Natural Resources
Conservation Service
Ecological site R030XB102NV
GRAVELLY LOAM 5-7 P.Z.
Last updated: 3/10/2025
Accessed: 03/15/2025
General information
Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
Ecological site concept
This site occurs on summits and sideslopes of erosional fan remnants and mountains. Slopes range from 2 to 30 percent, but slope gradients of 2 to 15 percent are most typical. Elevations are 1800 to 4000 feet.
These soils have formed in alluvium high in carbonates. Surface cover of rock fragments is typically greater than 60 percent with gravel-sized fragments comprising at least 80 percent of the total rock cover.
Associated sites
| R030XB075NV |
GRAVELLY FAN 5-7 P.Z. |
|---|
Similar sites
| R030XB075NV |
GRAVELLY FAN 5-7 P.Z. KRLA2 minor species, if present. |
|---|---|
| R030XB053NV |
SHALLOW HILL 5-7 P. Z. MUPO2 major grass. |
| R030XB044NV |
COBBLY CLAYPAN 5-7 P.Z. More productive site; KRLA2 minor species, if present. |
| R030XB080NV |
STONY LOAM 5-7 P.Z. More productive site; KRLA2 dominant shrub. |
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
(1) Ambrosia dumosa |
| Herbaceous |
(1) Pleuraphis rigida |
Physiographic features
This site occurs on summits and sideslopes of erosional fan remnants and mountains. Slopes range from 2 to 30 percent, but slope gradients of 2 to 15 percent are most typical. Elevations are 1800 to 4000 feet.
Table 2. Representative physiographic features
| Landforms |
(1)
Mountain
(2) Fan remnant |
|---|---|
| Flooding frequency | None |
| Ponding frequency | None |
| Elevation | 549 – 1,219 m |
| Slope | 2 – 30% |
| Water table depth | 0 cm |
| Aspect | Aspect is not a significant factor |
Climatic features
The climate on this site is arid, characterized by cool winters, and hot, dry summers. Average annual precipitation is 5 to 7 inches. Mean annual air temperature is 56 to 65 degrees F. The average growing season is about 190 to 240 days.
Table 3. Representative climatic features
| Frost-free period (average) | 240 days |
|---|---|
| Freeze-free period (average) | |
| Precipitation total (average) | 178 mm |
Figure 1. Monthly average minimum and maximum temperature
Influencing water features
There are no influencing water features associated with this site.
Soil features
The soils associated with this site are shallow to very deep. These soils have formed in alluvium high in carbonates. Surface cover of rock fragments is typically greater than 60 percent with gravel-sized fragments comprising at least 80 percent of the total rock cover. Runoff is low to very high. The soils series associated with this site include Ifteen, Wechech, and Weiser.
Table 4. Representative soil features
| Surface texture |
(1) Extremely gravelly fine sandy loam (2) Very gravelly sandy loam (3) Extremely gravelly sandy loam |
|---|---|
| Family particle size |
(1) Loamy |
| Drainage class | Well drained |
| Permeability class | Moderate to moderately rapid |
| Soil depth | 20 – 213 cm |
| Surface fragment cover <=3" | 45 – 70% |
| Surface fragment cover >3" | 1 – 3% |
| Available water capacity (0-101.6cm) |
2.29 – 13.97 cm |
| Calcium carbonate equivalent (0-101.6cm) |
10 – 60% |
| Electrical conductivity (0-101.6cm) |
0 – 4 mmhos/cm |
| Sodium adsorption ratio (0-101.6cm) |
0 – 5 |
| Soil reaction (1:1 water) (0-101.6cm) |
7.9 – 9 |
| Subsurface fragment volume <=3" (Depth not specified) |
7 – 69% |
| Subsurface fragment volume >3" (Depth not specified) |
5 – 14% |
Ecological dynamics
Please refer to group concept R030XB029NV to view the provisional STM.
As ecological condition deteriorates, creosotebush and white bursage increase as perennial grasses decline in the community. Snakeweed, burrobrush, and annual grasses and forbs greatly increase following major disturbance such as wildfire. Non-native annual forbs and grasses are invaders on this site.
Fire Ecology:
Fires in the desert are infrequent and of low severity because production of annual and perennial herbs seldom provides a fuel load capable of sustaining fire. Fire generally kills white bursage.
Winterfat is either killed or top-killed by fire, depending on fire severity. Severe fire can kill the perennating buds located several inches above the ground surface, thus killing the plant. In addition, severe fire usually destroys seed on the plant. Low-severity fire scorches or only partially consumes the above ground portions of winterfat and thus does not cause high mortality.
Damage to big galleta from fire varies. If big galleta is dry, damage may be severe. However, when plants are green, fire will tend to be less severe and damage may be minimal, with big galleta recovering quickly.
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
Ecosystem states
State 1 submodel, plant communities
State 1
Reference State
Community 1.1
Reference Plant Community
The reference plant community is dominated by white bursage, creosotebush, and winterfat. Spiny hopsage and spiny menodora occur sporadically throughout the range of this plant community. Potential vegetative composition is about 20% grasses, 5% annual and perennial forbs and 75% shrubs and trees. Approximate ground cover (basal and crown) is 5 to 10 percent.
Figure 2. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
| Plant type | Low (kg/hectare) |
Representative value (kg/hectare) |
High (kg/hectare) |
|---|---|---|---|
| Shrub/Vine | 168 | 295 | 420 |
| Grass/Grasslike | 45 | 78 | 112 |
| Forb | 11 | 19 | 28 |
| Total | 224 | 392 | 560 |
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. AMDU and KRLA2 would persist after this invasion by non-native annuals, but the other shrubs and desirable grasses would either be unsuccessful in competing with the non-natives or removed from the system. The threshold that is crossed, is the introduction of non-native annuals that cannot be removed from the system and will alter disturbance regimes significantly from their natural or historic range of disturbances.
Additional community tables
Table 6. Community 1.1 plant community composition
| Group | Common name | Symbol | Scientific name | Annual production (kg/hectare) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Grass/Grasslike
|
||||||
| 1 | Primary Perennial Grasses | 22–122 | ||||
| big galleta | PLRI3 | Pleuraphis rigida | 20–59 | – | ||
| Indian ricegrass | ACHY | Achnatherum hymenoides | 1–31 | – | ||
| desert needlegrass | ACSP12 | Achnatherum speciosum | 1–31 | – | ||
| 2 | Secondary Perennial Grasses | 1–20 | ||||
| threeawn | ARIST | Aristida | 2–7 | – | ||
| low woollygrass | DAPU7 | Dasyochloa pulchella | 2–7 | – | ||
| bush muhly | MUPO2 | Muhlenbergia porteri | 2–7 | – | ||
| 3 | Annual Grasses | 1–24 | ||||
|
Forb
|
||||||
| 4 | Annual Forbs | 1–39 | ||||
| threeawn | ARIST | Aristida | 2–8 | – | ||
| bush muhly | MUPO2 | Muhlenbergia porteri | 2–8 | – | ||
| desert globemallow | SPAM2 | Sphaeralcea ambigua | 2–7 | – | ||
| 5 | Perennial Forbs | 1–39 | ||||
|
Shrub/Vine
|
||||||
| 6 | Primary shrubs | 128–370 | ||||
| burrobush | AMDU2 | Ambrosia dumosa | 59–138 | – | ||
| winterfat | KRLA2 | Krascheninnikovia lanata | 20–59 | – | ||
| littleleaf ratany | KRER | Krameria erecta | 16–39 | – | ||
| spiny hopsage | GRSP | Grayia spinosa | 8–31 | – | ||
| creosote bush | LATR2 | Larrea tridentata | 8–31 | – | ||
| spiny menodora | MESP2 | Menodora spinescens | 1–31 | – | ||
| Nevada jointfir | EPNE | Ephedra nevadensis | 8–20 | – | ||
| Torrey's jointfir | EPTO | Ephedra torreyana | 8–20 | – | ||
| 7 | Secondary shrubs | 20–59 | ||||
| fourwing saltbush | ATCA2 | Atriplex canescens | 3–10 | – | ||
| Virgin River brittlebush | ENVI | Encelia virginensis | 3–10 | – | ||
| water jacket | LYAN | Lycium andersonii | 3–10 | – | ||
| pricklypear | OPUNT | Opuntia | 3–10 | – | ||
| Fremont's dalea | PSFR | Psorothamnus fremontii | 3–10 | – | ||
| Mojave woodyaster | XYTO2 | Xylorhiza tortifolia | 3–10 | – | ||
| Joshua tree | YUBR | Yucca brevifolia | 3–10 | – | ||
| Mojave yucca | YUSC2 | Yucca schidigera | 3–10 | – | ||
Interpretations
Animal community
Livestock Interpretations:
This site is suitable for spring grazing by sheep and also cattle where water is available. Grazing management should be keyed to big galleta and winterfat. Big galleta is considered a valuable forage plant for cattle and domestic sheep in the Mohave Desert. Big galleta has been referred to as highly palatable to cattle and horses during growth periods following rain. White bursage is an important browse species. Browsing pressure on white bursage is particularly heavy during years of low precipitation, when production of winter annuals is low. White bursage is of intermediate forage value. It is fair to good forage for horses and fair to poor for cattle and sheep.
Winterfat is an important forage plant for livestock in salt-desert shrub rangelands, especially during winter when forage is scarce.
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 highly valuable to browsing animals. Many desert rodents, including kangaroo rats, eat white bursage seeds.
Animals that browse winterfat include mule deer, desert bighorn sheep, and pronghorn. Winterfat seeds are eaten by rodents including the chisel-toothed kangaroo rat and Great Basin pocket mouse.
Big galleta is valuable forage for desert bighorn sheep.
Hydrological functions
Runoff is low to very high. Permeability is moderatel to moderately rapid.
Recreational uses
Aesthetic value is derived from the diverse floral and faunal composition and the colorful flowering of wild flowers and shrubs during the spring and early summer. This site offers rewarding opportunities to photographers and for nature study.
Other products
White bursage is a host for sandfood (Pholisma sonorae), a parasitic plant with a sweet, succulent, subterranean flowerstalk. Sandfood was a valuable food supply for Native Americans.
Other information
White bursage may be used to revegetate disturbed sites in southwestern deserts. White bursage may be planted from containerized plants with a high probability of success. Plantings should be made in late winter or early spring, although the time of planting is less important than the vigor of the seedlings. Rodent protectors should be used.
Winterfat is a useful shrub for reclamation and revegetation of disturbed sites in arid climates. Winterfat adapts well to most site conditions, and its extensive root system stabilizes soil. However, winterfat is intolerant of flooding, excess water, and acidic soils.
Big galleta's clumped growth form stabilizes blowing sand and stabilizes sand dunes.
Supporting information
Inventory data references
NV-ECS-1: 3 records
Type locality
| Location 1: Clark County, NV |
|---|
Other references
USDA-NRCS Plant Database (Online; http://plants.usda.gov/).
Fire Effects Information System (Online;http://www.fs.fed.us/database/feis/).
Contributors
GKB
Approval
Kendra Moseley, 3/10/2025
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) | |
|---|---|
| Contact for lead author | |
| Date | 03/15/2025 |
| Approved by | Sarah Quistberg |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
Number and extent of rills:
-
Presence of water flow patterns:
-
Number and height of erosional pedestals or terracettes:
-
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
-
Number of gullies and erosion associated with gullies:
-
Extent of wind scoured, blowouts and/or depositional areas:
-
Amount of litter movement (describe size and distance expected to travel):
-
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
-
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
-
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
-
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
-
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:
Sub-dominant:
Other:
Additional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
-
Average percent litter cover (%) and depth ( in):
-
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
-
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:
-
Perennial plant reproductive capability:
Print Options
Sections
Font
Other
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.