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Ecological site R027XY046NV

COBBLY CLAYPAN 12-14 P.Z.

Last updated: 6/03/2024
Accessed: 09/10/2026

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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.

MLRA notes

Major Land Resource Area (MLRA): 027X–Fallon-Lovelock Area

Physiography
Found in the Great Basin Section of the Basin and Range Province of the Intermontane Plateaus this area is characterized by isolated uplifted fault block mountain ranges trending north to south that are separated by broad, hydrologically closed basins. The entire area occurs in the rain-shadow of the Sierra Nevada mountains and is influenced by Pleistocene Lake Lahontan which reached its most recent high stand about 12,000 years ago. There is substantial evidence suggesting the western Great Basin has been the site of pluvial-interpluvial cycles for at least the past two million years.
The mountains and valleys are dissected by the Humboldt, Truckee, Carson, and Walker Rivers and their tributaries, all of which terminate within MLRA 27. Extensive playas can be found throughout this area and are the result of drying of ancient Lake Lahontan. Elevation generally ranges from 3,300 to 5,900 feet (1,005 to 1,800 meters) in valleys, but on some mountain peaks it is more than 7,870 feet (2,400 meters).

Geology
Landforms and soils of this MLRA have been heavily influenced by fluctuating lake level over the last 40,000 years. There is a level line evident on the higher slopes marking the former extent of glacial Lake Lahontan. Almost half of this area has surface deposits of alluvial valley fill influenced by lacustrine sediment. The rest has andesite and basalt rocks of different ages. Mesozoic and Tertiary intrusives are concentrated along the western border of the area, and Lower Volcanic Rocks (17 to 43 million years old) are common on the eastern side of the area. Also, some scattered outcrops of Mesozoic sedimentary and volcanic rocks and tuffaceous sedimentary rocks are in the mountains within the interior of this MLRA.

Climate
The average annual precipitation is 5 to 10 inches (125 to 255 millimeters) in most of the area but is as much as 19 inches (485 millimeters) on high mountain slopes. Most of the rainfall occurs as high-intensity, convective thunderstorms during the growing season. The amount of precipitation is very low from summer to midautumn. The precipitation in winter occurs mainly as snow. The average annual temperature is 43 to 54 degrees F (6 to 12 degrees C). The freeze-free period averages 155 days and ranges from 110 to 195 days, decreasing in length with elevation.

Water
The amount of precipitation is very low, and water for irrigation is obtained principally from diversions on the four large rivers in the area and from water stored in the Lahontan, Rye Patch, and Weber Reservoirs. Pyramid Lake and Walker Lakes are terminal lakes for the Truckee and Walker Rivers, respectively. Much of the annual flow of both rivers is diverted for irrigation, causing lake levels to fall and levels of dissolved salts to increase causing problems for the native Lahontan cutthroat trout.

Soils
The dominant soil orders are Aridisols and Entisols. The soils in the area are predominantly a mesic temperature regime, aridic moisture regime, and have a mixed mineralogy. They are generally well drained, loamy or sandy, commonly skeletal, and shallow to very deep. Accumulation of salts, tufa deposits, and eolian sediments with soluble salts over lacustrine deposits influence most of the soils in the basin landforms of this MLRA. Soils on bedrock-controlled landforms are typically comprised of volcanic or tuffaceous sedimentary colluvium over residuum.

Biological Resources
This area supports extensive areas of salt-desert shrub vegetation. Shadscale and Bailey’s greasewood are widespread, occurring both individually and together. Grasses are generally sparse, although Indian ricegrass is prominent, especially on the sandy soils. Fourwing saltbush, winterfat, spiny hopsage, wolfberry, ephedra, dalea, and bud sagebrush are common shrubs. Basin wildrye, creeping wildrye, alkali sacaton, saltgrass, black greasewood, rubber rabbitbrush, and big saltbush are important plants on saline bottom lands and terraces. A few marsh areas support cattail, bulrushes, sedges, and rushes. Big sagebrush, along with scattered Utah juniper and singleleaf pinyon, is associated with Thurber needlegrass, desert needlegrass, Sandberg bluegrass, and squirreltail on the higher elevation piedmont slopes and mountains.

Ecological site concept

The Cobbly Claypan 12-14 P.Z. site occurs on mountain summits and sideslopes on all aspects. Slopes gradients of 30 to 75 percent are typical. Elevations are 5500 to 8700 feet. The soils are typically very deep and well drained. An argillic horizon that restricts root development is present within 10 to 14 inches of the surface. The soil surface is stony, cobbly or very gravelly with more than 65 percent total surface cover of rock fragments.

Associated sites

R027XY083NV	MOUNTAIN RIDGE Less productive site

R027XY083NV

MOUNTAIN RIDGE

Less productive site

Similar sites

R027XY020NV	SHALLOW CLAYPAN 8-10 P.Z. ARARL3 dominant shrub; ACSP12 dominant grass
R027XY079NV	GRAVELLY CLAYPAN 8-10 P.Z. ARARL3 dominant grass; ACTH7 dominant grass
R027XY070NV	DROUGHTY CLAYPAN 8-10 P.Z. ARARL3 dominant shrub; SAVEB major shrub
R027XY068NV	GRANITIC CLAYPAN 8-10 P.Z. ARARL3 dominant shrub; ACSP12 dominant grass
R027XY087NV	CLAYPAN 14+ P.Z. More productive site; surface rock fragments typically <45%; gentler slopes
R027XY049NV	COBBLY CLAYPAN 8-10 P.Z. ACTH7 dominant grass

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Artemisia arbuscula
Herbaceous	(1) Festuca idahoensis

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Physiographic features

The Cobbly Claypan 12-14 P.Z. site occurs on mountain summits and sideslopes on all aspects. Slopes range from 4 to 75 percent, but slope gradients of 30 to 75 percent are typical. Elevations are 5500 to 8700 feet.

Table 2. Representative physiographic features

Landforms	(1) Mountain slope
Runoff class	Very high
Elevation	5500 – 8700 ft
Slope	4 – 75 %
Water table depth	72 – 0 in
Aspect	Aspect is not a significant factor

Climatic features

Average annual precipitation is 12 to 14 (16) inches. Mean annual air temperature is 40 to 48 degrees F. The average growing season is about 70 to 100 days. There is no climate station available for this site.

Table 3 Representative climatic features

Frost-free period (average)	100 days
Freeze-free period (average)
Precipitation total (average)	10 in

Soil features

The soils associated with this site have formed in residuum and colluvium from volcanic rocks. These soils are typically very deep and well drained. An argillic horizon that restricts root development is present within 10 to 14 inches of the surface. The soil surface is stony, cobbly or very gravelly with more than 65 percent total surface cover of rock fragments. Available water capacity is very low to low. The moisture distribution is such that limits depth of wetting to about 15 to 20 inches in most years. The soil moisture regime is aridic bordering on xeric and the soil temperature regime is frigid. Permeability is very slow to moderately slow and surface runoff is very high. Potential for sheet and rill erosion is moderate. The soil series associated with this site include: Belate, Cleavage, Ninemile, and Walti.

The representative soil series is Belate, a loamy-skeletal, mixed, superactive, frigid Aridic Argixerolls. A mollic epipedon occurs from the soil surface to 46 cm and an argillic horizon occurs from 30 to 152 cm.

Table 4. Representative soil features

Parent material	(1) Colluvium – rhyolite (2) Residuum – andesite
Surface texture	(1) Very gravelly loam (2) Very gravelly loam
Family particle size	(1) Loamy
Drainage class	Well drained
Permeability class	Very slow to moderately slow
Soil depth	60 – 84 in
Surface fragment cover <=3"	9 – 30 %
Surface fragment cover >3"	2 – 5 %
Available water capacity (0-40in)	1.4 – 4.9 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)	6.8 – 7.8
Subsurface fragment volume <=3" (Depth not specified)	25 – 55 %
Subsurface fragment volume >3" (Depth not specified)	0 – 5 %

Ecological dynamics

As ecological condition deteriorates, Idaho fescue, needlegrass, and fibrous-rooted perennial forbs decrease, while rabbitbrush, snowberry and low sagebrush increase. Bluegrasses will initially increase in the shrub understory as Idaho fescue and needlegrass are displaced. Species likely to invade this site are cheatgrass, singleleaf pinyon and Utah juniper.

Fire Ecology:
Prior to 1897, mean fire return intervals for low sagebrush communities have been estimated to be from 35 to over 100 years. Fire most often occurs during wet years with high forage production. Low sagebrush is very susceptible to fire damage. Low sagebrush is usually killed by fire and does not re-sprout. The recovery in burned areas is usually via small, light, wind-dispersed seed for all low sagebrush subspecies. Partially injured low sagebrush may re-grow from living branches, but sprouting does not occur.
Idaho fescue grows in a dense, fine-leaved tuft. Fires tend to burn within the accumulated fine leaves at the base of the plant and may produce temperatures sufficient to kill some of the root crown. Mature Idaho fescue plants are commonly reported to be severely damaged by fire in all seasons.

State and transition model

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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 plant community is dominated by low sagebrush and Idaho fescue. Potential vegetative composition is about 55% grasses, 10% forbs and 35% shrubs and trees. Approximate ground cover (basal and crown) is 15 to 25 percent.

Figure 1. 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	137	220	330
Shrub/Vine	88	140	210
Forb	25	40	60
Total	250	400	600

Additional community tables

Table 6. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production ()	Foliar cover (%)
Grass/Grasslike
1	Primary Perennial Grasses			140–240
	Idaho fescue	FEID	Festuca idahoensis	100–140	–
	Cusick's bluegrass	POCU3	Poa cusickii	7–20	–
	muttongrass	POFE	Poa fendleriana	7–20	–
	Sandberg bluegrass	POSE	Poa secunda	6–20	–
	western needlegrass	ACOCO	Achnatherum occidentale ssp. occidentale	10–20	–
	Thurber's needlegrass	ACTH7	Achnatherum thurberianum	10–20	–
2	Secondary Perennial Grasses			8–20
	Indian ricegrass	ACHY	Achnatherum hymenoides	2–12	–
	squirreltail	ELEL5	Elymus elymoides	2–12	–
Forb
3	Perennial Forbs			20–60
	arrowleaf balsamroot	BASA3	Balsamorhiza sagittata	2–16	–
	hawksbeard	CREPI	Crepis	2–16	–
	buckwheat	ERIOG	Eriogonum	2–16	–
	lupine	LUPIN	Lupinus	2–16	–
	phlox	PHLOX	Phlox	2–16	–
Shrub/Vine
4	Primary Shrubs			80–120
	little sagebrush	ARAR8	Artemisia arbuscula	80–120	–
5	Secondary Shrubs			12–44
	yellow rabbitbrush	CHVI8	Chrysothamnus viscidiflorus	2–12	–
	antelope bitterbrush	PUTR2	Purshia tridentata	2–12	–
	snowberry	SYMPH	Symphoricarpos	2–12	–
Tree
6	Evergreen			4–16
	Utah juniper	JUOS	Juniperus osteosperma	2–8	–
	singleleaf pinyon	PIMO	Pinus monophylla	2–8	–

Interpretations

Animal community

Livestock Interpretation:
This site is suitable for livestock grazing. Grazing management should be keyed to Idaho fescue. Idaho fescue provides important forge for many types of domestic livestock. The foliage cures well and is preferred by livestock in late fall and winter.
Domestic sheep and to a much lesser degree cattle consume low sagebrush, particularly during the spring, fall and winter.

Stocking rates vary over time depending upon season of use, climate variations, site, and previous and current management goals. A safe starting stocking rate is an estimated stocking rate that is fine tuned by the client by adaptive management through the year and from year to year.

Wildlife Interpretations:
Idaho fescue provides important forge for several wildlife species. It is reported to be good forage for pronghorn, and deer in ranges of northern Nevada.
Low sagebrush is considered a valuable browse plant during the spring, fall and winter months. In some areas it is of little value in winter due to heavy snow. Mule deer utilize and sometimes prefer low sagebrush, particularly in winter and early spring.

Hydrological functions

Runoff is very high. Permeability is very slow to moderately slow.

Recreational uses

Aesthetic value is derived from the diverse floral and faunal composition and the colorful flowering of wild flowers and shrubs during the spring and early summer. This site offers rewarding opportunities to photographers and for nature study. This site is used for camping and hiking and has potential for upland and big game hunting.

Other information

Low sagebrush can be successfully transplanted or seeded in restoration.

Supporting information

Inventory data references

NASIS soil component data.

Type locality

Location 1: Churchill County, NV
Township/Range/Section	T20N R33E S27
General legal description	South fork of Pete's Canyon, Stillwater Range, Churchill County, Nevada.

Other references

Fire Effects Information System (Online; http://www.fs.fed.us/database/feis/plants/).

USDA-NRCS Plants Database (Online; http://www.plants.usda.gov).

Contributors

DK/GD

Approval

Kendra Moseley, 6/03/2024

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)	P NOVAK-ECHENIQUE
Contact for lead author	State Rangeland Management Specialist
Date	07/12/2012
Approved by
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
Rills are none. Rock fragments armor the surface.
Presence of water flow patterns:
Waterflow patterns are none to rare. Rock fragments armor the surface.
Number and height of erosional pedestals or terracettes:
Pedestals are none to rare. Occurrence is usually limited to areas of water flow patterns. Frost heaving of shallow rooted plants should not be considered an indicator of soil erosion.
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare Ground ± 5-20%, depending on amount of surface rock fragments
Number of gullies and erosion associated with gullies:
None
Extent of wind scoured, blowouts and/or depositional areas:
None
Amount of litter movement (describe size and distance expected to travel):
Fine litter (foliage from grasses and annual & perennial forbs) expected to move distance of slope length during intense summer convection storms or rapid snowmelt events. Persistent litter (large woody material) will remain in place except during large rainfall events.
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil stability values should be 3 to 6 on most soil textures found on this site. (To be field tested.)
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Surface structure is typically very fine to thick platy or subangular blocky. Soil surface colors are dark gray-browns and soils have a mollic epipedon. Organic matter of the surface 2 to 4 inches is typically less than 1 percent dropping off quickly below. Organic matter content can be more or less depending on micro-topography.
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Perennial herbaceous plants (especially deep-rooted bunchgrasses [i.e., Idaho fescue]) slow runoff and increase infiltration. Shrub canopy and associated litter break raindrop impact. Snow catch and accumulation is limited on windswept slopes.
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
Compacted layers are none. Massive sub-surface structure or subsoil argillic horizons are not to be interpreted as compacted.
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:
Deep-rooted, cool season, perennial bunchgrasses > low shrubs (low sagebrush)

Sub-dominant:
associated shrubs = deep-rooted, cool season perennial forbs > shallow-rooted, cool season, perennial bunchgrasses > fibrous, shallow-rooted, cool season, perennial forbs = annual forbs

Other:
evergreen trees

Additional:
After wildfires, perennial bunchgrasses and forbs dominate. Low sagebrush is removed for several years.
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Dead branches within individual shrubs common and standing dead shrub canopy material may be as much as 25% of total woody canopy; some of the mature bunchgrasses (<10%) have dead centers.
Average percent litter cover (%) and depth ( in):
Under canopy and between plant interspaces (±25%) and litter depth is <¼ inch.
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
For normal or average growing season (through mid-June) ± 400 lbs/ac; Favorable years ± 600 lbs/ac; Unfavorable years ± 250 lbs/ac
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:
Potential invaders include halogeton, annual mustards, and cheatgrass.
Perennial plant reproductive capability:
All functional groups should reproduce in average (or normal) and above average growing season years. Reduced growth and reproduction occur during extreme or extended drought periods.

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