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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) Larrea tridentata var. tridentata
(2) Krameria grayiHerbaceous Not specified
Physiographic features
This site occurs on fan terraces, ridgetops, pediments and mesa tops. Slopes are from 1 to 15%. Elevations range from 1000 to 2200 feet.
Table 2. Representative physiographic features
Landforms (1) Terrace
(2) Ridge
(3) Mesa
Elevation 1000 – 2200 ft Slope 1 – 15 % 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 over strongly cemented lime pans (duripans or petrocalcic horizons). These lime pans stop water movement and turn roots. They are coarse to loamy textured soils formed in old alluvium of mixed origins. They are very calcareous. Plant-soil moisture relationships are poor. This site is mapped in 9 Soil Survey areas in the D40-2 CRA of South Western Arizona.
Soils mapped on this site are: SSA-627 Southern Mohave County MU's Cacique family-16 & Cline-33; SSA-645 Aguila-Carefree area MU's Cave-39, Cipriano-9, 21, 47, 68, 74, 106 & 110, & Suncity-110; SSA-651 Central Maricopa County MU's Cherioni-CO, Pinal-GWD, PsA, PsB, PT, PvB & PWB, Suncity-PWB, Toltec-Ta; SSA-653 Gila Bend-Ajo area MU's Cherioni-7, Cipriano-10 & 35, Comobabi-51 & Pompeii-3; SSA-658 Gila River Indian Reservation MU's Cavelt-9 & Pompeii-25; SSA-659 Western Pinal County MU's Cipriano-8 & 25; SSA-661 Eastern Pinal-Southern Gila Counties MU's Gunsight-211 & 212, Hickiwan-204, 211 & 285; SSA-669 Eastern Pima County MU Pinamt-63; SSA-703 Tohono O'odham MU Hickiwan-36. Subsurface texture may be skeletal.Table 4. Representative soil features
Surface texture (1) Gravelly sandy loam
(2) Very gravelly fine sandy loam
(3) Extremely gravelly loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderately rapid to rapid Soil depth 4 – 20 in Surface fragment cover <=3" 20 – 60 % Surface fragment cover >3" 1 – 5 % Available water capacity
(0-40in)0.24 – 2 in Calcium carbonate equivalent
(0-40in)10 – 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)20 – 60 % Subsurface fragment volume >3"
(Depth not specified)1 – 5 % 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, and perennial and annual grasses and forbs. The aspect is shrubland.
Most of the perennial species found in the potential community are unpalatable. As a result, little change has occurred in species composition with past heavy grazing use. A few cool season, introduced annuals like; red brome, Mediterranean grass, London rocket mustard and black 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 protcted by either covers of gravels and cobbles or cryptogam or a combination of both. Plant populations for major species are from 50 to 200 plants per acre for creosotebush, 50 to 150 plants per acre for ratany species, 20 to 1000 plants per acre for cholla species, and 1 to 10 plants per acre for trees and saguaro.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 120 – 150 Tree 10 – 20 Forb 4 – 20 Grass/Grasslike 4 – 20 Total 138 – 210 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 2–10 bush muhly MUPO2 Muhlenbergia porteri 0–5 – blue threeawn ARPUN Aristida purpurea var. nealleyi 0–3 – low woollygrass DAPU7 Dasyochloa pulchella 0–2 – nineawn pappusgrass ENDE Enneapogon desvauxii 0–1 – purple threeawn ARPU9 Aristida purpurea 0–1 – big galleta PLRI3 Pleuraphis rigida 0–1 – slim tridens TRMU Tridens muticus 0–1 – 2 2–10 sixweeks threeawn ARAD Aristida adscensionis 0–5 – prairie threeawn AROL Aristida oligantha 0–5 – needle grama BOAR Bouteloua aristidoides 0–5 – sixweeks fescue VUOC Vulpia octoflora 0–5 – sixweeks grama BOBA2 Bouteloua barbata 0–3 – Rothrock's grama BORO2 Bouteloua rothrockii 0–3 – 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 – Eastwood fescue VUMIC Vulpia microstachys var. ciliata 0–1 – Pacific fescue VUMIP Vulpia microstachys var. pauciflora 0–1 – 3 20–30 Alga 2ALGA Alga 5–15 – Fungus 2FUNGI Fungus 0–5 – Lichen 2LICHN Lichen 0–5 – Moss 2MOSS Moss 0–5 – Forb4 2–10 lacy tansyaster MAPIP4 Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida 0–2 – desert globemallow SPAM2 Sphaeralcea ambigua 0–2 – dwarf desertpeony ACNA2 Acourtia nana 0–2 – desert trumpet ERIN4 Eriogonum inflatum 0–2 – California fagonbush FALA Fagonia laevis 0–1 – Parry's false prairie-clover MAPA7 Marina parryi 0–1 – trailing windmills ALIN Allionia incarnata 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 – pricklyleaf dogweed THAC Thymophylla acerosa 0–1 – evening primrose OENOT Oenothera 0–1 – Coues' cassia SECO10 Senna covesii 0–1 – 5 2–10 common fiddleneck AMMEI2 Amsinckia menziesii var. intermedia 0–5 – bristly fiddleneck AMTE3 Amsinckia tessellata 0–5 – desert Indianwheat PLOV Plantago ovata 0–5 – desert unicorn-plant PRAL4 Proboscidea althaeifolia 0–1 – velvet turtleback PSRA Psathyrotes ramosissima 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 – longbeak streptanthella STLO4 Streptanthella longirostris 0–1 – woollyhead neststraw STMI2 Stylocline micropoides 0–1 – woolly tidestromia TILA2 Tidestromia lanuginosa 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 – combseed PECTO Pectocarya 0–1 – Emory's rockdaisy PEEM Perityle emoryi 0–1 – manybristle chinchweed PEPA2 Pectis papposa 0–1 – phacelia PHACE Phacelia 0–1 – slimjim bean PHFI3 Phaseolus filiformis 0–1 – smallflowered milkvetch ASNU4 Astragalus nuttallianus 0–1 – aster ASTER Aster 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 – desert mariposa lily CAKE Calochortus kennedyi 0–1 – naked mariposa lily CANU2 Calochortus nudus 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 – sand pygmyweed CRCO34 Crassula connata 0–1 – cryptantha CRYPT Cryptantha 0–1 – 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 – desert trumpet ERIN4 Eriogonum inflatum 0–1 – buckwheat ERIOG Eriogonum 0–1 – common woolly sunflower ERLA6 Eriophyllum lanatum 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 – hairy desertsunflower GECA2 Geraea canescens 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 – shrubby deervetch LORI3 Lotus rigidus 0–1 – coastal bird's-foot trefoil LOSAB Lotus salsuginosus var. brevivexillus 0–1 – Arizona lupine LUAR4 Lupinus arizonicus 0–1 – Coulter's lupine LUSP2 Lupinus sparsiflorus 0–1 – macaranga MACAR Macaranga 0–1 – onyxflower ACCO3 Achyronychia cooperi 0–1 – Shrub/Vine6 20–40 creosote bush LATR2 Larrea tridentata 20–40 – 7 60–80 triangle bur ragweed AMDE4 Ambrosia deltoidea 20–30 – burrobush AMDU2 Ambrosia dumosa 20–30 – brittlebush ENFA Encelia farinosa 5–10 – woody crinklemat TICAC Tiquilia canescens var. canescens 0–5 – 8 10–20 white ratany KRGR Krameria grayi 5–15 – littleleaf ratany KRER Krameria erecta 0–5 – 9 1–10 lotebush ZIOB Ziziphus obtusifolia 0–2 – whitethorn acacia ACCO2 Acacia constricta 0–1 – rayless goldenhead ACSP Acamptopappus sphaerocephalus 0–1 – Wright's beebrush ALWR Aloysia wrightii 0–1 – Nevada jointfir EPNE Ephedra nevadensis 0–1 – Eastern Mojave buckwheat ERFA2 Eriogonum fasciculatum 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 – whitestem paperflower PSCO2 Psilostrophe cooperi 0–1 – jojoba SICH Simmondsia chinensis 0–1 – turpentinebroom THMO Thamnosma montana 0–1 – Parish's goldeneye VIPA14 Viguiera parishii 0–1 – 10 10–20 beavertail pricklypear OPBA2 Opuntia basilaris 0–1 – senita cactus PASC14 Pachycereus schottii 0–1 – nightblooming cereus PEGRG Peniocereus greggii var. greggii 0–1 – organpipe cactus STTH3 Stenocereus thurberi 0–1 – desert agave AGDE Agave deserti 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 – Tree11 10–20 ocotillo FOSP2 Fouquieria splendens 2–10 – yellow paloverde PAMI5 Parkinsonia microphylla 0–3 – velvet mesquite PRVE Prosopis velutina 0–2 – desert ironwood OLTE Olneya tesota 0–2 – 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 lacks the cover and diversity for the larger desert mammals. It is home mainly to small mammals, reptiles and their predators.Other information
T&E: Antilocapra Americana sonoriensis
(Sonoran pronghorn)
Leptonycteris curasoae yerbe buena
(Lesser long-nosed bat)Supporting information
Type locality
Location 1: Pima County, AZ Township/Range/Section T9S R5W S23 General legal description Tucson FO - Barry Goldwater Gunnery Rnage - relict area on top of Hat Mountain Location 2: Maricopa County, AZ Township/Range/Section T5N R10W S23 General legal description Phoenix FO - Bonar Ranch Location 3: Maricopa County, AZ Township/Range/Section T2N R7E S31 General legal description Chandler FO - South of Spook Hill Location 4: Pima County, AZ Township/Range/Section T13S R8E S5 General legal description Sells FO - Shuck Toak Dist., Aguirre Valley Location 5: Pima County, AZ Township/Range/Section T14S R6W S19 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, Byron Lambeth, Dan Robinett 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:
Common on this site where gravel cover is low. -
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:
Accumulated pedestals on most perennial plants, not so much so in high gravel cover areas, 2-5 inches high. 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):
10-60% (low values due to high gravel cover and El Nino years) -
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):
Most litter size classes stay in place due to high gravel cover. -
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 to moderate fine subangular blocky; color is 7.5YR6/4 dry, 7.5YR5/6 moist; thickness to 1 inch. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Canopy cover estimated at 20-25%, Basal cover 1-2%: 50% is shrubs, 20% trees and 30% 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 > subshrubs > trees > succulents > forbs = perennial grasses (note: in El Nino years annual forbs & 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):
100 lbs/ac unfavorable precipitation; 200 lbs/ac normal precipitation; 300 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 -
Perennial plant reproductive capability:
Not impaired for shrubs, drought impaired for perennial grasses and forbs.
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