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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.
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Figure 1. Mapped extent
Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.
MLRA notes
Major Land Resource Area (MLRA): 040X–Sonoran Basin and Range
AZ 40.3 – Colorado Sonoran Desert
Elevations range from 300 to 1200 feet and precipitation averages 3 to 7 inches per year. Vegetation includes creosotebush, white bursage, brittlebush, Mormon tea, teddybear cholla, elephant tree, smoke tree, ocotillo, and big galleta. The soil temperature regime is hyperthermic and the soil moisture regime is typic aridic. This unit occurs within the Basin and Range Physiographic Province and is characterized by numerous mountain ranges that rise abruptly from broad, plain-like valleys and basins. Igneous and metamorphic rock classes dominate the mountain ranges and sediments filling the basins represent combinations of fluvial, lacustrine, colluvial and alluvial deposits.Table 1. Dominant plant species
Tree (1) Parkinsonia microphylla
Shrub (1) Ambrosia dumosa
(2) Encelia farinosaHerbaceous (1) Pleuraphis rigida
(2) Tridens muticusPhysiographic features
This site occurs as gently sloping and rolling hills to very steep hill slopes. Inclusions of schist or other rock outcrop can make up 0-5% of the area.
Table 2. Representative physiographic features
Landforms (1) Hill
Elevation 75 – 1000 ft Slope 1 – 70 % Climatic features
Precipitation in this common resource area ranges from 3-7 inches yearly. Despite historical averages in rainfall amounts, as one moves from east to west in this resource area rains become more unpredictable and variable with Coefficients of Variation of annual rainfall equal to 44% at Gila Bend and 65% at Mohawk. Winter-Summer rainfall ratios are 40-60%. Summer rains fall July-September, originate in the Gulf of Mexico and are convective, usually brief intense thunderstorms. Summer thunderstorms usually form over the mountains in the afternoon and spread to the valleys and plains in the evening. The intensity of this precipitation is moderate to heavy, but rarely lasts more than half an hour. Many times these storms produce little more than gusty winds and light showers. Cool season moisture tends to be frontal, originate in the Pacific and Gulf of California and falls in widespread storms with long duration and low intensity. Snow is very rare and falls normally only in the higher mountains.
Mean temperatures for the hottest month (Jul) is 93 F; the coldest month (Jan) is 53 F. Extreme temperatures of 125 F and 10 F have been recorded. Long periods with little or no effective moisture occur frequently.
The winter-spring precipitation is the most dependable on the site. Perennial grasses, though classed as warm season growers, grow actively year-round when moisture is available. Shrubs and trees generally respond to seasonal moisture. The two rainy periods bring about their respective production of either winter or summer annual grasses and forbs.Table 3 Representative climatic features
Frost-free period (average) 360 days Freeze-free period (average) 0 days Precipitation total (average) 10 in BarLineFigure 2. Monthly precipitation range
BarLineFigure 3. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
Soils are very shallow to moderately deep. They are gravelly to very gravelly loams, calcareous to the surface, and underlain by schist and metomorphic granitic type rock. The surface is gravel covered. Some soils have lime pans on top of the rock. Plant-soil moisture relationships are poor.
Soils mapped on this site include: in SSA-627 Southern Mohave county MU Gunsight-57 and SSA-656 Colorado River Indian Reservation MU Gunsight-16 & 17.Table 4. Representative soil features
Surface texture (1) Very gravelly loam
(2) Extremely gravelly loam
Family particle size (1) Loamy
Drainage class Somewhat excessively drained to excessively drained Permeability class Moderate to moderately rapid Soil depth 10 – 40 in Surface fragment cover <=3" 35 – 80 % Calcium carbonate equivalent
(0-40in)0 – 15 % Electrical conductivity
(0-40in)0 – 15 mmhos/cm Soil reaction (1:1 water)
(0-40in)7.8 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)35 – 80 % Ecological dynamics
The plant communities found on an ecological site are naturally variable. Composition and production will vary with yearly conditions, location, aspect, and the natural variability of the soils. The Historical Climax Plant Community represents the natural potential plant communities found on relict or relatively undisturbed sites. Other plant communities described here represent plant communities that are known to occur when the site is disturbed by factors such as fire, grazing, or drought.
Production data provided in this site description is standardized to air dry weight at the end of the summer growing season. The plant communities described in this site description are based on near normal rainfall years.
NRCS uses a Similarity Index to compare existing plant communities to the plant communities described here. Similarity index is determined by comparing the production and composition of a plant community to the production and composition of a plant community described in this site description. To determine Similarity index, compare the production (air dry weight) of each species to that shown in the plant community description. For each species, count no more than the maximum amount shown for the species, and for each group, count no more than the maximum amount shown for each group. Divide the resulting total by the total normal year production shown in the plant community description. If the rainfall has been significantly above or below normal, use the total production shown for above or below normal years. If field data is not collected at the end of the summer growing season, then the field data must be corrected to the end of the year production before comparing it to the site description. The growth curve can be used as a guide for estimating production at the end of the summer growing season.
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 1
Historic Climax Plant CommunityCommunity 1.1
Historic Climax Plant CommunityThe native plant community on this site is a mixture of desert trees, shrubs and cacti. The understory is a scattering of perennial and annual grasses and forbs.
As palatable species decline from lack of management, less palatable species like bristlebush and cholla increase to dominate the site.Figure 4. 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 150 175 200 Tree 150 175 200 Forb 25 38 50 Grass/Grasslike 25 38 50 Total 350 426 500 Figure 5. Plant community growth curve (percent production by month). AZ4041 , 40.3 3-7" p.z. all sites. Most growth occurs in the winter to early spring, plants are dormant May through October..
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec J F M A M J J A S O N D 5 20 40 25 0 0 0 0 0 0 5 5 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike0 Dominant Grass 8–13 big galleta PLRI3 Pleuraphis rigida 8–13 – 1 Other Grasses 5–13 slim tridens TRMU Tridens muticus 3–8 – bush muhly MUPO2 Muhlenbergia porteri 2–5 – threeawn ARIST Aristida 1–3 – 2 Annual Grasses 13–25 sixweeks threeawn ARAD Aristida adscensionis 2–4 – needle grama BOAR Bouteloua aristidoides 2–4 – sixweeks grama BOBA2 Bouteloua barbata 2–4 – nineawn pappusgrass ENDE Enneapogon desvauxii 2–4 – littleseed muhly MUMI Muhlenbergia microsperma 2–4 – Bigelow's bluegrass POBI Poa bigelovii 2–4 – Texas fluffgrass TRTE2 Tridens texanus 2–4 – sixweeks fescue VUOC Vulpia octoflora 2–4 – Forb3 8–25 trailing windmills ALIN Allionia incarnata 2–4 – cryptantha CRYPT Cryptantha 2–4 – desert trumpet ERIN4 Eriogonum inflatum 2–4 – lacy tansyaster MAPIP4 Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida 2–4 – desert Indianwheat PLOV Plantago ovata 2–4 – Coues' cassia SECO10 Senna covesii 2–4 – desert globemallow SPAM2 Sphaeralcea ambigua 2–4 – 4 8–25 New Mexico silverbush ARNE2 Argythamnia neomexicana 2–4 – milkvetch ASTRA Astragalus 2–4 – desert marigold BAMU Baileya multiradiata 2–4 – spiderling BOERH2 Boerhavia 2–4 – hoary bowlesia BOIN3 Bowlesia incana 2–4 – California suncup CACA32 Camissonia californica 2–4 – exserted Indian paintbrush CAEXE Castilleja exserta ssp. exserta 2–4 – brittle spineflower CHBR Chorizanthe brevicornu 2–4 – devil's spineflower CHRI Chorizanthe rigida 2–4 – hairy prairie clover DAMO Dalea mollis 2–4 – larkspur DELPH Delphinium 2–4 – western tansymustard DEPI Descurainia pinnata 2–4 – bluedicks DICA14 Dichelostemma capitatum 2–4 – flatcrown buckwheat ERDE6 Eriogonum deflexum 2–4 – woolly sunflower ERIOP2 Eriophyllum 2–4 – California poppy ESCAM Eschscholzia californica ssp. mexicana 2–4 – spurge EUPHO Euphorbia 2–4 – Gordon's bladderpod LEGO Lesquerella gordonii 2–4 – pepperweed LEPID Lepidium 2–4 – foothill deervetch LOHU2 Lotus humistratus 2–4 – strigose bird's-foot trefoil LOSTT Lotus strigosus var. tomentellus 2–4 – Coulter's lupine LUSP2 Lupinus sparsiflorus 2–4 – Parry's false prairie-clover MAPA7 Marina parryi 2–4 – blazingstar MENTZ Mentzelia 2–4 – wishbone-bush MILAV Mirabilis laevis var. villosa 2–4 – glandular threadplant NEGL Nemacladus glanduliferus 2–4 – evening primrose OENOT Oenothera 2–4 – combseed PECTO Pectocarya 2–4 – Emory's rockdaisy PEEM Perityle emoryi 2–4 – phacelia PHACE Phacelia 2–4 – sleepy silene SIAN2 Silene antirrhina 2–4 – Coulter's globemallow SPCO2 Sphaeralcea coulteri 2–4 – woollyhead neststraw STMI2 Stylocline micropoides 2–4 – brownplume wirelettuce STPA4 Stephanomeria pauciflora 2–4 – trailing windmills ALIN Allionia incarnata 2–4 – cryptantha CRYPT Cryptantha 2–4 – desert trumpet ERIN4 Eriogonum inflatum 2–4 – lacy tansyaster MAPIP4 Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida 2–4 – desert Indianwheat PLOV Plantago ovata 2–4 – Coues' cassia SECO10 Senna covesii 2–4 – desert globemallow SPAM2 Sphaeralcea ambigua 2–4 – Shrub/Vine5 Dominant Shrubs 55–138 burrobush AMDU2 Ambrosia dumosa 38–50 – narrowleaf silverbush ARLA12 Argythamnia lanceolata 3–13 – brittlebush ENFA Encelia farinosa 0–13 – white ratany KRGR Krameria grayi 0–13 – creosote bush LATRT Larrea tridentata var. tridentata 0–13 – desert ironwood OLTE Olneya tesota 3–8 – 6 Misc Shrubs 13–25 catclaw acacia ACGR Acacia greggii 9–18 – angel's trumpets ACLO2 Acleisanthes longiflora 9–18 – triangle bur ragweed AMDE4 Ambrosia deltoidea 9–18 – Coulter's brickellbush BRCO Brickellia coulteri 9–18 – button brittlebush ENFR Encelia frutescens 9–18 – starry bedstraw GASTE2 Galium stellatum ssp. eremicum 9–18 – pink velvetmallow HOAL Horsfordia alata 9–18 – Newberry's velvetmallow HONE Horsfordia newberryi 9–18 – American threefold TRCA8 Trixis californica 9–18 – Berlandier's wolfberry LYBE Lycium berlandieri 9–18 – desert-thorn LYCIU Lycium 9–18 – Fremont's desert-thorn LYFR Lycium fremontii 9–18 – slender poreleaf POGR5 Porophyllum gracile 9–18 – whitestem paperflower PSCO2 Psilostrophe cooperi 9–18 – Mexican bladdersage SAME Salazaria mexicana 9–18 – Hall's shrubby-spurge TEHA Tetracoccus hallii 9–18 – woody crinklemat TICAC Tiquilia canescens var. canescens 1–5 – southern goldenbush ISPL Isocoma pluriflora 1–5 – 7 Other Shrubs 0–25 San Felipe dogweed ADPO Adenophyllum porophylloides 0–18 – Nevada jointfir EPNE Ephedra nevadensis 0–18 – California fagonbush FALA Fagonia laevis 0–18 – slender janusia JAGR Janusia gracilis 0–18 – littleleaf ratany KRER Krameria erecta 0–18 – toothleaf goldeneye VIDE3 Viguiera dentata 0–5 – 8 Succulents 0–13 saguaro CAGI10 Carnegiea gigantea 0–9 – buckhorn cholla CYACA2 Cylindropuntia acanthocarpa var. acanthocarpa 0–9 – teddybear cholla CYBI9 Cylindropuntia bigelovii 0–9 – Wiggins' cholla CYEC3 Cylindropuntia echinocarpa 0–9 – Christmas cactus CYLE8 Cylindropuntia leptocaulis 0–9 – Engelmann's hedgehog cactus ECEN Echinocereus engelmannii 0–9 – Johnson's fishhook cactus ECJO3 Echinomastus johnsonii 0–9 – candy barrelcactus FEWI Ferocactus wislizeni 0–9 – ocotillo FOSP2 Fouquieria splendens 0–9 – Graham's nipple cactus MAGR9 Mammillaria grahamii 0–9 – common fishhook cactus MATE4 Mammillaria tetrancistra 0–9 – desert ironwood OLTE Olneya tesota 2–9 – beavertail pricklypear OPBA2 Opuntia basilaris 0–9 – Tree9 Tree 8–25 yellow paloverde PAMI5 Parkinsonia microphylla 8–25 – brittlebush ENFA Encelia farinosa 0–9 – creosote bush LATR2 Larrea tridentata 0–9 – Interpretations
Animal community
These hills are easily traversed by all classes of livestock. Water developments may be needed to permit use of the areas and to control grazing.
A lack of natural water and cover limit the vlaue of this site for wildlife habitat. The area is mainly a forage site for species living in the canyon bottoms associated with it.Recreational uses
This site is located on rolling hills to steep slopes. The rugged terrain, along with the mixture of grasses, trees and shrubs, enhances the aesthetics of the site. Very few days in the fall, winter or spring are too uncomfortable to enjoy outdoor activities. Jun, Jul and Aug afternoon heat restricts activity. Activities suited to the site include horseback riding, wildlife observation, hunting, hiking, photography, camping and picnicking.
Supporting information
Type locality
Location 1: Yuma County, AZ Township/Range/Section T9N R15W S2 General legal description Muse Ranch, E. end Buckskin Mountains Location 2: Maricopa County, AZ Township/Range/Section T2S R9W S20 General legal description Gable Ranch, E end of Gila Bend Mountains Contributors
Larry D. Ellicott
Steve BarkerRangeland 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 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
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Presence of water flow patterns:
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Number and height of erosional pedestals or terracettes:
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Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
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Number of gullies and erosion associated with gullies:
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Extent of wind scoured, blowouts and/or depositional areas:
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Amount of litter movement (describe size and distance expected to travel):
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Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
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Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
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Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
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Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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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:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
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Average percent litter cover (%) and depth ( in):
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Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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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:
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Perennial plant reproductive capability:
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