Natural Resources
Conservation Service
Ecological site R030XB077NV
STEEP SOUTH SLOPE
Last updated: 2/26/2025
Accessed: 04/17/2025
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 steep, southerly exposures of hills and low mountains. Slopes range from 15 to over 75 percent, but slope gradients of 50 to 75 percent are most typical. Elevations are 500 to about 3500 feet. The soil associated with this site are shallow to very shallow, calcareous, and well drained to somewhat excessively drained.
This site is part of group concept R030XB164CA.
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
(1) Encelia farinosa |
| Herbaceous |
Not specified |
Physiographic features
This site occurs on steep, southerly exposures of hills and low mountains. Slopes range from 15 to over 75 percent, but slope gradients of 50 to 75 percent are most typical. Elevations are 500 to about 3500 feet.
Table 2. Representative physiographic features
| Landforms |
(1)
Hill
(2) Mountain |
|---|---|
| Elevation | 500 – 3,500 ft |
| Slope | 15 – 75% |
| Aspect | S |
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 3 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) | 7 in |
Figure 1. Monthly average minimum and maximum temperature
Influencing water features
There are no influencing water features associated with this site.
Soil features
The soil associated with this site are shallow to very shallow, calcareous, and well drained to somewhat excessively drained. The soils are formed in colluvium and/or residuum from either granite, limestone, or volcanic rock. These soils have very high amounts of cobbles and stones at the surface (greater than 60 percent ground cover) that can reduce evaporation rates and have a stabilizing affect on soil erosion. Available water capacity is very low. Water intake rates are moderately rapid to moderate. Runoff is very high. The soil temperature regime is typically hyperthermic. Soil series associated with this site includes Goldroad, Haleburu, Iceberg, Redneedle, and Sunrock.
Table 4. Representative soil features
| Parent material |
(1)
Colluvium
–
granite
(2) Residuum – limestone |
|---|---|
| Surface texture |
(1) Extremely stony sandy loam (2) Very gravelly sandy loam (3) Extremely stony fine sandy loam |
| Family particle size |
(1) Loamy |
| Drainage class | Well drained to somewhat excessively drained |
| Permeability class | Moderate to moderately rapid |
| Soil depth | 4 – 20 in |
| Surface fragment cover <=3" | 20 – 70% |
| Surface fragment cover >3" | 10 – 45% |
| Available water capacity (0-40in) |
0.2 – 1.6 in |
| Calcium carbonate equivalent (0-40in) |
50% |
| Electrical conductivity (0-40in) |
4 mmhos/cm |
| Sodium adsorption ratio (0-40in) |
5 |
| Soil reaction (1:1 water) (0-40in) |
7.4 – 8.4 |
| Subsurface fragment volume <=3" (Depth not specified) |
22 – 68% |
| Subsurface fragment volume >3" (Depth not specified) |
45% |
Ecological dynamics
The plant community is dominated by brittlebush. Brittlebush prefers steep slopes with a southern exposure. Brittlebush is drought tolerant and provides important soil stabilization on steep sites. Alleopathic properties make it an extremely successful competitor with winter annuals (Tesky 1993). California buckwheat thrives on rocky shallow soils. This site provides important habitat and feed for numerous wildlife species, including butterflies, lizards, and bighorn sheep (Montalov 2010).
Brittlebush is valuable for rehabilitating critical stabilization areas and disturbed sites, and is easily transplanted and can also be established from direct seeding. Creosostebush is poorly adapted to fire and experiences almost no recruitment under natural conditions. The life strategy of short-lived perennials like brittlebush may be better adapted to the current climatic conditions and disturbance regimes. In a long term plant succession study at a site fully protected from human impacts, the abundance of creosotebush obviously declined, while brittlebush experienced high recruitment and noticeable establishment within the stand (Turner 1990). Such changes in species composition can be attributed to the natural successional processes of this desert ecosystem.
Introduced annual forbs and grasses readily invade this site. Desert globemallow, plantain, red brome and other introduced annual grasses and forbs often dominate this site following wildfire.
The low fuel loads limits the ability of fire to spread on these sites. Yearly variation in fuel conditions can be contributed to production of annual species, native and nonnative. In years with high production of annual species, the risk of fire is greater to perennial shrubs, due to the continuous fuel load. The native species of this ecological site are well adapted to disturbance, easily establish from seed and will persist throughout the successional process on this ecological site.
Fire generally kills white bursage. However, most white bursage plants burned because their canopies contained numerous small branches in proximity to herbaceous fuels. White brittlebush is often top-killed or completely killed by fire. Following a fast-moving, low-severity fire, white brittlebush plants are mostly scorched. Only leaves and branches near the ground burn, leaving foliage on stems. White brittlebush is a good initial offsite colonizer of postfire communities via wind dispersed seed; it also has some ability to sprout from the root crown, which may be limited by intolerance of heat. Creosotebush is poorly adapted to fire because of its limited sprouting ability. Creosotebush survives some fires that burn patchily or are of low severity. Range ratany is top-killed by fire but will resprout from the root crown.
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 and is dominated by drought tolerant native shrubs. Primary natural disturbance mechanisms affecting this ecological site are wildfire, long-term drought and insect attack. The plant communities of this site are dynamic in response to changes in disturbance regimes and weather patterns.
Community 1.1
Reference Plant Community
The reference plant community is dominated by white brittlebush. Potential vegetative composition is about 10% annual and perennial grasses, 10% annual and perennial forbs and 80% shrubs. Approximate ground cover (basal and crown) is less than 15 percent.
Figure 2. 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) |
|---|---|---|---|
| Shrub/Vine | 80 | 200 | 400 |
| Forb | 10 | 25 | 50 |
| Grass/Grasslike | 10 | 25 | 50 |
| Total | 100 | 250 | 500 |
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. ENFA would persist after invasion by non-native annuals, but the other shrubs and desirable grasses would may be unsuccessful in competing with the non-natives.A biotic threshold has been crossed, with the introduction of non-native annuals that cannot be removed from the system. Ecological resiliency has been reduced by the presence of non-native annuals which have the potential to alter disturbance regimes significantly from their natural or historic range of variability.
Community 2.1
Plant Community Phase 2.1
This plant community is compositionally similar to the Reference Plant Community with a trace of non-native annuals in the understory. 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. Native shrubs persist through invasion, while the native bunchgrasses and perennial forbs are at a competitive disadvantage for space and resources.
Community 2.2
Plant Community Phase 2.2
This plant community is characterized by the regeneration of disturbance tolerant native shrubs. Non-native annuals persist.
Pathway 2.1a
Community 2.1 to 2.2
Following disturbance native shrubs readily establish from seed, assuming the presence of an offsite seed source.
Pathway 2.2a
Community 2.2 to 2.1
With time shrubs mature and dominate the site.
Transition 1
State 1 to 2
The introduction of non-natives 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 (lb/acre) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Grass/Grasslike
|
||||||
| 1 | Perennial Grasses | 5–25 | ||||
| Indian ricegrass | ACHY | Achnatherum hymenoides | 1–8 | – | ||
| desert needlegrass | ACSP12 | Achnatherum speciosum | 1–8 | – | ||
| threeawn | ARIST | Aristida | 1–8 | – | ||
| big galleta | PLRI3 | Pleuraphis rigida | 1–8 | – | ||
| 2 | Annual Grasses | 1–12 | ||||
|
Forb
|
||||||
| 3 | Primary Perennial forbs | 5–20 | ||||
| desert globemallow | SPAM2 | Sphaeralcea ambigua | 5–20 | – | ||
| 4 | Secondary Perennial forbs | 3–12 | ||||
| 5 | Annual forbs | 1–25 | ||||
| desert trumpet | ERIN4 | Eriogonum inflatum | 1–5 | – | ||
| plantain | PLANT | Plantago | 1–5 | – | ||
|
Shrub/Vine
|
||||||
| 6 | Primary shrubs | 182–249 | ||||
| brittlebush | ENFA | Encelia farinosa | 175–200 | – | ||
| creosote bush | LATR2 | Larrea tridentata | 5–25 | – | ||
| burrobush | AMDU2 | Ambrosia dumosa | 1–12 | – | ||
| 7 | Secondary shrubs | 5–25 | ||||
| catclaw acacia | ACGR | Acacia greggii | 3–8 | – | ||
| hedgehog cactus | ECHIN3 | Echinocereus | 3–8 | – | ||
| Virgin River brittlebush | ENVI | Encelia virginensis | 3–8 | – | ||
| jointfir | EPHED | Ephedra | 3–8 | – | ||
| Eastern Mojave buckwheat | ERFAP | Eriogonum fasciculatum var. polifolium | 3–8 | – | ||
| California barrel cactus | FECY | Ferocactus cylindraceus | 3–8 | – | ||
| beavertail pricklypear | OPBA2 | Opuntia basilaris | 3–8 | – | ||
| Parish's goldeneye | VIPA14 | Viguiera parishii | 3–8 | – | ||
| Mojave yucca | YUSC2 | Yucca schidigera | 3–8 | – | ||
Interpretations
Animal community
Livestock Interpretations:
This site has limited value for livestock grazing, due to the low forage production, steep slopes, and stony surfaces. 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 and is sensitive to browsing. White brittlebush has no forage value for domestic livestock. Creosotebush is unpalatable to livestock. Consumption of creosotebush may be fatal to sheep. Range ratany is an important forage species for all classes of livestock. Palatability of range ratany is rated fair to good for cattle and sheep.
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:
White bursage is an important browse species for wildlife. White brittlebush is a browse species of desert mule deer and desert bighorn sheep. Creosotebush is unpalatable to most browsing wildlife. Range ratany is an important forage species for deer. Mule deer browse range ratany year-long with seasonal peaks.
Hydrological functions
Available water capacity is low. Water intake rates are moderately rapid. Runoff is medium to rapid depending on slope.
Recreational uses
Aesthetic value is derived from the colorful flowering of white brittlebush during the spring and early summer. This site offers rewarding opportunities to photographers and for nature study. This site is used for hiking and has potential for upland and big game hunting.
Other products
White bursage is a host for sandfood, a parasitic plant. Sandfood was a valuable food supply for Native Americans. The stems of brittle bush exude a clear resin used by the Indians as glue and chewing gum. Creosotebush has been highly valued for its medicinal properties by Native Americans. It has been used to treat at least 14 illnesses. Twigs and leaves may be boiled as tea, steamed, pounded into a powder, pressed into a poultice, or heated into an infusion.
Other information
Creosotebush, white brittlebush and white bursage may be used to revegetate disturbed sites in southwestern deserts. Once established, these species may improve sites for annuals that grow under their canopy by trapping fine soil, organic matter, and symbiont propagules. Water infiltration and storage may also increase. Brittlebush is easily transplanted or can be established by direct seeding.
Supporting information
Type locality
| Location 1: Clark County, NV | |
|---|---|
| Township/Range/Section | T25S R63E S4 |
| General legal description | Approximately 2 miles south of the junction of US Highway 95 and Nevada Highway 165. Steep south-facing sideslopes of low hills to west of US Highway 95 on east side of Eldorado Valley, Clark County, Nevada. |
| Location 2: Clark County, NV | |
| Township/Range/Section | T23S R62E S16 |
| General legal description | South-facing mountain backslopes on Black Mountain southeast of Henderson, Clark County, Nevada. |
Other references
Brown, D.E. and R.A. Minnich. 1986. Fire and changes in creosotebush Scrub of the western Sonoran Desert, California. American Midland Naturalist. 116.2: 411-422.
Fire Effects Information System (Online; http://www.fs.fed.us/database/feis/plants/).
Montalvo, A.M. 2010. Eriogonum fasciculatum Benth. Available: www.fs.fed.us [2010, May 28].
Turner, R.M. 1990. Long-Term Vegetation Change at a Fully Protected Sonoran Desert Site. Ecology. 71.2: 464-477
USDA-NRCS Plants Database (Online; http://www.plants.usda.gov).
Contributors
GKB
Approval
Sarah Quistberg, 2/26/2025
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 | 07/19/2010 |
| Approved by | Sarah Quistberg |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
Number and extent of rills:
Rills are none to rare. A few rills can be expected on steeper slopes in areas recently subjected to summer convection storms. Rock fragments armor the surface. -
Presence of water flow patterns:
Water flow patterns are none to rare but can be expected in areas recently subjected to summer convection storms, usually on steeper slopes. -
Number and height of erosional pedestals or terracettes:
Pedestals are none to rare. Occurrence is usually limited to areas of water flow patterns. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare Ground 15-25%; surface cover of rock fragments to 70%; shrub canopy to 5%; foliar cover of perennial herbaceous plants ± 1%. -
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 1 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 thick platy to weak fine subangular blocky structure. Soil surface colors are light brown and soils are typified by an ochric epipedon. Organic matter of the surface horizon is typically <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:
Shrub canopy 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 not typical. -
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 shrubsSub-dominant:
deep-rooted, warm-season, bunchgrasses > perennial forbs > annual forbs > deep-rooted, cool-season, bunchgrassesOther:
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; some of the mature bunchgrasses (<10%) have dead centers. -
Average percent litter cover (%) and depth ( in):
Between plant interspaces up to 5%. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
For normal or average growing season ± 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:
Invaders on this site include red-stem filaree, red brome, and Mediterranean grass. -
Perennial plant reproductive capability:
All functional groups should reproduce in average (or normal) and above average growing season years.
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