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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 florida
(2) Parkinsonia microphyllaShrub (1) Ambrosia deltoidea
(2) Lycium berlandieriHerbaceous (1) Pleuraphis mutica
(2) Pleuraphis rigidaPhysiographic features
This site occurs on relatively flat fan terraces and mesa tops, mostly associated with basalt bedrock types. The site has cracking clay soils with high shrink-swell capability. Slopes typically range from 1 to 10 percent. In the historic climax plant community, the site is dominated by tobosa.
Table 2. Representative physiographic features
Landforms (1) Fan
(2) Terrace
(3) Mesa
Elevation 1100 – 2000 ft Slope 1 – 10 % 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 clay rich alluvium from basaltic origin. They are moderately deep and have high shrink-swell potential. They crack and churn with wetting and drying. Plant-soil relationships are good. The soil surface is clay or heavy clay loam textured, over a calcic horizon, duripan, or bedrock at moderate depths. In some areas there is a thin lighter textured surface less than 3 inches thick.
Soils mapped on this site include: in
SSA-645 Aguila-Carefree area MU's Carefree-12, Beardsley & Carefree-13, Contine-23 & Mohall-79;
SSA-651 Central Maricopa County MU's Glenbar-Gv & Mohall-Ms;
SSA-659 Western Pinal County MU's Contine-10 & Saminiego-41.Table 4. Representative soil features
Parent material (1) Alluvium – basalt
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.
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 perennial and annual grasses and forbs with a scattering of shrubs and cacti. The aspect is open grassland.
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.
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)Grass/Grasslike 270 – 340 Forb 45 – 110 Shrub/Vine 45 – 90 Total 360 – 540 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Summer Native Dominant Perennial Colonizing Mid Gr 200–270 tobosagrass PLMU3 Pleuraphis mutica 200–270 – 2 20–45 big galleta PLRI3 Pleuraphis rigida 0–15 – purple threeawn ARPU9 Aristida purpurea 0–5 – Parish's threeawn ARPUP5 Aristida purpurea var. parishii 0–3 – Wright's threeawn ARPUW Aristida purpurea var. wrightii 0–3 – spidergrass ARTE3 Aristida ternipes 0–2 – spidergrass ARTEG Aristida ternipes var. gentilis 0–2 – curly-mesquite HIBE Hilaria belangeri 0–2 – bush muhly MUPO2 Muhlenbergia porteri 0–1 – low woollygrass DAPU7 Dasyochloa pulchella 0–1 – 3 20–65 sixweeks fescue VUOC Vulpia octoflora 0–10 – 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 – 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 – 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 – sticky sprangletop LEVI5 Leptochloa viscida 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 5–20 Alga 2ALGA Alga 2–10 – Lichen 2LICHN Lichen 2–5 – Moss 2MOSS Moss 1–3 – Fungus 2FUNGI Fungus 1–2 – Forb5 20–45 Louisiana vetch VILU Vicia ludoviciana 2–10 – dwarf desertpeony ACNA2 Acourtia nana 2–5 – bluedicks DICA14 Dichelostemma capitatum 2–5 – Indian rushpea HOGL2 Hoffmannseggia glauca 2–5 – desert globemallow SPAM2 Sphaeralcea ambigua 2–5 – globemallow SPHAE Sphaeralcea 2–5 – 6 Native Occasional Forbs 20–65 common fiddleneck AMMEI2 Amsinckia menziesii var. intermedia 0–10 – desert Indianwheat PLOV Plantago ovata 0–10 – redseed plantain PLRH Plantago rhodosperma 0–10 – bristly fiddleneck AMTE3 Amsinckia tessellata 0–10 – western tansymustard DEPI Descurainia pinnata 0–5 – evening primrose OENOT Oenothera 0–5 – combseed PECTO Pectocarya 0–5 – manybristle chinchweed PEPA2 Pectis papposa 0–1 – phacelia PHACE Phacelia 0–1 – lineleaf whitepuff OLLI Oligomeris linifolia 0–1 – Florida pellitory PAFL3 Parietaria floridana 0–1 – touristplant DIWI2 Dimorphocarpa wislizeni 0–1 – flatcrown buckwheat ERDE6 Eriogonum deflexum 0–1 – miniature woollystar ERDI2 Eriastrum diffusum 0–1 – spreading fleabane ERDI4 Erigeron divergens 0–1 – fleabane ERIGE2 Erigeron 0–1 – woolly sunflower ERIOP2 Eriophyllum 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 – Arizona poppy KAGR Kallstroemia grandiflora 0–1 – California goldfields LACA7 Lasthenia californica 0–1 – Gordon's bladderpod LEGO Lesquerella gordonii 0–1 – shaggyfruit pepperweed LELA Lepidium lasiocarpum 0–1 – pepperweed LEPID Lepidium 0–1 – Bigelow's linanthus LIBI2 Linanthus bigelovii 0–1 – flax LINUM Linum 0–1 – coastal bird's-foot trefoil LOSA Lotus salsuginosus 0–1 – Arizona lupine LUAR4 Lupinus arizonicus 0–1 – Coulter's lupine LUSP2 Lupinus sparsiflorus 0–1 – hollowleaf annual lupine LUSU3 Lupinus succulentus 0–1 – disc mayweed MADI6 Matricaria discoidea 0–1 – Nuttall's povertyweed MONU Monolepis nuttalliana 0–1 – bristly nama NAHI Nama hispidum 0–1 – tuber anemone ANTU Anemone tuberosa 0–1 – milkweed ASCLE Asclepias 0–1 – milkvetch ASTRA Astragalus 0–1 – Coulter's spiderling BOCO2 Boerhavia coulteri 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 – whitemargin sandmat CHAL11 Chamaesyce albomarginata 0–1 – brittle spineflower CHBR Chorizanthe brevicornu 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 – New Mexico plumeseed RANE Rafinesquia neomexicana 0–1 – sleepy silene SIAN2 Silene antirrhina 0–1 – 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 – carelessweed AMPA Amaranthus palmeri 0–1 – weakleaf bur ragweed AMCO3 Ambrosia confertiflora 0–1 – Shrub/Vine7 20–45 triangle bur ragweed AMDE4 Ambrosia deltoidea 0–5 – creosote bush LATR2 Larrea tridentata 0–5 – Berlandier's wolfberry LYBE Lycium berlandieri 0–2 – desert-thorn LYCIU Lycium 0–2 – pale desert-thorn LYPA Lycium pallidum 0–2 – desert ironwood OLTE Olneya tesota 0–2 – blue paloverde PAFL6 Parkinsonia florida 0–2 – yellow paloverde PAMI5 Parkinsonia microphylla 0–2 – velvet mesquite PRVE Prosopis velutina 0–2 – banana yucca YUBA Yucca baccata 0–1 – lotebush ZIOB Ziziphus obtusifolia 0–1 – whitethorn acacia ACCO2 Acacia constricta 0–1 – catclaw acacia ACGR Acacia greggii 0–1 – 8 20–45 dollarjoint pricklypear OPCH Opuntia chlorotica 0–3 – cactus apple OPEN3 Opuntia engelmannii 0–2 – candy barrelcactus FEWI Ferocactus wislizeni 0–2 – globe cactus MAMMI Mammillaria 0–1 – Engelmann's hedgehog cactus ECEN Echinocereus engelmannii 0–1 – Interpretations
Animal community
Tobosa, the dominant forage species, is very unpalatable when cured and is best used when green (in either spring or summer growing season). It will grow year round with available moisture. Utilization in the growing season should not exceed 50%. The potential plant community on this site is deficient in digestible protein in the fall and winter. In wet winters, the production of annual grasses and forbs can provide for very high stocking rates through a March-May grazing season.
Water developments are very important to wildlife species on this site. Cover and diversity is lacking for the larger desert mammals like mule deer and Javalina, but the high production of spring annuals make this site an important springtime forage area for those species. This site is home to a variety of small mammals and their preditors.Recreational uses
Recreation on this site includes hiking, backpacking, horse riding, and hunting. Due to hot summer temperatures, recreational activities are mostly limited to the fall through spring.
Wood products
No significant wood products are produced on this site.
Supporting information
Type locality
Location 1: Maricopa County, AZ Township/Range/Section T5N R2E S3 General legal description Phoenix FO - Black Canyon Shooting Range Location 2: Pinal County, AZ Township/Range/Section T8S R2E S2 General legal description Casa Grande FO - Top of Table Top Mountain 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, and 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):
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 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; 5-7.5YRS5/6 dry, 5-7.5YR4/6 moist, to 16 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 occyupy 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 > crytogamsSub-dominant:
Other:
Additional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
0-50% canopy mortality on trees & shrubs, 90-100% mortality on perennial grasses. -
Average percent litter cover (%) and depth ( in):
Herbaceous litter not persistant on the site. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
300 lbs/ac unfavorable precipitation; 450 lbs/ac normal precipitation; 1000 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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