(key to state/province abbreviations)
UNITED STATES

AZ

MD

NM

TX

VA

MEXICO

Chih.	Coah.	Dgo.	Edo. Méx.	Gro.
N.L.	Oax.	Pue.	Qro.	S.L.P.
Son.	Tamps.	Zac.

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This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

BLM PHYSIOGRAPHIC REGIONS [3]:

7 Lower Basin and Range

12 Colorado Plateau

13 Rocky Mountain Piedmont

14 Great Plains

The distribution of whitethorn acacia is disjunct. Whitethorn acacia is widespread in Texas, New Mexico, Arizona, and in northern and central Mexico [7,76]. It ranges from western Arizona east to western Texas and south to Oaxaca, Mexico [7,36]. Acacia constricta var. constricta also occurs in Maryland and Virginia [76]. A distributional map for whitethorn acacia and its varieties can be accessed through the Plants database.

Vachellia constricta (Benth.) Seigler & Ebinger:
Mexico (Mesoamerica)
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Acacia constricta var. paucispina Wooton & Standl.:
Mexico (Mesoamerica)
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Acacia constricta Benth.:
Mexico (Mesoamerica)
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

More info for the term: shrub

This description provides characteristics that may be relevant to the fire ecology of whitethorn acacia and is not meant for identification. Keys for identification are available (e.g., see [7,34,36,43,58,80]).

Whitethorn acacia is a drought, cold, and heat tolerant deciduous shrub [21,30]. It may terminate leaf and/or flower production during severe drought [30]. Whitethorn acacia can reach 19.7 feet (6 m) tall [7]. It is armed with straight spines that are 3 to 6 mm long and occur in pairs at the stem nodes. The compound leaves are thick, 1 to 2 inches (2.5-5 cm) long, and have 3 to 6 paired leaflets per leaf [7,80]. Extrafloral nectaries occur along leaf rachises [83]. Ants feed on these nectaries. The fruit is a legume. Seeds average about 3 mm wide, 5-6 mm long, and weigh an average of 0.67 ounces (19.1 g) [7,62]. The fruit pod has a woody or papery texture and is compressed tightly between the seeds. Seeds are oblong shaped and flattened [7].

Acacia constricta var. paucispina is most common at high elevations and can be twice as large as A. constricta var. constricta [80,92]. Commonly the spines of A. constricta var. constricta are fewer and reduced, while the leaves are typically larger on A. constricta var. paucispina. It is rare to see A. constricta var. paucispina growing in dense stands, while A. constricta var. constricta does occur in dense stands [92].

Whitethorn acacia plants are long lived. Plants in the Sonoran Desert were more than 72 years old. While long-term and short-term survival probabilities are high for this species, recruitment years are few, and the time required to see a 50% population turnover is likely much longer than 72 years [22].

Perennial, Trees, Shrubs, Woody throughout, Nodules present, Stems erect or ascending, Stems or branches arching, spreading or decumbent, Stems less than 1 m tall, Stems 1-2 m tall, Stems greater than 2 m tall, Trunk or stems armed with thorns, spines or prickles, Stems solid, Stems or young twigs glabrous or sparsely glabrate, Stems or young twigs sparsely to densely hairy, Leaves alternate, Leaves clustered on spurs or fasicles, Leaves petiolate, Extrafloral nectary glands on petiole, Stipules conspicuous, Stipules persistent, Stipules free, Stip ules spinose or bristles, Leaves compound, Leaves even pinnate, Leaves bipinnate, Leaf or leaflet margins entire, Leaflets opposite, Leaflets 10-many, Leaves viscid, sticky, Leaves glabrous or nearly so, Inflorescences globose heads, capitate or subcapitate, Inflorescence axillary, Bracts very small, absent or caducous, Flowers actinomorphic or somewhat irregular, Calyx 5-lobed, Calyx glabrous, Petals united, valvate, Petals white, Stamens numerous, more than 10, Stamens completely free, separate, Stamens long exserted, Filaments glabrous, Style terete, Fruit a legume, Fruit stipitate, Fruit unilocular, Fruit freely dehiscent, Fruit tardily or weakly dehiscent, Fruit elongate, straight, Fruit oblong or ellipsoidal, Fruit coriaceous or becoming woody, Fruit exserted from calyx, Fruit compressed between seeds, Fruit torulose or moniliform, strongly constricted between seeds, Fruit glabrous or glabrate, Fruit 3-10 seeded, Seed with elliptical line or depression, pleurogram, See ds ovoid to rounded in outline, Seed surface smooth, Seeds olive, brown, or black.

Type collection for Acacia constricta var. paucispina Wooton & Standl.
Catalog Number: US 497972
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Preparation: Pressed specimen
Collector(s): O. B. Metcalfe
Year Collected: 1904
Locality: S end of Blacke Range., Grant, New Mexico, United States, North America

Isolectotype for Acacia constricta Benth. in A. Gray
Catalog Number: US 73768
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Card file verified by examination of alleged type specimen
Preparation: Pressed specimen
Collector(s): C. Wright
Year Collected: 1849
Locality: Western Texas to El Paso, New Mexico., United States, North America

More info for the terms: association, caliche, shrub, shrubs

Whitethorn acacia tolerates a range of seemingly harsh environmental conditions. This shrub persists in both riparian and dry upland desert sites [57,90]. It is commonly found on dry hills, mesas, slopes, canyons, and intermittently wet washes, floodplains, and drainages in southwestern desert ecosystems [7,43].

Climate: The climatic conditions that characterize whitethorn acacia's range can be extreme. In the Rio Grande Valley of New Mexico, summer maximum temperatures can exceed 109 °F (42.8 °C) and winter lows can drop to 10 °F (-12.2 °C) [19]. Precipitation is commonly distributed in a bimodal pattern with most rain falling in intense spring and summer storms and less rain falling in the winter months in more moderate storms. In southeastern Arizona, the precipitation is still bimodal, but summer precipitation is more tightly restricted to July and August with often no precipitation in April, May, and June [5]. Campbell and others [6] describe droughts for the winters in New Mexico and Texas. Average yearly precipitation for these arid environments ranges from 8.5 to 10 inches (216-254 mm) with extremes of 3.5 to 19.6 inches (89-498 mm) reported [6,19]. Drying winds are also common, and in the summer months evaporation can exceed the annual precipitation by 50% [19].

Soils: Sandy to loamy soils are most often described in association with whitethorn acacia [6,18]. An impervious caliche or lime layer is also commonly associated with most of these soils [6,21,86]. Whitethorn acacia was found on soils with 6.3% to 10.9% moisture content during the period of most intense drought conditions, and dominated where the moisture content was 6.3% [41]. Wagner [83] found soil moisture, nitrate, ammonium, and phosphorus concentrations were higher when shrubs had ant nests beneath their canopies.

Elevation: A range of elevations is tolerated by whitethorn acacia:

AZ	2,500 to 5,000 feet (762-1524 m) [36] In Huachuca Mts., predominantly below 4,500 feet (1,372 m) [86]
NM	4,500 to 5,500 feet (1,372-1,676 m) in southern New Mexico [43]
TX	1,500 to 6,500 feet (457-1,981 m) [58]
Guadalupe Escarpment, NM & TX	3,600 to 5,000 feet (1,097-1,524 m) [21]

More info for the term: shrub

Whitethorn acacia is common in desert shrub,
desert scrub, desert grassland, and desert riparian communities [6,9,26,42,86,90].
Tree-shrub, shrub, and
sub-shrub species that are commonly associated with whitethorn acacia and are
not listed above include prickly-pear (Opuntia spp.), Yucca spp., catclaw acacia (Acacia
greggii), lotebush (Ziziphus obtusifolia), ocotillo (Fouquieria splendens), ironwood (Olneya tesota),
Agave spp., and allthorn (Koeberlinia spinosa) [6,9,26,42,45,65,86,90].
While several of these shrub species occur in riparian desert communities, some
preferentially or exclusively riparian shrub species that occur with whitethorn
acacia are desert hackberry (Celtis pallida), lemon verbana (Aloysia wrightii),
desert willow (Chilopsis linearis), Goodding willow (Salix gooddingii),
lanceleaf cottonwood (Populus × acuminata), and guayacan (Guajacum
angustifolium) [87,88].

Grasses that are commonly found with whitethorn acacia in desert grassland
communities and are not presented in the above lists include bush muhly (Muhlenbergia porteri),
Arizona cottontop (Digitaria californica), plains lovegrass (Eragrostis
intermedia), dropseed (Sporobolus spp.), and
curlymesquite (Hilaria belangeri) [6,9,26,42,45,65,86,90]. Red brome (Bromus
madritensis spp. rubens) and Mediterranean grasses (Schismus spp.) are exotic species
that occur with whitethorn acacia in desert shrub and grassland communities [12].

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This species is known to occur in association with the following Rangeland Cover Types (as classified by the Society for Range Management, SRM):

More info for the terms: cover, shrub

SRM (RANGELAND) COVER TYPES [69]:

212 Blackbush

505 Grama-tobosa shrub

506 Creosotebush-bursage

507 Palo verde-cactus

508 Creosotebush-tarbush

701 Alkali sacaton-tobosagrass

702 Black grama-alkali sacaton

703 Black grama-sideoats grama

704 Blue grama-western wheatgrass

705 Blue grama-galleta

706 Blue grama-sideoats grama

707 Blue grama-sideoats grama-black grama

708 Bluestem-dropseed

712 Galleta-alkali sacaton

713 Grama-muhly-threeawn

714 Grama-bluestem

715 Grama-buffalo grass

716 Grama-feathergrass

718 Mesquite-grama

719 Mesquite-liveoak-seacoast bluestem

727 Mesquite-buffalo grass

728 Mesquite-granjeno-acacia

729 Mesquite

734 Mesquite-oak

735 Sideoats grama-sumac-juniper

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This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

More info for the term: cover

SAF COVER TYPES [13]:

68 Mesquite

235 Cottonwood-willow

242 Mesquite

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the term: shrub

KUCHLER [39] PLANT ASSOCIATIONS:

K027 Mesquite bosques

K039 Blackbrush
K041 Creosote bush

K042 Creosote bush-bur sage

K043 Paloverde-cactus shrub

K044 Creosote bush-tarbush

K045 Ceniza shrub

K053 Grama-galleta steppe

K054 Grama-tobosa prairie

K058 Grama-tobosa shrubsteppe

K059 Trans-Pecos shrub savanna

K060 Mesquite savanna

K061 Mesquite-acacia savanna

K062 Mesquite-live oak savanna

K065 Grama-buffalo grass

K085 Mesquite-buffalo grass

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

ECOSYSTEMS [20]:

FRES30 Desert shrub

FRES32 Texas savanna

FRES33 Southwestern shrubsteppe

FRES38 Plains grasslands

FRES40 Desert grasslands

More info for the term: natural

Likely fire will not eliminate whitethorn acacia, as it sprouts following low- to moderate-severity fires. However, severe fires could potentially damage the root crown, and regeneration would be limited to seed germination and seedling establishment. Fire intervals that are shorter than the time required for seedlings to mature reproductively could reduce recruitment of whitethorn acacia.

The following are prescribed burning guidelines for desert grassland ecosystems that are thought to contain woody vegetation because of the lack of natural fires in the ecosystem. If burning in semidesert grass-shrublands, greater than 600 lb/acre (675 kg/ha) of fine fuels is required to sufficiently carry the fire. If present, burrowweed (Ambrosia spp.) can aid in carrying the fire and may reduce the amount of fine fuels needed. Burning in May or June is suggested. Air temperatures should be near 70 °F (21 °C), relative humidity should be 15%-30%, and winds should be less than 8 mi/hr (13 km/hr). Fire is not suggested for black grama- (Bouteloua eriopoda) dominated grasslands. These provided instructions need to be adjusted when fuels are lighter or heavier [93], and some test burning should occur to assess whether desired fire effects are being achieved. 

More info for the terms: density, fire severity, prescribed burn, root crown, severity, shrub, tree

Fire research on upland sites in the central Arizona Sonoran Desert showed that
whitethorn acacia coverage and density
were significantly (p<0.05) greater on repeatedly burned plots compared
to unburned plots. Burned sites were near a highway where fires had occurred 4
times in the last 30 years. In the same area, following a fire that occurred
less than 5 years before sampling burned and unburned plots, whitethorn acacia
coverage was lower and density was greater on the burned plots, although not
significantly. On a 7-year-old burn site, coverage and density of whitethorn
acacia were both slightly lower on the burned plots [2].
Following a prescribed burn designed to study fire effects on small mammal
populations in Cochise County, Arizona, the authors noted a reduction in tree
and shrub foliage on burned sites but no notable tree or shrub coverage
differences between the burned and unburned sites [16]. This finding is purely
qualitative, as preburn and postburn vegetation
differences were not measured.

Likely the response of whitethorn acacia following fire depends on fire severity
and damage to the root crown. One year following an arson fire near Phoenix,
Arizona, the density of whitethorn acacia was 76 shrubs/0.5 ha on burned plots
and 72 shrubs/0.5 ha on nearby unburned plots. All 72 whitethorn acacias on the burned sites
sprouted. No data were given on the severity of this fire [91]. After being top-killed by a propane torch, which
may have produced heating greater than that of the arson fire, whitethorn density had declined
80%, 70%, and 33% when plots were revisited 3 months, 15 months, and 2 years
later, respectively [78]. In burned areas of Carlsbad Caverns and Guadalupe
Mountains National Parks, Ahlstrand [1] suggests that prefire and postfire communities are
compositionally the same, just changed in relative coverage and
"competitive" ability.

The Research Project Summary Ibarra-F
and others 1996 provides information on mortality of whitethorn
acacia after prescribed fires in buffelgrass (Pennisetum ciliare)
pastures in Sonora, Mexico.

More info for the term: top-kill

Whitethorn acacia sprouts "vigorously" following top-kill by fire [44].

Low- to moderate-severity fires may only kill aboveground portions of whitethorn acacia, while severe fires can kill this species [2]. Seed buried in soil may survive fire. Whitethorn acacia seed 0.79 inch (2 cm) under the soil surface survived a prescribed desert grassland fire, while all seeds on the soil surface were killed [8].

More info for the term: crown residual colonizer

POSTFIRE REGENERATION STRATEGY [73]:
Crown residual colonizer (on-site, initial community)

More info for the terms: fire cycle, fire exclusion, fire frequency, frequency, fuel, natural, shrub, shrubs

Fire adaptations: Whitethorn acacia readily sprouts following fire; sprouting can occur as early as 1 month after fire [44].

FIRE REGIMES: The historic FIRE REGIMES for areas where whitethorn acacia occurs are likely different over the range of this species. They likely differ as the vegetation types change across the arid and semiarid desert ecosystems. Humphrey [28] separates the Sonoran Desert, Chihuahuan Desert, tobosa grasslands, and desert grasslands when attempting to describe the FIRE REGIMES of the Southwest. As a rule, he suggests that "the more arid the desert, the less fuel is produced, and the less frequent and severe are any fires that may occur." Fires were rare in the Sonoran Desert due to the noncontinuous fuels that result from dominance by trees and shrubs that are not well suited to burning. Fires were more frequent in the Chihuahuan Desert than in the Sonoran Desert. The greater abundance of perennial grasses and low-growing shrubs in the Chihuahuan Desert makes the landscape better able to carry fire. Where these desert systems meet what Humphrey [28] calls the desert grasslands, fires were more common, and the reduction of fires at these ecotones has likely facilitated the encroachment of woody vegetation and the conversion of grasslands to shrublands.

Reliance on fire-scarred trees to determine fire history is impossible in grass and shrubland systems; the use of historical records, plant adaptations, and other means is necessary to estimate FIRE REGIMES in these ecosystems. Miksicek [47] recovered whitethorn acacia and other woody desert vegetation charcoal from central Arizona. He suggested that vegetation charcoal and other agricultural features is evidence that the Hohokam people (2,205 B.P.-555 B.P.) used fire in central Arizona to clear areas for cultivation.

Cactus-shrub dominated ecosystems: Areas of the Sonoran Desert in Arizona that are dominated by saguaro (Carnegiea gigantea) and paloverde (Cercidium spp.) are thought to have burned less frequently than the desert grassland areas, and have historically burned less frequently than they do today [2,12,44]. This assertion is based on the postfire vegetation response in these areas: most of the vegetation in these communities does not sprout following fire, which suggests that fire was not evolutionarily important to these communities [44]. However, anthropogenic changes that include the increase of red brome, an exotic species that readily carries fire, and an increase in the number of fire ignitions is thought to have increased the probability of fires in saguaro- and paloverde-dominated communities [2,12,44]. These anthropogenic influences are especially evident following above-average winter precipitation or El Niño events that favor the growth of red brome [44]. Esque and Schwalbe [12] suggest red brome may favor a fire cycle similar to that of cheatgrass (Bromus tectorum) in sagebrush communities and may forever alter FIRE REGIMES in these communities. The return of Sonoran Desert communities to prefire structure and species composition is likely to take many decades, as recovery time for saguaro and paloverde is slow [12,63].

Grassland-dominated ecosystems: The grassland ecosystems of southwestern deserts now dominated by shrubs are thought to have burned regularly enough to restrict woody vegetation to riparian and drainage areas [15,27]. Cox and others [8] partially attribute the increasing abundance of whitethorn acacia in once grass-dominated desert areas to fire exclusion. Humphrey [26] suggests that periodic fires likely maintained the grasslands of Yavapai County, Arizona. However, since the 1800s woody vegetation has occupied several million acres that were historically grasslands with a few scattered shrubs. Livestock grazing is often the reason given for this fire frequency change. Grazing animals may have played a role in dispersing shrub seed, especially mesquite, from riparian to upland areas. The selective removal of grasses decreased the "competitive" ability of grasses as shrubs were establishing, and the resulting decrease in grass coverage and fuels removed the ability of the ecosystem to carry fire [27]. Dick-Peddie and Alberico [10] likewise attribute decreased fire frequency within the Chisos Mountains of Texas to grazing influences on fuels and the exclusion of natural fires.

While research has not addressed differences in the FIRE REGIMES for Acacia constricta var. paucispina and A. constricta var. constricta, the latter variety can grow in dense stands [92] and likely fire behaves differently when densely and sparsely vegetated shrublands are compared.

The following list provides fire return intervals for plant communities and ecosystems where whitethorn acacia is important. For further information, see the FEIS reviews on the dominant species listed below.

Community or Ecosystem	Dominant Species	Fire Return Interval Range (years)
desert grasslands	Bouteloua eriopoda and/or Pleuraphis mutica	5-100 [56]
plains grasslands	Bouteloua spp.	< 35
blue grama-buffalo grass	B. gracilis-Buchloe dactyloides	56,94]
grama-galleta steppe	Bouteloua gracilis-Pleuraphis jamesii	< 35 to < 100
blue grama-tobosa prairie	B. gracilis-P. mutica	< 35 to < 100
paloverde-cactus shrub	Cercidium microphyllum-Opuntia spp.	< 35 to < 100
blackbrush	Coleogyne ramosissima	< 35 to < 100
creosotebush	Larrea tridentata	< 35 to < 100
Ceniza shrub	L. tridentata-Leucophyllum frutescens-Prosopis glandulosa	< 35
galleta-threeawn shrubsteppe	Pleuraphis jamesii-Aristida purpurea	56]
mesquite	Prosopis glandulosa	46,56]
mesquite-buffalo grass	P. glandulosa-Buchloe dactyloides	< 35
Texas savanna	P. glandulosa var. glandulosa	56]

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More info for the terms: density, shrub, succession

There is much disagreement regarding succession and the vegetation types that represent late-seral communities in desert shrub and grassland ecosystems. Regardless, whitethorn acacia can be present in all developmental stages. Gardner [19] and Whitfield and Anderson [89] studied what were historically grass-dominated desert communities and suggest that these now shrub-dominated (typically whitethorn acacia, creosotebush (Larrea tridentata), and mesquite (Prosopis spp.)) communities represent a degenerated successional stage facilitated by grazing. Similarly, sites in the Chisos Mountains with high coverages of whitethorn acacia, whitebrush (Aloysia gratissima), lemon verbana, and catclaw acacia were considered by the authors to be indicative of past disturbance in the area [10]. However, Humphrey [28] suggests that an overstory of woody vegetation in grasslands represents the late-seral community, and that grasslands are early- or mid-seral communities persisting through reoccurring disturbances, chiefly fire.

In a study designed to address the effect of disturbance on desert scrub vegetation in southeastern Arizona, whitethorn acacia density was greatest on those sites disturbed by grazing alone. Whitethorn acacia density was lowest on sites that were plowed at depths of 17.7 to 21.7 inches (45-55 cm) for 5 years. Completely undisturbed sites supported a density of whitethorn acacia intermediate between the undisturbed and plowed sites [64].

More info for the terms: root crown, shrubs, top-kill

Whitethorn acacia reproduces by seed. Following top-kill, this species sprouts from the root crown [44,78,91].

Breeding system: Cross pollination is predominant in whitethorn acacia, although self pollination can occur [84].

Pollination: Honey bees are thought to be the most common pollinator for whitethorn acacia [84]. Flowers are short lived, and bees only pollinate flowers on the day flower buds open. Two- and three-day-old inflorescences are wilted and uninviting. In a controlled study, Wagner [84] found that significantly (p=0.004) fewer seed pods per flower were produced in self-pollinated flowers than in outcrossed flowers.

Seed production: Whitethorn acacia seeds are large, and production may vary with environmental stress. Wagner [83] found that when ant (Formica perpilosa) colonies were located at the base of whitethorn acacia shrubs, seed production averaged double that of shrubs without ant nests. During periods of severe drought, whitethorn acacia may not produce flowers [30].

Seed dispersal: It is likely that whitethorn acacia seed is dispersed by a variety of birds and mammals. In a southeastern New Mexico study, whitethorn acacia seed was identified in 41.4% of scaled quail crops that were harvested in the fall and winter [6]. Whitethorn acacia seed was also recovered from the stomachs and cheek pouches of Merriam's kangaroo rats and Arizona, Bailey's, and rock pocket mice in the Sonoran Desert [61]. While large mammals do not prefer whitethorn acacia, deer occasionally feed on leaves and pods [30]. When 1,000 and 2,500 seeds were fed to domestic sheep and cattle, 5.6 % and 1.9% respectively, of whitethorn acacia seeds germinated, suggesting that livestock dispersal of whitethorn acacia seed may be limited. There was no comparison between digested and undigested seed germination in the aforementioned studies, but whitethorn acacia seed does require scarification and increased germination occurs with increased seed coat removal [8].

Seed banking: Whitethorn acacia produces a seed bank, a portion of which may be the result of small mammal caches. Cox and others [8] found that kangaroo rats buried whitethorn acacia seed 0.8 to 1.6 inches (2-4 cm) below the soil surface after partially or fully removing seed coats. It is noteworthy that all whitethorn acacia seed on the soil surface was killed following a prescribed grassland fire, while seed buried 0.8 inch (2 cm) under the soil surface suffered no damage from the same fire [8].

Germination: Whitethorn acacia germinates best at warm temperatures. In the laboratory, optimal germination temperatures of whitethorn acacia seed were between 78.8 °F and 87.8 °F (27 °C and 30 °C). However, some germination (≥26%) occurred at all tested temperatures ( 60.8 °F  to 100.4 °F (16 °C-38 °C)). Germination improved with increased seed coat removal [8].

Seedling establishment/growth: Seedling establishment success is likely increased when seed is buried or protected. On a grassland site in southeastern Arizona, whitethorn acacia seed on the soil surface germinated, but seedlings did not establish. In the same area, the largest quantity of seedlings emerged when seed was planted 0.4 to 0.8 inch (1-2 cm) below the surface of sandy loam soils [8]. Whitethorn acacia seedling growth rates increased when seedlings were grown in soil inoculated with this species' associated rhizobia [85].

Several distinguishing seedling characteristics have been noted by Zisner [95]. Upon uprooting, whitethorn acacia seedlings emit a strong nitrogenous odor. A similar odor was found in other Acacia species but not in all Fabaceae species. Using this information along with other botanical characteristics, whitethorn acacia seedlings about 45 days old can be distinguished from other common Sonoran Desert species. An early identification key is available [95].

The growth of this desert species is likely regulated by moisture availability. During a normal precipitation year on Chihuahuan Desert rangeland, whitethorn acacia shrubs increased twig diameter by 47%. Shrubs produced fewer flowers, seeds, and twigs during a drought year [29].

Asexual regeneration: Following top-kill, this species sprouts from the root crown [44,78,91].

More info on this topic.

More info for the term: phanerophyte

RAUNKIAER [60] LIFE FORM:
Phanerophyte

More info for the terms: shrub, tree

Shrub-tree

More info on this topic.

Whitethorn acacia commonly flowers once in spring (April-June) and again in the summer or fall (July-October) [5,30]. Flower buds may form in November or December, but full flowers rarely develop. In a study in the Tucson Mountains of the Sonoran Desert, researchers found that whitethorn acacia flowering began when rainfall exceeded 0.43 inch (11 mm) and was followed by a heat sum of approximately 522 degree-days above 15 °C [5].

The following is a representative barcode sequence, the centroid of all available sequences for this species.


No available public DNA sequences.

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 3
Specimens with Barcodes: 3
Species With Barcodes: 1

Rounded Global Status Rank: G5 - Secure

United States

Rounded National Status Rank: NNR - Unranked

Rounded Global Status Rank: T4 - Apparently Secure

Reasons: In Arizona Acacia constricta var. paucispina is found occasionally (Kearney and Peebles 1951); in New Mexico, Martin and Hutchins (1980) recorded it in fewer counties than Acacia constricta var. constricta.

United States

Rounded National Status Rank: NNR - Unranked

More info for the terms: cover, density

Many have studied the control of whitethorn acacia as a means of increasing herbaceous cover.
Tebuthiuron controls whitethorn acacia
[25]. When below-average precipitation followed chemical and mechanical brush removal,
herbaceous vegetation density was not increased [52]. For more
information on chemical and mechanical control of whitethorn acacia see [11,50,51,52,66,67,79,82].

Within the Tamaulipan brushland of southern Texas and
northeastern Mexico, whitethorn acacia
was among many species
considered threatened by the native plant project of the lower Rio
Grande Texas valley [31]. Approximately 95% of this unique Rio
Grande floodplain ecosystem has been converted to agriculture and urban use.

More info for the terms: reclamation, restoration

Whitethorn acacia provides increased diversity and may decrease grazing pressure in revegetated and/or rehabilitated sites. Some suggest using whitethorn acacia in restoration projects, although it is often slow to establish, as a means of increasing the diversity of revegetated sites [30,32]. In the revegetation of disturbed desert sites, the use of diverse seed mixes may increase the establishment success of individual species, especially perennials [32]. Whitethorn acacia protects newly revegetated areas from grazing [30]. It also provides erosion control and tolerates saline soils [59]. Revegetation of a pipeline corridor in Arizona in 1986, using whitethorn acacia among several other native species, successfully resembled undisturbed sites after 10 years [33]. Whitethorn acacia seed is commercially available [33,59,77].

Whitethorn acacia's success in revegetation of mine reclamation sites depended on the protection of the revegetated sites. Whitethorn acacia seedlings suffered 100% mortality on the revegetated exposed east slopes of copper mine waste areas of Tucson, Arizona. On the more protected north slopes, some seedlings survived for at least 7 years following the initial seeding [53]. However, actual survival rates were unclear.

More info for the terms: cactus, cover, density, frequency, shrub, shrubs

Domestic livestock: Whitethorn acacia is not considered a preferred browse species for cattle. Some suggest that whitethorn acacia legumes are grazed by cattle when no better food source is available [80]. When assessing the effects of cattle grazing on the Kofa Wildlife Refuge in Yuma County, Arizona, a browse line was evident on Acacia spp. in areas where the density of cattle was high. In the same study, Acacia spp. were present in 16% of recovered fecal samples [68]. In a study in the southern Arizona Sonoran Desert, researchers found no difference in the frequency of whitethorn acacia on grazed and ungrazed sites [4].

Wildlife:
Large mammals: Desert mule deer do not feed extensively on whitethorn acacia, but whitethorn acacia often makes up a small amount of their diets. Ishaque and others [30] report that deer browse whitethorn acacia leaves and pods. A study conducted in the Belmont Mountains of Arizona found the diets of desert mule deer were 0.4% whitethorn acacia in the winter months. Likewise, when the researchers reviewed and compiled results from other desert mule deer diet studies, they found the use of whitethorn acacia was low (1%-5%) in summer, fall, and winter months and 0% in spring months [38]. Short [70] also found mule deer diets contained low amounts of whitethorn acacia (0.1-3%), with mule deer consuming the highest percentage of whitethorn acacia in summer months. In Carlsbad Caverns National Park, mule deer browsed whitethorn acacia from August to November, with most usage in October and November [37]. This low yet common usage of whitethorn acacia by mule deer suggests that whitethorn acacia may offer some needed trace nutrient and/or that whitethorn acacia may be utilized when more palatable plants are scarce.

Other large desert mammals may also utilize whitethorn acacia as a food source. Fecal samples of bighorn sheep collected from the Kofa Wildlife Refuge in Yuma County, Arizona, contained Acacia spp. [68].

Small mammals: Many small desert mammals feed on whitethorn acacia. Rodents prefer whitethorn acacia seed. Rabbit species likely browse whitethorn acacia when more preferred food sources are unavailable. In the lower Sonoran Desert, whitethorn acacia is a key food source of the southwestern pack rat [48]. Whitethorn acacia seed was recovered from the stomachs and cheek pouches of 3 pocket mouse species and 1 kangaroo rat species in the Sonoran Desert, and the researcher considered whitethorn acacia a preferred food for these rodents [61]. In desert shrub areas near Phoenix, Arizona, Stamp and Ohmart [72] found that whitethorn acacia seed made up 3.6% of the cheek pouch contents of desert pocket mice. Black-tailed and antelope jackrabbits, cottontail rabbits, and rodents utilize whitethorn acacia bark as a food source when other food is unavailable [30,81]. Arizona desert cottontails showed high preference for Acacia spp. in early spring. There had been no precipitation in the preceding 5 months and more palatable vegetation was not available [75].

Game birds: Whitethorn acacia is important to the survival of several southwestern bird species. Scaled quail feed extensively on whitethorn acacia seed [6,30]. In a southeastern New Mexico study, whitethorn acacia seed was identified in 41.4% of the crops of scaled quail that were harvested in the fall and winter, but whitethorn acacia seed was just 8.3% of crop content in summer harvested birds [6]. However, for this study the fall and winter sample size was 277, while just 12 birds were sampled in the summer. Gullion [24] notes that Acacia spp. are an important seed source for Gambel's quail.

Other avifauna: Other bird species that utilize desert shrub habitats where whitethorn acacia is commonly present include black-chinned hummingbirds, ladder-backed woodpeckers, ash-throated flycatchers, verdins, cactus wrens, mockingbirds, black-tailed gnatcatchers, brown-headed cowbirds, pyrrhuloxias, and house finches [88].

In Organ Pipe Cactus National Monument, verdins used Acacia spp. most when foraging [55]. Whitethorn acacia provides habitat and forage for phainopeplas, a bird species that disperses desert mistletoe (Phoradendron californicum) seed [40]. Desert mistletoe is parasitic on whitethorn acacia. Phainopeplas used Acacia spp. second only to honey mesquite (Prosopis glandulosa) for foraging in Organ Pipe Cactus National Monument [55].

Research by Stamp [71] suggests that whitethorn acacia may provide important avian breeding habitat. In the Lower Verde River region of Arizona where whitethorn acacia occurs, Abert's towhees, Lucy's warblers, mourning doves, and white-winged doves were found in densities greater than 20 breeding pairs per 40 ha [71]. In another study, whitethorn acacia shrubs taller than 6.6 feet (2 m) were selected by southwestern breeding birds for nesting sites in desert scrub communities [74].

Amphibians/Reptiles: It is possible that whitethorn acacia provides habitat for some southwestern herptiles. The narrow-mouthed toad and yellow mud turtle are commonly found in spring or man-made water areas where whitethorn acacia is common [88].

Palatability/nutritional value: Since the utilization of whitethorn acacia is low for most herbivores, it is reasonable to consider its palatability to be low. Ishaque [30] reports that the crude protein content of whitethorn acacia leaves is 25% in mid-summer and decreases to 18% to 22% by the end of the growing season. Whitethorn acacia is high in cyanide-forming compounds, and death may result when it is eaten in high concentrations  [30].

Whitethorn acacia seeds contain on average 93.57 calories/seed or 4,912 calories/g [62].

Cover value: Southwestern bird and small mammal species use whitethorn acacia for cover. Campbell and others [6] consider whitethorn acacia an important cover species for scaled quail. Acacia spp. provide important habitat for Gambel's quail [23,24]. In southern Arizona, Goodwin and Hungerford [23] report that 11 of 87 Gambel's quail roosting sites were in Acacia spp. Whitethorn acacia provides den cover for the southwestern packrat [48].

Whitethorn acacia has several cultural uses. Native Americans of Arizona and New Mexico used whitethorn acacia fruits to make pinole [58,80]. Seri Native Americans of Sonora, Mexico, used the seeds and leaves of whitethorn acacia, pulverized and heated in water, to treat stomach aches and diarrhea [14]. When ground into a powder, whitethorn acacia leaves and pods can stop bleeding, relieve diaper rashes and chafed skin, and may be used as an antimicrobial wash. A similar powder has been used by Native Americans to soothe aching back muscles of people and flank muscles of horses. A tea from the flowers and leaves has sedative properties and eases hangovers. The root, when made into a tea, treats sore throats, coughing, and mouth inflammations [30,49].