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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 Not specified
Herbaceous (1) Muhlenbergia porteri
(2) Digitaria californicaPhysiographic features
This site occurs on fan terraces and stream terraces. Slopes are from 1 to 15%. Elevations range from 1000 to 2200.
Table 2. Representative physiographic features
Landforms (1) Fan
(2) Terrace
(3) Stream terrace
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 deep soils formed in loamy alluvium of mixed origin. Surface textures range from sandyloam (less than four inches thick) to loam. Immediately below the surface layer is an argillic or clayey cambic horizon which acts to slow water infiltration in the subsoil. Subsurface texture group includes clayey skeletal, loamy skeletal, and fine loamy. These soils are non-calcareous in the surface. Plant-soil moisture relationships are fair. This site is mapped on 6 Soil Survey areas in the D40-2 CRA in South Western Arizona.
Soils mapped on this site include: SSA-645 Aguila-Carefree Area MU's Estrella-50, Gilman-55 & 58, Glenbar-60, Mohall-75 & 80, Pinamt-48, & Tremant-80, 98, 113 & 116; SSA-651
Central Maricopa County MU's Beardsley-BE, Glenbar-Gr, Mohall-Mp, MTB & MV, Tremant-AHC, PYD, Te, TfA, TfB & TpB; SSA-659 Western Pinal County MU's Marana-29, Mohall-31 & Sasco-42; SSA-661 Eastern Pinal-Southern Gila Counties MU's Ajo-285, Beardsley-204 & 605, Contine sandy loam-570, Mohall-215 & 595, Momoli-315, & Pinamt(less than 50% gravels, non calcareous)-212; SSA-669 Eastern Pima County MU Mohall-44; SSA-703 Tohono O'odham area MU Mohall-42 & 59.Table 4. Representative soil features
Surface texture (1) Gravelly sandy loam
(2) Very gravelly fine sandy loam
(3) Loam
Family particle size (1) Clayey
Drainage class Well drained Permeability class Moderately slow to slow Soil depth 60 in Surface fragment cover <=3" 1 – 45 % Surface fragment cover >3" 0 – 5 % Available water capacity
(0-40in)4.8 – 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)0 – 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 desert shrubs, cacti and annual grasses and forbs. Perennial grasses and forbs are a minor part of the native plant community. The aspect is shrubland.
Perennial forage species lilke bush muhly, threeawn, and globemallow ae quickly removed from the plant community with heavy grazing, or from periodic drought. Several introduced, cool season, annual grasses and forbs like; filaree, mediterranean grass and London rocket mustard have become entrenched on areas of this site and compete with the native annual forbs and grasses. Due to the presence of clayey horizons near the soil surface, this site is a poor user of intense summer thundersotrms. Much of the heavy summer rainfall received is lost as runoff. Desert trees are found in minor amounts on the site and tend to be shrubby in nature due to clayey horizons near the soil surface. The populations for major shrub species are; 50 to 200 plants per acre for creosotebush, 400-800 per acre for triangle bursage, 1 to 5 per acre for the trees and saguaro group and 50-200 plants per acre for cholla.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 255 – 330 Forb 20 – 80 Grass/Grasslike 20 – 80 Tree 5 – 10 Total 300 – 500 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 20–40 bush muhly MUPO2 Muhlenbergia porteri 10–25 – purple threeawn ARPU9 Aristida purpurea 0–10 – big galleta PLRI3 Pleuraphis rigida 0–5 – 2 4–20 Parish's threeawn ARPUP5 Aristida purpurea var. parishii 0–5 – Wright's threeawn ARPUW Aristida purpurea var. wrightii 0–5 – spidergrass ARTE3 Aristida ternipes 0–5 – spidergrass ARTEG Aristida ternipes var. gentilis 0–5 – blue threeawn ARPUN Aristida purpurea var. nealleyi 0–3 – low woollygrass DAPU7 Dasyochloa pulchella 0–1 – tobosagrass PLMU3 Pleuraphis mutica 0–1 – slim tridens TRMU Tridens muticus 0–1 – 3 0–40 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 – sixweeks threeawn ARAD Aristida adscensionis 0–5 – prairie threeawn AROL Aristida oligantha 0–5 – needle grama BOAR Bouteloua aristidoides 0–5 – sixweeks grama BOBA2 Bouteloua barbata 0–5 – Rothrock's grama BORO2 Bouteloua rothrockii 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 – Forb4 20–80 Florida pellitory PAFL3 Parietaria floridana 3–10 – manybristle chinchweed PEPA2 Pectis papposa 3–10 – phacelia PHACE Phacelia 3–10 – desert Indianwheat PLOV Plantago ovata 3–10 – doubleclaw PRPA2 Proboscidea parviflora 3–10 – New Mexico plumeseed RANE Rafinesquia neomexicana 3–10 – sleepy silene SIAN2 Silene antirrhina 3–10 – blazingstar MENTZ Mentzelia 3–10 – Nuttall's povertyweed MONU Monolepis nuttalliana 3–10 – bristly nama NAHI Nama hispidum 3–10 – desert globemallow SPAM2 Sphaeralcea ambigua 0–5 – Coulter's globemallow SPCO2 Sphaeralcea coulteri 0–5 – spear globemallow SPHA Sphaeralcea hastulata 3–5 – globemallow SPHAE Sphaeralcea 0–5 – common fiddleneck AMMEI2 Amsinckia menziesii var. intermedia 0–5 – western tansymustard DEPI Descurainia pinnata 0–5 – evening primrose OENOT Oenothera 0–3 – dwarf desertpeony ACNA2 Acourtia nana 0–1 – brownfoot ACWR5 Acourtia wrightii 0–1 – trailing windmills ALIN Allionia incarnata 0–1 – weakleaf bur ragweed AMCO3 Ambrosia confertiflora 0–1 – fringed amaranth AMFI Amaranthus fimbriatus 0–1 – bluedicks DICAC5 Dichelostemma capitatum ssp. capitatum 0–1 – touristplant DIWI2 Dimorphocarpa wislizeni 0–1 – fetid marigold DYPA Dyssodia papposa 0–1 – flatcrown buckwheat ERDE6 Eriogonum deflexum 0–1 – miniature woollystar ERDI2 Eriastrum diffusum 0–1 – buckwheat ERIOG Eriogonum 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 – spurge EUPHO Euphorbia 0–1 – hairy desertsunflower GECA2 Geraea canescens 0–1 – gilia GILIA Gilia 0–1 – Indian rushpea HOGL2 Hoffmannseggia glauca 0–1 – Arizona poppy KAGR Kallstroemia grandiflora 0–1 – Gordon's bladderpod LEGO Lesquerella gordonii 0–1 – broadleaved pepperweed LELA2 Lepidium latifolium 0–1 – pepperweed LEPID Lepidium 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 – disc mayweed MADI6 Matricaria discoidea 0–1 – lacy tansyaster MAPIP4 Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida 0–1 – milkvetch ASTRA Astragalus 0–1 – wheelscale saltbush ATEL Atriplex elegans 0–1 – wheelscale saltbush ATELF Atriplex elegans var. fasciculata 0–1 – Wright's saltbush ATWR Atriplex wrightii 0–1 – Coulter's spiderling BOCO2 Boerhavia coulteri 0–1 – spiderling BOERH2 Boerhavia 0–1 – hoary bowlesia BOIN3 Bowlesia incana 0–1 – yellow tackstem CAPA7 Calycoseris parryi 0–1 – white tackstem CAWR Calycoseris wrightii 0–1 – whitemargin sandmat CHAL11 Chamaesyce albomarginata 0–1 – lambsquarters CHAL7 Chenopodium album 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 – sand pygmyweed CRCOC Crassula connata var. connata 0–1 – cryptantha CRYPT Cryptantha 0–1 – fingerleaf gourd CUDI Cucurbita digitata 0–1 – pricklyburr DAIN2 Datura inoxia 0–1 – hairy prairie clover DAMO Dalea mollis 0–1 – American wild carrot DAPU3 Daucus pusillus 0–1 – woollyhead neststraw STMI2 Stylocline micropoides 0–1 – brownplume wirelettuce STPA4 Stephanomeria pauciflora 0–1 – sand fringepod THCU Thysanocarpus curvipes 0–1 – woolly tidestromia TILA2 Tidestromia lanuginosa 0–1 – Louisiana vetch VILUL2 Vicia ludoviciana ssp. ludoviciana 0–1 – 5 5–20 Alga 2ALGA Alga 5–10 – Lichen 2LICHN Lichen 1–5 – Moss 2MOSS Moss 1–3 – Fungus 2FUNGI Fungus 1–2 – Shrub/Vine6 120–200 creosote bush LATR2 Larrea tridentata 120–200 – 7 60–100 triangle bur ragweed AMDE4 Ambrosia deltoidea 60–100 – 8 0–4 burroweed ISTE2 Isocoma tenuisecta 0–2 – broom snakeweed GUSA2 Gutierrezia sarothrae 0–1 – alkali goldenbush ISACA2 Isocoma acradenia var. acradenia 0–1 – 9 20–40 beavertail pricklypear OPBA2 Opuntia basilaris 0–1 – Engelmann's hedgehog cactus ECEN Echinocereus engelmannii 0–1 – candy barrelcactus FEWI Ferocactus wislizeni 0–1 – senita cactus PASC14 Pachycereus schottii 0–1 – nightblooming cereus PEGR3 Peniocereus greggii 0–1 – organpipe cactus STTH3 Stenocereus thurberi 0–1 – 10 4–12 ocotillo FOSP2 Fouquieria splendens 0–3 – littleleaf ratany KRER Krameria erecta 0–1 – white ratany KRGR Krameria grayi 0–1 – water jacket LYAN Lycium andersonii 0–1 – Berlandier's wolfberry LYBE Lycium berlandieri 0–1 – Arizona desert-thorn LYEX Lycium exsertum 0–1 – lotebush ZIOB Ziziphus obtusifolia 0–1 – whitethorn acacia ACCO2 Acacia constricta 0–1 – burrobush AMDU2 Ambrosia dumosa 0–1 – crucifixion thorn CAEM4 Castela emoryi 0–1 – Nevada jointfir EPNE Ephedra nevadensis 0–1 – Tree11 4–10 yellow paloverde PAMI5 Parkinsonia microphylla 1–3 – velvet mesquite PRVE Prosopis velutina 0–2 – desert ironwood OLTE Olneya tesota 0–2 – Interpretations
Animal community
Due to the lack of perennial, herbaceous forage species, this site is not well suited to yearlong grazing use. In wet winters the production of annual grasses and forbs can be high and provide for considerable grazing during the March-May season.
Water developments are very important to wildlife species on this site. Cover and diversity are lacking for the larger desert mammals. This site is home to several small mammals 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 T14S R1E S29 General legal description Sells FO - Pisinimo Dist. - 1 mile west of old dirt road to Pisinimo from Ajo Highway Location 2: Maricopa County, AZ Township/Range/Section T1S R7E S14 General legal description Chandler FO - General Motors Proving Grounds Location 3: Pima County, AZ Township/Range/Section T16S R5W S25 General legal description Tucson FO - Organ Pipe Mational 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 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 the absence of high gravel cover. -
Presence of water flow patterns:
Water flow patterns are common, continuous, and occupy 15-20% of the 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 fragements 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 raindop impact. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Weak thin platy to granular; 7.5-10YR5/4 dry, 7.5-10YR3/4 Moist; to 2 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 ounds 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:
large shrubs > subshrubs > 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 and shrubs, 90-100% mortality on perennial grasses. -
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; 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, schismus, filaree -
Perennial plant reproductive capability:
Not impaired for shrubs, drought impaired for perennial grasses and forbs.
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