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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 40.2 – Middle Sonoran Desert
Elevations range from 1200 to 2000 feet and precipitation averages 7 to 10 inches per year. Vegetation includes saguaro, palo verde, creosotebush, triangle bursage, brittlebush, prickly pear, cholla, desert saltbush, wolfberry bush muhly, threeawns, 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) Encelia farinosa
(2) Ambrosia dumosaHerbaceous (1) Muhlenbergia porteri
(2) Pleuraphis rigidaPhysiographic features
This site occurs on hillslopes and ridgetops associated with basalt, diabase, and related bedrock. Ths soils are shallow loams. Large areas of talus or rock slides occur intermingled with soil areas and make up about 15 to 30 percent of the site. Rock outcrop makes up a small percentage of the area.
Table 2. Representative physiographic features
Landforms (1) Hill
(2) Mountain
(3) Ridge
Elevation 1100 – 2000 ft Slope 15 – 50 % Climatic features
Precipitation in the sub-resource area ranges from 7 to 10 inches. Elevations range from 900 to 2050 feet. Winter-summer rainfall ratios range from 40% to 60% in the southern part along the international boundary, to 60% to 40% in the central and northern parts of the sub-resource area. 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 38% at Florence and 46% at Aguila. Summer rains fall July- September, originate in the Gulf of Mexico, and are convective, usually brief, intense thunderstorms. Summer precipitation is extremely erratic and undependable in this area. Cool season moisture tends to be frontal, originates in the Pacific and Gulf of California, and falls in widespread storms with long duration and low intensity. This is the dependable moisture supply for vegetation in the area. Snow is very rare and usually melts on contact. May-June is the driest time of the year. Humidity is very low.
Winter temperatures are very mild with very few days recording freezing for short periods of time. Summertime temperatures are hot to very hot with many days in June-July exceeding 105 degrees F. Frost-free days range from 280 at stations in major river valleys with cold air drainage to 320 to 350 days at upland stations.
Both the spring and the summer growing seasons are equally important for perennial grass, forb and shrub growth. Cool and warm season annual forbs and grasses can be common in their respective seasons with above average rainfall. Perennial forage species can remain green throughout the year with available moisture.Table 3 Representative climatic features
Frost-free period (average) 350 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
These are shallow soils formed on basalt, diabase, and related igneous rock. They are calcareous, loamy textured, and have a well developed cover of stones and cobbles (malapais). Cobble and stone cover averages 80 to 90 percent. Bedrock is dark colored, very hard and unweathered. Soil moisture reltionships are fair to poor. Well developed cobble and stone cover protects the surface from erosion. The dark surface of stones warms the soil in the winter allowing the plants to grow in the coolest weather. Percent bare ground averages 15 percent.
Soils mapped on this site include: in
SSA-627 Southern Mohave County MU Cherioni-2;
SSA-645 Aguila-Carefree area MU Cherioni-18;
SSA-651 Central Maricopa County MU Cherioni-RS;
SSA-653 Gila Bend-Ajo area MU's Cipriano-9 & Hyder-9;
SSA-658 Gila River Indian Reservation MU Lomitas-25;
SSA-659 Western Pinal County MU Cherioni-7;
SSA-661 Eastern Pinal-Southern Gila Counties MU Cherioni-202;
SSA-703 Tohono O'odham area MU's Guvo-37 & Hyder all greater than 15% slopes-37.
Parent material kind may include slope alluvium.Table 4. Representative soil features
Parent material (1) Slope alluvium – diabase
Surface texture (1) Gravelly loam
(2) Very gravelly fine sandy loam
(3) Very cobbly sandy loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderately rapid Soil depth 4 – 20 in Surface fragment cover <=3" 15 – 45 % Surface fragment cover >3" 10 – 25 % Available water capacity
(0-40in)0.3 – 2.2 in Calcium carbonate equivalent
(0-40in)5 – 25 % Electrical conductivity
(0-40in)0 – 8 mmhos/cm Sodium adsorption ratio
(0-40in)0 – 5 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 – 15 % 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 the 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
Historical Climax Plant CommunityCommunity 1.1
Historical Climax Plant CommunityThe perennial plant community is a mixture of desert trees, shrubs and cacti. The aspect is shrubland. Crytogam cover is low on the bare ground portion. Lichens on stone exist in trace amounts even on northern exposures. Perennial plant basal cover is about 1% on the site. Plant populations of major species range from 300 to 600 plants per acre for the brittlebush, globemallow group, 25 to 100 for palo verde, 50 to 200 for creosotebush, 100 to 400 for cholla species, 1 to 25 for saguaro, and 1 to 50 for ocotillo. Desert globemallow tends to dominate on north aspects, and brittlebush on south aspects. Both species are very sensitive to drought on this site and it is not uncommon to have 50 to 75 percent mortlity on the site after a severe drought period. Teddybear cholla predominateds on southern exposures and buckhorn cholla on northern exposures.
Both the spring and the summer growing seasons are equally important for perennial grass, forb, and shrub growth. Cool and warm season annual forbs and grasses can be common in their respective seasons with available moisture.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 260 – 320 Forb 40 – 100 Grass/Grasslike 20 – 80 Tree 5 – 20 Total 325 – 520 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 5–20 bush muhly MUPO2 Muhlenbergia porteri 0–3 – big galleta PLRI3 Pleuraphis rigida 0–2 – slim tridens TRMU Tridens muticus 0–2 – southwestern bristlegrass SESC2 Setaria scheelei 0–1 – purple threeawn ARPU9 Aristida purpurea 0–1 – blue threeawn ARPUN Aristida purpurea var. nealleyi 0–1 – Parish's threeawn ARPUP5 Aristida purpurea var. parishii 0–1 – Wright's threeawn ARPUW Aristida purpurea var. wrightii 0–1 – spidergrass ARTE3 Aristida ternipes 0–1 – spidergrass ARTEG Aristida ternipes var. gentilis 0–1 – low woollygrass DAPU7 Dasyochloa pulchella 0–1 – Arizona cottontop DICA8 Digitaria californica 0–1 – nineawn pappusgrass ENDE Enneapogon desvauxii 0–1 – tanglehead HECO10 Heteropogon contortus 0–1 – 2 20–60 sixweeks threeawn ARAD Aristida adscensionis 0–10 – prairie threeawn AROL Aristida oligantha 0–10 – needle grama BOAR Bouteloua aristidoides 0–10 – sixweeks grama BOBA2 Bouteloua barbata 0–10 – sixweeks fescue VUOC Vulpia octoflora 0–10 – delicate muhly MUFR Muhlenbergia fragilis 0–5 – littleseed muhly MUMI Muhlenbergia microsperma 0–5 – Rothrock's grama BORO2 Bouteloua rothrockii 0–5 – Bigelow's bluegrass POBI Poa bigelovii 0–5 – Eastwood fescue VUMIC Vulpia microstachys var. ciliata 0–5 – Pacific fescue VUMIP Vulpia microstachys var. pauciflora 0–5 – Arizona brome BRAR4 Bromus arizonicus 0–1 – desert lovegrass ERPEM Eragrostis pectinacea var. miserrima 0–1 – tufted lovegrass ERPEP2 Eragrostis pectinacea var. pectinacea 0–1 – Mexican sprangletop LEFUU Leptochloa fusca ssp. uninervia 0–1 – mucronate sprangletop LEPA6 Leptochloa panicea 0–1 – witchgrass PACA6 Panicum capillare 0–1 – Hall's panicgrass PAHA Panicum hallii 0–1 – Forb3 20–40 desert tobacco NIOB Nicotiana obtusifolia 1000–5000 – slender janusia JAGR Janusia gracilis 2–10 – Parry's false prairie-clover MAPA7 Marina parryi 2–8 – California fagonbush FALA Fagonia laevis 2–8 – narrowleaf silverbush ARLA12 Argythamnia lanceolata 2–5 – whitemargin sandmat CHAL11 Chamaesyce albomarginata 0–3 – desert trumpet ERIN4 Eriogonum inflatum 0–3 – Graham's nipple cactus MAGR9 Mammillaria grahamii 0–2 – lacy tansyaster MAPIP4 Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida 0–2 – 4 20–60 California evening primrose OECA2 Oenothera californica 0–5 – combseed PECTO Pectocarya 0–5 – bristly fiddleneck AMTE3 Amsinckia tessellata 0–5 – western tansymustard DEPI Descurainia pinnata 0–5 – desert Indianwheat PLOV Plantago ovata 0–5 – slender poreleaf POGR5 Porophyllum gracile 0–3 – brownplume wirelettuce STPA4 Stephanomeria pauciflora 0–3 – glandular threadplant NEGL Nemacladus glanduliferus 0–3 – foothill deervetch LOHU2 Lotus humistratus 0–3 – pebble pincushion CHCA Chaenactis carphoclinia 0–2 – devil's spineflower CHRI Chorizanthe rigida 0–2 – Esteve's pincushion CHST Chaenactis stevioides 0–1 – New Mexico thistle CINE Cirsium neomexicanum 0–1 – cryptantha CRYPT Cryptantha 0–1 – hairy prairie clover DAMO Dalea mollis 0–1 – American wild carrot DAPU3 Daucus pusillus 0–1 – desert larkspur DEPA Delphinium parishii 0–1 – lipfern CHEIL Cheilanthes 0–1 – goosefoot CHENO Chenopodium 0–1 – hyssopleaf sandmat CHHY3 Chamaesyce hyssopifolia 0–1 – coastal bird's-foot trefoil LOSA Lotus salsuginosus 0–1 – strigose bird's-foot trefoil LOSTT Lotus strigosus var. tomentellus 0–1 – Coulter's lupine LUSP2 Lupinus sparsiflorus 0–1 – blazingstar MENTZ Mentzelia 0–1 – rough menodora MESC Menodora scabra 0–1 – green carpetweed MOVE Mollugo verticillata 0–1 – bristly nama NAHI Nama hispidum 0–1 – cloak fern NOTHO Notholaena 0–1 – Florida pellitory PAFL3 Parietaria floridana 0–1 – Emory's rockdaisy PEEM Perityle emoryi 0–1 – cliffbrake PELLA Pellaea 0–1 – manybristle chinchweed PEPA2 Pectis papposa 0–1 – phacelia PHACE Phacelia 0–1 – tall mountain larkspur DESC Delphinium scaposum 0–1 – bluedicks DICA14 Dichelostemma capitatum 0–1 – flatcrown buckwheat ERDE6 Eriogonum deflexum 0–1 – miniature woollystar ERDI2 Eriastrum diffusum 0–1 – spreading fleabane ERDI4 Erigeron divergens 0–1 – buckwheat ERIOG Eriogonum 0–1 – woolly sunflower ERIOP2 Eriophyllum 0–1 – wand fleabane EROX2 Erigeron oxyphyllus 0–1 – Texas stork's bill ERTE13 Erodium texanum 0–1 – California poppy ESCAM Eschscholzia californica ssp. mexicana 0–1 – beetle spurge EUER2 Euphorbia eriantha 0–1 – starry bedstraw GASTE2 Galium stellatum ssp. eremicum 0–1 – desert rosemallow HICO Hibiscus coulteri 0–1 – paleface HIDE Hibiscus denudatus 0–1 – Newberry's velvetmallow HONE Horsfordia newberryi 0–1 – Gordon's bladderpod LEGO Lesquerella gordonii 0–1 – shaggyfruit pepperweed LELA Lepidium lasiocarpum 0–1 – flax LINUM Linum 0–1 – milkvetch ASTRA Astragalus 0–1 – Coulter's spiderling BOCO2 Boerhavia coulteri 0–1 – hoary bowlesia BOIN3 Bowlesia incana 0–1 – Tucson Mountain spiderling BOME Boerhavia megaptera 0–1 – exserted Indian paintbrush CAEXE Castilleja exserta ssp. exserta 0–1 – white tackstem CAWR Calycoseris wrightii 0–1 – brittle spineflower CHBR Chorizanthe brevicornu 0–1 – California copperleaf ACCA3 Acalypha californica 0–1 – poreleaf dogweed ADPO2 Adenophyllum porophyllum 0–1 – trailing windmills ALIN Allionia incarnata 0–1 – carelessweed AMPA Amaranthus palmeri 0–1 – sand fringepod THCU Thysanocarpus curvipes 0–1 – woolly tidestromia TILA2 Tidestromia lanuginosa 0–1 – New Mexico plumeseed RANE Rafinesquia neomexicana 0–1 – chia SACO6 Salvia columbariae 0–1 – Coues' cassia SECO10 Senna covesii 0–1 – sleepy silene SIAN2 Silene antirrhina 0–1 – Coulter's globemallow SPCO2 Sphaeralcea coulteri 0–1 – Shrub/Vine5 100–180 brittlebush ENFA Encelia farinosa 60–100 – desert globemallow SPAM2 Sphaeralcea ambigua 40–80 – 6 60–100 yellow paloverde PAMI5 Parkinsonia microphylla 20–50 – creosote bush LATR2 Larrea tridentata 10–30 – ocotillo FOSP2 Fouquieria splendens 5–20 – 7 20–40 8 20–40 triangle bur ragweed AMDE4 Ambrosia deltoidea 5–20 – white ratany KRGR Krameria grayi 5–10 – water jacket LYAN Lycium andersonii 2–5 – Fremont's desert-thorn LYFR Lycium fremontii 2–5 – 9 5–20 saguaro CAGI10 Carnegiea gigantea 0–3 – organpipe cactus STTH3 Stenocereus thurberi 0–2 – candy barrelcactus FEWI Ferocactus wislizeni 0–2 – Thornber's nipple cactus MATH Mammillaria thornberi 0–1 – beavertail pricklypear OPBA2 Opuntia basilaris 0–1 – cactus apple OPEN3 Opuntia engelmannii 0–1 – senita cactus PASC14 Pachycereus schottii 0–1 – Engelmann's hedgehog cactus ECEN Echinocereus engelmannii 0–1 – Leconte's barrel cactus FECYL Ferocactus cylindraceus var. lecontei 0–1 – Emory's barrel cactus FEEM Ferocactus emoryi 0–1 – 10 5–20 burrobush AMDU2 Ambrosia dumosa 0–3 – Sonoran croton CRSO Croton sonorae 0–2 – sweetbush BEJU Bebbia juncea 0–2 – Coulter's brickellbush BRCO Brickellia coulteri 0–1 – fragrant bursera BUFA Bursera fagaroides 0–1 – elephant tree BUMI Bursera microphylla 0–1 – Nevada jointfir EPNE Ephedra nevadensis 0–1 – desert lavender HYEM Hyptis emoryi 0–1 – sangre de cristo JACA2 Jatropha cardiophylla 0–1 – littleleaf ratany KRER Krameria erecta 0–1 – desert ironwood OLTE Olneya tesota 0–1 – bush arrowleaf PLPL Pleurocoronis pluriseta 0–1 – Mexican bladdersage SAME Salazaria mexicana 0–1 – arrow poision plant SEBI9 Sebastiania bilocularis 0–1 – American threefold TRCA8 Trixis californica 0–1 – Parish's goldeneye VIPA14 Viguiera parishii 0–1 – rush milkweed ASSU Asclepias subulata 0–1 – Indian mallow ABUTI Abutilon 0–1 – whitethorn acacia ACCOP9 Acacia constricta var. paucispina 0–1 – Interpretations
Animal community
Steep slopes, very cobbly and stony surfaces and large areas of rock slides severely limit livestock distribution. Stocker cattle are best adapted to use of this site. The plant community provides limited amounts of usable forage in the winter-spring season. Natural water is unavailable on this site.
Water developments are very important to wildlife species on this site. Cover, diversity and topography make this site home to a variety of desert animals. Large mammals use this site seasonally unless permanent water supplies exist nearby. Desert tortoises den on cobbly or stony southern aspects. Javalina bed on north aspects in palo verde thickets.Recreational uses
Hot summertime temperatures limit the use of this site to primarily fall through spring periods. Steep slopes and the extensive cover of cobbles and gravels make traversing the site difficult. Hiking and hunting are the primary uses of this ecological site.
Wood products
No significant wood products are produced on the site.
Supporting information
Type locality
Location 1: Pima County, AZ Township/Range/Section T12S R4W S5 General legal description Tucson FO - Childs Ranch, by Burro Gap Well Location 2: Maricopa County, AZ Township/Range/Section T7S R2E S6 General legal description Buckeye FO - AK Ranch, Palo Verde Mountains Location 3: Maricopa County, AZ Township/Range/Section T3N R6E S32 General legal description Chandler FO - Salt River Indian Community, Sawik Mountains Location 4: Maricopa County, AZ Township/Range/Section T4N R3E S10 General legal description Phoenix FO - Union Hills Location 5: Pima County, AZ Township/Range/Section T8S R4E S17 General legal description Sells FO - Sif Oidak District, Vaiva Vo Hills Contributors
Dan Robinett
Dan Robinett, Jack Norris
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) Dave Womack, Dan Robinett, Emilio Carrillo Contact for lead author NRCS Tucson Area Office Date 03/07/2005 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
Common on this site only in areas where rock and gravel cover is low. Rills follow joints, fractures and bedding planes in the bedrock parent materials. -
Presence of water flow patterns:
Water flow patterns are common, continuous, and cover 15-20% of area. -
Number and height of erosional pedestals or terracettes:
There are no pedestals or terracettes on this site. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
1-5% -
Number of gullies and erosion associated with gullies:
none -
Extent of wind scoured, blowouts and/or depositional areas:
No evidence of soil movement by wind. -
Amount of litter movement (describe size and distance expected to travel):
Herbaceous litter can move by wind and water. Woody litter remains under shrub canopies. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil surface resistance to erosion is good under shrub canopies & areas with high rock and gravel cover to moderate in soil interspaces due to crusts formed by raindrop impact. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Weak thin platy to granular; 7.5-10YR6/4 dry; 7.5-10YR4/4 moist, to 2 inches -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Canopy 10-15%; 70-80% shrubs, 5% trees and 10-15% succulents. Cover is well dispersed throughout site. -
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:
subshrubs > large shrubs > winter annuals > summer annuals > perennial grasses and forbs > cryptgams (Note: In El Nino years annual forbs and grasses are #1 in above ground weight)Sub-dominant:
Other:
Additional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
0-50% canopy mortality -
Average percent litter cover (%) and depth ( in):
Herbaceous litter is not persistent on the site and may be 20-60% in El Nino years. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
250 lbs/ac unfavorable precipitation; 400 lbs/ac normal precipitation; 650 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 (potential) -
Perennial plant reproductive capability:
Not impaired for shrubs, drought impaired for perennial grasses and forbs
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