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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.Ecological site concept
Limy Upland, deep, 7”-10” p.z., is found on gently sloping terrain; it is often intermingled with Desert Pavement and Sandy Loam Swale ecological sites. Soils are deep, skeletal, and calcareous throughout.
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Larrea tridentata
(2) Ambrosia dumosaHerbaceous Not specified
Physiographic features
This site occurs on fan terraces. Slopes are from 1 to 15%. Elevations range from 1000 to 2100 feet.
Table 2. Representative physiographic features
Landforms (1) Fan
(2) Terrace
Elevation 1000 – 2100 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 very gravelly alluvium of various ages and from mixed origins. They are calcareous and have over 35% gravels in the soil profile. Plant-soil moisture relationships are poor.
Soil series most characteristic of this ecological site is Gunsight; it is correlated to several other series including Momoli and Pinamt.
Figure 4. Gunsight
Table 4. Representative soil features
Surface texture (1) Very gravelly sandy loam
(2) Extremely gravelly fine sandy loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderately rapid to rapid Soil depth 60 in Surface fragment cover <=3" 10 – 60 % Surface fragment cover >3" 1 – 10 % Available water capacity
(0-40in)2.4 – 4.8 in Calcium carbonate equivalent
(0-40in)5 – 35 % Electrical conductivity
(0-40in)0 – 2 mmhos/cm Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)7.9 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)10 – 60 % Subsurface fragment volume >3"
(Depth not specified)1 – 10 % Ecological dynamics
Limy Upland, deep, 7”-10” p.z., is found on gently sloping terrain; it is often intermingled with Desert Pavement and Sandy Loam Swale ecological sites. Rainfall infiltration is low. Soil is moderately deep to deep and skeletal, lending to poor plant-soil relationships. The potential plant community is dominated by creosote with an understory of white bursage; other shrubs present are range ratany and ocotillo. A variety of succulents are scattered across this site. Annual forbs and grasses flourish under the canopy of shrubs after rainfall events. Percentage canopy cover (line-point intercept) ranges from 3% - 9%. Percentage ground cover (line-point intercept) is rock 29-85%, bare soil 11%-66%, litter 1%-7%, lichen crust
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
Desert ShrublandCommunity 1.1
Creosote-Bursage Community
Figure 5. Limy Upland, deep
The potential plant community is dominated by scattered creosotebush with a few other shrub and cacti species. Annual grasses and forbs make up a small percentage of the plant community. The aspect is shrubland.
Due to the unpalatable nature of creosotebush and associated shrubby species in the potential community, there is little change in species composition even with heavy grazing pressure. A few cool season, introduced annuals like; red brome, mediterranean grass and london rocket mustard occur on the site and may compete with native annual grasses and forbs. The surface of these soils usually have well developed covers of gravels and caliche fragments. Cryptogam cover us usually very low. Plant populations for creosotebush range from 300 to 800 plants per acre, from 20 to 100 plants per acre for the ratany group and from 10 to 100 plants per acre for cholla species.Figure 6. 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 200 – 225 Forb 13 – 25 Grass/Grasslike 5 – 25 Tree 0 – 1 Total 218 – 276 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Perennial Grasses 1–6 bush muhly MUPO2 Muhlenbergia porteri 0–2 – big galleta PLRI3 Pleuraphis rigida 0–2 – slim tridens TRMU Tridens muticus 0–1 – purple threeawn ARPU9 Aristida purpurea 0–1 – blue threeawn ARPUN Aristida purpurea var. nealleyi 0–1 – low woollygrass DAPU7 Dasyochloa pulchella 0–1 – nineawn pappusgrass ENDE Enneapogon desvauxii 0–1 – 2 Annual Grasses 0–4 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 – Eastwood fescue VUMIC Vulpia microstachys var. ciliata 0–1 – Pacific fescue VUMIP Vulpia microstachys var. pauciflora 0–1 – sixweeks fescue VUOC Vulpia octoflora 0–1 – Microbiotic Crusts3 Biotic Crusts 0–1 Alga 2ALGA Alga 0–1 – Fungus 2FUNGI Fungus 0–1 – Lichen 2LICHN Lichen 0–1 – Moss 2MOSS Moss 0–1 – Forb4 Annual and Perennial Forbs 0–12 desert Indianwheat PLOV Plantago ovata 0–5 – common fiddleneck AMMEI2 Amsinckia menziesii var. intermedia 0–5 – cryptantha CRYPT Cryptantha 0–3 – bristly fiddleneck AMTE3 Amsinckia tessellata 0–3 – combseed PECTO Pectocarya 0–3 – evening primrose OENOT Oenothera 0–3 – desert globemallow SPAM2 Sphaeralcea ambigua 0–3 – Coulter's globemallow SPCO2 Sphaeralcea coulteri 0–3 – western tansymustard DEPI Descurainia pinnata 1–2 – touristplant DIWI2 Dimorphocarpa wislizeni 1–2 – sleepy silene SIAN2 Silene antirrhina 1–2 – weakleaf bur ragweed AMCO3 Ambrosia confertiflora 0–2 – carelessweed AMPA Amaranthus palmeri 0–1 – hairy prairie clover DAMO Dalea mollis 0–1 – American wild carrot DAPU3 Daucus pusillus 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 – hyssopleaf sandmat CHHY3 Chamaesyce hyssopifolia 0–1 – devil's spineflower CHRI Chorizanthe rigida 0–1 – Esteve's pincushion CHST Chaenactis stevioides 0–1 – sand pygmyweed CRCO34 Crassula connata 0–1 – flatcrown buckwheat ERDE6 Eriogonum deflexum 0–1 – miniature woollystar ERDI2 Eriastrum diffusum 0–1 – fleabane ERIGE2 Erigeron 0–1 – buckwheat ERIOG Eriogonum 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 – California goldfields LACA7 Lasthenia californica 0–1 – Gordon's bladderpod LEGO Lesquerella gordonii 0–1 – shaggyfruit pepperweed LELA Lepidium lasiocarpum 0–1 – shrubby deervetch LORI3 Lotus rigidus 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 – woollyhead neststraw STMI2 Stylocline micropoides 0–1 – pricklyleaf dogweed THAC Thymophylla acerosa 0–1 – sand fringepod THCU Thysanocarpus curvipes 0–1 – woolly tidestromia TILA2 Tidestromia lanuginosa 0–1 – lineleaf whitepuff OLLI Oligomeris linifolia 0–1 – blazingstar MENTZ Mentzelia 0–1 – bristly nama NAHI Nama hispidum 0–1 – glandular threadplant NEGL Nemacladus glanduliferus 0–1 – manybristle chinchweed PEPA2 Pectis papposa 0–1 – phacelia PHACE Phacelia 0–1 – New Mexico plumeseed RANE Rafinesquia neomexicana 0–1 – chia SACO6 Salvia columbariae 0–1 – Shrub/Vine5 175–210 creosote bush LATR2 Larrea tridentata 175–210 – 6 12–50 triangle bur ragweed AMDE4 Ambrosia deltoidea 5–15 – burrobush AMDU2 Ambrosia dumosa 5–15 – white ratany KRGR Krameria grayi 5–15 – littleleaf ratany KRER Krameria erecta 0–10 – 7 0–2 whitethorn acacia ACCO2 Acacia constricta 0–1 – brittlebush ENFA Encelia farinosa 0–1 – ocotillo FOSP2 Fouquieria splendens 0–1 – crown of thorns KOSP Koeberlinia spinosa 0–1 – water jacket LYAN Lycium andersonii 0–1 – Arizona desert-thorn LYEX Lycium exsertum 0–1 – 8 2–5 Engelmann's hedgehog cactus ECEN Echinocereus engelmannii 0–1 – Leconte's barrel cactus FECYL Ferocactus cylindraceus var. lecontei 0–1 – candy barrelcactus FEWI Ferocactus wislizeni 0–1 – beavertail pricklypear OPBA2 Opuntia basilaris 0–1 – Tree9 0–1 desert ironwood OLTE Olneya tesota 0–1 – yellow paloverde PAMI5 Parkinsonia microphylla 0–1 – velvet mesquite PRVE Prosopis velutina 0–1 – Interpretations
Animal community
This site produces no herbaceous forage for year round use by livestock. Shrubby species on the site are not palatable. Even in wet winters the production of cool season annual species is low and provides for little additional carrying capacity.
Cover, forage and diversity are lacking for most desert mammals on this site. It is home mainly to a few small burrowing mammals, reptiles and their predators.Supporting information
Type locality
Location 1: Pima County, AZ Township/Range/Section T185S R6W S2 General legal description Tucson FO - Organ Pipe National Monument, LaAbra Plain Location 2: Pima County, AZ Township/Range/Section T11S R5E S20 General legal description Sells FO - Tat Momoli Wash Location 3: Maricopa County, AZ Township/Range/Section T3N R5E S34 General legal description Chandler FO - Salt River Res. Contributors
Dan Robinett
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:
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:
Accumulated pedestals on most perennial plants, not so much so in high gravel cover areas, 2-5 inches high. Erosional pedestals not present on most perennial plants. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
10-60% (low values in high gravel cover areas and/or El Nino years) -
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):
Woody litter mostly stays under plant canopy, herbaceous litter can travel long distances. -
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 impact5. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
single grain; color is 7.5-10YR6/4 dry, 7.5-10YR5/4 moist; Entisol - no A horizon -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Cover estimated as: canopy 20-25%, basal 1-2%; 50% canopy cover is shrubs, 20% trees and 30% succulents. 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 > forbs = perennial grasses (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. -
Average percent litter cover (%) and depth ( in):
-
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
150 lbs/ac unfavorable precipitation; 250 lbs/ac normal precipitation; 350 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, schismus, filaree -
Perennial plant reproductive capability:
Not impaired for shrubs, drought impaired for perennial grasses and forbs.
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