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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
Shrub (1) Ambrosia deltoidea
(2) Encelia farinosaHerbaceous (1) Muhlenbergia porteri
(2) Tridens muticusPhysiographic features
This site occurs on hillslopes and ridgetops. Slopes range from 15 to 65%. Elevations are from 1000 to 2500 feet. Slope aspect is site differentiating at elevations near land resource area boundaries.
Table 2. Representative physiographic features
Landforms (1) Hill
(2) Ridge
Elevation 1000 – 2500 ft Slope 15 – 65 % 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 formed on acid igneous materials; granite and rhyolite, or on quartzite, arkose, shist, and gneiss. Parent material includes schist & gneiss. Bedrock is usually slightly weathered into grus material at the soil juncture. They are non-calcareous, coarse textured and have well developed covers of gravels and cobbles. Bedrock usually has some lime in the fractures. Large areas of rock outcrop and boulders occur intermingled with soil areas. Outcrops can be as high as 25% of the area. Plant-soil moisture relationships are fair.
Soils mapped on this site include: in
SSA-645 Aguila-Carefree area MU's Quilotosa & Vaiva-100;
SSA-653 Gila Bend-Ajo area MU Quilotosa-54;
SSA-658 Gila River Indian Reservation MU's Quilotosa & Vaiva-27;
SSA-703 Tohono O'odham area MU's Chiuchu-12, Gachado non STV phase & Lomitas non calcareous-23, Quilotosa & Vaiva-51.Table 4. Representative soil features
Surface texture (1) Gravelly sandy loam
(2) Very gravelly loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderately slow to moderately rapid Soil depth 4 – 20 in Surface fragment cover <=3" 35 – 65 % Surface fragment cover >3" 1 – 10 % Available water capacity
(0-40in)0.2 – 1.6 in Calcium carbonate equivalent
(0-40in)1 – 10 % 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)35 – 65 % Subsurface fragment volume >3"
(Depth not specified)1 – 10 % 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 is a diverse mixture of desert trees, shrubs, and cacti. The aspect is shrubland.
Continuous, heavy grazing removes the small percentage of perennial grasses and forbs from the plant community. Cobble and gravel covers are continuous and average over 90%. Basal cover of perennial plants average 1% and bare ground averages 7%. Cryptogam cover is lacking or very low due to extensive gravel covers. Plant populations of major species range from 500 to 1500 plants per acre for triangle bursage; 50 to 150 trees per acre for paloverde and ironwood and 1 to 50 plants per acre for saguaro. In the northern part of this land resource sub-area, introduced cool season annual grasses; red brome and schismus have invaded native plant communities and have reduced production of the native shrubs significantly, especially on cooler, northern exposures. Club moss and ferns occur only in trace amounts on the northern aspects. Teddy bear cholla predominates on south aspects and buckhorn cholla and prickley pear on the north aspects.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 350 – 450 Forb 25 – 100 Grass/Grasslike 25 – 75 Total 400 – 625 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 10–25 bush muhly MUPO2 Muhlenbergia porteri 0–5 – Parish's threeawn ARPUP5 Aristida purpurea var. parishii 0–3 – purple threeawn ARPU9 Aristida purpurea 0–3 – big galleta PLRI3 Pleuraphis rigida 0–2 – slim tridens TRMU Tridens muticus 0–2 – blue threeawn ARPUN Aristida purpurea var. nealleyi 0–2 – Wright's threeawn ARPUW Aristida purpurea var. wrightii 0–1 – spidergrass ARTE3 Aristida ternipes 0–1 – spidergrass ARTEG Aristida ternipes var. gentilis 0–1 – low woollygrass DAPU7 Dasyochloa pulchella 0–1 – Arizona cottontop DICA8 Digitaria californica 0–1 – nineawn pappusgrass ENDE Enneapogon desvauxii 0–1 – tanglehead HECO10 Heteropogon contortus 0–1 – Fendler's threeawn ARPUF Aristida purpurea var. fendleriana 0–1 – 2 Annuals 5–50 sixweeks fescue VUOC Vulpia octoflora 0–10 – Eastwood fescue VUMIC Vulpia microstachys var. ciliata 0–5 – Pacific fescue VUMIP Vulpia microstachys var. pauciflora 0–5 – 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 – 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 – witchgrass PACA6 Panicum capillare 0–1 – Bigelow's bluegrass POBI Poa bigelovii 0–1 – Forb3 10–25 desert globemallow SPAM2 Sphaeralcea ambigua 0–5 – brownplume wirelettuce STPA4 Stephanomeria pauciflora 0–3 – desert trumpet ERIN4 Eriogonum inflatum 0–3 – narrowleaf silverbush ARLA12 Argythamnia lanceolata 0–3 – slender poreleaf POGR5 Porophyllum gracile 0–3 – slender janusia JAGR Janusia gracilis 0–2 – lacy tansyaster MAPIP4 Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida 0–1 – rough menodora MESC Menodora scabra 0–1 – New Mexico silverbush ARNE2 Argythamnia neomexicana 0–1 – whitemargin sandmat CHAL11 Chamaesyce albomarginata 0–1 – California fagonbush FALA Fagonia laevis 0–1 – desert rosemallow HICO Hibiscus coulteri 0–1 – Newberry's velvetmallow HONE Horsfordia newberryi 0–1 – poreleaf dogweed ADPO2 Adenophyllum porophyllum 0–1 – 4 5–75 desert Indianwheat PLOV Plantago ovata 0–10 – combseed PECTO Pectocarya 0–5 – common fiddleneck AMMEI2 Amsinckia menziesii var. intermedia 0–5 – green carpetweed MOVE Mollugo verticillata 0–3 – globemallow SPHAE Sphaeralcea 0–3 – woolly tidestromia TILA2 Tidestromia lanuginosa 0–1 – bristly nama NAHI Nama hispidum 0–1 – glandular threadplant NEGL Nemacladus glanduliferus 0–1 – desert tobacco NIOB Nicotiana obtusifolia 0–1 – cloak fern NOTHO Notholaena 0–1 – evening primrose OENOT Oenothera 0–1 – Florida pellitory PAFL3 Parietaria floridana 0–1 – Emory's rockdaisy PEEM Perityle emoryi 0–1 – cliffbrake PELLA Pellaea 0–1 – manybristle chinchweed PEPA2 Pectis papposa 0–1 – phacelia PHACE Phacelia 0–1 – brownfoot ACWR5 Acourtia wrightii 0–1 – trailing windmills ALIN Allionia incarnata 0–1 – New Mexico plumeseed RANE Rafinesquia neomexicana 0–1 – chia SACO6 Salvia columbariae 0–1 – Arizona spikemoss SEAR2 Selaginella arizonica 0–1 – Coues' cassia SECO10 Senna covesii 0–1 – ragwort SENEC Senecio 0–1 – sleepy silene SIAN2 Silene antirrhina 0–1 – Coulter's globemallow SPCO2 Sphaeralcea coulteri 0–1 – carelessweed AMPA Amaranthus palmeri 0–1 – rockcress ARABI2 Arabis 0–1 – milkvetch ASTRA Astragalus 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 – brittle spineflower CHBR Chorizanthe brevicornu 0–1 – lipfern CHEIL Cheilanthes 0–1 – hyssopleaf sandmat CHHY3 Chamaesyce hyssopifolia 0–1 – New Mexico thistle CINE Cirsium neomexicanum 0–1 – cryptantha CRYPT Cryptantha 0–1 – bigseed alfalfa dodder CUIN Cuscuta indecora 0–1 – American wild carrot DAPU3 Daucus pusillus 0–1 – desert larkspur DEPA Delphinium parishii 0–1 – western tansymustard DEPI Descurainia pinnata 0–1 – tall mountain larkspur DESC Delphinium scaposum 0–1 – bluedicks DICA14 Dichelostemma capitatum 0–1 – flatcrown buckwheat ERDE6 Eriogonum deflexum 0–1 – miniature woollystar ERDI2 Eriastrum diffusum 0–1 – erigenia ERIGE Erigenia 0–1 – buckwheat ERIOG Eriogonum 0–1 – common woolly sunflower ERLA6 Eriophyllum lanatum 0–1 – California poppy ESCAM Eschscholzia californica ssp. mexicana 0–1 – desert poppy ESGL Eschscholzia glyptosperma 0–1 – pygmy poppy ESMI Eschscholzia minutiflora 0–1 – gilia GILIA Gilia 0–1 – Gordon's bladderpod LEGO Lesquerella gordonii 0–1 – shaggyfruit pepperweed LELA Lepidium lasiocarpum 0–1 – Bigelow's linanthus LIBI2 Linanthus bigelovii 0–1 – shrubby deervetch LORI3 Lotus rigidus 0–1 – coastal bird's-foot trefoil LOSA Lotus salsuginosus 0–1 – Coulter's lupine LUSP2 Lupinus sparsiflorus 0–1 – tansyaster MACHA Machaeranthera 0–1 – Parry's false prairie-clover MAPA7 Marina parryi 0–1 – blazingstar MENTZ Mentzelia 0–1 – Shrub/Vine5 25–75 6 5–25 organpipe cactus STTH3 Stenocereus thurberi 0–5 – beavertail pricklypear OPBA2 Opuntia basilaris 0–2 – Leconte's barrel cactus FECYL Ferocactus cylindraceus var. lecontei 0–2 – candy barrelcactus FEWI Ferocactus wislizeni 0–2 – Engelmann's hedgehog cactus ECEN Echinocereus engelmannii 0–1 – senita cactus PASC14 Pachycereus schottii 0–1 – 7 125–175 triangle bur ragweed AMDE4 Ambrosia deltoidea 75–125 – brittlebush ENFA Encelia farinosa 25–50 – 8 50–75 Mexican bladdersage SAME Salazaria mexicana 0–10 – Parish's goldeneye VIPA14 Viguiera parishii 0–5 – white ratany KRGR Krameria grayi 0–5 – rush milkweed ASSU Asclepias subulata 0–5 – elephant tree BUMI Bursera microphylla 0–5 – fairyduster CAER Calliandra eriophylla 0–3 – starry bedstraw GASTE2 Galium stellatum ssp. eremicum 0–3 – sangre de cristo JACA2 Jatropha cardiophylla 0–3 – littleleaf ratany KRER Krameria erecta 0–2 – creosote bush LATR2 Larrea tridentata 0–2 – singlewhorl burrobrush HYMO Hymenoclea monogyra 0–2 – Sonoran croton CRSO Croton sonorae 0–2 – Nevada jointfir EPNE Ephedra nevadensis 0–2 – Eastern Mojave buckwheat ERFA2 Eriogonum fasciculatum 0–2 – bastardsage ERWR Eriogonum wrightii 0–2 – sweetbush BEJU Bebbia juncea 0–2 – Coulter's brickellbush BRCO Brickellia coulteri 0–2 – Wright's beebrush ALWR Aloysia wrightii 0–2 – burrobush AMDU2 Ambrosia dumosa 0–2 – California copperleaf ACCA3 Acalypha californica 0–2 – catclaw acacia ACGR Acacia greggii 0–1 – arrow poision plant SEBI9 Sebastiania bilocularis 0–1 – American threefold TRCA8 Trixis californica 0–1 – water jacket LYAN Lycium andersonii 0–1 – Fremont's desert-thorn LYFR Lycium fremontii 0–1 – desert lavender HYEM Hyptis emoryi 0–1 – 9 75–150 ocotillo FOSP2 Fouquieria splendens 60–120 – desert ironwood OLTE Olneya tesota 60–120 – yellow paloverde PAMI5 Parkinsonia microphylla 60–120 – yellow paloverde PAMI5 Parkinsonia microphylla 30–50 – ocotillo FOSP2 Fouquieria splendens 20–40 – saguaro CAGI10 Carnegiea gigantea 10–30 – desert ironwood OLTE Olneya tesota 0–20 – Interpretations
Animal community
Steep slopes and very cobbly to stony surfaces hinder livestock distribution. Stocker cattle are best adapted to use this site. The plant community provides limited amounts of useable forage in the winter-spring season. Natural water is unavailable on this site.
Water developments are very important to wildlife species on this site. Cover, diversity, and topography make areas of this site home to a variety of desert animals. Large mammals use the site seasonally unless permanent water supplies exist in the area. Desert tortoises den on cobble or stony slopes. Javalina bed on north aspects in paloverde thickets.Other information
T&E: Leptonycteris cursoae yerbe buena
(Lesser long-nosed bat)Supporting information
Type locality
Location 1: Maricopa County, AZ Township/Range/Section T3S R2E S33 General legal description Chandler FO - Gila River Indian Community, Sierra Estrella Mountains Location 2: Pima County, AZ Township/Range/Section T9S R4E S11 General legal description Sells FO - Tat Momolikat Mountains Location 3: Maricopa County, AZ Township/Range/Section T6S R1W S16 General legal description Buckeye FO - Maricopa Mountains, Ryff Ranch Location 4: Pinal County, AZ Township/Range/Section T7S R2E S5 General legal description Casa Grande FO - Ak Ranch, Antelope Peak Location 5: Maricopa County, AZ Township/Range/Section T4N R6W S32 General legal description Phoenix FO - Belmont Mountains Location 6: Pima County, AZ Township/Range/Section T17S R1E S26 General legal description Sells FO - Pisinemo District Kupk Hills 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, Emilio Carrillo 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
-
Number and extent of rills:
Follow faults and bedding planes in parent materials. -
Presence of water flow patterns:
Discontinuous, 10-15 feet in length. Will see shorter flow paths with high surface coarse fragments. -
Number and height of erosional pedestals or terracettes:
No accumulated or erosional pedestals. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
1-15% (low values due to high rock and gravel cover) -
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 rock and gravel cover. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
No slake test done. Expect ratings of 1-3 in perennial plant interspaces, 4-5 under shrub canopies. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
weak granular; color is 7.5-10YR6/3 dry, 7.5-1-YR5/4 moist, thickness to 2 inches. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
canopy 15-20%; 50% shrubs, 23% trees, 25% succulents and 1-2% perennial grasses. 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 > annual forbs and grasses > perennial forbs > perennial grasses.Sub-dominant:
Other:
Additional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
20-50% tree & shrub canopy mortality, 75-90% perennial grass mortality. -
Average percent litter cover (%) and depth ( in):
-
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
300 lbs/ac unfavorable precipitation, 500 lbs/ac normal precipitation, 800 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, London Rocket -
Perennial plant reproductive capability:
Not impaired for shrubs, drought impaired for perennial grasses and forbs.
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