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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) Prosopis velutina
(2) Atriplex polycarpaHerbaceous (1) Sporobolus airoides
(2) Trichloris crinitaPhysiographic features
This site occurs on floodplains and alluvial fans. It benefits on a regular basis from extra moisture received as overbank flooding and/or runoff from adjacent upland sites.
Table 2. Representative physiographic features
Landforms (1) Flood plain
(2) Alluvial fan
Elevation 900 – 2050 ft Slope 0 – 1 % 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
Soils are deep, well-drained, saline and sodic. Texture is loamy. Subsurface texture group includes fine loamy and coarse silty. Plant-soil moisture relationships are good due to the extra water these soils receive as runoff from adjacent upland areas.
Soils mapped on this site include: SSA-651 Central Maricopa county MU's Cashion-Cn, Gadsden (saline)-Gd, Gilman-Gf, Gh, GL & Gp, Glenbar-Gs & Gu; SSA-658 Gila River Indian Reservation MU's Cuerda-12, Gadsden (saline)-15 & 16, Glenbar-15 & 17; SSA-703 Tohono O'odham area MU's Kamato-8, Tatai-57 & Valencia-9.Table 4. Representative soil features
Surface texture (1) Loam
(2) Clay loam
(3) Silty clay loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Very slow to moderate Soil depth 60 in Surface fragment cover <=3" Not specified Surface fragment cover >3" Not specified Available water capacity
(0-40in)9.6 – 11.4 in Calcium carbonate equivalent
(0-40in)1 – 10 % Electrical conductivity
(0-40in)2 – 16 mmhos/cm Sodium adsorption ratio
(0-40in)13 – 30 Soil reaction (1:1 water)
(0-40in)7.9 – 9 Subsurface fragment volume <=3"
(Depth not specified)Not specified Subsurface fragment volume >3"
(Depth not specified)Not specified 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 each group. Divide the resulting total by the total normal year production shown in the plant community description. If the rainfall has ben 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
Historic Climax Plant CommunityCommunity 1.1
Historic Climax Plant CommunityThe native plant community on this site is dominated by a diverse mixture of perennial grasses, salt desert shrubs, and desert trees. The aspect is shrubland.
With continuous heavy grazing, midgrasses are removed from the plant community. When perennial grass cover is depleted, the site is extremely susceptible to gully erosion. Mesquite can increase quickly to dominate the plant community under conditions of heavy grazing and accelerated erosion and/or sedimentation. Base level changes in large watersheds will lead to eventual gullying of the site. With severe erosion, the effectiveness of flooding is greatly reduced as is the site's ability to produce vegetation. PLant populations of major tree and shrub species range from 100-400 trees/ac. for both Andersons wolfberry and iodinebush. Tree canopy ranges from 10-20%. Perennial plant basal cover ranges from 5-10%. The atriplex species are very sensitive to fires in the summer.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 810 945 1080 Grass/Grasslike 540 675 810 Forb 180 225 270 Total 1530 1845 2160 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 101–169 alkali sacaton SPAI Sporobolus airoides 101–169 – false Rhodes grass TRCR9 Trichloris crinita 101–169 – 2 34–68 Havard's threeawn ARHA3 Aristida havardii 34–68 – spidergrass ARTEG Aristida ternipes var. gentilis 34–68 – Arizona cottontop DICA8 Digitaria californica 34–68 – bush muhly MUPO2 Muhlenbergia porteri 34–68 – plains bristlegrass SEVU2 Setaria vulpiseta 34–68 – 3 7–34 Parish's threeawn ARPUP5 Aristida purpurea var. parishii 7–34 – cane bluestem BOBA3 Bothriochloa barbinodis 7–34 – saltgrass DISP Distichlis spicata 7–34 – tanglehead HECO10 Heteropogon contortus 7–34 – vine mesquite PAOB Panicum obtusum 7–34 – tobosagrass PLMU3 Pleuraphis mutica 7–34 – big galleta PLRI3 Pleuraphis rigida 7–34 – spike dropseed SPCO4 Sporobolus contractus 7–34 – sand dropseed SPCR Sporobolus cryptandrus 7–34 – mesa dropseed SPFL2 Sporobolus flexuosus 7–34 – 4 34–68 sixweeks threeawn ARAD Aristida adscensionis 34–68 – prairie threeawn AROL Aristida oligantha 34–68 – needle grama BOAR Bouteloua aristidoides 34–68 – sixweeks grama BOBA2 Bouteloua barbata 34–68 – Rothrock's grama BORO2 Bouteloua rothrockii 34–68 – Arizona brome BRAR4 Bromus arizonicus 34–68 – feather fingergrass CHVI4 Chloris virgata 34–68 – tapertip cupgrass ERACA Eriochloa acuminata var. acuminata 34–68 – desert lovegrass ERPEM Eragrostis pectinacea var. miserrima 34–68 – tufted lovegrass ERPEP2 Eragrostis pectinacea var. pectinacea 34–68 – Mexican sprangletop LEFUU Leptochloa fusca ssp. uninervia 34–68 – mucronate sprangeltop LEPAB Leptochloa panicea ssp. brachiata 34–68 – sticky sprangletop LEVI5 Leptochloa viscida 34–68 – delicate muhly MUFR Muhlenbergia fragilis 34–68 – littleseed muhly MUMI Muhlenbergia microsperma 34–68 – witchgrass PACA6 Panicum capillare 34–68 – Bigelow's bluegrass POBI Poa bigelovii 34–68 – Madagascar dropseed SPPY2 Sporobolus pyramidatus 34–68 – Arizona signalgrass URAR Urochloa arizonica 34–68 – sixweeks fescue VUOC Vulpia octoflora 34–68 – Forb5 0–1 dwarf desertpeony ACNA2 Acourtia nana 0–1 – weakleaf bur ragweed AMCO3 Ambrosia confertiflora 0–1 – field anoda ANPE4 Anoda pentaschista 0–1 – coyote gourd CUPA Cucurbita palmata 0–1 – Indian rushpea HOGL2 Hoffmannseggia glauca 0–1 – desert tobacco NIOBO Nicotiana obtusifolia var. obtusifolia 0–1 – violet wild petunia RUNU Ruellia nudiflora 0–1 – desert globemallow SPAM2 Sphaeralcea ambigua 0–1 – spear globemallow SPHA Sphaeralcea hastulata 0–1 – 6 15–90 Navajo Mountain beardtongue PENA4 Penstemon navajoa 1000–5000 – alpine gooseberry RILA2 Ribes lasianthum 1000–5000 – Elliott's bluestem ANGYS Andropogon gyrans var. stenophyllus 0–5 – Watson's dutchman's pipe ARWA Aristolochia watsonii 0–1 – clasping milkweed ASAM Asclepias amplexicaulis 0–1 – milkvetch ASTRA Astragalus 0–1 – desert marigold BAMU Baileya multiradiata 0–1 – hoary bowlesia BOIN3 Bowlesia incana 0–1 – canaigre dock RUHY Rumex hymenosepalus 0–1 – violet wild petunia RUNU Ruellia nudiflora 0–1 – spreading fanpetals SIAB Sida abutifolia 0–1 – sleepy silene SIAN2 Silene antirrhina 0–1 – silverleaf nightshade SOEL Solanum elaeagnifolium 0–1 – desert globemallow SPAM2 Sphaeralcea ambigua 0–1 – spear globemallow SPHA Sphaeralcea hastulata 0–1 – woollyhead neststraw STMI2 Stylocline micropoides 0–1 – brownplume wirelettuce STPA4 Stephanomeria pauciflora 0–1 – woolly tidestromia TILA2 Tidestromia lanuginosa 0–1 – Tumamoc globeberry TUMA Tumamoca macdougalii 0–1 – manybristle chinchweed PEPA2 Pectis papposa 0–1 – phacelia PHACE Phacelia 0–1 – orange fameflower PHAU13 Phemeranthus aurantiacus 0–1 – slimjim bean PHFI3 Phaseolus filiformis 0–1 – Arizona popcornflower PLAR Plagiobothrys arizonicus 0–1 – desert Indianwheat PLOV Plantago ovata 0–1 – purslane PORTU Portulaca 0–1 – doubleclaw PRPA2 Proboscidea parviflora 0–1 – New Mexico plumeseed RANE Rafinesquia neomexicana 0–1 – brownfoot ACWR5 Acourtia wrightii 0–1 – weakleaf bur ragweed AMCO3 Ambrosia confertiflora 0–1 – fringed amaranth AMFI Amaranthus fimbriatus 0–1 – carelessweed AMPA Amaranthus palmeri 0–1 – bristly fiddleneck AMTE3 Amsinckia tessellata 0–1 – fringed redmaids CACI2 Calandrinia ciliata 0–1 – yellow tackstem CAPA7 Calycoseris parryi 0–1 – white tackstem CAWR Calycoseris wrightii 0–1 – goosefoot CHENO Chenopodium 0–1 – hyssopleaf sandmat CHHY3 Chamaesyce hyssopifolia 0–1 – New Mexico thistle CINE Cirsium neomexicanum 0–1 – cryptantha CRYPT Cryptantha 0–1 – fingerleaf gourd CUDI Cucurbita digitata 0–1 – coyote gourd CUPA Cucurbita palmata 0–1 – desert thorn-apple DADI2 Datura discolor 0–1 – American wild carrot DAPU3 Daucus pusillus 0–1 – sacred thorn-apple DAWR2 Datura wrightii 0–1 – western tansymustard DEPI Descurainia pinnata 0–1 – Palmer's spectaclepod DICA31 Dimorphocarpa candicans 0–1 – miniature woollystar ERDI2 Eriastrum diffusum 0–1 – spreading fleabane ERDI4 Erigeron divergens 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 – Mexican fireplant EUHE4 Euphorbia heterophylla 0–1 – haplopappus HAPLO11 Haplopappus 0–1 – Indian rushpea HOGL2 Hoffmannseggia glauca 0–1 – Arizona poppy KAGR Kallstroemia grandiflora 0–1 – biannual lettuce LALU Lactuca ludoviciana 0–1 – Gordon's bladderpod LEGO Lesquerella gordonii 0–1 – shaggyfruit pepperweed LELA Lepidium lasiocarpum 0–1 – coastal bird's-foot trefoil LOSAB Lotus salsuginosus var. brevivexillus 0–1 – Lindley's silverpuffs MILI5 Microseris lindleyi 0–1 – Nuttall's povertyweed MONU Monolepis nuttalliana 0–1 – green carpetweed MOVE Mollugo verticillata 0–1 – bristly nama NAHI Nama hispidum 0–1 – desert tobacco NIOBO Nicotiana obtusifolia var. obtusifolia 0–1 – evening primrose OENOT Oenothera 0–1 – Florida pellitory PAFL3 Parietaria floridana 0–1 – combseed PECTO Pectocarya 0–1 – 8 11–34 wheelscale saltbush ATEL Atriplex elegans 11–34 – wheelscale saltbush ATELF Atriplex elegans var. fasciculata 11–34 – aridland goosefoot CHDE Chenopodium desiccatum 11–34 – boraxweed NIOC2 Nitrophila occidentalis 11–34 – Coulter's globemallow SPCO2 Sphaeralcea coulteri 11–34 – Shrub/Vine9 236–378 velvet mesquite PRVE Prosopis velutina 236–378 – 10 142–189 fourwing saltbush ATCA2 Atriplex canescens 142–189 – cattle saltbush ATPO Atriplex polycarpa 142–189 – water jacket LYAN Lycium andersonii 142–189 – 11 9–47 slender sandbur CEGR3 Cenchrus gracillimus 9–47 – buckhorn cholla CYACA2 Cylindropuntia acanthocarpa var. acanthocarpa 9–47 – Arizona pencil cholla CYAR14 Cylindropuntia arbuscula 9–47 – jumping cholla CYFUF Cylindropuntia fulgida var. fulgida 9–47 – Christmas cactus CYLE8 Cylindropuntia leptocaulis 9–47 – walkingstick cactus CYSP8 Cylindropuntia spinosior 9–47 – devil's cholla GRKU Grusonia kunzei 9–47 – common fishhook cactus MATE4 Mammillaria tetrancistra 9–47 – limestone adderstongue OPEN Ophioglossum engelmannii 9–47 – 12 9–47 whitethorn acacia ACCO2 Acacia constricta 9–47 – catclaw acacia ACGR Acacia greggii 9–47 – iodinebush ALOC2 Allenrolfea occidentalis 9–47 – Tucson bur ragweed AMCO4 Ambrosia cordifolia 9–47 – burrobush AMDU2 Ambrosia dumosa 9–47 – fourwing saltbush ATCAL2 Atriplex canescens var. laciniata 9–47 – desertbroom BASA2 Baccharis sarothroides 9–47 – crucifixion thorn CAEM4 Castela emoryi 9–47 – Palmer's cock's comb CEPA5 Celosia palmeri 9–47 – Drummond's clematis CLDR Clematis drummondii 9–47 – fringed twinevine FUCY Funastrum cynanchoides 9–47 – creosote bush LATRT Larrea tridentata var. tridentata 9–47 – Arizona desert-thorn LYEX Lycium exsertum 9–47 – Gila manroot MAGI Marah gilensis 9–47 – Jerusalem thorn PAAC3 Parkinsonia aculeata 9–47 – blue paloverde PAFL6 Parkinsonia florida 9–47 – chokecherry PRVI Prunus virginiana 9–47 – greasewood SAVE4 Sarcobatus vermiculatus 9–47 – Mojave seablite SUMO Suaeda moquinii 9–47 – soaptree yucca YUEL Yucca elata 9–47 – lotebush ZIOB Ziziphus obtusifolia 9–47 – 13 9–19 triangle bur ragweed AMDE4 Ambrosia deltoidea 9–19 – holywood GUSA Guaiacum sanctum 9–19 – alkali goldenbush ISACA2 Isocoma acradenia var. acradenia 9–19 – burroweed ISTE2 Isocoma tenuisecta 9–19 – Interpretations
Animal community
The plant community on this site is suitable for grazing by all classes of horses and cattle. Because of water availability in the rainy seasons, long green periods, shade, and easy accessibility, this site is often overused. Large areas should be fenced and managed separately from adjacent upland areas. Grazing during the summer flood season will result in trampling damage to grasses and reduce livestock performance due to heat, humidity and insect pests. The plant community provides adequte nutrition throughout the year. Salt desert shrub species provide digestable protein. Perennial grasses provide energy.
Free water is available during rainy seasons in natural charcos and discontinuous gullies. Forage diversity, shade and cover are very good and make this site home to a great veriety of wildlife, including large desert mammals. Water developments which prolong availability of free water are important to large wildlife. A moderate mesquite canopy makes the site home to a variety of tree-nesting bird species.Other information
T&E Species: Tumamoc Globe berry, perennial vine (Tumomoca Macdougalii)
Supporting information
Contributors
DGR
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) Emilio Carrillo, Dave Womack, Dan Robinett 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 present on the site, but are discontinuous due to low slopes. -
Presence of water flow patterns:
Water flow patterns are uncommon due to low slopes. -
Number and height of erosional pedestals or terracettes:
There are no pedestals or terracettes present. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
5-50%. 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 except in very high flows. -
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 inpact. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Weak thin platy to single grane; 7.5-10YR6/4 dry, 7.5-10YR3/4 Moist, entisol - no A horizon -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
15-25%. Herbaceous litter is present in some years, 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:
mesquite > other trees shrubs > alkai sacaton > winter annuals > summer annuals > other perennial grasses and forbs > succulents > cryptogamsSub-dominant:
Other:
Additional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
30-70% canopy mortality on trees and shrubs, 50-60% 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):
800 lbs/ac unfavorable precipitation, 1800 lbs/ac normal precipitation, 3000 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), London Rocket, Cheeseweed, salt cedar, mesquite, Bermuda grass, jimmyweed -
Perennial plant reproductive capability:
Not impaired for shrubs; drought impaired for perenial grasses and forbs.
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