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Conservation Service
Ecological site R030XC041NV
GRAVELLY FAN APRON 9-11 P.Z.
Last updated: 2/25/2025
Accessed: 08/22/2026
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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 fan aprons. Slopes range from 4 to 15 percent. Elevations are 4000 to 6000 feet. The soils associated with site are deep to very deep, well drained soils that formed in alluvium derived from limestone. The soil profile is characterized by 50 to 75 percent rock fragments, mainly gravel with some cobbles and stones.
This is a group concept and provisional STM that also covers the following ecological sites: R030XC042NV, R030XC235CAAssociated sites
R030XC032NV UPLAND WASH
R030XC042NV GRAVELLY LOAM 9-11 P.Z.
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Table 1. Dominant plant species
Tree Not specified
Shrub (1) Coleogyne ramosissima
Herbaceous (1) Achnatherum hymenoides
(2) Muhlenbergia porteriPhysiographic features
This site occurs on fan aprons. Slopes range from 4 to 15 percent. Elevations are 4000 to 6000 feet.
Table 2. Representative physiographic features
Landforms (1) Fan apron
Flooding frequency None Ponding frequency None Elevation 4000 – 6000 ft Slope 4 – 15 % Climatic features
The climate is arid with warm, dry summers and cool, moist winters. Precipitation is greatest in the winter with a lesser secondary peak in the summer. Average annual precipitation is 7 to 11 inches. Mean annual air temperature is 52 to 58 degrees F. The average growing season is about 130 to 180 days.
Table 3 Representative climatic features
Frost-free period (average) 180 days Freeze-free period (average) Precipitation total (average) 10 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. 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 site are deep to very deep, well drained soils that formed in alluvium derived from limestone. The soil profile is characterized by 50 to 75 percent rock fragments, mainly gravel with some cobbles and stones. Available water capacity is low and runoff is low. The soil moisture regime is typic-aridic, with soil moisture dry and only moist for short periods during winter and early spring. Soil series correlated to this ecological site include Quijinump, a loamy-skeletal, carbonatic, mesic, Typic Torriorthents.
Table 4. Representative soil features
Parent material (1) Alluvium – limestone
Surface texture (1) Very gravelly fine sandy loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderately slow Soil depth 60 – 84 in Surface fragment cover <=3" 60 – 70 % Surface fragment cover >3" 2 – 5 % Available water capacity
(0-40in)1.81 – 4.76 in Calcium carbonate equivalent
(0-40in)30 – 70 % Electrical conductivity
(0-40in)0 – 2 mmhos/cm Sodium adsorption ratio
(0-40in)0 – 5 Soil reaction (1:1 water)
(0-40in)7.9 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)35 – 45 % Subsurface fragment volume >3"
(Depth not specified)3 – 10 % Ecological dynamics
Blackbrush communities are most prevalent in the transitional zone between the Mojave Desert and Great Basin. Blackbrush is a paleoendemic species as originally postulated by Stebbins and Major (1965). Blackbrush is a transitional species that occupies a boundary that has shifted in recent geologic time. Analysis of packrat middens suggests a 50–100-m downward movement of the blackbrush zone along elevational gradients in the Mojave Desert (Cole and Webb, 1985; Hunter and McAuliffe, 1994).
Blackbrush is a long-lived and generally considered a climax species. It is a non-sprouter; regeneration depends on wind pollinated seed and heavy winter precipitation, and is therefore slow to re-colonize burned areas (Anderson 2001). Blackbrush recruitment is episodic, like many shrubs in arid systems, when conditions are favorable large seed crops are produced and the rest of the time is characterized by minimal seed output (Pendleton and Meyer 2004). Blackbrush seeds are frequently cached away by rodents, until conditions are conducive for germination. Typically, germination occurs during the winter and early spring, given the proper moisture conditions and cool soil temperatures (Pendleton 2008). Seeds require cold stratification before germination and the survival of seedlings following germination is dependent on the availability of spring time moisture (Pendleton 2008).
On undisturbed sites, blackbrush dominates the landscape and species diversity is generally low. Undisturbed blackbrush communities are fairly resistant to invasion by non-natives (Brooks and Matchett 2003). Mature blackbrush plants are well adapted to persist under less than optimal conditions, and individuals’ may live as long as 400 years (Pendleton and Meyer 2004). Communities are characterized by a flammable shrub architecture allowing fire to easily spread, thus these communities experience stand replacing fire regimes. The short-lived seed of blackbrush is readily destroyed by fire. There is frequently 100 percent mortality of blackbrush following fire (Brooks and Matchett 2003).
Fire ecology:
Blackbrush communities are characterized by an extended fire return interval. The species is considered to be extremely sensitive to fire; it may take more than 60 years for blackbrush to achieve pre-fire conditions. Blackbrush is extremely flammable, readily killed by fire, and reestablishes solely from seed. Post-fire plant communities vary, depending on land use history and species present before the fire. Post-fire, resprouting species such as ephedra, yucca, fourwing saltbush and perennial grasses are dominant. Ephedra establishes early following fire and is known to sprout vigorously from the roots or root crown. It quickly produces above ground biomass and is able to reestablish disturbed areas through seed. Range ratany is only top killed by fire and will resprout from the root crown. All species of yucca found on this site are capable of sprouting from the root crown or rhizomes following wildfire. However, banana yucca can experience high mortality rates if the level of water stress is high when burned. If the fire reaches the root crown many yuccas are killed. Indian ricegrass can be killed by fire, depending of the seasonality and severity of the burn. However, it will reestablish by seed from nearby unburned areas. Fire top kills bush muhly. It regenerates from soil-stored seed following fire, depending on post fire weather and competition.
Post-fire plant communities vary, depending on use history and species present prior to the fire. Post fire sprouting shrub species such as yucca, spiny menodora and ephedra increase along with perennial grasses. Species that readily reestablish from seed such as snakeweed also increase. Generally, non-natives increase and native species decrease post fire (Brooks and Matchett 2003). The effects of fire on blackbrush appear to be long term, it is killed by fire and is slow to reestablish.State and transition model
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Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 2 submodel, plant communities
State 1
Reference StateThe reference state is representative of the natural range of variability under pristine conditions. It is dominated by the long-lived evergreen shrub, blackbrush with an understory of cool and warm season perennial bunchgrasses. Plant community phase changes are primarily driven by fire, long-term drought and insect attack. Historically, blackbrush associations were long-lived stable communities that rarely experienced fire due to low fuel loading. Reproduction and recruitment are episodic, based on favorable climatic conditions.
Community 1.1
Reference Plant CommunityThe reference plant community is representative of a healthy mid-seral condition and is dominated by blackbrush. Range ratany, Indian ricegrass and Nevada ephedra are other important species associated with this site. This plant community is stable and long-live, it is able to persist for extended periods of time under undisturbed conditions. Potential vegetative composition by weight is about 10 percent grasses, 5 percent annual and perennial forbs and 85 percent shrubs. Approximate ground cover (basal and crown) is 25 to 35 percent.
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)Shrub/Vine 215 297 425 Grass/Grasslike 25 35 50 Forb 10 18 25 Total 250 350 500 Community 1.2
Plant Community 1.2This plant community is characterized by an early seral, post-disturbance community phase and is initially dominated by herbaceous vegetation. Sprouting shrubs quickly return and provide favorable environment for the establishment of other shrubs seedlings. Fast moving, low intensity fires result in the incomplete removal of blackbrush allowing for direct reestablishment. This plant community is ‘at-risk’ of invasion by non-native annuals, such as red brome, due to the increased availability of critical resources following a disturbance. Composition of the post-fire plant community may vary depending on season of burn.
Pathway 1.1a
Community 1.1 to 1.2Wildfire, prolonged drought or disease/insect attack
Pathway 1.2a
Community 1.2 to 1.1Absence from disturbance and natural regeneration over time. Recovery of blackbrush to pre-fire conditions may take greater than 60 years.
State 2
Invaded StateThe Invaded State is characterized by the presence of non-natives in the understory. A biotic threshold has been crossed, with the introduction of non-natives that cannot be easily removed from the system and have the potential to significantly alter disturbance regimes from their historic range of variation. These non-native annuals are highly flammable and promote wildfires where fires historically have been infrequent. 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. The presence of non-natives has reduced the ecological resilience of the site. Following a disturbance this state relies on the availability of an offsite seed source.
Community 2.1
Invaded Plant Community 2.1This plant community is compositionally similar to the reference plant community with a trace of non-native species in the understory. Primary ecological processes have not been compromised at this time. However the presence of non-natives has reduced the ecological resilience of the site. This plant community responds differently following a disturbance, when compared to the reference plant community. Management focused on reducing anthropogenic impacts and other disturbances is important for maintaining the health perennial native species.
Community 2.2
Invaded Plant Community 2.2This plant community is characteristic of an early-seral, post-disturbance plant community. Initially this community phase is heavily dominated by herbaceous vegetation. Sprouting shrubs quickly recover and provide favorable sites of the establishment of the shrubs seedlings. Fast moving, low intensity fires result in the incomplete removal of blackbrush allowing for direct reestablishment. Abundance of non-native biomass varies annually depending on the weather. Post-fire plant communities may vary in response to the season of burn.
Community 2.3
Invaded Plant Community 2.3This plant community is characteristic of a mid-seral plant community. Woody perennials are increasing and non-natives are present. Atriplex and other species that readily establish from seed post disturbance are common. Wildfire has long term effects on blackbrush communities. Abundance of non-native biomass varies annually depending on weather, droughty conditions favor native perennials and decrease abundance of non-natives. Species composition of this plant community may vary greatly depending on the species present prior to the disturbance.
Pathway 2.1a
Community 2.1 to 2.2Wildfire, prolonged drought or insect/disease attack.
Pathway 2.2a
Community 2.2 to 2.3Absence from disturbance and natural regeneration over time.
Pathway 2.3a
Community 2.3 to 2.1Absence from disturbance and natural regeneration over time. Recovery of blackbrush to pre-disturbance conditions may take a significant amount of time (>60years).
Pathway 2.3b
Community 2.3 to 2.2Wildfire, prolonged drought or insect/disease attack.
Transition T1
State 1 to 2Introduction of non-native species due to a combination of factors including: 1) surface disturbance, 2) changes in the kinds of animals and their grazing patterns, 3) drought and/or 4) changes in fire history.
Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Primary Perennial Grasses 25–53 Indian ricegrass ACHY Achnatherum hymenoides 18–35 – bush muhly MUPO2 Muhlenbergia porteri 7–18 – 2 Secondary Perennial Grasses 7–18 desert needlegrass ACSP12 Achnatherum speciosum 2–7 – threeawn ARIST Aristida 2–7 – low woollygrass DAPU7 Dasyochloa pulchella 2–7 – squirreltail ELEL5 Elymus elymoides 2–7 – Forb3 Perennial Forbs 7–18 desert marigold BAMU Baileya multiradiata 2–7 – desert trumpet ERIN4 Eriogonum inflatum 2–7 – desert globemallow SPAM2 Sphaeralcea ambigua 2–7 – princesplume STANL Stanleya 2–7 – Shrub/Vine4 Primary Shrubs 208–318 blackbrush CORA Coleogyne ramosissima 175–230 – Nevada jointfir EPNE Ephedra nevadensis 18–53 – littleleaf ratany KRER Krameria erecta 7–18 – yucca YUCCA Yucca 7–18 – 5 Secondary Shrubs 18–53 rayless goldenhead ACSP Acamptopappus sphaerocephalus 3–11 – fourwing saltbush ATCA2 Atriplex canescens 3–11 – Torrey's jointfir EPTO Ephedra torreyana 3–11 – spiny hopsage GRSP Grayia spinosa 3–11 – winterfat KRLA2 Krascheninnikovia lanata 3–11 – spiny menodora MESP2 Menodora spinescens 3–11 – Fremont's dalea PSFR Psorothamnus fremontii 3–11 – Mexican bladdersage SAME Salazaria mexicana 3–11 – turpentinebroom THMO Thamnosma montana 3–11 – beavertail pricklypear OPBA2 Opuntia basilaris 1–3 – Wiggins' cholla CYEC3 Cylindropuntia echinocarpa 1–3 – hedgehog cactus ECHIN3 Echinocereus 1–3 – Table 7. Community 1.2 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 8. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 9. Community 2.2 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 10. Community 2.3 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
Livestock interpretations: This site has limited value for livestock grazing, due to low forage production and distance from adequate water resources. Grazing management should be keyed to dominant perennial grasses and palatable shrubs. Indian ricegrass benefits from moderate grazing use in winter and early spring. Inappropriate season of grazing may sharply reduce vigor of decrease overall cover. Indian ricegrass is high palatable to all classes of livestock in both the green and cured condition. Bush muhly is readily eaten by livestock throughout the year when available. However, it is generally not abundant enough to provide much forage. It is extremely susceptible to heavy grazing due to its highly branched growth form. Bush muhly experiences its high rate of use in the winter months when other species become scarce. Dominant shrubs provide additional grazing resource on this ecological site. Blackbrush is economically important forage in the winter especially for domestic sheep. It is considered poor forage during the spring, summer and fall for domestic cattle, horses and sheep. Nevada ephedra is also highly important winter forage for domestic cattle, sheep and goats. It is generally heavily grazed without inducing toxicity in ewes or cows. Range ratany is palatable to domestic cattle and sheep, but many decrease under heavy grazing pressure. Yucca species can provide browse for domestic livestock. However, palatability is generally considered to be low and consumption is limited to accessible blooms and fruits. Signs of heavy browsing by domestic livestock should be considered an indication of poor range condition. Stocking rates vary over time depending upon season of use, climate variation, 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:
A variety of wildlife species find valuable foraging and habitat resources on this ecological site. Indian ricegrass is eaten by pronghorn when available. It is also the preferred seed of a variety of rodents and small mammals. Indian ricegrass makes up a significant portion of jackrabbit diets in the spring and summer. It also provides seed for many species of birds. The palatability of bush muhly is considered fair to poor for most wildlife species. Blackbrush provides an important winter browsing resource for several species of wildlife, including mule deer and bighorn sheep. Nevada ephedra is browsed by mule deer, bighorn sheep and pronghorn in the spring to late summer when new growth is available. Range ratany is a valuable foraging resource for mule deer. They will browse it year long, but peak use is from February to April and August to October. Mule deer often seek out new growth on banana yucca, especially as it sprouts after fire. Bighorn sheep browse leave and fruit of banana yucca. Multiple parts of the plant are also used by small mammals, birds and insects. Joshua tree provides important habitat and food for small mammals, birds, insects and reptiles. Utilization by large wildlife is limited by the height of blossoms and fruit. Palatability is poor for pronghorn, mule deer and small mammals.Hydrological functions
The soils associated with this site are characterized by low runoff and moderately slow permeability.
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 for photography and nature study. This site is used for camping and hiking and has potential for upland and big game hunting.
Other products
Indian ricegrass was a staple food for many American Indian tribes. Ephedra was traditionally used a beverage and medicine. Native Americans made tea from the slender twigs and inner bark by boiling them. The beverage was used as tonic and blood purifier. However, ephedra is considered toxic and should be used with caution.
Banana yucca was used by Native Americans as a food source. Fruits were consumed raw before fully ripening. Cakes were also made by pit roasting the fruits, grinding them into a paste, and drying the resulting material. Fermented banana yucca has been used for beverages, its juices used as a preservative, its seeds dried and ground into a meal and the central leaves were incorporated into soups and meat dishes.Other information
Indian ricegrass is well adapted to stabilization of disturbed sandy soils and is especially valuable for controlling wind erosion. It is well suited for reclamation projects in areas receiving 8 to 14 inches annual precipitation.
Supporting information
Type locality
Location 1: Clark County, NV Township/Range/Section T13S R60E S1 UTM zone N UTM northing 660746 UTM easting 4077666 Latitude 36° 49′ 52″ Longitude 115° 11′ 50″ General legal description Approximately 1.7 miles west from Mule Deer Ridge at the south end of Desert Valley; approximately 3.3 miles east from the head of Snow Canyon; Desert National Wildlife Refuge. Other references
Anderson, Michelle D. 2001. Coleogyne ramosissima. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [ 2011, August 16].
Brooks, M.L. and J.R. Matchett. 2003. Plant community patterns in unburned and burned blackbrush (Coleogyne ramosissima Torr.) shrublands in the Mojave Desert. Western North American Naturalist. 63.3: 283-298.
Cole, K.L., and Webb, R.H. 1985. Late Holocene vegetation changes in Greenwater Valley, Mojave Desert, California, Quaternary Research. 23. 2: 227-235.
Hunter, K.L. and J.R. McAuliffe. 1994. Elevational Shifts of Coleogyne ramosissima in the Mojave Desert during the Little Ice Age. Quaternary Research. 42. 2: 216-221.
Pendleton, B.K. and S.E. Meyer. 2004. Habitat-correlated variation in blackbrush (Coleogyne ramosissima: Rosaceae) seed germination response. J. of Arid Environments. 59: 229-243.
Pendleton, B.K. 2008. Coleogyne ramosissima Torr. Available: http://www.nsl.fs.fed.us.wpsm/index.html
Fire Effects Information System (Online; http://fs.fed.us/database/feis/plants/).
USDA-NRCS Plants Database (Online; http://www.plants.usda.gov).
Contributors
E. Hourihan
PN-EApproval
Sarah Quistberg, 2/25/2025
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) E.Hourihan/P.Novak-Echenique Contact for lead author State Range Management Specialist Date 08/16/2011 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
None -
Presence of water flow patterns:
Water flow patterns are none to rare but can be expected in areas recently subjected to summer convection storms. Flow patterns are short (<3ft) and not connected. -
Number and height of erosional pedestals or terracettes:
None -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare Ground 2-10% depending on amount of surface cover of 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 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):
A horizon thickness is 2 inches. Surface structure is typically moderate, medium subangular blocky. Soil surface colors are pale brown and soils are typified by an ochric epipedon. Organic matter of the surface 2 to 4 inches is typically <1.0 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 and provide opportunity for snow catch and accumulation on this site. Deep-rooted perennial bunchgrasses slow runoff and increase infiltration. -
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. Subsoil massive 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:
Reference Plant Community: evergreen shrub (blackbrush) >>Sub-dominant:
associated shrubs > deep-rooted perennial bunchgrasses > perennial forbs > annual forbs > shallow-rooted perennial bunchgrassesOther:
SucculentsAdditional:
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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):
Litter mostly concentrated under shrubs. Total litter cover between and under plants 15-25% and depth is 0.25 inches. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
For normal or average growing season ± 350 lbs/ac, below average 250 lbs/ac; above-average 500 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:
Cheatgrass and red brome are potential invaders on this site. -
Perennial plant reproductive capability:
All functional groups should reproduce in average (or normal) and above average growing season years. Less reproduction, although rarely none, will occur in below average precipitation years.
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