Natural Resources
Conservation Service
Ecological site R040XB224AZ
Sandy Upland, Saline 7"-10" p.z.
Accessed: 11/21/2024
General information
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.
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) Atriplex polycarpa |
| Herbaceous |
(1) Sporobolus contractus |
Physiographic features
This site occurs on nearly level to moderately steep dunes.
Table 2. Representative physiographic features
| Landforms |
(1)
Dune
|
|---|---|
| Elevation | 1,000 – 2,000 ft |
| Slope | 1 – 30% |
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 |
Figure 2. Monthly precipitation range
Figure 3. Monthly average minimum and maximum temperature
Influencing water features
Soil features
These are deep, somewhat excessively drained, saline sandy soils. Parent material kind may include stream alluvium. The plant-soil moisture relationships are good. These soils have high infiltration rates, but the sodic conditions somewhat limit the availability of water for plant growth.
Soils mapped on this site include: SSA-658 Gila River Indian Reservation MU's Rositas (sodic)-30 & 31 and SSA-703 Tohono O'odham area MU Rositas (sodic)-9.
Table 4. Representative soil features
| Surface texture |
(1) Sand (2) Loamy sand |
|---|---|
| Family particle size |
(1) Sandy |
| Drainage class | Excessively drained to somewhat excessively drained |
| Permeability class | Rapid to very rapid |
| Soil depth | 60 in |
| Surface fragment cover <=3" | Not specified |
| Surface fragment cover >3" | Not specified |
| Available water capacity (0-40in) |
3.6 – 6 in |
| Calcium carbonate equivalent (0-40in) |
1 – 5% |
| Electrical conductivity (0-40in) |
16 mmhos/cm |
| Sodium adsorption ratio (0-40in) |
13 |
| Soil reaction (1:1 water) (0-40in) |
8.5 – 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 grazing, fire, 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 shown for the group. Divide the resulting total by the total normal year production shown in the plant community description. If 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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Ecosystem states
State 1 submodel, plant communities
State 1
Historic Climax Plant Community
Community 1.1
Historic Climax Plant Community
The native plant community on this site is a mixture of perennial and annual grasses and forbs and salt desert shrubs. Winter and summer annual forbs are very well represented on thesite. With severe disturbance, such as heavy continuous grazing, species like big galleta, fourwing saltbush and desert saltbush are replaced by greasewood, mesquite and annuals. Loss of shrub and grass cover on this site can result in severely accelerated wind erosion. The Atriplex species are very sensitive to summer fires on this site.
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) |
|---|---|---|---|
| Grass/Grasslike | 180 | 225 | 270 |
| Shrub/Vine | 80 | 225 | 270 |
| Forb | 60 | 80 | 120 |
| Total | 320 | 530 | 660 |
Additional community tables
Table 6. Community 1.1 plant community composition
| Group | Common name | Symbol | Scientific name | Annual production (lb/acre) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Grass/Grasslike
|
||||||
| 1 | 150–210 | |||||
| big galleta | PLRI3 | Pleuraphis rigida | 56–79 | – | ||
| spike dropseed | SPCO4 | Sporobolus contractus | 56–79 | – | ||
| 2 | 30–60 | |||||
| California threeawn | ARCA9 | Aristida californica | 11–23 | – | ||
| Santa Rita threeawn | ARCAG | Aristida californica var. glabrata | 11–23 | – | ||
| sand dropseed | SPCR | Sporobolus cryptandrus | 11–23 | – | ||
| mesa dropseed | SPFL2 | Sporobolus flexuosus | 11–23 | – | ||
| 3 | 5–90 | |||||
| sixweeks threeawn | ARAD | Aristida adscensionis | 2–39 | – | ||
| prairie threeawn | AROL | Aristida oligantha | 2–39 | – | ||
| needle grama | BOAR | Bouteloua aristidoides | 2–39 | – | ||
| sixweeks grama | BOBA2 | Bouteloua barbata | 2–39 | – | ||
| Rothrock's grama | BORO2 | Bouteloua rothrockii | 2–39 | – | ||
| Arizona brome | BRAR4 | Bromus arizonicus | 2–39 | – | ||
| feather fingergrass | CHVI4 | Chloris virgata | 2–39 | – | ||
| tufted lovegrass | ERPEP2 | Eragrostis pectinacea var. pectinacea | 2–39 | – | ||
| little barley | HOPU | Hordeum pusillum | 2–39 | – | ||
| Mexican sprangletop | LEFUU | Leptochloa fusca ssp. uninervia | 2–39 | – | ||
| mucronate sprangeltop | LEPAB | Leptochloa panicea ssp. brachiata | 2–39 | – | ||
| littleseed muhly | MUMI | Muhlenbergia microsperma | 2–39 | – | ||
| witchgrass | PACA6 | Panicum capillare | 2–39 | – | ||
| Bigelow's bluegrass | POBI | Poa bigelovii | 2–39 | – | ||
| sixweeks fescue | VUOC | Vulpia octoflora | 2–39 | – | ||
|
Forb
|
||||||
| 4 | 5–30 | |||||
| desert sand verbena | ABVI | Abronia villosa | 1–4 | – | ||
| goldenhead | ACAMP | Acamptopappus | 1–4 | – | ||
| desert marigold | BAMU | Baileya multiradiata | 1–4 | – | ||
| whitemargin sandmat | CHAL11 | Chamaesyce albomarginata | 1–4 | – | ||
| desert lily | HEUN2 | Hesperocallis undulata | 1–4 | – | ||
| birdcage evening primrose | OEDE2 | Oenothera deltoides | 1–4 | – | ||
| canaigre dock | RUHY | Rumex hymenosepalus | 1–4 | – | ||
| smooth threadleaf ragwort | SEFLM | Senecio flaccidus var. monoensis | 1–4 | – | ||
| 5 | 30–60 | |||||
| desert Indianwheat | PLOV | Plantago ovata | 0–5 | – | ||
| desert unicorn-plant | PRAL4 | Proboscidea althaeifolia | 0–1 | – | ||
| New Mexico plumeseed | RANE | Rafinesquia neomexicana | 0–1 | – | ||
| desert globemallow | SPAM2 | Sphaeralcea ambigua | 0–1 | – | ||
| Coulter's globemallow | SPCO2 | Sphaeralcea coulteri | 0–1 | – | ||
| small wirelettuce | STEX | Stephanomeria exigua | 0–1 | – | ||
| longbeak streptanthella | STLO4 | Streptanthella longirostris | 0–1 | – | ||
| woolly tidestromia | TILA2 | Tidestromia lanuginosa | 0–1 | – | ||
| onyxflower | ACCO3 | Achyronychia cooperi | 0–1 | – | ||
| common fiddleneck | AMMEI2 | Amsinckia menziesii var. intermedia | 0–1 | – | ||
| bristly fiddleneck | AMTE3 | Amsinckia tessellata | 0–1 | – | ||
| New Mexico silverbush | ARNE2 | Argythamnia neomexicana | 0–1 | – | ||
| Cedros milkvetch | ASIN6 | Astragalus insularis | 0–1 | – | ||
| spiderling | BOERH2 | Boerhavia | 0–1 | – | ||
| Booth's suncup | CABOB | Camissonia boothii ssp. boothii | 0–1 | – | ||
| brittle spineflower | CHBR | Chorizanthe brevicornu | 0–1 | – | ||
| Esteve's pincushion | CHST | Chaenactis stevioides | 0–1 | – | ||
| Panamint cryptantha | CRAN4 | Cryptantha angustifolia | 0–1 | – | ||
| redroot cryptantha | CRMI | Cryptantha micrantha | 0–1 | – | ||
| wingnut cryptantha | CRPT | Cryptantha pterocarya | 0–1 | – | ||
| hairy prairie clover | DAMO | Dalea mollis | 0–1 | – | ||
| soft prairie clover | DAMO2 | Dalea mollissima | 0–1 | – | ||
| California shieldpod | DICA7 | Dithyrea californica | 0–1 | – | ||
| miniature woollystar | ERDI2 | Eriastrum diffusum | 0–1 | – | ||
| kidneyleaf buckwheat | ERRE3 | Eriogonum reniforme | 0–1 | – | ||
| Thomas' buckwheat | ERTH | Eriogonum thomasii | 0–1 | – | ||
| little deserttrumpet | ERTR8 | Eriogonum trichopes | 0–1 | – | ||
| California poppy | ESCAM | Eschscholzia californica ssp. mexicana | 0–1 | – | ||
| spurge | EUPHO | Euphorbia | 0–1 | – | ||
| Arizona poppy | KAGR | Kallstroemia grandiflora | 0–1 | – | ||
| Great Basin langloisia | LASE3 | Langloisia setosissima | 0–1 | – | ||
| shaggyfruit pepperweed | LELA | Lepidium lasiocarpum | 0–1 | – | ||
| Bigelow's linanthus | LIBI2 | Linanthus bigelovii | 0–1 | – | ||
| Cusick's biscuitroot | LOCU | Lomatium cusickii | 0–1 | – | ||
| foothill deervetch | LOHU2 | Lotus humistratus | 0–1 | – | ||
| desert deervetch | LOMI | Lotus micranthus | 0–1 | – | ||
| bajada lupine | LUCO | Lupinus concinnus | 0–1 | – | ||
| Coulter's lupine | LUSP2 | Lupinus sparsiflorus | 0–1 | – | ||
| California desertdandelion | MACA6 | Malacothrix californica | 0–1 | – | ||
| yellowcomet | MEAF2 | Mentzelia affinis | 0–1 | – | ||
| whitestem blazingstar | MEAL6 | Mentzelia albicaulis | 0–1 | – | ||
| cottonheads | NEDE | Nemacaulis denudata | 0–1 | – | ||
| glandular threadplant | NEGL | Nemacladus glanduliferus | 0–1 | – | ||
| desert evening primrose | OEPR | Oenothera primiveris | 0–1 | – | ||
| giant Spanish needle | PAARG | Palafoxia arida var. gigantea | 0–1 | – | ||
| chuckwalla combseed | PEHE | Pectocarya heterocarpa | 0–1 | – | ||
| manybristle chinchweed | PEPA2 | Pectis papposa | 0–1 | – | ||
| broadfruit combseed | PEPL | Pectocarya platycarpa | 0–1 | – | ||
|
Shrub/Vine
|
||||||
| 6 | 120–180 | |||||
| fourwing saltbush | ATCA2 | Atriplex canescens | 45–68 | – | ||
| cattle saltbush | ATPO | Atriplex polycarpa | 45–68 | – | ||
| 7 | 30–60 | |||||
| water jacket | LYAN | Lycium andersonii | 11–23 | – | ||
| greasewood | SAVE4 | Sarcobatus vermiculatus | 11–23 | – | ||
| 8 | 5–30 | |||||
| triangle bur ragweed | AMDE4 | Ambrosia deltoidea | 1–11 | – | ||
| burrobush | AMDU2 | Ambrosia dumosa | 1–11 | – | ||
| fourwing saltbush | ATCAL2 | Atriplex canescens var. laciniata | 1–11 | – | ||
| California croton | CRCA5 | Croton californicus | 1–11 | – | ||
| wedgeleaf prairie clover | DAEM2 | Dalea emarginata | 1–11 | – | ||
| longleaf jointfir | EPTR | Ephedra trifurca | 1–11 | – | ||
| burroweed | ISTE2 | Isocoma tenuisecta | 1–11 | – | ||
| littleleaf ratany | KRER | Krameria erecta | 1–11 | – | ||
| white ratany | KRGR | Krameria grayi | 1–11 | – | ||
| creosote bush | LATRT | Larrea tridentata var. tridentata | 1–11 | – | ||
| Arizona desert-thorn | LYEX | Lycium exsertum | 1–11 | – | ||
| Torrey wolfberry | LYTO | Lycium torreyi | 1–11 | – | ||
| honey mesquite | PRGLG | Prosopis glandulosa var. glandulosa | 1–11 | – | ||
| seepweed | SUAED | Suaeda | 1–11 | – | ||
| lotebush | ZIOB | Ziziphus obtusifolia | 1–11 | – | ||
| 9 | Succulents | 30 | ||||
| Engelmann's hedgehog cactus | ECEN | Echinocereus engelmannii | 0–11 | – | ||
| erect pricklypear | OPST2 | Opuntia stricta | 0–11 | – | ||
Interpretations
Animal community
This site produces forage for year-round use by livestock. Adequate protein and energy levels are available throughout the year, however, very hot summer temperatures and very sandy soils with moderate slopes will preclude summer use. Spring is the main season for shrub growth and annual and perennial grass and forb production. Proper use of the shrub species and big galleta should be no more than 50% of the spring production of leaves and stems. Water developments are very important on the site and grazing can be controlled by controlling livestock access to water.
Due to sandy soils and good diversity of forage plants, this site is host to a variety of small burrowing mammals and is an important forage site for the predators of these species (i.e., kit fox, badger, burrowing owl, sidewinder rattlesnake and Gila monster).
Other information
T&E Species: Sonoran pronghorn
Supporting information
Contributors
Larry D. Ellicott
Steve Barker
Unknown
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) | Dave Womack, Dan Robinett, Emilio Carrillo |
|---|---|
| Contact for lead author | NRCS Tucson Area Office |
| Date | 03/07/2005 |
| Approved by | S. Cassady |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
Number and extent of rills:
None present on this site due to high infiltration rates. -
Presence of water flow patterns:
Water flow patterns are uncommon due to high infiltration rates. -
Number and height of erosional pedestals or terracettes:
All shrubs have symmetrical mounds 2-5 inches tall formed by combined action of splash, erosion and rodents. There are no pedestals on rock or gravel fragments and no terracettes are pesent -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
60-70% -
Number of gullies and erosion associated with gullies:
none -
Extent of wind scoured, blowouts and/or depositional areas:
Minor evidence of soil movement by wind. -
Amount of litter movement (describe size and distance expected to travel):
Herbaceous litter can move by wind. 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 raindrop impact. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Weak thin platy to granular; 7.5-10YR6/4 dry, 7.5-10YR4/4 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, absent in others. Large shrubs with large coppice mounds with high infiltration rates. Subshrubs with small mounds with high infiltration rates. -
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:
perennial grass = salt bush shrubs > winter annuals > trees & shrubs > summer annuals > succulents = perennial forbs > crytogamsSub-dominant:
Other:
Additional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
0-50% canopy mortality; 90-100% perennial grass mortality. -
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):
400 lbs/ac unfavorable precipitation, 600 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 (potential), mesquite -
Perennial plant reproductive capability:
Not impaired for shrubs, drought impaired for perennial grasses and forbs.
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