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): 030X–Mojave Basin and Range
The Mojave Desert Major Land Resource Area (MLRA 30) is found in southern California, southern Nevada, the extreme southwest corner of Utah and northwestern Arizona within the Basin and Range Province of the Intermontane Plateaus. The Mojave Desert is a transitional area between hot deserts and cold deserts where close proximity of these desert types exert enough influence on each other to distinguish these desert types from the hot and cold deserts beyond the Mojave. Kottek et. al 2006 defines hot deserts as areas where mean annual air temperatures are above 64 F (18 C) and cold deserts as areas where mean annual air temperatures are below 64 F (18 C). Steep elevation gradients within the Mojave create islands of low elevation hot desert areas surrounded by islands of high elevation cold desert areas.
The Mojave Desert receives less than 10 inches of mean annual precipitation. Mojave Desert low elevation areas are often hyper-arid while high elevation cold deserts are often semi-arid with the majority of the Mojave being an arid climate. Hyper-arid areas receive less than 4 inches of mean annual precipitation and semi-arid areas receive more than 8 inches of precipitation (Salem 1989). The western Mojave receives very little precipitation during the summer months while the eastern Mojave experiences some summer monsoonal activity.
In summary, the Mojave is a land of extremes. Elevation gradients contribute to extremely hot and dry summers and cold moist winters where temperature highs and lows can fluctuate greatly between day and night, from day to day and from winter to summer. Precipitation falls more consistently at higher elevations while lower elevations can experience long intervals without any precipitation. Lower elevations also experience a low frequency of precipitation events so that the majority of annual precipitation may come in only a couple precipitation events during the whole year. Hot desert areas influence cold desert areas by increasing the extreme highs and shortening the length of below freezing events. Cold desert areas influence hot desert areas by increasing the extreme lows and increasing the length of below freezing events. Average precipitation and temperature values contribute little understanding to the extremes which govern wildland plant communities across the Mojave.
Arid Eastern Mojave Land Resource Unit (XB)
LRU notes
The Mojave Desert is currently divided into 4 Land Resource Units (LRUs). This ecological site is within the Arid Eastern Mojave LRU where precipitation is bi-modal, occurring during the winter months and summer months. The Arid Eastern Mojave LRU is designated by the 'XB' symbol within the ecological site ID. This LRU is found across the eastern half of California, much of the mid-elevations of Nevada, the southernmost portions of western Utah, and the mid-elevations of northwestern Arizona. This LRU is essentially equivalent to the Eastern Mojave Basins and Eastern Mojave Low Ranges and Arid Footslopes of EPA Level IV Ecoregions
Elevations range from 1650 to 4000 feet and precipitation is between 4 to 8 inches per year. This LRU is distinguished from the Arid Western Mojave (XA) by the summer precipitation, falling between July and September, which tends to support more warm season plant species. The 'XB' LRU is generally east of the Mojave River and the 117 W meridian (Hereford et. al 2004). Vegetation includes creosote bush, burrobush, Nevada jointfir, ratany, Mojave yucca, Joshua tree, cacti, big galleta grass and several other warm season grasses. At the upper portions of the LRU, plant production and diversity are greater and blackbrush is a common dominant shrub.
Ecological site concept
This ecological site occurs on eroded fan remnants in the upper fan piedmont below 3100 feet. Soils formed in alluvium derived from extrusive igneous material where surface fragments over 3 inches diameter cover more than 15 percent of the soil surface.
This site occurs on summits and sideslopes of fan remnants. Slopes range from 2 to 8 percent. Elevations are 1800 to about 3100 feet.
Table 2. Representative physiographic features
Landforms
(1) Fan remnant
Elevation
1,800–3,100 ft
Slope
2–8%
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 5 inches. Mean annual air temperature is 64 to 69 degrees F. The average growing season is about 240 to 300 days.
Table 3. Representative climatic features
Frost-free period (average)
300 days
Freeze-free period (average)
Precipitation total (average)
5 in
Bar
Line
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 of this site are derived from basalt and other mafic, extrusive, volcanic rock. The soils are shallow to very deep and well drained. Rock fragments cover more than 75 percent of the soil surface, with stones and cobbles predominating. These soils have medium to very high runoff and moderately slow permeability. Available water holding capacity is very low. Potential for sheet and rill erosion is low. Soil series associated with this site include Cafetal.
Table 4. Representative soil features
Parent material
(1) Alluvium–basalt
Surface texture
(1) Extremely stony loam
(2) Extremely cobbly loam
Family particle size
(1) Loamy
Drainage class
Well drained
Permeability class
Moderately slow
Soil depth
10–84 in
Surface fragment cover <=3"
35–40%
Surface fragment cover >3"
35–40%
Available water capacity (0-40in)
1.8–2.4 in
Calcium carbonate equivalent (0-40in)
20%
Electrical conductivity (0-40in)
4 mmhos/cm
Sodium adsorption ratio (0-40in)
12
Soil reaction (1:1 water) (0-40in)
7.9–9
Subsurface fragment volume <=3" (Depth not specified)
23–56%
Subsurface fragment volume >3" (Depth not specified)
28–40%
Ecological dynamics
Ambrosia generally dominates more developed soils with the ability to hold moisture in the upper soil profile. The shallow roots of white bursage are able to effectively use moisture stored in the upper horizons when it is available and survive for extended periods of time when it is not (Hamerlynck et al. 2002). Ambrosia is not able to dominate the deep, weakly developed, coarse textured soils that store water deep in the profile, which is ideal for Larrea. The spatial distribution of soils allows Ambrosia and Larrea to share dominance on these ecological sites. Ambrosia and Larrea can share dominance throughout the successional process, although the relative abundance is likely to change (Marshall 1994). Creosotebush commonly uses white bursage as a nurse plant, young creosotebushes are frequently found rooted beneath mature white bursage plants (Marshall 1995). White bursage is well adapted to the desert environment but prolonged periods of drought will result a reduction of biomass and possibly kill the plant. Under natural conditions, low available fuel and low fire return interval allowed the establishment of long-lived desert perennial communities.
Fine, sandy alluvium on these sites provides material that the wind redistributes to mound-like coppice dunes beneath creosotebush canopies. Heights of coppice dunes increase as a function of creosotebush cover and are tallest on young alluvial surfaces. Moisture absorbed by and stored in the coppice dune enhances plant performance, in turn contributing to the plant’s effectiveness as a windbreak allowing for further deposition of eolian sands (McAuliffe et al 2007). Nutrient concentrations in this shrub community are spatially variable. Nutrient resources are concentrated under shrub canopy relative to the interspaces, called islands of fertility (Kieft et al. 1998).
White bursage and creosotebush dominated shrublands are susceptible to wildfire resulting from annual variations in rainfall. Years with increased rainfall stimulate the growth of non-native annual grasses creating a continuous fuel bed that facilitates the spread of fire (Brooks and Matchett 2006). However, the creosotebush dominated ecotone has a low potential of conversion to an annual grassland. Years of elevated precipitation rarely occur, precluding the development of an extensive layer of herbaceous biomass required to significantly change the local fire dynamics.
The primary effect of fire is the reduction of perennial shrub cover. White bursage has little success resprouting post fire. However, regeneration from seed has been observed to be successful several years post fire (Brown and Minnich 1986). Creosotebush recovers poorly following fire. It very rarely resprouts and establishment by seed is very slow (Brown and Minnich 1986). Damage to big galleta varies, though it is generally top-killed. If big galleta is dry, the damage may be severe. When plants are green, the damage is less, survival is likely and the plants will most likely resprout from rhizomes.
Initial post-burn plant communities in the white bursage/creosotebush ecotone will be composed primarily of brittlebush and white bursage seedlings, as well as, herbaceous vegetation, including an abundance of non-native annuals (cheatgrass, red brome, Mediterranean grass, and red stem filiaree). Brown and Minnich (1986) observed brittlebush seedlings to be prolific on burned Larrea sites the first growing season post-fire. Big galleta, white bursage and Opuntia spp. were observed on burned sites after the first growing season.
Large scale disturbances, such as fire, have long-term impacts on the species composition and structure of this plant community, due to the slow recovery of long-lived desert perennials. The loss of shrub cover results in overall habitat degradation. Disturbances, natural and anthropogenic alike, that result in the removal of the native vegetation increase the likelihood of habitat invasibility. Plants adapted to the Mojave Desert have phenotypic specialization and tolerances, making it difficult for alien plants to establish. However, disturbance can decrease the cover and competitive ability of natives, increasing the available nutrients and favoring the establishment of non-natives (Brooks 1999). Recently, dramatic changes have occurred in the mid-elevation zone occupied by this ecological site, which has resulted in the establishment of an annual grassland fire regime. The conversion occurs because non-native annuals often dominate the post fire landscape due to their efficient use of nutrient and light resources. The fuel conditions they produce can increase the size, decrease the spatial variability, and shorten the time interval between fires in the Mojave Desert (Brooks and Matchett 2006). The amount of area that burns in the mid-elevation shrubland is strongly tied to the production of fine fuels produced by non-native annuals following years of high rainfall.
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
This state represents the natural range of variability under pristine conditions. Community phase changes are primarily driven by long-term drought and insect attack. Wildfire is infrequent and patchy in this ecological site due to low fuel loading and widely spaced shrubs
Community 1.1 Reference Plant Community
The visual aspect of this reference plant community is dominated by creosotebush and white bursage for most of the year. In the spring, particularly after above normal winter period precipitation, wildflowers predominate. 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 5% grasses, 50% annual and perennial forbs and 45% shrubs. Approximate ground cover (basal and crown) is 5 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 (lb/acre)
Representative value (lb/acre)
High (lb/acre)
Forb
25
175
300
Shrub/Vine
23
158
270
Grass/Grasslike
2
17
30
Total
50
350
600
State 2 Representative State
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. A combination of factors including surface disturbance, changes in the kinds of animals and their grazing patterns, drought, changes in fire history or any other type of vegetation removal can introduce non-native species to the system. The ability of non-native species to fill the interstitial spaces between shrubs provides a continuous fuel load which may increase fire frequency, contributing to the difficultly in returning this site to the reference state.
LATR and AMDU persist after invasion by non-native annuals, but the other shrubs and desirable grasses 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 due to their widespread naturalization. At this time ecological function has not changed, however the resiliency of the state has been reduced by the presence of non-native annual species. The non-natives have 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 plant community with the presence of non-native species in the understory. At this time ecological processes remain largely unchanged at this time.
Community 2.2 Plant Community Phase 2.2
This plant community is dominated by seedlings of native species tolerant of post fire conditions and non-native annuals. Limited creosotebush and other mature shrubs will remain, surviving individuals act as nurse plants. Seedlings are dominated by white bursage and brittlebush.
Community 2.3 Plant Community Phase 2.3
This plant community is characterized by the heavy disturbance. Total shrub canopy is reduced. Remaining vegetation exists as islands on the landscape. Non-natives are able to persist with increased disturbance. Shrubs experience reduced vigor due to increased soil compaction.
Community 2.4 Plant Community Phase 2.4
This plant community is characterized by an increased in non-native annual biomass. This plant community is identified as “at-risk”. Few species from the reference community remain in this community phase due to unfavorable conditions created by a shorter fire return interval.
Pathway 2.1a Community 2.1 to 2.2
Large or small scale fire removes long-lived shrub community and herbaceous vegetation. Mature shrubs experience high rates of mortality.
Pathway 2.1b Community 2.1 to 2.3
Heavy reoccurring disturbance decrease shrub canopy.
Pathway 2.2a Community 2.2 to 2.1
With time and the absence of fire shrubs mature and densities increase.
Pathway 2.2b Community 2.2 to 2.4
Reoccurring fire favors establishment non-native annuals and excludes native woody perennials.
Pathway 2.3a Community 2.3 to 2.2
With time and continued absence of fire and/or removal of disturbance native perennial seedlings establish from adjacent in-tack shrub communities.
Pathway 2.4a Community 2.4 to 2.2
Time without fire allows shrub seedlings to establish from nearby seed source.
State 3 Non-Native Annual Grassland
An abiotic threshold has been crossed, triggered by a frequent and repeated wildfire. This alternative stable state is extremely persistent due to strong feedbacks, including fire regimes, energy capture and nutrient cycling.
Community 3.1 Plant Community Phase 3.1
This plant community is characterized by frequent fire return interval and a monoculture of non-native annual grasses. Native species are unable to establish and persist in the presence of increased fire, favoring the establishment of annual grassland.
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.
Transition 2 State 2 to 3
Frequent and repeated fire excludes woody vegetation and favors the establishment of non-native annual grassland.
Restoration pathway R State 3 to 2
Fire suppression
Additional community tables
Table 6. Community 1.1 plant community composition
Livestock Interpretations:
This site is suitable for livestock grazing. 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. 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. 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. The pads of Opuntia species can be used as emergency forage for livestock after the spines have been singed off. Prickly-pear is regarded as an important emergency forage for livestock. Although the moisture content of aboveground tissues of plains prickly-pear is high, nutrient content is low. The palatability of prickly-pear to livestock is generally considered poor to fair, because spines deter grazing.
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. 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. Mule deer peak use is from February to April and from August to October. Antelope, deer and mountain sheep feed on the vegetable parts and fruits of buckhorn cholla. Buckhorn cholla is grazing tolerant. Beavertail pricklypear is browsing tolerant and is used as a food source for small and large mammals, upland game birds, and waterfowl. The palatability of plains prickly-pear to wildlife is generally considered poor to fair, because spines deter grazing.
Hydrological functions
These soils have medium to very high runoff and moderately slow permeability. Available water holding capacity is very low.
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. Sandfood was a valuable food supply for Native Americans. 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. The Papago Indians used an infusion of the twigs externally for treating sore eyes and internally for dysentery. The roots provided them with a red dye for wool and other materials. The dye was also used as an ink.
Other information
Big galleta's clumped growth form stabilizes blowing sand. White bursage may be used to revegetate disturbed sites in southwestern deserts. Creosotebush may be used to rehabilitate disturbed environments in southwestern deserts. Once established, creosotebush may improve sites for annuals that grow under its canopy by trapping fine soil, organic matter, and symbiont propagules. It may also increase water infiltration and storage.
Supporting information
Type locality
Location 1: Clark County, NV
Township/Range/Section
T24S R62E S1
UTM zone
N
UTM northing
3972616
UTM easting
680814
Latitude
35° 52′ 52″
Longitude
114° 59′ 49″
General legal description
Approximately 3.5 miles southwest of Blue Quartz Mine in Eldorado Valley, Clark County, Nevada. Latitude: 35 degrees, 52 minutes, 52 seconds. Longitude: 114 degrees, 59 minutes, 49 seconds.
Other references
Brooks, M.L. 1999. Habitat invisibility and dominance by alien annual plants in the western Mojave Desert. Biological Invasions. 1: 325-337.
Brooks, M.L. and J.R. Matchett. 2006. Spatial and temporal patterns of wildfire in the Mojave Desert, 1980-2004. J. of Arid Environments. 67: 148-164.
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.
Hamerlynck, E.P., J.R. McAuliffe, E.V. McDonald and S.D. Smith. 2002. Ecological Responses of Two Mojave Desert Shrubs to Soils Horizon Development and Soil Water Dynamics. Ecology. 83.3: 768-779.
Hereford, R., R.H. Webb and C. I. Longpre. 2004. Precipitation history of the Mojave Desert region, 1893-2001 (No. 117-03).
Kottek, M., Grieser, J., Beck, C., Rudolf, B., & Rubel, F. (2006). World map of the Köppen-Geiger climate classification updated. Meteorologische Zeitschrift, 15(3), 259-263.
McAuliffe, J.R., E.P. Hamerlynck, and M.C. Eppes. 2007. Landscape dynamics fostering the development and persistence of long-lived creosotebush (Larrea tridentata) clones in the Mojave Desert. J. of Arid Environments. 69:96-126.
Salem, B. B. (1989). Arid zone forestry: a guide for field technicians (No. 20). Food and Agriculture Organization (FAO).
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 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.
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 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 strong thin and medium platy. Soil surface colors are light and soils 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):
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 (10-15%) 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 ± 350lbs/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.
The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.
Click on box and path labels to scroll to the respective text.
