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Ecological site R040XA124AZ

Loamy Bottom, Woodland 10"-13" p.z.

Last updated: 10/17/2024
Accessed: 12/22/2024

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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) 40-1, Upper Sonoran Desert, is characterized by desert scrub vegetation with no desert pavement present. Trees grow on uplands as well as in washes and on hillslopes. Elevations range from 2000 to 3800 feet, and precipitation averages 10 to 13 inches per year. Vegetation includes saguaro, palo verde, mesquite, creosotebush, triangle bursage, prickly pear, cholla, limberbush, wolfberry, bush muhly, threeawns, ocotillo, and globe mallow. The soil temperature regime is thermic 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 1 - Upper Sonoran Desert Ecological Site Loamy Bottom, Woodland, 10"-13" 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

Loamy Bottom, Woodland, 10"-13" p.z., occurs in a bottom position, receiving both rainfall and run-on moisture. The water table is available to the plant community. Soils do not have redoximorphic features within 80" of surface.

Associated sites

R040XA125AZ	Sandy Bottom, Woodland 10"-13" p.z. adjacent water flow channel, soils with redox features
R040XA112AZ	Loamy Swale 10"-13" p.z. non-saline bottom site without permanent, deep, water table; often associated adjacent opposite water channel

R040XA125AZ

Sandy Bottom, Woodland 10"-13" p.z.

adjacent water flow channel, soils with redox features

R040XA112AZ

Loamy Swale 10"-13" p.z.

non-saline bottom site without permanent, deep, water table; often associated adjacent opposite water channel

Similar sites

F040XB214AZ	Loamy Bottom, Woodland 7"-10" p.z. Elevations 1,200' - 2,000', lower precipitation, soil hyperthermic
F040XC328AZ	Loamy Bottom, Woodland 3"-7" p.z. Elevations 300' - 1,200', lower precipitation, soil hyperthermic

F040XB214AZ

Loamy Bottom, Woodland 7"-10" p.z.

Elevations 1,200' - 2,000', lower precipitation, soil hyperthermic

F040XC328AZ

Loamy Bottom, Woodland 3"-7" p.z.

Elevations 300' - 1,200', lower precipitation, soil hyperthermic

Table 1. Dominant plant species

Tree	(1) Prosopis velutina
Shrub	Not specified
Herbaceous	(1) Sporobolus wrightii

Download full description

Physiographic features

This site occurs on stream terraces of major drainageways. It does not experience regular overbank flooding. Some extra moisture may be received from valley side channel flooding. Water table depths are estimated to range from 10 to 50 feet. Stream channels are deeply entrenched.

Table 2. Representative physiographic features

Landforms	(1) Stream terrace
Flooding duration	Extremely brief (0.1 to 4 hours) to brief (2 to 7 days)
Flooding frequency	None to rare
Ponding duration	Very brief (4 to 48 hours) to brief (2 to 7 days)
Ponding frequency	None to rare
Elevation	2,000 – 3,800 ft
Slope	2%
Aspect	Aspect is not a significant factor

Climatic features

Annual precipitation ranges from 10 to 13 inches in the southern part of this LRU, with elevations between 1900 and 3200 feet. Annual precipitation in the northern part ranges from 11 to 14 inches, with elevations between 2000 and 3800 feet. Rainfall ratios range from 40:60 (winter:summer) in the southern part, 50:50 in the central portion, and 60:40 in the northern part.

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 29% at Tucson (east) to 36% at Carefree (west).
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. Snowfall is rare and seldom last for more than a few hours. During summer months (July-September), atmospheric activity in the Gulf of Mexico produces convective thunderstorms of short duration, usually less than 30 minutes, but of moderate to heavy intensity. May and June are the driest months of the year. Humidity is generally very low.

Winter temperatures are mild, with only a few days of freezing temperatures overnight. Summer temperatures are warm to hot, with several days in June and July exceeding 105°F.

Spring and the 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)	265 days
Freeze-free period (average)
Precipitation total (average)	13 in

Bar

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Figure 1. Monthly precipitation range

Bar

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Figure 2. Monthly average minimum and maximum temperature

Soil features

These are young soils formed in loamy or silty alluvium of mixed origin. Soils are deep, well drained and may be calcareous or slightly saline, and may contain 0%-5% gypsum. Plant-soil moisture relationships are excellent for deep rooted trees due to a deep ground water table.

Table 4. Representative soil features

Surface texture	(1) Fine sandy loam (2) Loam (3) Silt loam
Family particle size	(1) Loamy
Drainage class	Well drained
Permeability class	Moderate to moderately slow
Soil depth	60 in
Surface fragment cover <=3"	10%
Surface fragment cover >3"	1%
Available water capacity (0-40in)	5.8 – 10.8 in
Calcium carbonate equivalent (0-40in)	10%
Electrical conductivity (0-40in)	4 mmhos/cm
Sodium adsorption ratio (0-40in)	13
Soil reaction (1:1 water) (0-40in)	7 – 8.2
Subsurface fragment volume <=3" (Depth not specified)	5%

Ecological dynamics

Loamy Bottom, Woodland, 10-13” p.z. supports a mixed plant community, with an overstory of mesquite and an understory of shrubs, perennial grasses and forbs. Leaf-out for mesquite occurs midspring, after the last frost, produces flowers in late spring or early summer, and mature fruits begin dropping by July. The trees lose their leaves with the first hard frost. The aspect is deciduous woodland.

The site is very susceptible to channel and streambank erosion. Drainageways are deeply entrenched and, if streamside vegetation is disturbed, bank cutting can greatly increase. If the mesquite overstory is reduced, shrub cover will readily expand and become dominant in the plant community. Herbaceous understory density varies with varying canopy cover. Mesquite canopy cover ranges from 30%–65%. Trees can reach maximum size and height on the site. Excessive groundwater pumping can, over time, lower water tables beyond the reach of tree roots and cause extensive tree loss. Tree species vigorously sprout after a fire or manual cutting. Natural fires may have been important in maintaining herbaceous understories. Saltcedar can invade and dominate following disturbance of the native tree cover. Bermudagrass, Johnson grass, foxtail barley and London rocket are introduced species commonly found on this site.

State and transition model

Custom diagram

Standard diagram

Figure 3. Loamy Bottom, Woodland STM

Figure 4. Loamy Bottom, woodland, 10-13" p.z. STM Legend

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 text

Ecosystem states

1. Mesquite Bosque, Native State

2. Mesquite Bosque, Exotics State

3. Abandoned Farmland State

4. Mesquite Scrubland State

5. Non-Native Woodland State

State 1 submodel, plant communities

1.1. Mesquite, Native Community (Reference)

State 1
Mesquite Bosque, Native State

Community 1.1
Mesquite, Native Community (Reference)

Mesquite dominates the reference plant community with a mixed understory.

Figure 5. 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)
Tree	300	475	650
Shrub/Vine	350	400	450
Grass/Grasslike	250	275	300
Forb	200	225	250
Total	1100	1375	1650

State 2
Mesquite Bosque, Exotics State

Mesquite canopy intact, and groundwater table within normal range. Non-native annual forbs and grasses, such as London rocket and foxtail barley, dominate the understory. Shrubs and succulents are sparsely present. No flooding occurs.

State 3
Abandoned Farmland State

Mesquite bosque absent, and groundwater table within normal range. Initially, native annual forbs and grasses occupy the site, with some patches of non-native annuals. With time, desert broom, greythorn and other shrubs come to dominate the community, with patches of perennial grasses occurring in depressions.

State 4
Mesquite Scrubland State

Water table depleted. Mesquite bosque has altered to a shrubby aspect with a 5%-20% canopy, intermingled with greythorn and other large shrubs.

State 5
Non-Native Woodland State

Saltcedar dominates, becoming an impenetrable thicket.

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				28–41
	Arizona cottontop	DICA8	Digitaria californica	28–41	–
	bush muhly	MUPO2	Muhlenbergia porteri	28–41	–
	whiplash pappusgrass	PAVA2	Pappophorum vaginatum	28–41	–
	plains bristlegrass	SEVU2	Setaria vulpiseta	28–41	–
	spike dropseed	SPCO4	Sporobolus contractus	28–41	–
	big sacaton	SPWR2	Sporobolus wrightii	28–41	–
2				14–28
	Santa Rita threeawn	ARCAG	Aristida californica var. glabrata	14–28	–
	Havard's threeawn	ARHA3	Aristida havardii	14–28	–
	purple threeawn	ARPU9	Aristida purpurea	14–28	–
	Parish's threeawn	ARPUP5	Aristida purpurea var. parishii	14–28	–
	spidergrass	ARTE3	Aristida ternipes	14–28	–
	low woollygrass	DAPU7	Dasyochloa pulchella	14–28	–
	saltgrass	DISP	Distichlis spicata	14–28	–
	squirreltail	ELELE	Elymus elymoides ssp. elymoides	14–28	–
	vine mesquite	PAOB	Panicum obtusum	14–28	–
	tobosagrass	PLMU3	Pleuraphis mutica	14–28	–
	cane bluestem	BOBA3	Bothriochloa barbinodis	14–28	–
	sand dropseed	SPCR	Sporobolus cryptandrus	14–28	–
	sideoats grama	BOCU	Bouteloua curtipendula	14–28	–
	slim tridens	TRMU	Tridens muticus	14–28	–
3				28–41
	prairie threeawn	AROL	Aristida oligantha	28–41	–
	needle grama	BOAR	Bouteloua aristidoides	28–41	–
	sixweeks grama	BOBA2	Bouteloua barbata	28–41	–
	Rothrock's grama	BORO2	Bouteloua rothrockii	28–41	–
	Arizona brome	BRAR4	Bromus arizonicus	28–41	–
	brome	BROMU	Bromus	28–41	–
	feather fingergrass	CHVI4	Chloris virgata	28–41	–
	bearded cupgrass	ERAR5	Eriochloa aristata	28–41	–
	canyon cupgrass	ERLE7	Eriochloa lemmonii	28–41	–
	desert lovegrass	ERPEM	Eragrostis pectinacea var. miserrima	28–41	–
	tufted lovegrass	ERPEP2	Eragrostis pectinacea var. pectinacea	28–41	–
	little barley	HOPU	Hordeum pusillum	28–41	–
	Mexican sprangletop	LEFUU	Leptochloa fusca ssp. uninervia	28–41	–
	mucronate sprangeltop	LEPAB	Leptochloa panicea ssp. brachiata	28–41	–
	delicate muhly	MUFR	Muhlenbergia fragilis	28–41	–
	littleseed muhly	MUMI	Muhlenbergia microsperma	28–41	–
	witchgrass	PACA6	Panicum capillare	28–41	–
	Bigelow's bluegrass	POBI	Poa bigelovii	28–41	–
	Arizona signalgrass	URAR	Urochloa arizonica	28–41	–
	sixweeks fescue	VUOC	Vulpia octoflora	28–41	–
Forb
4				2–11
	bigseed alfalfa dodder	CUIN	Cuscuta indecora	2–11	–
	mesquite mistletoe	PHCA8	Phoradendron californicum	2–11	–
5				23–34
	dwarf desertpeony	ACNA2	Acourtia nana	23–34	–
	wheelscale saltbush	ATEL	Atriplex elegans	23–34	–
	Wright's saltbush	ATWR	Atriplex wrightii	23–34	–
	hedge bamboo	BAMU2	Bambusa multiplex	23–34	–
	New Mexico thistle	CINE	Cirsium neomexicanum	23–34	–
	fingerleaf gourd	CUDI	Cucurbita digitata	23–34	–
	Missouri gourd	CUFO	Cucurbita foetidissima	23–34	–
	coyote gourd	CUPA	Cucurbita palmata	23–34	–
	desert thorn-apple	DADI2	Datura discolor	23–34	–
	pricklyburr	DAIN2	Datura inoxia	23–34	–
	Indian rushpea	HOGL2	Hoffmannseggia glauca	23–34	–
	redstar	IPCO3	Ipomoea coccinea	23–34	–
	Gila manroot	MAGI	Marah gilensis	23–34	–
	lacy tansyaster	MAPIP4	Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida	23–34	–
	desert tobacco	NIOBO	Nicotiana obtusifolia var. obtusifolia	23–34	–
	Mexican passionflower	PAME2	Passiflora mexicana	23–34	–
	doubleclaw	PRPA2	Proboscidea parviflora	23–34	–
	canaigre dock	RUHY	Rumex hymenosepalus	23–34	–
	silverleaf nightshade	SOEL	Solanum elaeagnifolium	23–34	–
6				23–34
	brownfoot	ACWR5	Acourtia wrightii	23–34	–
	trailing windmills	ALIN	Allionia incarnata	23–34	–
	weakleaf bur ragweed	AMCO3	Ambrosia confertiflora	23–34	–
	carelessweed	AMPA	Amaranthus palmeri	23–34	–
	bristly fiddleneck	AMTE3	Amsinckia tessellata	23–34	–
	rockcress	ARABI	Arabidopsis	23–34	–
	milkvetch	ASTRA	Astragalus	23–34	–
	scarlet spiderling	BOCO	Boerhavia coccinea	23–34	–
	Coulter's spiderling	BOCO2	Boerhavia coulteri	23–34	–
	hoary bowlesia	BOIN3	Bowlesia incana	23–34	–
	Arizona wrightwort	CAAR7	Carlowrightia arizonica	23–34	–
	whitemargin sandmat	CHAL11	Chamaesyce albomarginata	23–34	–
	goosefoot	CHENO	Chenopodium	23–34	–
	hyssopleaf sandmat	CHHY3	Chamaesyce hyssopifolia	23–34	–
	cryptantha	CRYPT	Cryptantha	23–34	–
	hairy prairie clover	DAMO	Dalea mollis	23–34	–
	American wild carrot	DAPU3	Daucus pusillus	23–34	–
	western tansymustard	DEPI	Descurainia pinnata	23–34	–
	Palmer's spectaclepod	DICA31	Dimorphocarpa candicans	23–34	–
	flatcrown buckwheat	ERDE6	Eriogonum deflexum	23–34	–
	miniature woollystar	ERDI2	Eriastrum diffusum	23–34	–
	buckwheat	ERIOG	Eriogonum	23–34	–
	California poppy	ESCAM	Eschscholzia californica ssp. mexicana	23–34	–
	Mexican fireplant	EUHE4	Euphorbia heterophylla	23–34	–
	hairy desertsunflower	GECA2	Geraea canescens	23–34	–
	redstar	IPCO3	Ipomoea coccinea	23–34	–
	Arizona poppy	KAGR	Kallstroemia grandiflora	23–34	–
	Gordon's bladderpod	LEGO	Lesquerella gordonii	23–34	–
	shaggyfruit pepperweed	LELA	Lepidium lasiocarpum	23–34	–
	Coulter's lupine	LUSP2	Lupinus sparsiflorus	23–34	–
	lacy tansyaster	MAPIP4	Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida	23–34	–
	Nuttall's povertyweed	MONU	Monolepis nuttalliana	23–34	–
	glandular threadplant	NEGL	Nemacladus glanduliferus	23–34	–
	Florida pellitory	PAFL3	Parietaria floridana	23–34	–
	manybristle chinchweed	PEPA2	Pectis papposa	23–34	–
	phacelia	PHACE	Phacelia	23–34	–
	desert Indianwheat	PLOV	Plantago ovata	23–34	–
	purslane	PORTU	Portulaca	23–34	–
	sage	SALVI	Salvia	23–34	–
	sleepy silene	SIAN2	Silene antirrhina	23–34	–
	desert globemallow	SPAM2	Sphaeralcea ambigua	23–34	–
	scarlet globemallow	SPCO	Sphaeralcea coccinea	23–34	–
	woollyhead neststraw	STMI2	Stylocline micropoides	23–34	–
	brownplume wirelettuce	STPA4	Stephanomeria pauciflora	23–34	–
	sand fringepod	THCU	Thysanocarpus curvipes	23–34	–
	woolly tidestromia	TILA2	Tidestromia lanuginosa	23–34	–
Shrub/Vine
7				100–140
	fourwing saltbush	ATCA2	Atriplex canescens	100–140	–
	Palmer's cock's comb	CEPA5	Celosia palmeri	100–140	–
	Drummond's clematis	CLDR	Clematis drummondii	100–140	–
	western white clematis	CLLI2	Clematis ligusticifolia	100–140	–
	longleaf jointfir	EPTR	Ephedra trifurca	100–140	–
	water jacket	LYAN	Lycium andersonii	100–140	–
	desert-thorn	LYCIU	Lycium	100–140	–
	Arizona desert-thorn	LYEX	Lycium exsertum	100–140	–
	lotebush	ZIOB	Ziziphus obtusifolia	100–140	–
8				2–40
	whitethorn acacia	VACO9	Vachellia constricta	20–40	–
	iodinebush	ALOC2	Allenrolfea occidentalis	20–40	–
	cattle saltbush	ATPO	Atriplex polycarpa	20–40	–
	desertbroom	BASA2	Baccharis sarothroides	20–40	–
	singlewhorl burrobrush	HYMO	Hymenoclea monogyra	20–40	–
	alkali goldenbush	ISACA2	Isocoma acradenia var. acradenia	20–40	–
	southern goldenbush	ISPL	Isocoma pluriflora	20–40	–
	burroweed	ISTE2	Isocoma tenuisecta	20–40	–
	creosote bush	LATRT	Larrea tridentata var. tridentata	20–40	–
	nightblooming cereus	PEGRT	Peniocereus greggii var. transmontanus	20–40	–
	soaptree yucca	YUEL	Yucca elata	20–40	–
Tree
9				5–24
	catclaw acacia	SEGR4	Senegalia greggii	5–24	–
	Jerusalem thorn	PAAC3	Parkinsonia aculeata	5–24	–
	honey mesquite	PRGLG	Prosopis glandulosa var. glandulosa	5–24	–
10				143–285
	velvet mesquite	PRVE	Prosopis velutina	143–285	–
11				5–24
	netleaf hackberry	CELAR	Celtis laevigata var. reticulata	5–24	–
	desert willow	CHLI2	Chilopsis linearis	5–24	–
	Jerusalem thorn	PAAC3	Parkinsonia aculeata	5–24	–
	screwbean mesquite	PRPU	Prosopis pubescens	5–24	–
	American black elderberry	SANIC4	Sambucus nigra ssp. canadensis	5–24	–

Interpretations

Animal community

This site produces good quantities of spring annual forbs and grasses prior to canopy leaf-out in April. If summer bean crops are harvested, care should be taken to avoid overgrazing the warm season perennial grasses. Horses should not be grazed when a bean crop exists in the trees or on the ground in the summer rainy season.

This site is extremely important to a variety of wildlife, offering well-wooded habitat adjacent to free water in the streambeds for part or all of the year.

Wood products

Fuelwood harvest should not reduce canopy cover to less than 20% to limit an increase in undesirable shrub cover. Coppice sprouts achieve canopy dominance faster if stumps are greater than 30 inches in height. Coppice production cuts should occur every 20 to 30 years. Trees should not be cut near streambanks. There are no soil-site factors limiting wood production.

Supporting information

Type locality

Location 1: Pima County, AZ
Township/Range/Section	T8S R17E S7
General legal description	Tucson FO - San Pedro River - 7B Ranch at Mammoth, SW 1/4 Sec. 7
Location 2: Cochise County, AZ
Township/Range/Section	T11S R18E S23
General legal description	Willcox FO - San Pedro River
Location 3: Pinal County, AZ
Township/Range/Section	T4S R12E S6
General legal description	Casa Grande FO - Gila River - 15 Ranch
Location 4: Pima County, AZ
Township/Range/Section	T15S R13E S35
General legal description	Sells FO - San Xavier

Contributors

Dan Robinett
Larry D. Ellicott
Wilma J 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	10/20/2024
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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