Natural Resources
Conservation Service
Ecological site R030XY047NV
ALLUVIAL PLAIN
Last updated: 2/24/2025
Accessed: 04/08/2025
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 alluvial flats, fan skirts, and lake plains on all exposures. Slopes range from 0 to 8 percent, but slope gradients of 0 to 4 percent are typical. Elevations are 1700 to 4100 feet. The soils associated with this site are very deep alluvium derived from mixed sources. Available water capacity is low to moderate, runoff is low to very high, and the soils are well drained to somewhat excessively drained.
This site is part of group concept R030XB047NV.
Associated sites
| R030XB004NV |
SANDY 5-7 P.Z. |
|---|
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
(1) Atriplex polycarpa |
| Herbaceous |
(1) Achnatherum hymenoides |
Physiographic features
This site occurs on alluvial flats, fan skirts, and lake plains on all exposures. Slopes range from 0 to 8 percent, but slope gradients of 0 to 4 percent are typical. Elevations are 1700 to 4100 feet.
Table 2. Representative physiographic features
| Landforms |
(1)
Alluvial flat
(2) Fan skirt (3) Lake plain |
|---|---|
| Flooding duration | Extremely brief (0.1 to 4 hours) to very brief (4 to 48 hours) |
| Flooding frequency | Very rare to rare |
| Ponding frequency | None |
| Elevation | 1,700 – 4,100 ft |
| Slope | 8% |
| Aspect | Aspect is not a significant factor |
Climatic features
The climate is hot and arid, with mild winters and very hot summers. Precipitation is greatest in the winter with a lesser secondary peak in summer, typical of the Mojave Desert. The average annual precipitation ranges from 3 to 5 inches with most of the moisture falling as rain during the period November through March. At least 30% of the annual precipitation occurs from July to September as a result of summer convection storms. Mean annual air temperature is 64 to 69 degrees F. The average frost-free period is 240 to 300 days.
Table 3. Representative climatic features
| Frost-free period (average) | 300 days |
|---|---|
| Freeze-free period (average) | |
| Precipitation total (average) | 5 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 soils associated with this site are very deep alluvium derived from mixed sources. Available water capacity is low to moderate, runoff is low to very high, and the soils are well drained to somewhat excessively drained. The soils have a typic-aridic soil moisture regime. Soil reaction throughout the profile ranges from moderately to very strongly alkaline. The soils series associated with this site include:
Haymont, a coarse-silty, mixed, superactive, calcareous, thermic Typic Torriorthent;
Hypoint, a sandy, mixed, thermic Typic Torriorthent; and
Tipnat, a fine-loamy, mixed, superactive, thermic Typic Natrargid.
Table 4. Representative soil features
| Surface texture |
(1) Loamy sand (2) Gravelly sandy loam (3) Very fine sandy loam |
|---|---|
| Family particle size |
(1) Loamy |
| Drainage class | Well drained to somewhat excessively drained |
| Permeability class | Moderately slow to rapid |
| Soil depth | 72 – 84 in |
| Surface fragment cover <=3" | 20 – 25% |
| Surface fragment cover >3" | Not specified |
| Available water capacity (0-40in) |
3 – 10 in |
| Calcium carbonate equivalent (0-40in) |
35% |
| Electrical conductivity (0-40in) |
5 mmhos/cm |
| Sodium adsorption ratio (0-40in) |
45 |
| Soil reaction (1:1 water) (0-40in) |
8.4 – 9.5 |
| Subsurface fragment volume <=3" (Depth not specified) |
35% |
| Subsurface fragment volume >3" (Depth not specified) |
Not specified |
Ecological dynamics
The plant communities of this site are dynamic in response to changes in disturbance regimes and weather patterns. Community phase changes are primarily driven by long term drought. Historically, wildfire was infrequent and patchy, due to widely spaced vegetation and low herbaceous production.
Cattle saltbush flowers from May to August, with fruit ripening from October to December. Seeds are dispersed from November to May. Cattle saltbush is tolerant of alkaline conditions and relatively high pH, however, germination can be reduced if salt concentrations become too high. Large quantities of salt are accumulated in the shoots and on the leaf surface, this is thought to increase its salinity tolerance by reducing the salinity stress of photosynthetically active tissue (Kay et al. 1977).
Cattle saltbush and all Atriplex species are well adapted to the Mojave Desert environment. They are examples of extreme drought resistance, surviving more than a week at -6 Megapascals of water potential. The spatial distribution of vegetation of this site impacts runoff, infiltration, sediment redistribution and nutrient cycling. Patches of vegetation increase fine sediment deposition and reduce runoff producing positive feedback dynamics in the plant community. Shrub canopies shield the soil from radiation and rainfall (Puigdefabregas 2005). Shrubs partition the rainfall into interception, throughfall and stem flow. Interception diminishes net rainfall, while stemflow concentrates the water and results in deeper infiltration (Puigdefabregas 2005).
Fire Ecology:
The historic fire return interval for salt-desert shrub communities ranges from 35 to 100 years. Saltbush produces abundant seeds and is demonstrably fire resistant. Saltbush has been shown to have reduced flammability due to high moisture and salt content. Saltbush can survive at least some fires. Saltbush readily reproduces from seed following wildfire. Alkali sacaton is classified as tolerant of, but not resistant to, fire. Top-killing by fire is probably frequent, and the plants can be killed by severe fire. 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.
State and transition model
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Ecosystem states
State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 1
Reference State
The Reference State is representative of the natural range of variability under pristine conditions. The plant community is shrub dominated with few perennial grasses and forbs. Historically, this state experienced an extended fire return interval due to low fuel loading, resulting in long-lived stable salt-desert shrub plant communities. These communities were sparsely vegetated and soil stability was primarily provided by surface rock fragments and microbiotic soil crust.
Community 1.1
Reference Plant Community
The plant community is dominated by cattle saltbush. Potential vegetative composition is about 15% grasses and 5% forbs and 80% shrubs. Approximate ground cover (basal and crown) is ±7 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 | 200 | 320 | 400 |
| Grass/Grasslike | 38 | 60 | 75 |
| Forb | 12 | 20 | 25 |
| Total | 250 | 400 | 500 |
State 2
Invaded State
The invaded state is characterized by the presence of non-native annuals in the understory. Plant communities in this state function very similarly to the reference state. A biotic threshold has been crossed with the introduction of non-native annuals that cannot be easily removed from the system and have the potential to alter disturbance regimes significantly from their natural range of variation. Introduced annuals such as red brome, Mediterranean grass and redstem filaree have invaded the reference plant community and have become a 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.
Community 2.1
Invaded Plant Community 2.1
This plant community is characterized by the presence of non-natives in the understory. Functionally this plant community is similar to the reference plant community. Ecological function has been not compromised at this time, however, ecological resilience is reduced by the presence of the non-natives and may respond differently following a disturbance. Dominant shrubs persist throughout invasion by non-native annuals, however native grasses and forbs are at a competitive disadvantage and suffer reduced vigor and reproductive capacity.
Community 2.2
Invaded Plant Community 2.2
This plant community is characterized by reduced perennial vegetation and microbiotic soil crust and increased non-native biomass. Soil surface degradation has decreased aggregate stability and organic matter. Management should focus on reducing disturbance levels and protecting native vegetation to ensure a seed source in the future.
Community 2.3
Invaded Plant Community 2.3
This plant community is characterized by a short disturbance return interval. The soil surface is continually disturbed, decreasing stability of the soil surface. Non-native annuals take advantage of the increased availability of resources. The loss of perennial vegetation leads to decreased infiltration and increased runoff. Feedbacks contributing to the stability of this plant community include loss of functional and structural groups and the density, rate of spread, and dominance of non-natives. This plant community is identified as “at risk”. Management should focus on stabilizing the soil surface and protecting remaining native vegetation. If abusive land use practices continue it is possible that this plant community will cross on irreversible threshold into an alternative state 3.
Pathway 2.1a
Community 2.1 to 2.2
Further anthropogenic disturbance removes shrubs and microbiotic soil crust reducing soil stability.
Pathway 2.2a
Community 2.2 to 2.1
Removing surface disturbance, over the long term, allows woody perennials to recover contributing to increased ecological resilience.
Pathway 2.2b
Community 2.2 to 2.3
Continued disturbance removes cattle saltbush and other shrubby vegetation. Non-native annuals increase.
Pathway 2.3a
Community 2.3 to 2.2
Removing anthropogenic disturbance allows shrubby vegetation to reestablish on the site.
State 3
Eroded State
The Eroded State is characterized by increased bare ground and reduced soil stabilization. Prolonged soil surface disturbance has caused this site to cross an abiotic threshold. The loss of vegetation and soil crust has decreased the stability of the site. Ecological processes such as nutrient cycling and water storage are severely reduced.
Community 3.1
Plant Community 3.1
Vegetation is dominated by non-native annuals. Soil stability is severely reduced due to lack of perennial vegeation and active erosion easily occurs, even during typical rain and wind events.
Community 3.2
Plant Community 3.2
This plant community is characterized by a total loss of vegetation and soil crust, bare ground is dominant. Active soil erosion easily occurs.
Pathway 3.1a
Community 3.1 to 3.2
Continued surface disturbance.
Pathway 3.2a
Community 3.2 to 3.1
Non-native annuals germinate and establish even on a severely eroded site.
Transition T1
State 1 to 2
Introduction of non-natives due to anthropogenic impacts, including OHV use, dry land farming, changes in grazing animals and patterns, linear corridors, mining, military training operations and settlements, also drought and changes in fire history.
Transition T2
State 2 to 3
Continued soil surface disturbance, loss of perennial vegetation and soil crust.
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 | Primary Perennial Grasses | 20–60 | ||||
| Indian ricegrass | ACHY | Achnatherum hymenoides | 20–60 | – | ||
| 2 | Secondary Perennial Grasses | 5–32 | ||||
| big galleta | PLRI3 | Pleuraphis rigida | 1–8 | – | ||
|
Forb
|
||||||
| 3 | Perennial Forbs | 1–32 | ||||
| desert globemallow | SPAM2 | Sphaeralcea ambigua | 1–12 | – | ||
| 4 | Annual Forbs | 1–40 | ||||
| spineflower | CHORI2 | Chorizanthe | 1–12 | – | ||
| desert trumpet | ERIN4 | Eriogonum inflatum | 1–12 | – | ||
|
Shrub/Vine
|
||||||
| 5 | Primary Shrubs | 240–300 | ||||
| cattle saltbush | ATPO | Atriplex polycarpa | 240–300 | – | ||
| 6 | Secondary Shrubs | 20–80 | ||||
| burrobush | AMDU2 | Ambrosia dumosa | 1–20 | – | ||
| fourwing saltbush | ATCA2 | Atriplex canescens | 1–20 | – | ||
| desertholly | ATHY | Atriplex hymenelytra | 1–20 | – | ||
| Torrey's saltbush | ATTO | Atriplex torreyi | 1–20 | – | ||
| creosote bush | LATR2 | Larrea tridentata | 1–20 | – | ||
| desert-thorn | LYCIU | Lycium | 1–20 | – | ||
| Mojave seablite | SUMO | Suaeda moquinii | 1–20 | – | ||
Interpretations
Animal community
Livestock Interpretations:
This site is suited to livestock grazing. Grazing management should be keyed to maintaining shrub and perennial grass species. Indian ricegrass is a valuable forage species.
Indian ricegrass has good forage value for domestic sheep, cattle and horses. It supplies a source of green feed before most other native grasses have produced much new growth.
Cattle saltbush is one of the most palatable shrubs in the West. Its protein, fat, and carbohydrate levels are comparable to alfalfa. It provides nutritious forage for all classes of livestock. Palatability is rated as good for domestic sheep and domestic goats; fair for cattle; fair to good for horses in winter, poor for horses in other seasons.
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:
Cattle saltbush provides valuable habitat and year-round browse for wildlife. Cattle saltbush also provides browse and shelter for small mammals. Additionally, the browse provides a source of water for black-tailed jackrabbits in arid environments. Granivorous birds, including scaled and other quail species, grouse and gray partridge, consume the fruits. Wild ungulates, rodent and lagomorphs readily consume all aboveground portions of the plant. Palatability is rated good for deer, elk, pronghorn and bighorn sheep.
Hydrological functions
Runoff is very low to very high. Permeability is slow to rapid. Rills are none. Water flow patterns are often numerous on lake plains and alluvial flats. Sparse shrub canopy and associated litter provide some protection from raindrop impact.
Other products
Indian ricegrass was traditionally eaten by some Native American peoples. The Paiutes used seed as a reserve food source.
Seeds of cattle saltbush and fourwing saltbush were reportedly ground into flour. Other uses for fourwing saltbush may have been the use of the ground meal as an emetic, use of ground flowers or roots moistened with saliva in treating ant bites, and addition of ashes to water for dyeing meal greenish-blue.
Other information
Indian ricegrass is well-suited for surface erosion control and desert revegetation although it is not highly effective in controlling sand movement.
Cattle saltbush is a recommended revegetation species. It has been planted in projects with varied goals, including soil stabilization and improvement or creation of habitat and forage for wildlife and those with constraints, such as the need for quick growth or revegetation sites with high salinity.
Supporting information
Type locality
| Location 1: Clark County, NV | |
|---|---|
| Township/Range/Section | T23 S R64 E S31 |
| General legal description | About ½ mile east of US Highway 95, Eldorado Valley area, Clark County, Nevada. |
Other references
Fire Effects Information System (Online; http://www.fs.fed.us/database/feis/plants/).
Kay, B.L., C.R. Brown and W.L. Graves. 1977. Desert Saltbush. Mojave Revegetation Notes. UC Davis. No. 18.
Puigdefabregas, J. 2005. The role of vegetation patterns in structuring runoff and sediment fluxes in drylands. Earth Surface Processes and Landforms. 30:133-147.
USDA-NRCS Plants Database (Online; http://www.plants.usda.gov).
Contributors
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 | 10/19/2011 |
| Approved by | Sarah Quistberg |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
Number and extent of rills:
None -
Presence of water flow patterns:
Waterflow patterns are rare to common depending on site location relative to major inflow areas from higher landscape positions. -
Number and height of erosional pedestals or terracettes:
Pedestals are rare with occurrence typically limited to areas within waterflow patterns. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare Ground up to 85% -
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. Persistent litter (large woody material) will remain in place except large rainfall events. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil stability values should be 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):
Structure of soil surface is medium platy or massive. Soil surface colors are pale brown and soils are typified by an ochric epipedon. Organic matter of the surface 2 to 3 inches is less than 1 percent. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Sparse shrub canopy and associated litter break provide some protection from 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. Massive sub-soil horizons, argillic or natric horizons should not be interpreted as compaction. -
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:
Tall shrubs (cattle saltbush)Sub-dominant:
associated low-statured, shrubs (white bursage, shadscale, etc.) > deep-rooted, cool season, perennial bunchgrasses >annual forbs> perennial forbs = shallow-rooted, warm-season, perennial 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 30% of total woody canopy; mature bunchgrasses commonly (<20%) have dead centers. -
Average percent litter cover (%) and depth ( in):
Between plant interspaces and under canopy 10-15% and depth <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 ± 400lbs/ac; Favorable years 500 lbs/ac and unfavorable years 250 lbs/ac -
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
Potential invaders include red brome, Mediterranean grass, redstem filaree, Russian thistle and annual mustards. -
Perennial plant reproductive capability:
All functional groups should reproduce in average and above average growing season years. Little growth or reproduction occurs in drought years.
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