Natural Resources
Conservation Service
Ecological site R030XB066NV
BASALTIC FAN 5-7 P.Z.
Last updated: 2/24/2025
Accessed: 03/17/2025
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.
Ecological site concept
This site occurs on summits and sideslopes of upper fan piedmonts. Slopes range from 2 to over 30 percent, but slope gradients of 4 to 15 percent are most typical. Elevations are 2500 to 3500 feet.
The soils associated with this site are derived from basalt and other mafic extrusive volcanic rock. The soils are very deep and well drained. They have a calcic and an argillic horizon and are strongly to moderately alkaline.
Associated sites
| R030XB019NV |
Eroded Fan Remnant Pavette 4-6 P.Z. |
|---|
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
(1) Ambrosia dumosa |
| Herbaceous |
(1) Pleuraphis rigida |
Physiographic features
This site occurs on summits and sideslopes of upper fan piedmonts. Slopes range from 2 to over 30 percent, but slope gradients of 4 to 15 percent are most typical. Elevations are 2500 to 3500 feet.
Table 2. Representative physiographic features
| Landforms |
(1)
Fan remnant
(2) Pediment |
|---|---|
| Flooding frequency | None |
| Ponding frequency | None |
| Elevation | 762 – 1,067 m |
| Slope | 2 – 30% |
| Water table depth | 0 cm |
| Aspect | Aspect is not a significant factor |
Climatic features
The climate of the Mojave Desert has extreme fluctuations of daily temperatures, strong seasonal winds, and clear skies. The climate is arid and is characterized with cool, moist winters and hot, dry summers. Most of the rainfall falls between November and April. Summer convection storms from July to September may contribute up to 25 percent of the annual precipitation. Average annual precipitation is 5 to 7 inches. Mean annual air temperature is 60 to 70 degrees F. The average growing season is about 180 to 290 days.
Table 3. Representative climatic features
| Frost-free period (average) | 290 days |
|---|---|
| Freeze-free period (average) | |
| Precipitation total (average) | 178 mm |
Figure 1. Monthly average minimum and maximum temperature
Influencing water features
There are no influencing water features associated with this site.
Soil features
The soils associated with this site are derived from basalt and other mafic extrusive volcanic rock. The soils are very deep and well drained. They have a calcic and an argillic horizon and are strongly to moderately alkaline. More than 70 percent rock fragments cover the soil surface with stones and cobbles predominating. Soils associated with this site are classified as Durinodic Haplargids.
Table 4. Representative soil features
| Parent material |
(1)
Alluvium
–
basalt
|
|---|---|
| Surface texture |
(1) Extremely gravelly loam (2) Extremely gravelly sandy loam (3) Extremely gravelly fine sand |
| Family particle size |
(1) Loamy |
| Drainage class | Well drained |
| Permeability class | Moderate to moderately rapid |
| Soil depth | 152 – 213 cm |
| Surface fragment cover <=3" | 16 – 46% |
| Surface fragment cover >3" | 3 – 38% |
| Available water capacity (0-101.6cm) |
4.83 – 5.08 cm |
| Calcium carbonate equivalent (0-101.6cm) |
25 – 60% |
| Electrical conductivity (0-101.6cm) |
0 – 8 mmhos/cm |
| Sodium adsorption ratio (0-101.6cm) |
1 – 45 |
| Soil reaction (1:1 water) (0-101.6cm) |
8.4 – 9.5 |
| Subsurface fragment volume <=3" (Depth not specified) |
20 – 46% |
| Subsurface fragment volume >3" (Depth not specified) |
5 – 36% |
Ecological dynamics
Potential natural vegetation is dominanted by perennial grasses. This site is geographically located in the bottom or on fan toes, positively contributing to the run-in moisture. The argillic and calcic horizons found in the soil lead to increased water holding capacity, making this site more productive than the surrounding areas. Half of the annual precipitation comes in the summer, increasing production and the presence of warm season grasses. The dominant grasses on this ecological site are large bunchgrasses which provide valuable organic matter. Litter and old shoots are incorporated into the soil increasing the organic matter and therefore the nutrient availability compared to other desert soils. Run-in moisture is positively influenced by the abundance of vegetation on the landscape, providing more places for infiltration. Elevated levels of soil organic matter and infiltration help make this site more resilient, than the surrounding area, following a disturbance.
Grasses and shrubs of this ecological site are considered to be palatable to wildlife making it valuable habitat. Perennial grass species found on this ecological site include a combination of cool and warm season species. Big galleta, Indian ricegrass, desert needlegrass (Achnatherum speciosum), fluffgrass (Dasyochloa pulchella), and threeawn (Aristida spp.) are the most common. The relative species diversity of this site makes it more resilient. Species richness contributes to overall increased ecological stability. The ecological functions of different species overlap, so that even if a species is removed, ecological function will persist due to the compensation by other species with similar function (Peterson et al. 1998).
The fine fuels from annuals and perennial grasses facilitate the ignition and spread of wildfires. The relatively high yield of annual biomass makes this site susceptible to high intensity wildfire. Native annual plants usually break down rapidly during the summer and do not create a long-lived fuelbed. Fine fuels from non-native annual grasses currently represent the most important fuelbed component. Damage to big galleta from fire varies. If big galleta is dry, damage may be severe. However, when plants are green, fire will tend to be less severe and damage may be minimal, with big galleta recovering quickly. Fire top-kills bush muhly. A nonrhizomatous species, bush muhly regenerates following fire from soil-stored seed. Burning causes at least short-term decline of bush muhly. Recovery time is thought to vary considerably and is probably dependent on postfire weather and competition. When ungrazed, bush muhly's dense growth may contribute to fire spread. It may be most susceptible to fire damage when growing beneath shrubs because of increased fuels and higher temperatures as shrubs burn. Indian ricegrass can be killed by fire, depending on severity and season of burn. Indian ricegrass reestablishes on burned sites through seed dispersed from adjacent unburned areas.
Creosotebush is poorly adapted to fire because of its limited sprouting ability. Creosotebush survives some fires that burn patchily or are of low severity. Winterfat is either killed or top-killed by fire, depending on fire severity. Severe fire can kill the perennating buds located several inches above the ground surface and thus kills the plant. In addition, severe fire usually destroys seed on the plant. Low-severity fire scorches or only partially consumes the aboveground portions of winterfat and thus does not cause high mortality. Spiny hopsage is considered to be somewhat fire tolerant and often survives fires that kill sagebrush. Mature spiny hopsage generally sprout after being burned. Spiny hopsage is reported to be least susceptible to fire during summer dormancy. There is little mention of fire in relation to white bursage in the literature. Fire generally kills white bursage. Nevada ephedra generally sprouts after fire damages aboveground vegetation. Underground regenerative structures commonly survive when aboveground vegetation is consumed by fire. However, severe fires may kill shallowly buried regenerative structures. Range ratany is top-killed by fire. Range ratany resprouts from the root crown after fire.
Following low intensity wildfire the perennial grasses on this ecological site may increase in abundance, while shrubs will be temporally absent from the plant community. In the occurrence of repeated large scale fires, perennial grasses and shrubs will decrease in abundance and non-native annuals will increase. Even under a shorter fire return interval the perennial bunchgrass of this community are able to persist in small quantities, preventing conversion to annual grassland. The ability of these species to reproduce by tiller and seeds, allows them to persist in the presence of increased fire or prolonged drought .This ecological site is also susceptible to anthropogenic disturbances resulting in soil compaction. This negatively affects reproduction and vigor of native plant species, reduces infiltration and soil stability.
State and transition model
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Ecosystem states
State 1 submodel, plant communities
State 2 submodel, plant communities
State 1
Reference State
This state represents the natural range of variability under pristine conditions. Community phase changes are driven by natural disturbances such as periodic drought, wildfire and insect attack. This site experiences light to moderate grazing by wildlife. Timing of disturbances combined with weather events determines plant community dynamics.
Community 1.1
Reference Plant Community
The reference plant community is characterized by an open canopy of shrubs and perennial grasses. The plant community is dominated by big galleta and white bursage. A variety of cacti, including species of the genera Opuntia, Echinocereus, Ferocactus and Echinocactus are important constituents of the site. Potential vegetative composition is about 50% perennial and annual grasses, 10% annual and perennial forbs and 40% shrubs. Approximate ground cover (basal and crown) is 10 to 20 percent.
Figure 2. 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 | 224 | 336 | 448 |
| Shrub/Vine | 179 | 269 | 359 |
| Forb | 45 | 67 | 90 |
| Total | 448 | 672 | 897 |
State 2
Invaded
Introduced annuals such as red brome, schismus and redstem stork's bill have invaded the reference plant community and have become a dominant component of the herbaceous cover. This invasion of non-natives is attributed to a combination of factors including: 1) surface disturbances, 2) changes in the kinds of animals and their grazing patterns, 3) drought, and 4) changes in fire history. These non-natives annuals are highly flammable and promote wildfires where fires historically have been infrequent. A biotic threshold has been crossed, with the introduction of non-native annuals that cannot be removed from the system. The presence of non-natives has the potential to alter disturbance regimes significantly from their natural or historic range of disturbances.
Community 2.1
Plant Community Phase 2.1
This plant community is compositionally similar to the reference community with a trace of non-native annuals in the understory. Ecological processes have not changed at this time.
Community 2.2
Plant Community Phase 2.2
This plant community is characterized by an increase of non-native annual biomass. Non-native species take advantage of increased light and nutrient resources post fire. Perennial bunchgrasses sprout from the root crown post fire. Recruitment of early successional species increases dramatically from seed provided by an offsite source.
Community 2.3
Plant Community Phase 2.3
This plant community is dominated by non-native annuals. Minor amount of perennial bunchgrasses and shrubs remain in the plant community. Loss of perennial vegetation leads to altered ecological processes including increased erosion and changes in the nutrient cycling dynamics.
Community 2.4
Plant Community Phase 2.4
This plant community is characterized by heavy anthropogenic disturbance. Native grasses and shrubs have reduced vigor and are experiencing little to no recruitment. Non-native species persist even under an increased disturbance regime. Increase in amount of bare ground, site is susceptible to erosion.
Pathway 2.1a
Community 2.1 to 2.2
Fire reduces woody vegetation and favors an increase of herbaceous biomass, native and non-native.
Pathway 2.2a
Community 2.2 to 2.1
With time and exclusion of fire, native woody species mature. Non-native annuals persist through recovery.
Pathway 2.2b
Community 2.2 to 2.3
Frequent repeated fire removes native perennials from the site and favors non-native annuals.
Pathway 2.3a
Community 2.3 to 2.2
Exclusion of fire and time allows resilient native species to regenerate.
Pathway 2.3b
Community 2.3 to 2.4
Increased anthropogenic impacts will decrease native vegetation and increase bare ground.
Pathway 2.4a
Community 2.4 to 2.2
Removal of disturbance increases vigor and reproduction of native species.
Transition 1
State 1 to 2
Introduction of non-native species due to anthropogenic disturbances including OHV use, dry land farming, grazing, linear corridors, mining, military operations, and settlements.
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 | Primary Perennial Grasses | 203–370 | ||||
| big galleta | PLRI3 | Pleuraphis rigida | 202–336 | – | ||
| bush muhly | MUPO2 | Muhlenbergia porteri | 1–34 | – | ||
| 2 | Secondary Perennial Grasses | 1–34 | ||||
| Indian ricegrass | ACHY | Achnatherum hymenoides | 3–13 | – | ||
| threeawn | ARIST | Aristida | 3–13 | – | ||
| 3 | Annual Grasses | 1–20 | ||||
|
Forb
|
||||||
| 4 | Primary Perennial Forbs | 13–43 | ||||
| desert globemallow | SPAM2 | Sphaeralcea ambigua | 13–34 | – | ||
| low woollygrass | DAPU7 | Dasyochloa pulchella | 0–6 | – | ||
| 5 | Secondary Perennial Forbs | 1–34 | ||||
| 6 | Annual Forbs | 1–54 | ||||
|
Shrub/Vine
|
||||||
| 7 | Primary Shrubs | 148–303 | ||||
| burrobush | AMDU2 | Ambrosia dumosa | 135–269 | – | ||
| jointfir | EPHED | Ephedra | 13–34 | – | ||
| 8 | Secondary Shrubs | 34–101 | ||||
| bluestar | AMSON | Amsonia | 7–20 | – | ||
| cottontop cactus | ECPO2 | Echinocactus polycephalus | 7–20 | – | ||
| Virgin River brittlebush | ENVI | Encelia virginensis | 7–20 | – | ||
| Eastern Mojave buckwheat | ERFAP | Eriogonum fasciculatum var. polifolium | 7–20 | – | ||
| California barrel cactus | FECY | Ferocactus cylindraceus | 7–20 | – | ||
| creosote bush | LATR2 | Larrea tridentata | 7–20 | – | ||
| beavertail pricklypear | OPBA2 | Opuntia basilaris | 7–20 | – | ||
| Fremont's dalea | PSFR | Psorothamnus fremontii | 7–20 | – | ||
| Mojave yucca | YUSC2 | Yucca schidigera | 7–20 | – | ||
Interpretations
Animal community
Livestock Interpretations:
This site is suitable for livestock grazing during the spring where water is available. Grazing management should be keyed to perenial grass or palatable shrub production. Big galleta is considered a valuable forage plant for cattle and domestic sheep. Its coarse, rigid culms make it relatively resistant to heavy grazing and trampling. Bush muhly is readily eaten by livestock throughout the year when available; however, it is usually not abundant enough to provide much forage. It is grazed heavily in winter when other species become scarce. Because of its branching habit, it is extremely susceptible to heavy grazing. Bush muhly is damaged when continuously grazed to a stubble height of less than 4 inches (10 cm). White bursage is an important browse species. Browsing pressure on white bursage is particularly heavy during years of low precipitation, when production of winter annuals is low. White bursage is of intermediate forage value. It is fair to good forage for horses and fair to poor for cattle and sheep. However, because there is often little other forage where white bursage grows, it is often highly valuable to browsing animals. Nevada ephedra is important winter range browse for domestic cattle, sheep and goats.
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:
In southern Nevada, big galleta is heavily utilized by bighorn sheep and in some blackbrush communities it is referred to as 'preferred habitat.' Mule deer utilize trace amounts of big galleta. The palatability of bush muhly for wildlife species is rated fair to poor. White bursage is an important browse species for wildlife. Mule deer, bighorn sheep, and pronghorn browse Nevada ephedra, especially in spring and late summer when new growth is available.
Hydrological functions
Runoff is medium. Permeability is moderate to moderately rapid.
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 products
White bursage is a host for sandfood, a parasitic plant with a sweet, succulent, subterranean flowerstalk. Sandfood was a valuable food supply for Native Americans. Native Americans used Nevada ephedra as a tea to treat stomach and kidney ailments.
Other information
Big galleta's clumped growth form stabilizes blowing sand. White bursage may be used to revegetate disturbed sites in southwestern deserts. Nevada ephedra is useful for erosion control, and seedlings have been successfully planted onto reclaimed strip mines. Atrazine may be effective in controlling Nevada ephedra, though some plants can survive through crown sprouting. Irrigation may increase control by atrazine.
Supporting information
Inventory data references
NV-ECS-1: 2 records
NRCS-RANGE-417: 1 record
Type locality
| Location 1: Clark County, NV | |
|---|---|
| Township/Range/Section | T25 S R62 E. S20 |
| General legal description | West side of Eldorado Valley, upper fan piedmont before entering McCullough Pass (south side of road), Clark County, Nevada. |
Other references
Fire Effects Information System (Online; http://www.fs.fed.us/database/feis/plants/).
Peterson, G. C., R. Allen, and C.S. Holling. 1998. Ecological Resilience, Biodiversity, and Scale. Ecosystems 1:6-18.
USDA-NRCS Plants Database (Online; http://www.plants.usda.gov).
Contributors
RWA/GKB
Approval
Sarah Quistberg, 2/24/2025
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 | 04/26/2010 |
| Approved by | Sarah Quistberg |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
Number and extent of rills:
Rills none to rare. Rock fragments armor the surface. -
Presence of water flow patterns:
Water flow patterns none to rare. Rock fragments armor the surface. -
Number and height of erosional pedestals or terracettes:
Pedestals are none to rare. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare Ground to 10-20%. -
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 catastrophic 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 2 to 4 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 moderate fine and medium subangular blocky. Soil surface colors are light and are typified by an ochric epipedon. Organic matter of the surface 2 to 3 inches is <1 percent. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Sparse shrub canopy, surface rock, and associated litter break raindrop impact. -
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. -
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:
Mojave Desert shrubs> deep-rooted, warm-season, grasses (big galleta & bush muhly)Sub-dominant:
perennial forbs > annual forbs > annual grasses > deep-rooted, cool-season, grassesOther:
Additional:
-
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; mature bunchgrasses commonly (±25%) have dead centers. -
Average percent litter cover (%) and depth ( in):
Between plant interspaces (<5%) and depth (±¼-inch). -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
For normal or average growing season (February thru April [May]) ± 600lbs/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:
Invaders on this site include red brome, filaree, and Mediterranean grass. -
Perennial plant reproductive capability:
All functional groups should reproduce in above average growing season years.
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