Natural Resources
Conservation Service
Ecological site R030XB136NV
SHALLOW LIMESTONE 7-9 P.Z.
Last updated: 2/26/2025
Accessed: 05/11/2025
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 hills and lower elevation mountain sideslopes having a northerly exposure. Slopes range from 30 to 75 percent. Elevations are 3100 to about 5600 feet.The soils associated with this site are very shallow over limestone (sedimentary) bedrock.
Please refer to group concept R030XB135NV to view the provisional STM.
Similar sites
| R030XB108NV |
GRAVELLY INSET FAN 7-9 P.Z. More productive site; occurs on inset fans |
|---|---|
| R030XB057NV |
SHALLOW GRANITIC LOAM 5-7 P.Z. granitic parent materials soils |
| R030XB014NV |
SHALLOW GRAVELLY LOAM 7-9 P.Z. BOER4 major grass |
| R030XB136NV |
SHALLOW LIMESTONE 7-9 P.Z. Less productive site |
| R030XB015NV |
SHALLOW GRAVELLY SLOPE 7-9 P.Z. BOER4 major grass |
| R030XB107NV |
COARSE GRAVELLY LOAM 5-7 P.Z. PLRI3 codominant plant; more productive site |
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
(1) Coleogyne ramosissima |
| Herbaceous |
(1) Achnatherum speciosum |
Physiographic features
This site occurs on hills and lower elevation mountain sideslopes having a northerly exposure. Slopes range from 30 to 75 percent. Elevations are 3100 to about 5600 feet.
Table 2. Representative physiographic features
| Landforms |
(1)
Hill
(2) Mountain slope |
|---|---|
| Elevation | 3,100 – 5,600 ft |
| Slope | 30 – 75% |
| Aspect | N |
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. Average annual precipitation is (6)7 to 9 inches. Mean annual air temperature is 54 to 65 degrees F. The average growing season is about 150 to 180 days.
Table 3. Representative climatic features
| Frost-free period (average) | 180 days |
|---|---|
| Freeze-free period (average) | |
| Precipitation total (average) | 9 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 shallow over limestone (sedimentary) bedrock. Available water capacity is very low, runoff is very high, and the soils are well drained. A surface cover of more than 60 percent rock fragments (gravels, cobbles and stones) provides a stabilizing effect on surface erosion conditions. The soils have an aridic moisture regime bordering on ustic. Soil series associated with this site includes Boxspring.
Table 4. Representative soil features
| Parent material |
(1)
Colluvium
–
limestone
|
|---|---|
| Surface texture |
(1) Extremely gravelly loam |
| Family particle size |
(1) Loamy |
| Drainage class | Well drained |
| Permeability class | Moderate |
| Soil depth | 14 – 20 in |
| Surface fragment cover <=3" | 45 – 50% |
| Surface fragment cover >3" | 10 – 15% |
| Available water capacity (0-40in) |
0.8 – 0.9 in |
| Calcium carbonate equivalent (0-40in) |
30 – 40% |
| Electrical conductivity (0-40in) |
4 mmhos/cm |
| Sodium adsorption ratio (0-40in) |
5 |
| Soil reaction (1:1 water) (0-40in) |
7.9 – 9 |
| Subsurface fragment volume <=3" (Depth not specified) |
59 – 60% |
| Subsurface fragment volume >3" (Depth not specified) |
9 – 15% |
Ecological dynamics
Please refer to group concept R030XB135NV to view the provisional STM.
Following wildfire, fire tolerant/crown-sprouting shrubs (snakeweed, ephedra, etc.), threeawn, desert Indianwheat, and other annual forbs and grasses significantly increase and may dominate the site. Red brome readily invades this site. Turbinella oak, singleleaf pinyon, cliffrose, skunkbush sumac, and Utah agave occur at the upper elevations within the range of this plant community.
Fire Ecology:
Historical fire return intervals appear to have been on the order of centuries, allowing late seral blackbrush stands to reestablish. Low amounts of fine fuels in interspaces probably limited fire spread to only extreme fire conditions, during which high winds, low relative humidity, and low fuel moisture led to high intensity stand-replacing crown fires. Blackbrush stands are subject to fire, and fire will start and spread easily due to the dense, close spacing nature and resinous foliage of blackbrush. Blackbrush is slow to reestablish. Following fire, Virgin River encelia depends on off-site seed rather than on-site sprouts for regeneration. Nevada ephedra is top-killed by fire. Underground regenerative structures commonly survive when aboveground vegetation is consumed by fire. Nevada ephedra generally sprouts after fire damages aboveground vegetation and may increase in plant cover. Desert needlegrass has persistent dead leaf bases, which make it susceptible to burning. Fire removes the accumulation; a rapid, cool fire will not burn deep into the root crown and surviving tufts will resprout. A moderately hot fire will kill the aboveground portions of slim tridens, but survival of the rhizomes is usually good. Extremely hot fires will cause much more damage, especially among thin grasses not well protected by the buildup of vegetative material.
State and transition model
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Ecosystem states
State 1 submodel, plant communities
State 1
Reference State
Community 1.1
Reference Plant Community
The reference plant community is dominated by blackbrush. Desert needlegrass, Utah mortonia, and shrubby tequilia are other important species associated with this site. Potential vegetative composition is about 10% annual and perennial grasses, 5% annual and perennial forbs and 85% shrubs. Approximate ground cover (basal and crown) is 10 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) |
|---|---|---|---|
| Shrub/Vine | 170 | 298 | 383 |
| Grass/Grasslike | 20 | 35 | 45 |
| Forb | 10 | 17 | 22 |
| Total | 200 | 350 | 450 |
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 | 9–106 | ||||
| desert needlegrass | ACSP12 | Achnatherum speciosum | 7–53 | – | ||
| slim tridens | TRMU | Tridens muticus | 1–35 | – | ||
| threeawn | ARIST | Aristida | 1–18 | – | ||
| 2 | Secondary Perennial Grasses | 1–18 | ||||
| Indian ricegrass | ACHY | Achnatherum hymenoides | 2–7 | – | ||
| bush muhly | MUPO2 | Muhlenbergia porteri | 2–7 | – | ||
| big galleta | PLRI3 | Pleuraphis rigida | 2–7 | – | ||
| 3 | Annual Grasses | 1–18 | ||||
|
Forb
|
||||||
| 4 | Perennial forbs | 1–28 | ||||
| beardtongue | PENST | Penstemon | 2–7 | – | ||
| desert globemallow | SPAM2 | Sphaeralcea ambigua | 2–7 | – | ||
| 5 | Annual forbs | 1–28 | ||||
|
Shrub/Vine
|
||||||
| 6 | Primary shrubs | 233–410 | ||||
| blackbrush | CORA | Coleogyne ramosissima | 210–265 | – | ||
| Utah mortonia | MOUT | Mortonia utahensis | 7–53 | – | ||
| woody crinklemat | TICA3 | Tiquilia canescens | 7–28 | – | ||
| Virgin River brittlebush | ENVI | Encelia virginensis | 7–28 | – | ||
| Nevada jointfir | EPNE | Ephedra nevadensis | 1–18 | – | ||
| Utah agave | AGUT | Agave utahensis | 1–18 | – | ||
| 7 | Secondary shrubs | 18–53 | ||||
| catclaw acacia | ACGR | Acacia greggii | 4–11 | – | ||
| Utah butterflybush | BUUT | Buddleja utahensis | 4–11 | – | ||
| hedgehog cactus | ECHIN3 | Echinocereus | 4–11 | – | ||
| California barrel cactus | FECY | Ferocactus cylindraceus | 4–11 | – | ||
| creosote bush | LATR2 | Larrea tridentata | 4–11 | – | ||
| pricklypear | OPUNT | Opuntia | 4–11 | – | ||
| singleleaf pinyon | PIMO | Pinus monophylla | 4–11 | – | ||
| Stansbury cliffrose | PUST | Purshia stansburiana | 4–11 | – | ||
| Sonoran scrub oak | QUTU2 | Quercus turbinella | 4–11 | – | ||
| wirelettuce | STEPH | Stephanomeria | 4–11 | – | ||
| Joshua tree | YUBR | Yucca brevifolia | 4–11 | – | ||
| Mojave yucca | YUSC2 | Yucca schidigera | 4–11 | – | ||
Interpretations
Animal community
Livestock Interpretations:
This site has limited value for livestock grazing, due to the low forage production and steep slopes. Desert needlegrass produces considerable basal foliage and is good forage while young. Young desert needlegrass is palatable to all classes of livestock. Mature herbage is moderately grazed by horses and cattle but rarely grazed by sheep. Slim tridens is palatable and moderately nutritious. It is eaten by all classes of livestock. Blackbrush areas are economically important for winter grazing by domestic livestock, especially sheep. But it does provide poor forage during the spring, summer, and fall for domestic cattle, horses, and domestic sheep. Encelia has no forage value for domestic livestock. Nevada ephedra is important winter range browse for domestic cattle, sheep and goats. Nevada ephedra is usually grazed heavily and seems to be perfectly safe for grazing livestock since it induces neither toxicity in ewes or cows, nor congenital deformities in lambs.
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:
Blackbrush areas are economically important for winter grazing primarily for several wildlife species. Mule deer and bighorn sheep generally use the blackbrush vegetation type in winter. Virgin River encelia is important to the desert tortoise as a source of succulent forage in periods of low moisture. Encelia is a browse species of desert mule deer and desert bighorn sheep. Mule deer, bighorn sheep, and pronghorn browse Nevada ephedra, especially in spring and late summer when new growth is available. Mountain quail eat ephedra seeds. Desert bighorn sheep and feral horses and burros will graze desert needlegrass. Slim tridens seeds are a source of food for rodents and birds.
Hydrological functions
Runoff is very high. Permeability is moderate. Hydrologic soil grpup is D.
Other products
Some Native American tribes steeped the twigs of Nevada ephedra and drank the tea as a general beverage.
Other information
Desert needlegrass may be used for groundcover in areas of light disturbance, but it is susceptible to excessive trampling.
Supporting information
Type locality
| Location 1: Clark County, NV | |
|---|---|
| UTM zone | N |
| UTM northing | 4016910 |
| UTM easting | 761421 |
| General legal description | Azure Ridge area, about 5 air miles east of Gold Butte, Clark County, Nevada. |
Other references
Fire Effects Information System (Online; http://www.fs.fed.us/database/feis/plants/).
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) | |
|---|---|
| Contact for lead author | |
| Date | 02/27/2025 |
| 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:
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