Natural Resources
Conservation Service
Ecological site R040XB233AZ
Limy Slopes, Gypsum 7"-10" p.z.
Last updated: 10/17/2024
Accessed: 12/22/2024
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.
MLRA notes
Major Land Resource Area (MLRA): 040X–Sonoran Basin and Range
Major Land Resource Area (MLRA) 40 is the portion of Sonoran Desert that extends from northwest Mexico into southwestern Arizona and southeastern California. This MLRA is hot desert characterized by bimodal precipitation coupled with hot summers and mild winters. These conditions give rise to a rich biological diversity visually dominated by columnar cactus (saguaro) and leguminous trees (palo verde). 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 basin sediments are combinations of fluvial, lacustrine, colluvial and alluvial deposits.
LRU notes
Land Resource Unit (LRU) 40-2, Middle Sonoran Desert, is characterized by desert scrub vegetation on relict fan remnants with a moderate amount of desert pavement. Trees are common in washes, bottoms and hillslopes. 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.
Classification relationships
USDA-NRCS Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin: Western Range and Irrigated Region D Major Land Resource Area 40 - Sonoran Basin and Range Land Resource Unit 2 - Middle Sonoran Desert Ecological Site Limy Slopes, Gypsum, 7"-10" p.z.
U.S. Environmental Protection Agency, Ecological Regions of North America: Level I, Region 10 North American Deserts Level II, 10.2 Warm Deserts Level III, Ecoregion 81, Sonoran Basin and Range Level IV, 81l, 81n, 81o
USDA-USFS Ecological Subregions: Sections of the Conterminous United States Section 322 American Semidesert and Desert Province Section 322B, Sonoran Desert
Ecological site concept
Limy Slopes, Gypsum, 7"-10" p.z., occurs on moderately to steeply sloping uplands. Slopes are generally greater than 8%. The calcareous soils are deep with visible gypsum crystals. The gypsum content, combined with the steep slopes, make this ecological site extremely susceptible to water erosion, affecting use and management options.
Associated sites
| R040XB234AZ |
Limy Fan, Gypsum 7"-10" p.z. adjacent alluvial fans |
|---|
Similar sites
| R040XB209AZ |
Limy Slopes 7"-10" p.z. soils not gypsic |
|---|
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
(1) Ambrosia dumosa |
| Herbaceous |
(1) Pleuraphis rigida |
Physiographic features
This site occurs on hillslopes and ridgetops generally associated with relict lakebed sediments.
Table 2. Representative physiographic features
| Landforms |
(1)
Hill
(2) Ridge |
|---|---|
| Elevation | 1,200 – 2,000 ft |
| Slope | 8 – 45% |
Climatic features
Annual precipitation ranges from 7 to 10 inches. Annual rainfall is bimodal, with distinct rainy seasons occurring from December to March (winter) and July to September (summer). Rainfall ratios range from 40:60 (winter:summer) in the southern part, and 60:40 in the central and northern parts. Rainfall intensity differs between rainfall seasons. Winter frontal storms develop in the Pacific Ocean and Gulf of California, producing widespread, low-intensity and long duration precipitation events. Winter precipitation is the more dependable water source for vegetation, and snowfall is very rare. During summer months, atmospheric activity in the Gulf of Mexico produces convective thunderstorms when crossing over the mountains in the afternoon. These storms travel across the plains and valleys, producing precipitation of short duration, usually less than 30 minutes, but of moderate to heavy intensity. Between these two seasons, little to no effective precipitation can occur for several months at a time. May and June are the driest months, and overall humidity is very low. Overall, average annual rainfall is variable, but increases in variability from east to west across the region. For long-term precipitation data, the coefficient of variation, the ratio of the standard deviation to the mean expressed as a percentage, increases from 38% at Florence (east) to 46% at Aguila (west).
Winter temperatures are very mild, with very few days having short periods of freezing temperatures. Summertime temperatures are hot to very hot, with many days in June and July exceeding 105°F. The number of frost-free days ranges from 280 in major river valleys with cold air drainage to between 320 and 350 in upland areas.
Spring and summer growing seasons are equally important for perennial grass, forb and shrub growth. With above average precipitation, cool and warm season annual forbs and grasses can be common in their respective seasons. Perennial forage species can remain green throughout the year with sufficient available moisture.
Table 3. Representative climatic features
| Frost-free period (average) | 291 days |
|---|---|
| Freeze-free period (average) | 344 days |
| Precipitation total (average) | 10 in |
Figure 1. Monthly precipitation range
Figure 2. Monthly average minimum and maximum temperature
Influencing water features
Soil features
These are moderately deep to deep soils formed in relict lakebed deposits. They are very calcareous and gypsiferous, with greater than 15% gypsum content throughout the soil profile. Fine gypsum masses and fine gypsum crystals are visible in subsoils. The gypsum content makes the soil extremely vulnerable to water erosion. Plant-soil moisture relationships are poor.
Table 4. Representative soil features
| Parent material |
(1)
Lacustrine deposits
|
|---|---|
| Drainage class | Well drained |
| Permeability class | Moderate to moderately rapid |
| Soil depth | 40 – 60 in |
| Surface fragment cover <=3" | 15 – 65% |
| Surface fragment cover >3" | 1 – 10% |
| Available water capacity (0-40in) |
3 – 6 in |
| Calcium carbonate equivalent (0-40in) |
5 – 35% |
| Electrical conductivity (0-40in) |
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) |
15 – 65% |
| Subsurface fragment volume >3" (Depth not specified) |
1 – 10% |
Ecological dynamics
Limy Slopes, Gypsum, 7"-10" p.z., is a robust ecological site of limited areal extent. Only one state, Shrubland, has been observed. The soil gypsum content makes the site extremely vulnerable to water erosion. Any disturbance that removes the surface horizon could initiate extreme erosion. Areas of geological erosion are located adjacent to this ecological site (Figure 4). These barren areas are not caused by human disturbance, thus, are not considered to represent a separate state.
State and transition model
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Ecosystem states
State 1 submodel, plant communities
State 1
Shrubland (Reference)
Community 1.1
Creosote-Bursage-Mixed Shrub
Figure 3. Reference community on left, eroded slopes on right
The potential plant community on this site is a mixture of desert shrubs, cacti, perennial grasses and forbs. Annual grasses and forbs make up a small percentage of the potential community. The aspect is shrubland.
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 | 195 | 225 | 255 |
| Grass/Grasslike | 15 | 30 | 45 |
| Forb | 30 | 37 | 45 |
| Total | 240 | 292 | 345 |
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 | Perennial Grasses | 15–30 | ||||
| big galleta | PLRI3 | Pleuraphis rigida | 0–15 | – | ||
| bush muhly | MUPO2 | Muhlenbergia porteri | 0–5 | – | ||
| spidergrass | ARTE3 | Aristida ternipes | 0–1 | – | ||
| low woollygrass | DAPU7 | Dasyochloa pulchella | 0–1 | – | ||
| 2 | Annual Grasses | 3–15 | ||||
| needle grama | BOAR | Bouteloua aristidoides | 0–5 | – | ||
| Rothrock's grama | BORO2 | Bouteloua rothrockii | 0–5 | – | ||
| Arizona brome | BRAR4 | Bromus arizonicus | 0–1 | – | ||
| feather fingergrass | CHVI4 | Chloris virgata | 0–1 | – | ||
| Arizona signalgrass | URAR | Urochloa arizonica | 0–1 | – | ||
|
Forb
|
||||||
| 4 | Perennial Forbs | 15–30 | ||||
| desert globemallow | SPAM2 | Sphaeralcea ambigua | 5–10 | – | ||
| desert trumpet | ERIN4 | Eriogonum inflatum | 2–5 | – | ||
| Parry's false prairie-clover | MAPA7 | Marina parryi | 0–2 | – | ||
| lacy tansyaster | MAPIP4 | Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | 0–2 | – | ||
| rough menodora | MESC | Menodora scabra | 0–1 | – | ||
| evening primrose | OENOT | Oenothera | 0–1 | – | ||
| slender poreleaf | POGR5 | Porophyllum gracile | 0–1 | – | ||
| Coues' cassia | SECO10 | Senna covesii | 0–1 | – | ||
| California fagonbush | FALA | Fagonia laevis | 0–1 | – | ||
| paleface | HIDE | Hibiscus denudatus | 0–1 | – | ||
| slender janusia | JAGR | Janusia gracilis | 0–1 | – | ||
| dwarf desertpeony | ACNA2 | Acourtia nana | 0–1 | – | ||
| brownfoot | ACWR5 | Acourtia wrightii | 0–1 | – | ||
| poreleaf dogweed | ADPO2 | Adenophyllum porophyllum | 0–1 | – | ||
| trailing windmills | ALIN | Allionia incarnata | 0–1 | – | ||
| narrowleaf silverbush | ARLA12 | Argythamnia lanceolata | 0–1 | – | ||
| New Mexico silverbush | ARNE2 | Argythamnia neomexicana | 0–1 | – | ||
| rush milkweed | ASSU | Asclepias subulata | 0–1 | – | ||
| desert marigold | BAMU | Baileya multiradiata | 0–1 | – | ||
| whitemargin sandmat | CHAL11 | Chamaesyce albomarginata | 0–1 | – | ||
| desert larkspur | DEPA | Delphinium parishii | 0–1 | – | ||
| tall mountain larkspur | DESC | Delphinium scaposum | 0–1 | – | ||
| bluedicks | DICA14 | Dichelostemma capitatum | 0–1 | – | ||
| brownplume wirelettuce | STPA4 | Stephanomeria pauciflora | 0–1 | – | ||
| 5 | Annual Forbs | 3–15 | ||||
| sand pygmyweed | CRCO34 | Crassula connata | 0–3 | – | ||
| combseed | PECTO | Pectocarya | 0–3 | – | ||
| woolly tidestromia | TILA2 | Tidestromia lanuginosa | 0–3 | – | ||
| coastal bird's-foot trefoil | LOSAB | Lotus salsuginosus var. brevivexillus | 0–2 | – | ||
| strigose bird's-foot trefoil | LOSTT | Lotus strigosus var. tomentellus | 0–2 | – | ||
| cryptantha | CRYPT | Cryptantha | 0–2 | – | ||
| hairy prairie clover | DAMO | Dalea mollis | 0–1 | – | ||
| American wild carrot | DAPU3 | Daucus pusillus | 0–1 | – | ||
| western tansymustard | DEPI | Descurainia pinnata | 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 | – | ||
| 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 | – | ||
| gilia | GILIA | Gilia | 0–1 | – | ||
| Gordon's bladderpod | LEGO | Lesquerella gordonii | 0–1 | – | ||
| shaggyfruit pepperweed | LELA | Lepidium lasiocarpum | 0–1 | – | ||
| foothill deervetch | LOHU2 | Lotus humistratus | 0–1 | – | ||
| Arizona lupine | LUAR4 | Lupinus arizonicus | 0–1 | – | ||
| Coulter's lupine | LUSP2 | Lupinus sparsiflorus | 0–1 | – | ||
| blazingstar | MENTZ | Mentzelia | 0–1 | – | ||
| bristly nama | NAHI | Nama hispidum | 0–1 | – | ||
| glandular threadplant | NEGL | Nemacladus glanduliferus | 0–1 | – | ||
| Florida pellitory | PAFL3 | Parietaria floridana | 0–1 | – | ||
| manybristle chinchweed | PEPA2 | Pectis papposa | 0–1 | – | ||
| phacelia | PHACE | Phacelia | 0–1 | – | ||
| desert Indianwheat | PLOV | Plantago ovata | 0–1 | – | ||
| New Mexico plumeseed | RANE | Rafinesquia neomexicana | 0–1 | – | ||
| chia | SACO6 | Salvia columbariae | 0–1 | – | ||
| sleepy silene | SIAN2 | Silene antirrhina | 0–1 | – | ||
| Coulter's globemallow | SPCO2 | Sphaeralcea coulteri | 0–1 | – | ||
| woollyhead neststraw | STMI2 | Stylocline micropoides | 0–1 | – | ||
| common fiddleneck | AMMEI2 | Amsinckia menziesii var. intermedia | 0–1 | – | ||
| bristly fiddleneck | AMTE3 | Amsinckia tessellata | 0–1 | – | ||
| milkvetch | ASTRA | Astragalus | 0–1 | – | ||
| Esteve's pincushion | CHST | Chaenactis stevioides | 0–1 | – | ||
| New Mexico thistle | CINE | Cirsium neomexicanum | 0–1 | – | ||
| Coulter's spiderling | BOCO2 | Boerhavia coulteri | 0–1 | – | ||
| hoary bowlesia | BOIN3 | Bowlesia incana | 0–1 | – | ||
| California suncup | CACA32 | Camissonia californica | 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 | – | ||
| pebble pincushion | CHCA | Chaenactis carphoclinia | 0–1 | – | ||
| hyssopleaf sandmat | CHHY3 | Chamaesyce hyssopifolia | 0–1 | – | ||
| devil's spineflower | CHRI | Chorizanthe rigida | 0–1 | – | ||
|
Shrub/Vine
|
||||||
| 6 | Dominant Large Shrub | 90–135 | ||||
| creosote bush | LATR2 | Larrea tridentata | 90–135 | – | ||
| 7 | Dominant Half Shrubs | 20–45 | ||||
| burrobush | AMDU2 | Ambrosia dumosa | 15–30 | – | ||
| white ratany | KRGR | Krameria grayi | 5–15 | – | ||
| brittlebush | ENFA | Encelia farinosa | 0–5 | – | ||
| 9 | Miscellaneous Shrubs | 15–30 | ||||
| yellow paloverde | PAMI5 | Parkinsonia microphylla | 0–5 | – | ||
| desert ironwood | OLTE | Olneya tesota | 0–3 | – | ||
| ocotillo | FOSP2 | Fouquieria splendens | 0–2 | – | ||
| desert lavender | HYEM | Hyptis emoryi | 0–1 | – | ||
| sangre de cristo | JACA2 | Jatropha cardiophylla | 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 | – | ||
| desert wolfberry | LYMA | Lycium macrodon | 0–1 | – | ||
| whitethorn acacia | ACCO2 | Acacia constricta | 0–1 | – | ||
| catclaw acacia | ACGR | Acacia greggii | 0–1 | – | ||
| rayless goldenhead | ACSP | Acamptopappus sphaerocephalus | 0–1 | – | ||
| Coulter's brickellbush | BRCO | Brickellia coulteri | 0–1 | – | ||
| button brittlebush | ENFR | Encelia frutescens | 0–1 | – | ||
| Nevada jointfir | EPNE | Ephedra nevadensis | 0–1 | – | ||
| velvet mesquite | PRVE | Prosopis velutina | 0–1 | – | ||
| whitestem paperflower | PSCO2 | Psilostrophe cooperi | 0–1 | – | ||
| dwarf saltwort | SABI | Salicornia bigelovii | 0–1 | – | ||
| Mexican bladdersage | SAME | Salazaria mexicana | 0–1 | – | ||
| jojoba | SICH | Simmondsia chinensis | 0–1 | – | ||
| woody crinklemat | TICAC | Tiquilia canescens var. canescens | 0–1 | – | ||
| American threefold | TRCA8 | Trixis californica | 0–1 | – | ||
| Parish's goldeneye | VIPA14 | Viguiera parishii | 0–1 | – | ||
| desert zinnia | ZIAC | Zinnia acerosa | 0–1 | – | ||
| lotebush | ZIOB | Ziziphus obtusifolia | 0–1 | – | ||
| 10 | Cacti | 15–30 | ||||
| senita cactus | PASC14 | Pachycereus schottii | 0–2 | – | ||
| organpipe cactus | STTH3 | Stenocereus thurberi | 0–2 | – | ||
| beavertail pricklypear | OPBA2 | Opuntia basilaris | 0–1 | – | ||
| 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 | – | ||
| common fishhook cactus | MATE4 | Mammillaria tetrancistra | 0–1 | – | ||
Interpretations
Supporting information
Other references
Griffith, G.E., Omernik, J.M., Johnson, C.B., and Turner, D.S., 2014, Ecoregions of Arizona (poster): U.S. Geological Survey Open-File Report 2014-1141, with map, scale 1:1,325,000, https://dx.doi.org/10.3133/ofr20141141. ISSN 2331-1258 (online)
United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296.
Contributors
Wilma Renken
Approval
Kendra Moseley, 10/17/2024
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) | |
|---|---|
| Contact for lead author | |
| Date | 10/22/2019 |
| Approved by | Kendra Moseley |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
Number and extent of rills:
-
Presence of water flow patterns:
-
Number and height of erosional pedestals or terracettes:
-
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
-
Number of gullies and erosion associated with gullies:
-
Extent of wind scoured, blowouts and/or depositional areas:
-
Amount of litter movement (describe size and distance expected to travel):
-
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
-
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
-
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
-
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
-
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:
Sub-dominant:
Other:
Additional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
-
Average percent litter cover (%) and depth ( in):
-
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
-
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:
-
Perennial plant reproductive capability:
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