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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
(2) Prosopis glandulosaShrub (1) Olneya tesota
(2) Castela emoryiHerbaceous (1) Pleuraphis mutica
(2) Muhlenbergia porteriPhysiographic features
This site occurs on fan terraces and stream terraces. Slopes range from 1 to 3%. Elevations are from 1000 to 2050 feet.
Table 2. Representative physiographic features
Landforms (1) Fan
(2) Terrace
(3) Stream terrace
Elevation 1000 – 2050 ft Slope 1 – 3 % 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 old soils formed in clayey alluvium from mixed origins. They are deep and have moderate shrink-swell potentials. They do not crack and churn with wetting and dryng. Plant-soil moisture relationships are fair.
Soils mapped on this site include: in SSA-645 Aguila-Carefree area MU's Contine-22 & 46, Eba-39, Ebon-44, 45, 46, 47 & 48, Luke-74 & Mohall-77; SSA-651 Central Maricopa County MU's Tremant-AkB, Cs, MTB, Tg, Th, TPB, TrA, TrB & TSC, Ebon-CeD, EbD & EPD, Glenbar-Go3 & Gt, Laveen-Le, Mohall-Mr & MV, Trix-Tt; SSA-659 Western Pinal County MU's Contine-9 & Mohall-32; SSA-661 Eastern Pinal-Southern Gila Counties MU's Ebon-207 & 580.Table 4. Representative soil features
Surface texture (1) Gravelly loam
(2) Very gravelly clay loam
Family particle size (1) Clayey
Drainage class Well drained Permeability class Moderately slow to slow Soil depth 40 – 60 in Surface fragment cover <=3" 1 – 45 % Surface fragment cover >3" 0 – 5 % Available water capacity
(0-40in)3.2 – 9 in Calcium carbonate equivalent
(0-40in)5 – 30 % Electrical conductivity
(0-40in)Not specified Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)7.4 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)1 – 45 % Subsurface fragment volume >3"
(Depth not specified)0 – 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.
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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 perennial and annual grasses and forbs and desert shrubs and cacti. The aspect is shrubland.
With continuous, heavy grazing, forage species like Tobosa, threeawns and globemallow are removed from the plant community and replaced by species like; creosote bush, triangle bursage, mesquite and cacti. Several cool season, introduced annual species have become entrenched on areas of this site and have displaced native grasses and forbs. These species include; red brome, mediterranean grass, filaree, tumbleweed, and London rocket mustard. This site is a poor user of intense summer thunderstorms. Heavy surface textures, low plant cover and a lack of cracking combine to inefficient use of summer precipitation.
In areas where perennial plant cover has been lost and erosion is accelerated, mechanical treatments to harvest water onto seeded strips (contour borders, basins) has resulted in excellent stands of native trees and shrubs like; fourwing saltbush, mesquite and Mexican paloverde. Trees on this site occur as shrubby individuals due to the clayey soil textures near the surface. Cryptogam cover can be moderate on non-gravelly surfaces.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 140 – 220 Grass/Grasslike 100 – 140 Forb 60 – 100 Total 300 – 460 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 40–80 tobosagrass PLMU3 Pleuraphis mutica 40–80 – 2 20–40 purple threeawn ARPU9 Aristida purpurea 0–5 – bush muhly MUPO2 Muhlenbergia porteri 0–5 – Parish's threeawn ARPUP5 Aristida purpurea var. parishii 0–3 – Wright's threeawn ARPUW Aristida purpurea var. wrightii 0–3 – big galleta PLRI3 Pleuraphis rigida 0–3 – spidergrass ARTE3 Aristida ternipes 0–2 – spidergrass ARTEG Aristida ternipes var. gentilis 0–2 – red grama BOTR2 Bouteloua trifida 0–1 – Arizona cottontop DICA8 Digitaria californica 0–1 – whiplash pappusgrass PAVA2 Pappophorum vaginatum 0–1 – plains bristlegrass SEVU2 Setaria vulpiseta 0–1 – 3 Annuals 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 – Eastwood fescue VUMIC Vulpia microstachys var. ciliata 0–10 – Pacific fescue VUMIP Vulpia microstachys var. pauciflora 0–10 – sixweeks fescue VUOC Vulpia octoflora 0–10 – Rothrock's grama BORO2 Bouteloua rothrockii 0–5 – Arizona brome BRAR4 Bromus arizonicus 0–1 – feather fingergrass CHVI4 Chloris virgata 0–1 – desert lovegrass ERPEM Eragrostis pectinacea var. miserrima 0–1 – tufted lovegrass ERPEP2 Eragrostis pectinacea var. pectinacea 0–1 – bearded sprangletop LEFUF Leptochloa fusca ssp. fascicularis 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 – 4 4–20 Alga 2ALGA Alga 2–10 – Lichen 2LICHN Lichen 1–5 – Moss 2MOSS Moss 1–3 – Fungus 2FUNGI Fungus 1–2 – Forb5 20–40 desert globemallow SPAM2 Sphaeralcea ambigua 0–5 – Louisiana vetch VILU Vicia ludoviciana 0–5 – Emory's globemallow SPEM Sphaeralcea emoryi 0–3 – spear globemallow SPHA Sphaeralcea hastulata 0–3 – Indian rushpea HOGL2 Hoffmannseggia glauca 0–2 – dwarf desertpeony ACNA2 Acourtia nana 0–1 – 6 40–80 bristly fiddleneck AMTE3 Amsinckia tessellata 0–10 – western tansymustard DEPI Descurainia pinnata 0–10 – common fiddleneck AMMEI2 Amsinckia menziesii var. intermedia 0–10 – shaggyfruit pepperweed LELA Lepidium lasiocarpum 0–5 – Arizona lupine LUAR4 Lupinus arizonicus 0–5 – Coulter's lupine LUSP2 Lupinus sparsiflorus 0–5 – sleepy silene SIAN2 Silene antirrhina 0–3 – Coulter's globemallow SPCO2 Sphaeralcea coulteri 0–1 – woollyhead neststraw STMI2 Stylocline micropoides 0–1 – cutleaf thelypody THLA Thelypodium laciniatum 0–1 – woolly tidestromia TILA2 Tidestromia lanuginosa 0–1 – Bigelow's linanthus LIBI2 Linanthus bigelovii 0–1 – linanthus LINAN2 Linanthus 0–1 – coastal bird's-foot trefoil LOSA Lotus salsuginosus 0–1 – brownfoot ACWR5 Acourtia wrightii 0–1 – weakleaf bur ragweed AMCO3 Ambrosia confertiflora 0–1 – fringed amaranth AMFI Amaranthus fimbriatus 0–1 – disc mayweed MADI6 Matricaria discoidea 0–1 – Nuttall's povertyweed MONU Monolepis nuttalliana 0–1 – bristly nama NAHI Nama hispidum 0–1 – evening primrose OENOT Oenothera 0–1 – lineleaf whitepuff OLLI Oligomeris linifolia 0–1 – locoweed OXYTR Oxytropis 0–1 – Florida pellitory PAFL3 Parietaria floridana 0–1 – combseed PECTO Pectocarya 0–1 – manybristle chinchweed PEPA2 Pectis papposa 0–1 – phacelia PHACE Phacelia 0–1 – slimjim bean PHFI3 Phaseolus filiformis 0–1 – desert Indianwheat PLOV Plantago ovata 0–1 – redseed plantain PLRH Plantago rhodosperma 0–1 – New Mexico plumeseed RANE Rafinesquia neomexicana 0–1 – bluedicks DICA14 Dichelostemma capitatum 0–1 – touristplant DIWI2 Dimorphocarpa wislizeni 0–1 – flatcrown buckwheat ERDE6 Eriogonum deflexum 0–1 – miniature woollystar ERDI2 Eriastrum diffusum 0–1 – fleabane ERIGE2 Erigeron 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 – morningglory IPER Ipomoea eriocarpa 0–1 – Arizona poppy KAGR Kallstroemia grandiflora 0–1 – California goldfields LACA7 Lasthenia californica 0–1 – Gordon's bladderpod LEGO Lesquerella gordonii 0–1 – tuber anemone ANTU Anemone tuberosa 0–1 – milkvetch ASTRA Astragalus 0–1 – wheelscale saltbush ATELF Atriplex elegans var. fasciculata 0–1 – big saltbush ATLE Atriplex lentiformis 0–1 – Wright's saltbush ATWR Atriplex wrightii 0–1 – spiderling BOERH2 Boerhavia 0–1 – hoary bowlesia BOIN3 Bowlesia incana 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 – southern Sierra pincushion CHAL Chaenactis alpigena 0–1 – whitemargin sandmat CHAL11 Chamaesyce albomarginata 0–1 – brittle spineflower CHBR Chorizanthe brevicornu 0–1 – aridland goosefoot CHDE Chenopodium desiccatum 0–1 – hyssopleaf sandmat CHHY3 Chamaesyce hyssopifolia 0–1 – devil's spineflower CHRI Chorizanthe rigida 0–1 – New Mexico thistle CINE Cirsium neomexicanum 0–1 – sand pygmyweed CRCO34 Crassula connata 0–1 – cryptantha CRYPT Cryptantha 0–1 – fingerleaf gourd CUDI Cucurbita digitata 0–1 – hairy prairie clover DAMO Dalea mollis 0–1 – American wild carrot DAPU3 Daucus pusillus 0–1 – carelessweed AMPA Amaranthus palmeri 0–1 – Shrub/Vine7 40–80 triangle bur ragweed AMDE4 Ambrosia deltoidea 5–15 – burrobush AMDU2 Ambrosia dumosa 5–10 – white ratany KRGR Krameria grayi 2–10 – littleleaf ratany KRER Krameria erecta 2–5 – Nevada jointfir EPNE Ephedra nevadensis 0–3 – 8 40–80 fourwing saltbush ATCA2 Atriplex canescens 5–15 – water jacket LYAN Lycium andersonii 0–3 – Berlandier's wolfberry LYBE Lycium berlandieri 0–3 – Arizona desert-thorn LYEX Lycium exsertum 0–3 – yellow paloverde PAMI5 Parkinsonia microphylla 0–3 – desert ironwood OLTE Olneya tesota 0–2 – Jerusalem thorn PAAC3 Parkinsonia aculeata 0–2 – whitethorn acacia ACCO2 Acacia constricta 0–2 – catclaw acacia ACGR Acacia greggii 0–1 – crucifixion thorn CAEM4 Castela emoryi 0–1 – creosote bush LATR2 Larrea tridentata 0–1 – blue paloverde PAFL6 Parkinsonia florida 0–1 – velvet mesquite PRVE Prosopis velutina 0–1 – lotebush ZIOB Ziziphus obtusifolia 0–1 – 9 4–20 alkali goldenbush ISACA2 Isocoma acradenia var. acradenia 5–10 – burroweed ISTE2 Isocoma tenuisecta 0–3 – desertbroom BASA2 Baccharis sarothroides 0–2 – broom snakeweed GUSA2 Gutierrezia sarothrae 0–2 – 10 20–40 Leconte's barrel cactus FECYL Ferocactus cylindraceus var. lecontei 0–2 – Emory's barrel cactus FEEM Ferocactus emoryi 0–2 – candy barrelcactus FEWI Ferocactus wislizeni 0–2 – beavertail pricklypear OPBA2 Opuntia basilaris 0–2 – dollarjoint pricklypear OPCH Opuntia chlorotica 0–2 – nightblooming cereus PEGR3 Peniocereus greggii 0–1 – banana yucca YUBA Yucca baccata 0–1 – twistspine pricklypear OPMAM3 Opuntia macrorhiza var. macrorhiza 0–1 – Engelmann's hedgehog cactus ECEN Echinocereus engelmannii 0–1 – Interpretations
Animal community
Perennial grasses grow year-round with available moisture. The potential plant community on this site is deficient in digestible protein in the fall and winter. Due to the coarseness of tobosa, the other perennial grasses will usually be over-used before tobosa in grazed. Utilization of these grasses should not exceed 50% in either the spring or summer growing season. In wet winters the produciton of annual grasses and forbs can provide for very high stocking rates for a March-May grazing season.
Water developments are very important to wildlife species on this site. Cover and diversity are often lacking for the larger desert mammals like mule deer and javalina but the high production of winter annuals makes this site an important springtime forage area for those species. This site is home to a variety of small mammals and their predators.Other information
T&E: Antilocarpa Americana sonoriensis
Sonoran pronghornSupporting information
Type locality
Location 1: Maricopa County, AZ Township/Range/Section T1S R7E S15 General legal description Chandler FO - General Motors Proving Grounds Location 2: Pima County, AZ Township/Range/Section T8S R10E S29 General legal description Tucson FO - Deep Well Ranch Location 3: Pima County, AZ General legal description Sells FO - Shuck Toak Dist. Flat between the Vaca Hills west of Queen Well 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 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:
Rills are common and continuous in absence of high gravel cover. -
Presence of water flow patterns:
Water flow patterns are common, continuous, occupy 15-20% of area. -
Number and height of erosional pedestals or terracettes:
Shrubs have symmetrical mounds caused by the actions of splash, erosion and rodent activity. There are no pedestals on rock or gravel fragments and no terracettes are present. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare ground is 10-60%. Expect low values in dry years. -
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):
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 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 to subgranular blocky; 5-7.5YR5/6 dry, 5-7.5YR4/6 moist, to 4 inches thick -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Canopy 15-25%. Herbaceous litter is present in some years and absent in others. Large shrubs with large coppice mounds with high infiltration rates. Subshrubs with small mounds with high infiltration rates. Mounds occupy 15-30% of the surface and are evenly spaced over the area. -
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 & trees > winter annuals > summer annuals > perennial grasses and forbs > succulents > cryptogams (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 on trees & shrubs; 100% mortality on perennial grasses. -
Average percent litter cover (%) and depth ( in):
Herbaceous litter is not persistent on the site. -
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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