Natural Resources
Conservation Service
-
Search
Major Land Resource Area or ecological site by name and/or ID.
PreviousSectionsNextGeneral 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
AZ 40.3 – Colorado Sonoran Desert
Elevations range from 300 to 1200 feet and precipitation averages 3 to 7 inches per year. Vegetation includes creosotebush, white bursage, brittlebush, Mormon tea, teddybear cholla, elephant tree, smoke tree, ocotillo, 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) Eriogonum wrightii
(2) Ephedra fasciculataHerbaceous (1) Pleuraphis rigida
Physiographic features
This range site occurs as rolling to steep hills and low mountains. It is dissected by many steep-sided canyons and long drainageways.
Table 2. Representative physiographic features
Landforms (1) Hill
(2) Mountain
Elevation 75 – 1600 ft Slope 15 – 75 % Climatic features
Precipitation in this common resource area ranges from 3-7 inches yearly. Despite historical averages in rainfall amounts, 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 44% at Gila Bend and 65% at Mohawk. Winter-Summer rainfall ratios are 40-60%. Summer rains fall July-September, originate in the Gulf of Mexico and are convective, usually brief intense thunderstorms. Summer thunderstorms usually form over the mountains in the afternoon and spread to the valleys and plains in the evening. The intensity of this precipitation is moderate to heavy, but rarely lasts more than half an hour. Many times these storms produce little more than gusty winds and light showers. Cool season moisture tends to be frontal, originate in the Pacific and Gulf of California and falls in widespread storms with long duration and low intensity. Snow is very rare and falls normally only in the higher mountains.
Mean temperatures for the hottest month (Jul) is 93 F; the coldest month (Jan) is 53 F. Extreme temperatures of 125 F and 10 F have been recorded. Long periods with little or no effective moisture occur frequently.
The winter-spring precipitation is the most dependable on the site. Perennial grasses, though classed as warm season growers, grow actively year-round when moisture is available. Shrubs and trees generally respond to seasonal moisture. The two rainy periods bring about their respective production of either winter or summer annual grasses and forbs.Table 3 Representative climatic features
Frost-free period (average) 360 days Freeze-free period (average) 0 days Precipitation total (average) 10 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
These soils are shallow to moderately deep. Parent material is slope alluvium and residuum. They are loamy, usually moderately calcareous, and have a very cobbly or stony surface. Soils are underlain by rhyolite, andesite, dacite and related volcanic rock. They take rainfall well. Plant-soil moisture relationships are fair. Bedrock is weathered or fractured enough to allow good opportunity for plant root penetration. Rock outcrop occupies 10-35% of the area.
Soils mapped on this site include: in SSA-627 Southern Mohave county MU Hyder-103.Table 4. Representative soil features
Parent material (1) Alluvium – volcanic breccia
Surface texture (1) Gravelly loam
(2) Very gravelly fine sandy loam
(3) Cobbly sandy loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderately rapid to rapid Soil depth 10 – 40 in Surface fragment cover <=3" 25 – 55 % Surface fragment cover >3" 3 – 10 % Available water capacity
(0-40in)0.32 – 2.2 in Calcium carbonate equivalent
(0-40in)5 – 25 % Electrical conductivity
(0-40in)0 – 1 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 – 45 % Subsurface fragment volume >3"
(Depth not specified)3 – 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 each 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
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 textEcosystem states
State 1 submodel, plant communities
State 1
Historic Climax Plant CommunityCommunity 1.1
Historic Climax Plant CommunityThis site has a plant community that is a mixture of desert trees and shrubs with an understory of perennial and annual grasses and forbs.
As the better browse species and perennial grasses and forbs decline from overgrazing, species like cholla, brittlefush, and paloverde increase to dominate the site.Figure 3. 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 158 193 228 Forb 70 88 105 Grass/Grasslike 17 35 53 Tree 10 12 15 Total 255 328 401 Figure 4. Plant community growth curve (percent production by month). AZ4041 , 40.3 3-7" p.z. all sites. Most growth occurs in the winter to early spring, plants are dormant May through October..
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec J F M A M J J A S O N D 5 20 40 25 0 0 0 0 0 0 5 5 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike0 Dominant Perennial Grass 18–35 big galleta PLRI3 Pleuraphis rigida 18–35 – 1 Misc. Perennial Grasses 4–18 threeawn ARIST Aristida 0–7 – bush muhly MUPO2 Muhlenbergia porteri 2–6 – slim tridens TRMU Tridens muticus 2–5 – 2 Annual Grasses 15–35 low woollygrass DAPU7 Dasyochloa pulchella 2–8 – nineawn pappusgrass ENDE Enneapogon desvauxii 2–8 – littleseed muhly MUMI Muhlenbergia microsperma 2–8 – sixweeks fescue VUOC Vulpia octoflora 2–8 – Bigelow's bluegrass POBI Poa bigelovii 2–7 – sixweeks grama BOBA2 Bouteloua barbata 2–7 – sixweeks threeawn ARAD Aristida adscensionis 2–4 – needle grama BOAR Bouteloua aristidoides 2–4 – Forb3 Dominant Forbs 35–50 goldenweed PYRRO Pyrrocoma 17–25 – desert globemallow SPAM2 Sphaeralcea ambigua 18–25 – 4 Misc. Forbs 35–53 milkvetch ASTRA Astragalus 1–2 – spiderling BOERH2 Boerhavia 1–2 – cryptantha CRYPT Cryptantha 1–2 – fleabane ERIGE2 Erigeron 1–2 – buckwheat ERIOG Eriogonum 1–2 – phacelia PHACE Phacelia 1–2 – pepperweed LEPID Lepidium 1–2 – cloak fern NOTHO Notholaena 1–2 – evening primrose OENOT Oenothera 1–2 – combseed PECTO Pectocarya 1–2 – spurge EUPHO Euphorbia 1–2 – gilia GILIA Gilia 1–2 – Gordon's bladderpod LEGO Lesquerella gordonii 0–1 – Emory's rockdaisy PEEM Perityle emoryi 0–1 – desert deervetch LOMI Lotus micranthus 0–1 – Coulter's lupine LUSP2 Lupinus sparsiflorus 0–1 – Parry's false prairie-clover MAPA7 Marina parryi 0–1 – desert Indianwheat PLOV Plantago ovata 0–1 – Coues' cassia SECO10 Senna covesii 0–1 – sleepy silene SIAN2 Silene antirrhina 0–1 – woollyhead neststraw STMI2 Stylocline micropoides 0–1 – California poppy ESCAM Eschscholzia californica ssp. mexicana 0–1 – dainty desert hideseed EUMI2 Eucrypta micrantha 0–1 – desert trumpet ERIN4 Eriogonum inflatum 0–1 – desert larkspur DEPA Delphinium parishii 0–1 – tall mountain larkspur DESC Delphinium scaposum 0–1 – miniature woollystar ERDI2 Eriastrum diffusum 0–1 – hoary bowlesia BOIN3 Bowlesia incana 0–1 – Esteve's pincushion CHST Chaenactis stevioides 0–1 – desert marigold BAMU Baileya multiradiata 0–1 – pelotazo ABIN Abutilon incanum 0–1 – trailing windmills ALIN Allionia incarnata 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 – Shrub/Vine5 Dominant Shrubs 105–140 Nevada jointfir EPNE Ephedra nevadensis 20–40 – sweetbush BEJU Bebbia juncea 10–25 – bastardsage ERWR Eriogonum wrightii 10–20 – desert lavender HYEM Hyptis emoryi 5–15 – Mexican bladdersage SAME Salazaria mexicana 10–15 – 6 Misc. Shrubs 35–53 creosote bush LATRT Larrea tridentata var. tridentata 2–10 – desert-thorn LYCIU Lycium 2–5 – littleleaf ratany KRER Krameria erecta 2–5 – white ratany KRGR Krameria grayi 2–5 – triangle bur ragweed AMDE4 Ambrosia deltoidea 2–5 – burrobush AMDU2 Ambrosia dumosa 2–5 – brittlebush ENFA Encelia farinosa 2–5 – toothleaf goldeneye VIDE3 Viguiera dentata 2–4 – desert ironwood OLTE Olneya tesota 1–3 – Schott's pygmycedar PESC4 Peucephyllum schottii 1–3 – bush arrowleaf PLPL Pleurocoronis pluriseta 1–3 – American threefold TRCA8 Trixis californica 1–3 – ocotillo FOSP2 Fouquieria splendens 1–3 – slender janusia JAGR Janusia gracilis 1–3 – narrowleaf silverbush ARLA12 Argythamnia lanceolata 1–3 – Indian mallow ABUTI Abutilon 1–3 – San Felipe dogweed ADPO Adenophyllum porophylloides 1–3 – 7 Succulents 4–18 beavertail pricklypear OPBA2 Opuntia basilaris 1–2 – saguaro CAGI10 Carnegiea gigantea 1–2 – buckhorn cholla CYACA2 Cylindropuntia acanthocarpa var. acanthocarpa 1–2 – teddybear cholla CYBI9 Cylindropuntia bigelovii 1–2 – Christmas cactus CYLE8 Cylindropuntia leptocaulis 1–2 – Engelmann's hedgehog cactus ECEN Echinocereus engelmannii 0–1 – California barrel cactus FECYC Ferocactus cylindraceus var. cylindraceus 0–1 – candy barrelcactus FEWI Ferocactus wislizeni 0–1 – Graham's nipple cactus MAGR9 Mammillaria grahamii 0–1 – Tree8 Tree 5–15 yellow paloverde PAMI5 Parkinsonia microphylla 5–15 – Interpretations
Animal community
Steep slopes, rock outcrop and cobbly surfaces somewhat limit use of this site. Fencing, to restrict animals to the site, and stockwater developments are very important to permit proper management of these areas.
Natural waters are virtually nonexistant in these areas except for scattered rock tanks (tinajas) which are only seasonal. Stockwater developments are very important to wildlife on this site. The site has a varied diversity of both forage species and cover for a variety of wildlife species. Forage seasons are extended due to greenup differences in the north and south slopes and canyon bottoms. This is a very important site for the desert bighorn in this LRA.Recreational uses
This site is located on steep dissected hills and low mountains. It has an abundance of wildflowers following both winter and summer rains. The mixture of grasses, trees and shrubs enhances the aesthetics of these areas, as does the rugged terrain.
Very few days in the fall, winter or spring are too uncomfortable to enjoy outside activities. In Jun-Aug, however, after lunch heat restricts activity. Horseback riding, wildlife observation, hunting, hiking, photography, camping and picnicking are activities suitable to this site.Supporting information
Type locality
Location 1: La Paz County, AZ Township/Range/Section T4N R14W S23 General legal description Crowder-Weisser Allotment, near Pyramid Park, 3 mi. S of Hope, AZ Contributors
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) Contact for lead author Date Approved by 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:
Print Options
Sections
Font
AAAAOther
PrintThe Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.
Accessibility statement
