:
This site is suitable for livestock grazing use in the late fall, winter and early 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 beardless wheatgrass and Thurber’s needlegrass. Deferred grazing or rest is recommended at least once every three years.

Native Wildlife Associated with the Potential Climax Community:
This site is commonly used by pronghorn antelope, mule deer, rabbits, rodents, upland birds and various predators. It is a preferred site for sage grouse wintering. Antelope and mule deer make excellent use of the site for winter and early spring forage.

Hydrological functions

The soils of this site are typically in an upland topographic position. They have moderate runoff potential and medium infiltration rates when the hydrologic cover is high. Hydrologic cover is high when the beardless wheatgrass and Thurber’s needlegrass deep rooted bunchgrass component is greater than 70 percent of potential.

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)	Bob Gillaspy
Contact for lead author	State Rangeland Management Specialist for NRCS Oregon
Date	11/09/2016
Approved by	Bob Gillaspy
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
None, moderate to severe 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):
20% - 35% bare ground, typically bare patches are associated with shrubs. Larger bare patches may be 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 weak fine granular to moderate medium platy. The A horizon has a dry color of 6 and is 3 - 16 inches thick. The Soil Organic Matter (SOM) content is low to moderate (0.5 to 3.0%).
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 [Bluebunch Wheatgrass >= Thurber's Needlegrass] > Shrubs [sagebrush and hopsage]

Sub-dominant:
Perennial forbs >= other grasses > other shrubs

Other:

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):
Low 500 lbs/acre, Representative Value 700
lbs/acre, High 1000 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) and bulbous bluegrass 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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