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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) Olneya tesota
(2) Larrea tridentata var. tridentataHerbaceous (1) Muhlenbergia porteri
(2) Tridens muticusPhysiographic features
This range site occurs on steep to very steep granite, gneiss and schist hills and mountains. It benefits from runoff of the rock outcrop that occurs as the ridges and crests of the mountains. This site suffers excessively from runoff.
Table 2. Representative physiographic features
Landforms (1) Hill
(2) Mountain
Elevation 400 – 2000 ft Slope 15 – 75 % 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 temperature 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 of 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 shallow to moderately deep over bedrock. Parent material is slope alluvium and residuum. Surface soils are 3-6 inches thick, with a mixture of extremely gravelly loam. Underlying layers have moderate permeability that can absorb and hold all the moisture the climate provides. Soluble salt accumulations are low; pH is 7.9-8.4. With good vegetation cover, infiltration rates are moderate. Stability against erosion processes is moderate. Plant-soil moisture relationships are fair. Coarse fragments occur throughout the soil and are generally more than 35% of the total soil volume.
Soils mapped on this site include: in SSA-649 Yuma-Wellton area MU Laposa-20; SSA-653 Gila Bend-Ajo area MU's Quilotosa StxSL-62 & Vaiva StxSL-62 and SSA-656 Colorado River Indian Reservation MU Laposa-23.Table 4. Representative soil features
Parent material (1) Slope alluvium – granite
(2) Residuum – gneiss
Surface texture (1) Extremely gravelly loam
(2) Very gravelly fine sandy loam
(3) Cobbly sandy loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderately rapid to rapid Soil depth 4 – 40 in Surface fragment cover <=3" 15 – 45 % Surface fragment cover >3" 3 – 10 % Available water capacity
(0-40in)0.32 – 4.4 in Calcium carbonate equivalent
(0-40in)1 – 10 % Electrical conductivity
(0-40in)0 – 1 mmhos/cm Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)7.9 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)15 – 45 % Subsurface fragment volume >3"
(Depth not specified)3 – 10 % 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 CommunityThis site is predominantly a shrub site with an understory of perennial and annual grasses and forbs. Palatable plant species have a wide diversity in both time of production and seasonal availability to grazing animals.
Forage species on this site grow actively in the spring when the most dependable moisture comes. Continued grazing use at this time of year leads to replacement of these plants with less palatable species such as brittlebush, triangle bursage and cacti.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 115 162 210 Grass/Grasslike 20 32 45 Forb 15 25 35 Tree 8 12 16 Total 158 231 306 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/Grasslike1 Misc. Grasses 20–40 littleseed muhly MUMI Muhlenbergia microsperma 3–10 – slim tridens TRMU Tridens muticus 3–7 – nineawn pappusgrass ENDE Enneapogon desvauxii 3–7 – cliff muhly MUPO Muhlenbergia polycaulis 3–5 – purple threeawn ARPU9 Aristida purpurea 3–5 – Parish's threeawn ARPUP5 Aristida purpurea var. parishii 3–5 – needle grama BOAR Bouteloua aristidoides 3–5 – 2 Annual Grasses 1–5 threeawn ARIST Aristida 1–5 – sixweeks grama BOBA2 Bouteloua barbata 1–5 – sixweeks fescue VUOC Vulpia octoflora 1–5 – Forb3 Misc. Forbs 11–23 pelotazo ABIN Abutilon incanum 1–2 – New Mexico silverbush ARNE2 Argythamnia neomexicana 1–2 – California fagonbush FALA Fagonia laevis 1–2 – Newberry's velvetmallow HONE Horsfordia newberryi 1–2 – shrubby deervetch LORI3 Lotus rigidus 1–2 – wishbone-bush MILAV Mirabilis laevis var. villosa 1–2 – slender poreleaf POGR5 Porophyllum gracile 1–2 – desert globemallow SPAM2 Sphaeralcea ambigua 1–2 – globemallow SPHAE Sphaeralcea 1–2 – brownplume wirelettuce STPA4 Stephanomeria pauciflora 1–2 – 4 Other Forbs 2–11 brownfoot ACWR5 Acourtia wrightii 0–1 – trailing windmills ALIN Allionia incarnata 0–1 – whitestem milkweed ASAL Asclepias albicans 0–1 – American wild carrot DAPU3 Daucus pusillus 0–1 – flatcrown buckwheat ERDE6 Eriogonum deflexum 0–1 – desert trumpet ERIN4 Eriogonum inflatum 0–1 – buckwheat ERIOG Eriogonum 0–1 – spurge EUPHO Euphorbia 0–1 – pepperweed LEPID Lepidium 0–1 – Parry's false prairie-clover MAPA7 Marina parryi 0–1 – desert Indianwheat PLOV Plantago ovata 0–1 – Coues' cassia SECO10 Senna covesii 0–1 – Coulter's globemallow SPCO2 Sphaeralcea coulteri 0–1 – Shrub/Vine5 Dominant Shrubs 45–90 burrobush AMDU2 Ambrosia dumosa 11–34 – desert ironwood OLTE Olneya tesota 23–34 – creosote bush LATRT Larrea tridentata var. tridentata 11–23 – 6 Misc. Shrubs 30–50 narrowleaf silverbush ARLA12 Argythamnia lanceolata 3–5 – brittlebush ENFA Encelia farinosa 3–5 – Nevada jointfir EPNE Ephedra nevadensis 3–5 – slender janusia JAGR Janusia gracilis 3–5 – littleleaf ratany KRER Krameria erecta 3–5 – white ratany KRGR Krameria grayi 3–5 – desert-thorn LYCIU Lycium 3–5 – American threefold TRCA8 Trixis californica 3–5 – toothleaf goldeneye VIDE3 Viguiera dentata 3–5 – 7 Other Shrubs 30–50 pelotazo ABIN Abutilon incanum 2–4 – Indian mallow ABUTI Abutilon 2–4 – catclaw acacia ACGR Acacia greggii 2–4 – San Felipe dogweed ADPO Adenophyllum porophylloides 2–4 – Wright's beebrush ALWR Aloysia wrightii 2–4 – sweetbush BEJU Bebbia juncea 2–4 – spearleaf brickellbush BRAT Brickellia atractyloides 2–4 – Coulter's brickellbush BRCO Brickellia coulteri 2–4 – elephant tree BUMI Bursera microphylla 2–4 – Eastern Mojave buckwheat ERFA2 Eriogonum fasciculatum 2–4 – California fagonbush FALA Fagonia laevis 2–4 – starry bedstraw GAST Galium stellatum 2–4 – desert lavender HYEM Hyptis emoryi 2–4 – lacy tansyaster MAPIP4 Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida 2–4 – Schott's pygmycedar PESC4 Peucephyllum schottii 2–4 – Mexican bladdersage SAME Salazaria mexicana 2–4 – woody crinklemat TICAC Tiquilia canescens var. canescens 2–4 – Palmer's crinklemat TIPA Tiquilia palmeri 2–4 – 8 Succulents 10–20 saguaro CAGI10 Carnegiea gigantea 2–3 – ocotillo FOSP2 Fouquieria splendens 2–3 – beavertail pricklypear OPBA2 Opuntia basilaris 2–3 – globe cactus MAMMI Mammillaria 1–2 – buckhorn cholla CYACA2 Cylindropuntia acanthocarpa var. acanthocarpa 1–2 – Arizona pencil cholla CYAR14 Cylindropuntia arbuscula 1–2 – teddybear cholla CYBI9 Cylindropuntia bigelovii 1–2 – Engelmann's hedgehog cactus ECEN Echinocereus engelmannii 1–2 – candy barrelcactus FEWI Ferocactus wislizeni 1–2 – Tree9 Tree 8–16 yellow paloverde PAMI5 Parkinsonia microphylla 8–16 – Interpretations
Animal community
Steep slopes limit use on this site, however, fencing to restrict use and water developments will improve livestock distribution. Though forage is available for yearlong use by cows and calves, stocker cattle will work the steep slopes better. This site responds fairly rapidly to a grazing system with alternating deferment in the various growing seasons.
Natural water is scarce on the site. Stockwater developments are very important to wildlife in these areas. Forage diversity is good and the many drainages and canyons offer ample cover for large desert mammals. Small resident numbers of these animals (such as mule deer and desert bighorn sheep) occur on the site where drinking water is accessible.Recreational uses
The site is located on steep, low hills and mountains. It has a rugged appearance. The wide variety of cacti and other desert shrubs provides good aesthetic appeal. In winters with above average precipitation, brittlebush and spring forbs flower and lend color to the site. Very few days in the fall, winter, or spring are too uncomfortable to enjoy outdoor activities. Afternoon heat restricts activity during Jun-Aug. Horseback riding, wildlife observation, hunting, hiking, picnicking, camping and photography are activities suited to the site.
Other information
Large and small mining in localized areas is among the other uses of the site.
T&E Species: The elephant tree (Bursera microphylla - rare) is locally abundant near telegraph pass, Interstate 8 in the Gila Mountains.Supporting information
Type locality
Location 1: Maricopa County, AZ General legal description Typical pedon of Vaiva GrXSL is in unsectionized area about 14,100 feet North and 15,400 feet west of SouthEast corner of T2S, R9W. Location 2: Maricopa County, AZ Township/Range/Section T4S R3W S25 General legal description Typical pedon of Quilotosa StXCoSL is about 1,000 feet east and 850 feet south of northwest corner of Section 25 Township 4 South, Range 3 West. Contributors
Larry D. Ellicott
Steve Barker
UnknownRangeland 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) Dave Womack, Dan Robinett, Emilio Carrillo Contact for lead author NRCS Tucson Area Office Date 03/02/2005 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
Naturally occurring rills are infrequent on this site and seem to follow fractures, faults and the bedding planes of parent materials. -
Presence of water flow patterns:
Common on this site in areas lacking surface covers of cobbles and rocks. They are uncommon and hort in areas with well developed surface covers of coarse fragments. -
Number and height of erosional pedestals or terracettes:
None -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
1-20% -
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):
Woody litter stays in place under shrubs; herbaceous litter moves primarily by wind but also in occasional high rainfall events in water flow paths. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Expect ratings of 1-3 on the site. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Weak platy to granular; color is 7.5-10YR5/4 dry, 7.5-10YR4/4 moist; thickness to 3 inches. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Canopy 5-10%; 65-75% shrubs, 15-25% subshrubs, 1-5% trees. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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):
Dominant:
shrubs > subshrubs > trees > succulents > forbs = perennial grasses (note: annual forbs and grasses may be greater than shrubs in El Nino years).Sub-dominant:
Other:
Additional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
15-20% canopy mortality of trees and shrubs. -
Average percent litter cover (%) and depth ( in):
-
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
158 lbs/ac unfavorable precipitation; 232 lbs/ac normal precipitation; 306 lbs/ac favorable precipitation. -
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:
Sahara mustard, schismus -
Perennial plant reproductive capability:
Not impaired for shrubs and trees.
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