Natural Resources
Conservation Service
Ecological site R041XB206AZ
Limy Fan
8-12" p.z.
Last updated: 7/28/2020
Accessed: 08/16/2026
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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): 041X–Madrean Archipelago
AZ 41.2 – Chihuahuan – Sonoran Desert Shrubs
Elevations range from 2600 to 4000 feet and precipitation ranges from 8 to 12 inches per year. Vegetation includes mesquite, palo verde, catclaw acacia, soaptree yucca, creosotebush, whitethorn, staghorn cholla, desert saltbush, Mormon tea, burroweed, snakeweed, tobosa, black grama, threeawns, bush muhly, dropseed, and burrograss. The soil temperature regime is thermic 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.Associated sites
R041XB208AZ Limy Upland 8-12" p.z.
R041XB210AZ Loamy Upland 8-12" p.z.
R041XB213AZ Sandy Wash 8-12" p.z.
Similar sites
R040XA108AZ Limy Fan 10"-13" p.z.
R041XC320AZ Limy Fan 12-16" p.z.
Table 1. Dominant plant species
Tree Not specified
Shrub (1) larrea tridentata
Herbaceous (1) muhlenbergia porteri
Physiographic features
This site occurs in the lowest elevations of the Madrean Basin and Range province in southeastern Arizona. It occurs on fan terraces and alluvial fans.
Table 2. Representative physiographic features
Landforms (1) Fan piedmont
(2) Terrace
(3) Alluvial fan
Flooding frequency None Ponding frequency None Elevation 2600 – 4000 ft Slope 1 – 5 % Aspect Aspect is not a significant factor Climatic features
Precipitation ranges from 8-12 inches annually. More than half falls during July-Sep in brief, but often heavy, thunderstorms. The rest of the moisture comes as light rain or snow that falls slowly for a day or more, but rarely lasts more than a day. May and June are normally the driest months. Humidity is generally very low.
Temperatures are mild throughout most of the year. Freezing temperatures are common at night Dec-Feb; brief 0 F may be observed some nights. During June, July & August, some days may exceed 100 F.
In years of average or greater winter precipitation, annual grasses and forbs occur abundantly in the interspaces.Table 3 Representative climatic features
Frost-free period (average) 240 days Freeze-free period (average) Precipitation total (average) BarLineFigure 2. Monthly precipitation range
BarLineFigure 3. Monthly average minimum and maximum temperature
">Influencing water features
There are no water features associated with this site.
Soil features
These are deep, loamy soils; calcareous to the surface. Plant-soil moisture relationships are fair.
Soil series mapped to date on this site include: SSA-662 Safford area MU's CsB & GcB Gila, ThC Tres Hermanos; SSA-663 Gila-Duncan area MU's 9 Dona Ana, 29 43 & 45 Tres Hermanos; SSA-664 San Simon area MU's 14 & 15 Dona Ana, 40 Tres Hermanos; SSA-666 Cochise county Northwest part MU 1 Agustin & Kokan; SSA-671 Cochise county Douglas-Tombstone part MU's 36 Ugyp, 111 Ugyp, alluvial fans; SSA-675 San Carlos IR area MU's 1 Agustin, 5 Gila, 92 Agustin.Table 4. Representative soil features
Surface texture (1) Sandy loam
(2) Fine sandy loam
(3) Gravelly sandy loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderately rapid to moderate Soil depth 60 in Surface fragment cover <=3" 0 – 30 % Surface fragment cover >3" 0 – 2 % Available water capacity
(0-40in)5 – 7 in Calcium carbonate equivalent
(0-40in)5 – 30 % Electrical conductivity
(0-40in)0 – 2 mmhos/cm Sodium adsorption ratio
(0-40in)0 – 2 Soil reaction (1:1 water)
(0-40in)7.4 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)0 – 30 % Subsurface fragment volume >3"
(Depth not specified)0 – 2 % 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
Custom diagramStandard diagram
Figure 4. State and Transition Model, Limy Fan, 8"-12" p.z
More interactive model formats are also available. View Interactive Models
More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective textState 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 1
Historical Climax Plant CommunityCommunity 1.1
Historical Climax Plant Community
Figure 5. Limy Fan 8-12" pz
The potential plant community is a shrub-land dominated by creosotebush. Annual forbs and grasses are very important in the plant community on this site. Cryptogams (lichens, mosses) and blue-green algae are also important in the plant communities on this site.
With continuous heavy grazing, bush muhly is removed from the plant community and creosotebush increases. Areas of this site mapped in alluvial fan positions are very susceptible to rill and gully erosion.
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 70 150 250 Grass/Grasslike 10 30 170 Forb 1 20 110 Total 81 200 530 Table 6. Soil surface cover
Tree basal cover 0% Shrub/vine/liana basal cover 0% Grass/grasslike basal cover 0-0% Forb basal cover 0-0% Non-vascular plants 0% Biological crusts 10-20% Litter 10-60% Surface fragments >0.25" and <=3" 0-20% Surface fragments >3" 0-10% Bedrock 0% Water 0% Bare ground 20-90% Table 7. Canopy structure (% cover)
Height Above Ground (ft) Tree Shrub/Vine Grass/
GrasslikeForb <0.5 – 0-1% 0-20% 0-20% >0.5 <= 1 – 0-1% 0-20% 0-10% >1 <= 2 – 1-5% – 0-5% >2 <= 4.5 – 5-10% – – >4.5 <= 13 – – – – >13 <= 40 – – – – >40 <= 80 – – – – >80 <= 120 – – – – >120 – – – – State 2
AnnualsCommunity 2.1
AnnualsThis state occurs where the plant community is dominated by native and non-native annual forbs and grasses. The causes can include repeated burning, which removes the native shrub cover (creosote), and cultivation for irrigation and subsequent abandonment.
State 3
Shrubs, exotic annualsCommunity 3.1
Shrubs, exotic annualsThis state occurs where the creosote cover is still intact but the herbaceous layer of the plant community is dominated by non-native annuals. These can include, filaree, mediterranean grass, Sahara mustard, malta starthistle and red brome.
Transition T1A
State 1 to 2Usually results from clearing for irrigated agriculture and subsequent abandonment. Seed source for native shrubs is no longer present.
Transition T1B
State 1 to 3Introduction of a seed source of non-natives. Possible competition of exotics with native species of forbs or grasses.
Restoration pathway R2A
State 2 to 1Unknown. Possible seeding of creosote bush and white-thorn acacia with weed control.
Restoration pathway R3A
State 3 to 1Unknown
Additional community tables
Table 8. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Dominant perennial grasses 10–60 bush muhly MUPO2 Muhlenbergia porteri 10–40 – whiplash pappusgrass PAVA2 Pappophorum vaginatum 0–40 – false Rhodes grass TRCR9 Trichloris crinita 0–20 – Parish's threeawn ARPUP5 Aristida purpurea var. parishii 0–20 – spike dropseed SPCO4 Sporobolus contractus 0–10 – 2 Misc. perennial grasses 0–10 purple threeawn ARPU9 Aristida purpurea 0–10 – spidergrass ARTE3 Aristida ternipes 0–10 – tobosagrass PLMU3 Pleuraphis mutica 0–10 – spidergrass ARTEG Aristida ternipes var. gentilis 0–5 – low woollygrass DAPU7 Dasyochloa pulchella 0–2 – sand dropseed SPCR Sporobolus cryptandrus 0–2 – mesa dropseed SPFL2 Sporobolus flexuosus 0–2 – poverty threeawn ARDI5 Aristida divaricata 0–2 – Havard's threeawn ARHA3 Aristida havardii 0–2 – Arizona cottontop DICA8 Digitaria californica 0–1 – nineawn pappusgrass ENDE Enneapogon desvauxii 0–1 – plains bristlegrass SEVU2 Setaria vulpiseta 0–1 – 3 Annual grasses 0–100 needle grama BOAR Bouteloua aristidoides 0–50 – sixweeks grama BOBA2 Bouteloua barbata 0–50 – Rothrock's grama BORO2 Bouteloua rothrockii 0–20 – desert lovegrass ERPEM Eragrostis pectinacea var. miserrima 0–20 – tufted lovegrass ERPEP2 Eragrostis pectinacea var. pectinacea 0–20 – Arizona signalgrass URAR Urochloa arizonica 0–20 – sixweeks fescue VUOC Vulpia octoflora 0–20 – sixweeks threeawn ARAD Aristida adscensionis 0–20 – prairie threeawn AROL Aristida oligantha 0–20 – mucronate sprangeltop LEPAB Leptochloa panicea ssp. brachiata 0–20 – Bigelow's bluegrass POBI Poa bigelovii 0–10 – Mexican sprangletop LEFUU Leptochloa fusca ssp. uninervia 0–10 – Arizona brome BRAR4 Bromus arizonicus 0–5 – canyon cupgrass ERLE7 Eriochloa lemmonii 0–5 – delicate muhly MUFR Muhlenbergia fragilis 0–2 – littleseed muhly MUMI Muhlenbergia microsperma 0–2 – Forb4 Perennial forbs 1–10 dwarf desertpeony ACNA2 Acourtia nana 0–10 – trailing windmills ALIN Allionia incarnata 0–5 – lacy tansyaster MAPIP4 Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida 0–5 – desert globemallow SPAM2 Sphaeralcea ambigua 0–5 – weakleaf bur ragweed AMCO3 Ambrosia confertiflora 0–2 – hairyseed bahia BAAB Bahia absinthifolia 0–1 – desert marigold BAMU Baileya multiradiata 0–1 – whitemargin sandmat CHAL11 Chamaesyce albomarginata 0–1 – Coues' cassia SECO10 Senna covesii 0–1 – 5 Annual forbs 0–100 bristly fiddleneck AMTE3 Amsinckia tessellata 0–25 – Coulter's spiderling BOCO2 Boerhavia coulteri 0–20 – Esteve's pincushion CHST Chaenactis stevioides 0–20 – flatcrown buckwheat ERDE6 Eriogonum deflexum 0–20 – California poppy ESCAM Eschscholzia californica ssp. mexicana 0–20 – Gordon's bladderpod LEGO Lesquerella gordonii 0–20 – tanseyleaf tansyaster MATA2 Machaeranthera tanacetifolia 0–20 – combseed PECTO Pectocarya 0–20 – woolly tidestromia TILA2 Tidestromia lanuginosa 0–20 – wheelscale saltbush ATEL Atriplex elegans 0–15 – milkvetch ASTRA Astragalus 0–10 – carelessweed AMPA Amaranthus palmeri 0–10 – manybristle chinchweed PEPA2 Pectis papposa 0–10 – desert Indianwheat PLOV Plantago ovata 0–10 – shaggyfruit pepperweed LELA Lepidium lasiocarpum 0–10 – miniature woollystar ERDI2 Eriastrum diffusum 0–10 – cryptantha CRYPT Cryptantha 0–10 – American wild carrot DAPU3 Daucus pusillus 0–10 – western tansymustard DEPI Descurainia pinnata 0–10 – Coulter's globemallow SPCO2 Sphaeralcea coulteri 0–10 – intermediate pepperweed LEVIM Lepidium virginicum var. medium 0–5 – coastal bird's-foot trefoil LOSAB Lotus salsuginosus var. brevivexillus 0–5 – New Mexico plumeseed RANE Rafinesquia neomexicana 0–5 – sleepy silene SIAN2 Silene antirrhina 0–5 – phacelia PHACE Phacelia 0–5 – Arizona popcornflower PLAR Plagiobothrys arizonicus 0–5 – Nuttall's povertyweed MONU Monolepis nuttalliana 0–5 – slender goldenweed MAGR10 Machaeranthera gracilis 0–5 – exserted Indian paintbrush CAEXE Castilleja exserta ssp. exserta 0–5 – yellow tackstem CAPA7 Calycoseris parryi 0–5 – white tackstem CAWR Calycoseris wrightii 0–5 – brittle spineflower CHBR Chorizanthe brevicornu 0–2 – hyssopleaf sandmat CHHY3 Chamaesyce hyssopifolia 0–2 – fringed redmaids CACI2 Calandrinia ciliata 0–2 – desert evening primrose OEPR Oenothera primiveris 0–2 – Florida pellitory PAFL3 Parietaria floridana 0–2 – green carpetweed MOVE Mollugo verticillata 0–2 – Coulter's lupine LUSP2 Lupinus sparsiflorus 0–2 – hairy desertsunflower GECA2 Geraea canescens 0–2 – star gilia GIST Gilia stellata 0–2 – Arizona poppy KAGR Kallstroemia grandiflora 0–2 – hairy prairie clover DAMO Dalea mollis 0–2 – sorrel buckwheat ERPO4 Eriogonum polycladon 0–2 – Texas stork's bill ERTE13 Erodium texanum 0–2 – woollyhead neststraw STMI2 Stylocline micropoides 0–2 – common woolly sunflower ERLA6 Eriophyllum lanatum 0–1 – Mexican fireplant EUHE4 Euphorbia heterophylla 0–1 – bristly nama NAHI Nama hispidum 0–1 – glandular threadplant NEGL Nemacladus glanduliferus 0–1 – doubleclaw PRPA2 Proboscidea parviflora 0–1 – hoary bowlesia BOIN3 Bowlesia incana 0–1 – Shrub/Vine6 Dominant shrub 70–200 creosote bush LATRT Larrea tridentata var. tridentata 70–200 – 7 Miscellaneous shrubs 0–15 whitethorn acacia ACCO2 Acacia constricta 0–10 – cattle saltbush ATPO Atriplex polycarpa 0–10 – longleaf jointfir EPTR Ephedra trifurca 0–5 – burrobush AMDU2 Ambrosia dumosa 0–2 – fourwing saltbush ATCA2 Atriplex canescens 0–2 – mound saltbush ATOB Atriplex obovata 0–2 – burroweed ISTE2 Isocoma tenuisecta 0–1 – water jacket LYAN Lycium andersonii 0–1 – pale desert-thorn LYPA Lycium pallidum 0–1 – western honey mesquite PRGLT Prosopis glandulosa var. torreyana 0–1 – soaptree yucca YUEL Yucca elata 0–1 – lotebush ZIOB Ziziphus obtusifolia 0–1 – 8 Half shrubs 0–20 threadleaf snakeweed GUMI Gutierrezia microcephala 0–10 – broom snakeweed GUSA2 Gutierrezia sarothrae 0–10 – whitestem paperflower PSCO2 Psilostrophe cooperi 0–10 – desert zinnia ZIAC Zinnia acerosa 0–10 – littleleaf ratany KRER Krameria erecta 0–5 – rayless goldenhead ACSP Acamptopappus sphaerocephalus 0–2 – 9 Succulents 0–15 devil's cholla GRKU Grusonia kunzei 0–3 – Christmas cactus CYLE8 Cylindropuntia leptocaulis 0–2 – tulip pricklypear OPPH Opuntia phaeacantha 0–2 – nightblooming cereus PEGR3 Peniocereus greggii 0–1 – walkingstick cactus CYSP8 Cylindropuntia spinosior 0–1 – Engelmann's hedgehog cactus ECEN Echinocereus engelmannii 0–1 – candy barrelcactus FEWI Ferocactus wislizeni 0–1 – cactus apple OPEN3 Opuntia engelmannii 0–1 – buck-horn cholla CYAC8 Cylindropuntia acanthocarpa 0–1 – Table 9. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 10. Community 3.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
This site is more suitable for seasonal rather than year-long use as most of the forage produced consists of either winter or summer annual grasses and forbs in average or above average years. Perennial forage species can grow year round with available moisture but are in limited amounts in the plant community. Forage production on the site in dry years is very low. Bush muhly is shrub-like in character and plants supported by creosotebush should be utilized as browse plants.
Vegetative cover and forage diversity are lacking for large desert mammals on this site. It is home mainly to small, burrowing animals and rabbits.Hydrological functions
These soils are medium textured and usually poor producers of runoff.
Recreational uses
Hunting, horseback riding, hiking, four wheeling.
Supporting information
Contributors
Dan Robinett
Larry D. EllicottApproval
Scott Woodall, 7/28/2020
Rangeland 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) Wilma Renken, Dan Robinett, Larry Humphrey, Gwen Dominguez, Emilio Carrillo Contact for lead author Tucson MLRA Soil Survey Office Date 08/08/2013 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
None -
Presence of water flow patterns:
Water flow paths occupy less than 30-40% of the surface area. Flow paths are poorly defined and dominated by limited sheet flow among the hummocks among creosote. -
Number and height of erosional pedestals or terracettes:
Pedestals are common on all longer lived grasses (bush muhly) and subshrubs (zinnia) and are from 1-2 inches in height. Pedestals on creosote bush are from 4-8 inches tall and symmetrical. They are well stabilized and most have rodent activity. Terracettes are uncommon on the site but when they occur they are large (approx. 3-5’ diam x 4-8” ht) and bridged by the mounds of creosote bush. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare soil is 50-70%, gravel ranges from 7-10% and basal cover of live perennial grasses is 1%. Bare areas are 4-8 feet in diameter, well dispersed and generally connected. -
Number of gullies and erosion associated with gullies:
None -
Extent of wind scoured, blowouts and/or depositional areas:
Possible wind capture of dust around the bases of creosote bush. No wind scour. Deposition under creosote bush has symmetrical mounds. -
Amount of litter movement (describe size and distance expected to travel):
Fine and coarse litter size classes are moving short distances (1-2 feet) from water in open spaces and concentrating in dams. Under large shrubs, all litter classes are staying in place. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Values from soil slake test ratings were 2-4s under canopy and 1-2’s from open spaces. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Shrub canopy cover is 25-30%, annual forb and grass canopy is <15%, and perennial grass canopy is <5%. Perennial grasses are largely confined within creosote bush mounds. Shrubs are evenly distributed. Shrub canopy cover and soil texture (sandyloam) allow infiltration and limit run-off. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
None present, average depth of penetration from an ARS field penetrometer with a 2.2 kg. sliding hammer is 12.8 cm. -
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 shrubsSub-dominant:
annual grass= annual forbs> perennial grasses = sub shrubs >> succulentsOther:
Additional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Plant mortality is affected by recent droughty weather patterns; 10% mortality on perennial grasses and 30% on sub-shrubs. Some creosote canopy died back. Large crown-of-thorn shrubs have about 20% mortality. -
Average percent litter cover (%) and depth ( in):
Litter is absent from water flow patterns and bare areas. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
80 lbs/ac. in a below average year; 200 lbs/ac. in an average year; 530 lbs/ac. in an above average year. -
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:
Tumbleweed, Lehmann lovegrass in wet years -
Perennial plant reproductive capability:
Not impaired for any perennial species.
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