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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 Not specified
Shrub (1) Ambrosia deltoidea
(2) Encelia farinosaHerbaceous (1) Pleuraphis rigida
Physiographic features
This site occurs on hillslopes and ridgetops. Slopes are from 15 to 45%. Elevations range from 1000 to 2200 feet.
Table 2. Representative physiographic features
Landforms (1) Hill
(2) Ridge
Elevation 1000 – 2200 ft Slope 15 – 45 % 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 moderately deep to deep soils formed in very gravelly alluvium of moderate age and from mixed origins. They are very calcareous and have over 35% gravels in the soil profile. Plant-soil moisture relationships are poor.
Soils mapped on this site include: SSA-645 Aguila-Carefree area MU Nickel-39; SSA-651 Central Maricopa County MU, Calciorthids-CA2 & Torriorthents-CA2; SSA-653 Gila Bend-Ajo area MU Ajo-3.Table 4. Representative soil features
Surface texture (1) Gravelly sandy loam
(2) Very gravelly fine sandy loam
(3) Extremely gravelly
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderate to moderately rapid Soil depth 40 – 60 in Surface fragment cover <=3" 15 – 65 % Surface fragment cover >3" 1 – 10 % Available water capacity
(0-40in)3 – 6 in Calcium carbonate equivalent
(0-40in)5 – 35 % Electrical conductivity
(0-40in)0 – 2 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 – 65 % Subsurface fragment volume >3"
(Depth not specified)1 – 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 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 potential plant community on this site is a mixture of desert shrubs, cacti, perennial grasses and forbs. Annual grasses and forbs make up a small percentage of the potential community. The aspect is shrubland.
Perennial grasses and forbs quickly disappear from the plant community with heavy grazing or from drought. Most of the shrubby species on the site are unpalatable and little change has occurred in the composition of these species with past heavy grazing use. A few, cool season, introduced annuals like; red brome, mediterranean grass and london rocket mustard occur on areas of this site and may compete with native annual forbs and grasses. The surfaces of these soils are usually very well protected by covers of gravels, cobbles and caliche fragments. Cryptogam cover is usually very low. Plant populations per acre for major species include; 200 to 300 for creosotebush, 200 to 400 for the ratany-bursage group, and 50 to 100 for cholla species.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 195 – 255 Forb 30 – 45 Grass/Grasslike 15 – 45 Total 240 – 345 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 15–30 blue threeawn ARPUN Aristida purpurea var. nealleyi 0–10 – bush muhly MUPO2 Muhlenbergia porteri 0–10 – purple threeawn ARPU9 Aristida purpurea 0–5 – big galleta PLRI3 Pleuraphis rigida 0–5 – Parish's threeawn ARPUP5 Aristida purpurea var. parishii 0–2 – Wright's threeawn ARPUW Aristida purpurea var. wrightii 0–2 – 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 – plains bristlegrass SEVU2 Setaria vulpiseta 0–1 – sand dropseed SPCR Sporobolus cryptandrus 0–1 – slim tridens TRMU Tridens muticus 0–1 – whiplash pappusgrass PAVA2 Pappophorum vaginatum 0–1 – 2 3–15 needle grama BOAR Bouteloua aristidoides 0–5 – sixweeks grama BOBA2 Bouteloua barbata 0–5 – Rothrock's grama BORO2 Bouteloua rothrockii 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 – feather fingergrass CHVI4 Chloris virgata 0–1 – canyon cupgrass ERLE7 Eriochloa lemmonii 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 – delicate muhly MUFR Muhlenbergia fragilis 0–1 – littleseed muhly MUMI Muhlenbergia microsperma 0–1 – Bigelow's bluegrass POBI Poa bigelovii 0–1 – Arizona signalgrass URAR Urochloa arizonica 0–1 – 3 3–15 Alga 2ALGA Alga 0–10 – Fungus 2FUNGI Fungus 0–2 – Lichen 2LICHN Lichen 0–2 – Moss 2MOSS Moss 0–2 – strigose bird's-foot trefoil LOSTT Lotus strigosus var. tomentellus 0–1 – Forb4 15–30 desert globemallow SPAM2 Sphaeralcea ambigua 5–10 – desert trumpet ERIN4 Eriogonum inflatum 2–5 – Parry's false prairie-clover MAPA7 Marina parryi 0–2 – lacy tansyaster MAPIP4 Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida 0–2 – rough menodora MESC Menodora scabra 0–1 – evening primrose OENOT Oenothera 0–1 – slender poreleaf POGR5 Porophyllum gracile 0–1 – Coues' cassia SECO10 Senna covesii 0–1 – California fagonbush FALA Fagonia laevis 0–1 – paleface HIDE Hibiscus denudatus 0–1 – slender janusia JAGR Janusia gracilis 0–1 – brownplume wirelettuce STPA4 Stephanomeria pauciflora 0–1 – dwarf desertpeony ACNA2 Acourtia nana 0–1 – brownfoot ACWR5 Acourtia wrightii 0–1 – poreleaf dogweed ADPO2 Adenophyllum porophyllum 0–1 – trailing windmills ALIN Allionia incarnata 0–1 – narrowleaf silverbush ARLA12 Argythamnia lanceolata 0–1 – New Mexico silverbush ARNE2 Argythamnia neomexicana 0–1 – rush milkweed ASSU Asclepias subulata 0–1 – desert marigold BAMU Baileya multiradiata 0–1 – whitemargin sandmat CHAL11 Chamaesyce albomarginata 0–1 – desert larkspur DEPA Delphinium parishii 0–1 – tall mountain larkspur DESC Delphinium scaposum 0–1 – bluedicks DICA14 Dichelostemma capitatum 0–1 – 5 3–15 sand pygmyweed CRCO34 Crassula connata 0–3 – combseed PECTO Pectocarya 0–3 – woolly tidestromia TILA2 Tidestromia lanuginosa 0–3 – coastal bird's-foot trefoil LOSAB Lotus salsuginosus var. brevivexillus 0–2 – strigose bird's-foot trefoil LOSTT Lotus strigosus var. tomentellus 0–2 – cryptantha CRYPT Cryptantha 0–2 – hairy prairie clover DAMO Dalea mollis 0–1 – American wild carrot DAPU3 Daucus pusillus 0–1 – western tansymustard DEPI Descurainia pinnata 0–1 – flatcrown buckwheat ERDE6 Eriogonum deflexum 0–1 – miniature woollystar ERDI2 Eriastrum diffusum 0–1 – erigenia ERIGE Erigenia 0–1 – buckwheat ERIOG Eriogonum 0–1 – Texas stork's bill ERTE13 Erodium texanum 0–1 – California poppy ESCAM Eschscholzia californica ssp. mexicana 0–1 – pygmy poppy ESMI Eschscholzia minutiflora 0–1 – gilia GILIA Gilia 0–1 – Gordon's bladderpod LEGO Lesquerella gordonii 0–1 – shaggyfruit pepperweed LELA Lepidium lasiocarpum 0–1 – foothill deervetch LOHU2 Lotus humistratus 0–1 – common fiddleneck AMMEI2 Amsinckia menziesii var. intermedia 0–1 – bristly fiddleneck AMTE3 Amsinckia tessellata 0–1 – milkvetch ASTRA Astragalus 0–1 – Coulter's spiderling BOCO2 Boerhavia coulteri 0–1 – hoary bowlesia BOIN3 Bowlesia incana 0–1 – California suncup CACA32 Camissonia californica 0–1 – exserted Indian paintbrush CAEXE Castilleja exserta ssp. exserta 0–1 – yellow tackstem CAPA7 Calycoseris parryi 0–1 – white tackstem CAWR Calycoseris wrightii 0–1 – brittle spineflower CHBR Chorizanthe brevicornu 0–1 – pebble pincushion CHCA Chaenactis carphoclinia 0–1 – hyssopleaf sandmat CHHY3 Chamaesyce hyssopifolia 0–1 – devil's spineflower CHRI Chorizanthe rigida 0–1 – Esteve's pincushion CHST Chaenactis stevioides 0–1 – New Mexico thistle CINE Cirsium neomexicanum 0–1 – Arizona lupine LUAR4 Lupinus arizonicus 0–1 – Coulter's lupine LUSP2 Lupinus sparsiflorus 0–1 – blazingstar MENTZ Mentzelia 0–1 – bristly nama NAHI Nama hispidum 0–1 – glandular threadplant NEGL Nemacladus glanduliferus 0–1 – Florida pellitory PAFL3 Parietaria floridana 0–1 – manybristle chinchweed PEPA2 Pectis papposa 0–1 – phacelia PHACE Phacelia 0–1 – desert Indianwheat PLOV Plantago ovata 0–1 – New Mexico plumeseed RANE Rafinesquia neomexicana 0–1 – chia SACO6 Salvia columbariae 0–1 – sleepy silene SIAN2 Silene antirrhina 0–1 – Coulter's globemallow SPCO2 Sphaeralcea coulteri 0–1 – woollyhead neststraw STMI2 Stylocline micropoides 0–1 – Shrub/Vine6 90–135 creosote bush LATR2 Larrea tridentata 90–135 – 7 30–60 triangle bur ragweed AMDE4 Ambrosia deltoidea 15–30 – burrobush AMDU2 Ambrosia dumosa 15–30 – brittlebush ENFA Encelia farinosa 0–5 – 8 15–30 white ratany KRGR Krameria grayi 10–20 – littleleaf ratany KRER Krameria erecta 5–10 – 9 15–30 yellow paloverde PAMI5 Parkinsonia microphylla 0–5 – desert ironwood OLTE Olneya tesota 0–3 – ocotillo FOSP2 Fouquieria splendens 0–2 – desert lavender HYEM Hyptis emoryi 0–1 – sangre de cristo JACA2 Jatropha cardiophylla 0–1 – crown of thorns KOSP Koeberlinia spinosa 0–1 – water jacket LYAN Lycium andersonii 0–1 – Arizona desert-thorn LYEX Lycium exsertum 0–1 – desert wolfberry LYMA Lycium macrodon 0–1 – velvet mesquite PRVE Prosopis velutina 0–1 – whitestem paperflower PSCO2 Psilostrophe cooperi 0–1 – dwarf saltwort SABI Salicornia bigelovii 0–1 – Mexican bladdersage SAME Salazaria mexicana 0–1 – jojoba SICH Simmondsia chinensis 0–1 – woody crinklemat TICAC Tiquilia canescens var. canescens 0–1 – American threefold TRCA8 Trixis californica 0–1 – Parish's goldeneye VIPA14 Viguiera parishii 0–1 – desert zinnia ZIAC Zinnia acerosa 0–1 – lotebush ZIOB Ziziphus obtusifolia 0–1 – whitethorn acacia ACCO2 Acacia constricta 0–1 – catclaw acacia ACGR Acacia greggii 0–1 – rayless goldenhead ACSP Acamptopappus sphaerocephalus 0–1 – Coulter's brickellbush BRCO Brickellia coulteri 0–1 – button brittlebush ENFR Encelia frutescens 0–1 – Nevada jointfir EPNE Ephedra nevadensis 0–1 – 10 15–30 senita cactus PASC14 Pachycereus schottii 0–2 – organpipe cactus STTH3 Stenocereus thurberi 0–2 – beavertail pricklypear OPBA2 Opuntia basilaris 0–1 – Engelmann's hedgehog cactus ECEN Echinocereus engelmannii 0–1 – Leconte's barrel cactus FECYL Ferocactus cylindraceus var. lecontei 0–1 – candy barrelcactus FEWI Ferocactus wislizeni 0–1 – common fishhook cactus MATE4 Mammillaria tetrancistra 0–1 – Interpretations
Animal community
This site produces small amounts of herbaceous and shrubby forage for year-round use. Even in wet winters the production of cool season annuals is low and provides for little additional carrying capacity.
This site is home to a variety of desert mammals, birds and reptiles. Though cover is lacking, topography provides enough security for the site to support the larger desert mammals. Desert tortoises den in pockets and caverns under caliche outcrops on steep slopes and along drainage ways.Other information
T&E: Antilocapra Americanc sonoriensis
(Sonoran pronghorn)
Leptonycteris curasoae yerbe buena
(Lesser long-nosed bat)
Supporting information
Type locality
Location 1: Maricopa County, AZ Township/Range/Section T7S R2W S2 General legal description Buckeye FO - Sand Tank Mountains Location 2: Maricopa County, AZ Township/Range/Section T1N R8E S22 General legal description Chandler FO - Apache Junction Location 3: Pima County, AZ Township/Range/Section T13S R8E S20 General legal description Sells FO - Shuck Toak Dist., Aguirre Valley Location 4: Pima County, AZ Township/Range/Section T15S R7W S20 General legal description Tucson FO - Organ Pipe National Monument Contributors
Dan Robinett
Dan Robinett, J. 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 12/28/2005 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
Rills are common and continuous in absence of high gravel cover. -
Presence of water flow patterns:
Water flow patterns are common, continuous and occupy 15-20% of area. -
Number and height of erosional pedestals or terracettes:
Erosional pedestals not present on most perennial plants. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
10-30% (low values in high gravel cover areas and/or in El Nino years) -
Number of gullies and erosion associated with gullies:
noen -
Extent of wind scoured, blowouts and/or depositional areas:
none -
Amount of litter movement (describe size and distance expected to travel):
Woody litter mostly stays under plant canopy; herbaceous litter can travel long distances. -
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 to moderate in 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; A horizon is 4 inches. Accumulated pedestals on most perennial plants, not so much so in high gravel cover areas, 2-5 inches high. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Cover estimated as: canopy 5-10%, Basal 1%; 80-85% shrubs, 5-10% halfshrubs, 5-10% succulents. Cover is well dispersed throughout the 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:
shrubs > halfshrubs > succulents > trees > annual grasses & forbs > perennial forbs = perennial grasses (note: in El Nino years annual frobs 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):
-
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
250 lbs/ac unfavorable precipitation, 350 lbs/ac normal precipitation, 500 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, filaree -
Perennial plant reproductive capability:
Not impaired for shrubs, drought impaired for perennial grasses and forbs.
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