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Senegalia greggii

Table of Contents

• INTRODUCTORY
• DISTRIBUTION AND OCCURRENCE
• BOTANICAL AND ECOLOGICAL CHARACTERISTICS
• FIRE ECOLOGY
• FIRE EFFECTS
• MANAGEMENT CONSIDERATIONS
• REFERENCES

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INTRODUCTORY

AUTHORSHIP AND CITATION FEIS ABBREVIATION SYNONYMS NRCS PLANT CODE COMMON NAMES TAXONOMY LIFE FORM FEDERAL LEGAL STATUS OTHER STATUS

AUTHORSHIP AND CITATION:
Gucker, Corey L. 2005. Senegalia greggii. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.usda.gov/database/feis/plants/shrub/sengre/all.html [].

Revisions: On 8 September 2017, the scientific name of this species was changed in FEIS from: Acacia greggii
to: Senegalia greggii. Citations [9,24,72] were added to support the name change.

Hybrid: Catclaw acacia hybridizes with guajillo (S. berlandieri), producing Emory's acacia (S. × emoryana) Benth. [68,86].

LIFE FORM:
Shrub-tree

FEDERAL LEGAL STATUS:
None

OTHER STATUS:
None

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DISTRIBUTION AND OCCURRENCE

• GENERAL DISTRIBUTION
• ECOSYSTEMS
• STATES/PROVINCES
• BLM PHYSIOGRAPHIC REGIONS
• KUCHLER PLANT ASSOCIATIONS
• SAF COVER TYPES
• SRM (RANGELAND) COVER TYPES
• HABITAT TYPES AND PLANT COMMUNITIES

A distributional map of catclaw acacia can be accessed through the U.S. Geological Survey.

ECOSYSTEMS [43]:
FRES30 Desert shrub
FRES32 Texas savanna
FRES33 Southwestern shrubsteppe
FRES34 Chaparral-mountain shrub
FRES35 Pinyon-juniper
FRES38 Plains grasslands
FRES39 Prairie
FRES40 Desert grasslands

STATES/PROVINCES: (key to state/province abbreviations)

In drainages and minor waterways of the Lower Colorado Desert and parts of the Mohave Desert, catclaw acacia occurs in burrobush (Hymenoclea spp.)-dominated communities with Anderson wolfberry (Lycium andersonii), desertbroom (Baccharis sarothroides), cattle saltbush, and Mohave rabbitbrush [67,155].

Creosotebush (Larrea tridentata)-dominated communities are also typical in southern California. White bursage (Ambrosia dumosa), desert ironwood (Olneya tesota), blue paloverde (Parkinsonia florida), saguaro (Carnegiea gigantea), and catclaw acacia typify these communities [91,178]. Catclaw acacia is also typical of desert microphyll woodlands. Blue paloverde, smoketree, honey mesquite (Prosopis glandulosa), screwbean mesquite (P. pubescens), desert lavender (Hyptis emoryi), and creosotebush are typical of microphyll woodlands [151].

The Sonoran mixed woody and succulent scrub vegetation often includes catclaw acacia as well as desert agave (Agave deserti), brittle bush (Encelia farinosa), ocotillo (Fouquieria splendens), Schott's pygmycedar, Mohave yucca (Yucca schidigera), and prickly-pear (Opuntia spp.) [57].

Nevada:
Desert shrub communities of Nevada are dominated by smoketree, desert willow, Mohave desertrue (Thamnosma montana), brittle bush, triangle goldeneye (Viguiera deltoidea), pale wolfberry (Lycium pallidum), and catclaw acacia. Typical forb associates are strigose bird's-foot trefoil (Lotus strigosus var. tomentellus), foothill deervetch (L. humistratus), whitemargin sandmat Chamaesyce albomarginata, and desert globemallow (Sphaeralcea ambigua) [47].

Catclaw acacia occurs with desert wash vegetation. Common desert wash shrubs are desert willow, pale wolfberry, desertsenna (Senna armata), white burrobrush, bladdersage (Salazaria mexicana), and desert almond [47].

In Clark County, riparian areas are characterized by saltcedar (Tamarix ramosissma), velvet mesquite (P. velutina), desertbroom, and catclaw acacia [49].

Texas:
Catclaw acacia is typical of several juniper (Juniperus spp.)-dominated communities. In Pinchot juniper (J. pinchotii) communities of western and north-central Texas, catclaw acacia, velvet mesquite, and sideoats grama (Bouteloua curtipendula) are common. In the Rolling Plains of western Texas, common associates are prickly-pears, soapweed yucca (Y. glauca var. glauca), lotebush (Ziziphus obtusifolia), catclaw mimosa (Mimosa biuncifera), Texas tussockgrass (Nassella leucotricha), and Arizona cottontop (Digitaria californica) [97,98]. A similar community in the Rolling Plains of north-central Texas includes fragrant sumac (R. aromatica), littleleaf sumac (R. microphylla), agarito (Mahonia trifoliolata), lotebush, threeawn grasses (Aristida spp.), and little bluestem (Schizachyrium scoparium) [145].

In the Big Bend region of Texas, catclaw acacia is interspersed in sotol (Dasylirion spp.)- juniper-lechuguilla (Agave lechuguilla) and shortgrass/juniper communities characterized by the presence of oneseed juniper (J. monosperma). Other vegetation can include ocotillo, oaks (Quercus spp.), sumacs (Rhus spp.), gramas (Bouteloua spp.), and threeawns [27].

Northwest of Uvalde, Texas, catclaw acacia occurs with Ashe juniper (J. ashei), Texas persimmon (Diospyros texana), mescalbean sophora (Sophora secundiflora), agarito, and coyotillo (Karwinskia humboldtiana) [114].

Catclaw acacia also occurs in several mesquite-dominated communities. In the southern Texas Plains, catclaw acacia is found in mesquite-bunchgrass-annual forb savannas, mesquite-bristlegrass (Setaria spp.)-forb woodland communities, and mesquite-granjeno (Celtis pallida)-dominated communities [31,149]. The mesquite-granjeno community, considered indicative of disturbance, commonly includes ocotillo, Brazilian bluewood (Condalia hookeri var. hookeri), lime pricklyash (Zanthoxylum fagara), and sweet acacia (Acacia farnesiana) [149]. In the Chisos Mountains, the arroyo-mesquite-acacia association includes catclaw acacia, mesquite, mule's fat (Baccharis salicifolia), and desert willow [169].

Desert chaparral communities of the Rio Grande Plains and Texano-Mexican desert regions of Texas also include catclaw acacia [41,52]. Other species common to these desert chaparral communities are whitethorn acacia (Vachellia constricta), fragrant mimosa (Mimosa borealis), catclaw mimosa, featherplume (Dalea formosa), Brazilian bluewood, knifeleaf condalia (C. spathulata), and ocotillo [52].

Tarbush (Flourensia cernua) is often associated with catclaw acacia. In the creosote-tarbush association in Big Bend, catclaw acacia occurs with mariola (Parthenium incanum), white ratany (Krameria grayi), Big Bend barometerbush (Leucophyllum minus), longleaf jointfir (Ephedra trifurca), crown of thorns (Koeberlinia spinosa), yuccas, and javelin bush (C. ericoides). In the tobosa (Pleuraphis mutica)-tarbush habitat of Big Bend, grass cover is sparse. Acacias, velvetpod mimosa (M. dysocarpa), barometerbushes (Leucophyllum spp.), and snakeweeds (Gutierrezia spp.) dominate the community [27].

Catclaw acacia is also described with shortgrass-yucca communities. The shortgrasses are typically sideoats grama, muhly grasses (Muhlenbergia spp.), lovegrasses (Eragrostis spp.), and bluestems (Andropogon spp.) [27].

Northern Mexico/Texas:
Catclaw acacia is typical in Chihuahuan desert scrub and woodlands. Creosote, tarbush, viscid acacia (Acacia neovernicosa), barometerbushes, mesquite, desert honeysuckles (Anisacanthus spp.), and catclaw acacia characterize the creosote scrub vegetation. Apacheplume (Fallugia paradoxa), splitleaf brickellbush (Brickellia laciniata), granjeno, guajillo (Acacia berlandieri), little walnut (Juglans microcarpa), and American pistachio (Pistacia mexicana) characterize sandy arroyo scrub vegetation [53].

Mexico:
In both mesquite scrub and creosotebush desert communities catclaw acacia is characteristic [83].

New Mexico:
Catclaw acacia is associated with desert shrub, desert grassland, and arroyo riparian vegetation [19,28,172]. In the Guadalupe Mountains, catclaw acacia occurs with Pinchot juniper, lechuguilla, smooth sotol (Dasylirion leiophyllum), mariola, featherplume, threeawns, sideoats grama, and purple muhly (M. rigida) [172]. In the southern Great Plains of Lea County, black grama (Bouteloua eriopoda), tobosa, mesquite, whitethorn acacia, snakeweeds, and catclaw acacia are common [19].

Arizona/New Mexico:
In the Chihuahuan and Sonoran deserts, catclaw acacia populates the edges of secondary and lesser riparian systems [113].

In the Utah juniper (Juniperus osteosperma)/tobosa and redberry juniper (J. coahuilensis/shrub live oak (Q. turbinella) vegetation types of the Mogollon Rim, mesquite, redberry juniper, Utah juniper, and catclaw acacia are common. Singleleaf pinyon (Pinus monophylla), catclaw mimosa, broom snakeweed (G. sarothrae), and sacahuista (Nolina microcarpa) characterize the Utah juniper/tobosa community. Yellow paloverde (Parkinsonia microphylla), red barberry, and Fremont mahonia (Mahonia fremontii) occur in the redberry juniper/shrub live oak community [145].

Arizona:
Catclaw acacia is recognized in many grassland and shrub/grassland community types [25,58]. Grass-dominated communities include grassland-mesquite and grassland-desert shrub vegetation types. Typical grass species in both the grass and shrub dominated vegetation include gramas, threeawns, bullgrass (Muhly emersleyi), needlegrasses (Achnatherum spp.), dropseeds, and sacatons (both are Sporobolus spp.). Mesquite-grassland, desert shrub, desert shrub grassland, and desert shrub-half shrub vegetation types represent the shrub dominated communities. Mesquite, ocotillo, and acacias can be present in all the aforementioned shrub-dominated communities. The desert shrub-half shrub community has an understory of snakeweeds [25,50].

Desert wash and riparian vegetation described for south-central Arizona commonly includes catclaw acacia, paloverde, and mesquite [61,168,174]. Desert riparian communities are also habitat for whitethorn acacia, bursage (Ambrosia spp.), Berlandier's wolfberry, desert ironwood, Drummond's clematis (Clematis drummondii), and fingerleaf gourd (Cucurbita digitata) [174].

In central Arizona, catclaw acacia is associated with juniper- and shrub live oak-dominated vegetation. In the Coconino National Forest, catclaw acacia is found with Utah juniper, shrub liveoak, manzanitas (Arctostaphylos spp.), bitterbrushes (Purshia spp.), desert ceanothus (Ceanothus greggii), and mountain-mahogany (Cercocarpus spp.) [109]. Catclaw acacia is also present in shrub live oak-birchleaf mountain mahogany (C. betuloides), shrub live oak-mixed shrub, and pointleaf manzanita (A. pungens) communities [20].

Catclaw acacia in southeastern Arizona associates with desert scrub vegetation types. In the Santa Catalina Mountains, low densities of catclaw acacia are found in creosotebush desert scrub communities. Bursage desert scrub vegetation includes fishhook pincushion (Mammillaria grahamii var. grahamii), triangle bursage (Ambrosia deltoidea), and catclaw acacia. The arroyo margin woodland vegetation is often characterized by the presence of singlewhorl burrobush (Hymenoclea monogyra), honey mesquite, and catclaw acacia. Increased densities of catclaw acacia occur in disturbed desert scrub communities with burroweed (Isocoma tenuisecta) and brittle brush and in spinose suffrutescent desert scrub communities with slender janusia (Janusia gracilis), yellow paloverde, and ocotillo [110].

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BOTANICAL AND ECOLOGICAL CHARACTERISTICS

GENERAL BOTANICAL CHARACTERISTICS RAUNKIAER LIFE FORM REGENERATION PROCESSES SITE CHARACTERISTICS SUCCESSIONAL STATUS SEASONAL DEVELOPMENT
	© 2002 Dr. Louis Emmet Mahoney

Catclaw acacia is a native, long-lived, deciduous, spreading shrub or small tree [33,107,164]. Depending on the harshness of site conditions, catclaw acacia typically ranges from 3.3 to 29.5 feet (1-9 m) tall [107,164]. On the Lower Rio Grande River, catclaw acacia trees measured 35 feet (10.7 m) [52]. The main trunk can be 12 inches (30.5 cm) in diameter; the bark is commonly 3.2 mm thick, developing cracks and becoming scale-like with age [164]. Catclaw acacia is heavily armed with stout, curved spines (3-4 mm long) distributed along branches at the internodes [30,74,93,107,170].

Alternate leaves are bipinnate with 4 to 7 leaflet pairs. Leaves measure 0.8 to 2 inches (2-5 cm) long. Leaflets are between 2 and 12 mm long and are normally hairy [30,107,170]. Catclaw acacia has extrafloral nectaries on the primary rachis that are thought to promote mutualistic interactions between catclaw acacia and insects, commonly ants. The ants provide protection from other insect herbivores, while the extrafloral nectaries provide the ant with food and water [119]. Catclaw acacia's legume fruits are straight to twisted, constricted between the seeds, and measure 2 to 4.7 inches (5-12 cm) long by 0.4 to 0.8 inches (1-2 cm) wide [30,56,74,93,107]. Seeds are round and typically 5-7 mm in size [170]. Although catclaw acacia is a legume, in controlled experiments nodulation has not occurred [35,181].

Catclaw acacia is highly adapted to harsh desert conditions. A deep root system, high water use efficiency, high photosynthetic capacity, and use of the C3 photosynthetic pathway allow catclaw acacia to thrive in harsh desert climates [13,33,44,67,84]. Zimmerman [179] observed catclaw acacia roots greater than 18 feet (5.5 m) deep in southeastern Arizona. On a wash site in the Gold Valley of the Mohave Desert, 55% of the total catclaw acacia dry weight was root [42].

Catclaw acacia is long lived. Catclaw acacia shrubs were aged from repeat photographs of Grand Canyon sites. Photographs indicate that 85% of the plants on the sites were at least 104 years old. Other pictures showed that 5 of 6 plants were at least 120 years old. Researchers estimated 15% mortality and 27% recruitment in 100 years from the photographs [18].

RAUNKIAER [129] LIFE FORM:
phanerophyte

REGENERATION PROCESSES:
Catclaw acacia reproduces sexually through seed production, and when top-killed, catclaw acacia regenerates asexually through root crown sprouts [10,36,55,59,94].

Breeding system: No information is available on this topic.

Pollination: Catclaw acacia is considered an important honey plant [74,85,125], and likely bees are the chief flower pollinators.

Seed production: Seed predation is common for catclaw acacia (see IMPORTANCE TO LIVESTOCK AND WILDLIFE section).

Seed dispersal: Dispersal of catclaw acacia seed can result from animal movements and abiotic disturbances. In the Chihuahuan Desert of Arizona and New Mexico, researchers found that plant material used by cactus wrens to construct nests often include seeds. One of 12 cactus wren nests contained catclaw acacia seed. Collections are commonly made greater than 65.6 feet (20 m) from the nest site making nest construction a seed dispersal mechanism [100]. Likely grazing animals disperse catclaw acacia seed [6,60]. No studies addressed seed viability once passed through the digestive tract.

Following heavy rainfall (76% of annual average) in San Diego County, California, 612 catclaw seedlings per hectare occurred on a site void of mature catclaw acacia. However, catclaw acacia occurred in washes upstream from the site. Most likely the storm relocated seeds from the wash to produce the catclaw acacia seedling population [178].

Seed banking: Seed bank development by catclaw acacia is not well understood. While some suggest a persistent seed bank [15], others recovered no catclaw acacia seed from 240 soil samples taken from herbicide treated and control sites in the Chihuahuan Desert of Texas. Researchers suggested heavy seed predation, reliance on a short-lived seed bank, and/or dependence on asexual reproduction to explain the lack of catclaw acacia seed in soils samples [163].

Germination: Temperature and moisture requirements must be met for catclaw acacia seed to germinate. Bowers [15] suggests that August and September seed germination is triggered by 1.2 inches (30 mm) or more of rainfall. Jordan and Haferkamp [71] suggest temperatures above 45 °F (7.2 °C) are required to germinate catclaw acacia seed. In California's Joshua Tree National Monument, catclaw acacia germinated only in August and September [171]. However, factors other than temperature and moisture may affect germination. Even when able to control growing conditions, horticulturists were unable to germinate seed collected from plants in 1927, while seed collected in 1929 germinated [37].

Seedling establishment/growth: Site conditions and early disturbances affect catclaw acacia seedling development. Perkins and Owens [120] found seedling growth was greatest when plants were exposed to full sunlight. When defoliated early in development, catclaw acacia seedlings had significantly (p<0.01) less total biomass than nondefoliated seedlings.

Many Sonoran Desert species including catclaw acacia are described in a seedling identification key. Descriptions are provided for catclaw acacia seedlings from 1 to 45 days after emergence. A strong nitrogen odor is given off when seedlings are uprooted. This same trait is described for other Acacia spp. but not all Fabaceae species [180].

Asexual regeneration: Catclaw acacia readily reproduces vegetatively following the removal of aboveground biomass [10,36,55,59,94].

SITE CHARACTERISTICS:
Catclaw acacia occupies dry gravelly mesas, canyons, arroyo banks, rocky hillsides, desert flats, washes, floodplains, and riparian areas in arid to semiarid southwestern regions [16,89,101,164,175].

Elevation:

Soils: The desert soils typical of catclaw acacia habitat are low in organic matter, can be slightly acidic to slightly alkaline, are often shallow (< 12 inches (30.5 cm) deep), and commonly contain calcium carbonate in the upper 6.6 feet (2 m) of soil. The caliche layer can be thick and impenetrable [90,92].

Climate: The climate regimes described for catclaw acacia habitats range from mild to severe. In southwestern semiarid deserts, winters are often mild and summers are warm to hot. Annual average precipitation predominantly ranges from 8 to 20 inches (203-508 mm) [92]. Precipitation levels can be much lower in the Sonoran and Chihuahuan deserts where annual precipitation levels range from 2 to 12 inches (51-305 mm) and 3 to 16 inches (76-406 mm), respectively [62].

In the lower Colorado Desert of southern California, precipitation is between 2.5 and 4 inches (63.5-102 mm) annually, relative humidity is extremely low, and high summer temperatures can reach 120 °F (49 °C) [91]. The chaparral-desert ecotone of southern California on average receives 12.6 inches (321 mm) of precipitation annually, 69-78% of which falls from October through April [13]. A bimodal rain pattern is typical for Arizona deserts. The 14.5 to 17 inches (368-434 mm) of annual rain falls in the winter and early spring and again in mid- to late summer; late spring and early summer are arid [1,13]. April through June in Tucson received little over 0.5 inch (12.7 mm) for a recorded 27 year average [150]. In central Arizona, winter temperatures are between 32 °F and 68 °F (0 °C-21 °C) and summer temperatures range from 70 °F to 109 °F (21 °C-43 °C). Southern Nevada weather is also characterized by bimodal precipitation with widespread winter rain and intense summer monsoons [82]. Maximum high and low temperatures in Clark County, Nevada, are wide ranging. The winter minimum can be 32 °F (0 °C) and summer maximums are often as high as 102 °F (39 °C) [49]. Temperatures are more extreme for the Desert Plains of Brewster County, Texas, where lows and highs range from 10 °F (-12 °C) to 120 °F (49 °C). This area receives less than 10 inches (254 mm) of precipitation/year [27].

SUCCESSIONAL STATUS:
The concept of succession, in which community composition changes over time as a site is modified by past and present species, was developed in mesic eastern forests and does not apply well to southwestern desert ecosystem dynamics. In eastern forest ecosystems, pioneer species are typically not present in climax communities. In southwestern deserts, species that make up the predisturbed vegetation are the same species that make up the recovering vegetation [106]. While true Clementsian succession does not occur in semiarid and arid ecosystems, it is possible to see shifts in species dominance in relation to disturbance [135]. The continued use of many traditional succession terms to explain desert community change or development is likely due to the lack of more appropriate terms.

In the case of catclaw acacia, the terms "postclimax", "disclimax", and "subclimax" have been used to describe this species' response to various disturbances. In the southern desert plains, mesquite-acacia vegetation that increased in abundance and extent with disturbance is labeled "postclimax" [173]. Others classified catclaw acacia as an "invader" species when it appeared late in the stages of community degradation in the Guadalupe Mountains of New Mexico [172]. In the south Texas Plains, catclaw acacia is one of several species considered dominant in the mesquite-granjeno disturbance community type [149]. Dick-Peddie and Alberico [29] described vegetation dominated by beebrushes (Aloysia spp.), lechuguilla, tulip prickly pear (Opuntia phaeacantha), blue grama (Bouteloua gracilis), sideoats grama, whitethorn acacia, and catclaw acacia as "disclimax" vegetation maintained through grazing and fire reduction. Whitfield and Anderson [173] considered sacaton vegetation, typically including catclaw acacia, an edaphic "subclimax" community persisting on heavy clay or alkali soils of washes and flood plains.

When studying different-aged debris flows in the Grand Canyon of Arizona, Bowers and others [17] found catclaw acacia in almost all but the youngest and oldest communities. The percent coverage and densities of catclaw acacia on different aged debris flows are presented below.

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FIRE ECOLOGY

• FIRE ECOLOGY OR ADAPTATIONS
• POSTFIRE REGENERATION STRATEGY

Fire regimes: Across the range of habitats occupied by catclaw acacia, historical fire regimes vary widely. Semiarid grassland communities likely burned often while extremely arid thorn scrub communities rarely burned. European settlement and changes in land use have substantially affected the likelihood of fire in these communities.

Grassland communities: Early settlers and explorers described grasslands across large areas of the Southwest, while descriptions of woody vegetation suggested its restriction to waterways and rocky hillsides [144]. Decreased fire frequencies in grasslands are often considered the reason for dense shrub communities in areas once dominated by grasses [2,29]. Frequent fires limited woody vegetation establishment, maintaining grasslands [59]. Likely the fire frequency in desert grasslands was such that shrubs were killed in the seedling stage or prior to reaching reproductive maturity [62].

High numbers of cattle grazing these grasslands directly and indirectly promoted the rapid conversion of grassland-dominated areas to shrub-dominated areas [6]. Grazing animals likely dispersed shrub seed. The selective removal of grasses decreased the "competition" between grasses and establishing shrubs and decreased available fuels and eventually fire frequencies [6,60]. McPherson [96] predicted future changes in the desert grassland fire regime. Decreases in cattle grazing and increases in nonnative grasses may favor more frequent fires than did the last century, yet a return to historic fire frequencies is highly unlikely due to fragmented fuels and continued fire suppression efforts. However McPherson recognizes that changes in climate, political agendas, and land use will continue to affect desert grassland fire regimes [96].

Cactus and desert scrub communities: In the Mohave, Sonoran, and Chihuahuan deserts, the dominant vegetation is widely spaced, open-branched, and not prone to burning. Biomass production by native perennial grasses and forbs is low and coverage is sparse, resulting in noncontinuous fuels [62,162]. Historically in the Mohave Desert, the most arid of the North American deserts, fires were extremely rare. Fires were also rare in the Sonoran and Chihuahuan Deserts. The low-growing stature and dense shrub canopies of the Chihuahuan Desert make this desert slightly more fire prone than the taller and more widely spaced vegetation of the Sonoran Desert. Portions of the Sonoran and Chihuahuan deserts that bordered desert grassland systems burned more frequently [62]. The lack of fire-adapted vegetation in these deserts is further evidence of fire rarity [2]. Paloverde, saguaro, and other small cacti (pincushions (Scabiosa spp.) and prickly-pears) do not sprout following fire and are typically killed by even low-severity fires. It may take a century or more for saguaro and paloverde to develop from seed to large adult size [36,94].

As in grassland-dominated desert communities, European settlement and land use have inadvertently altered fire regimes in desert scrub and thorn scrub communities. Fires in these communities are more frequent than those that occurred historically [1,36,162]. The introduction and subsequent expansion of several nonnative species including red brome (Bromus madritensis spp. rubens), cheatgrass (B. tectorum), mediterranean grasses (Schismus spp.), buffelgrass (Pennisetum ciliare), and potentially ripgut brome (B. diandrus) increased fire risk in many desert scrub communities [1,36,122,162]. The displacement of native ephemeral species by these successful nonnative species creates easily ignited communities and supports large fires [94,122]. Increased fire frequencies in these fire-intolerant communities will likely alter their composition by removing fire sensitive species and increasing fire tolerant species [36,162]. Alford and Brock [1] studied the postburn vegetation response in fire sensitive Sonoran desert communities and found several native species (saguaro, foothill paloverde, white ratany, creosote bush, wolfberry) decreased while purple threeawn, senna, and red brome increased [1].

Fire-return intervals for plant communities and ecosystems where catclaw acacia is a common associate are summarized below. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find Fire Regimes".

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FIRE EFFECTS

• IMMEDIATE FIRE EFFECT ON PLANT
• DISCUSSION AND QUALIFICATION OF FIRE EFFECT
• PLANT RESPONSE TO FIRE
• DISCUSSION AND QUALIFICATION OF PLANT RESPONSE
• FIRE MANAGEMENT CONSIDERATIONS

Fire alone: The following studies illustrate the more typical postfire response for catclaw acacia. Following a fire in the Santa Rita Mountains of Arizona, 90% of catclaw acacia plants in wash areas were sprouting and 100% in the upland sites were sprouting. The timing of this fire was not clear [148]. Following an early May fire in a south-central Arizona giant saguaro community, the density of catclaw acacia on burned and unburned sites was compared. Catclaw acacia density (plant/0.5 ha) was 44 on unburned sites and 42 on burned sites [176]. In south-central Arizona following a June fire, the percentage of postfire catclaw acacia sprouts ranged from 75% to 100% [133].

In a study of the recovery of Sonoran Desert vegetation following fire, burned areas were sampled and compared to nearby unburned areas. Given below are the mean heights, canopy covers, and densities for catclaw acacia on 21-year-old burns, repeatedly burned sites (4 fires in 30 years), and unburned sites. Both canopy coverage and density increased with repeated burning [1]:

After a July fire in Los Angeles County, California, the postfire recovery of chaparral-desert ecotone vegetation was assessed. Catclaw acacia averaged 166 sprouts per plant following the fire, and survival by postfire sprouting was high. Density on the ridge sites was lower than on canyon sites. The postfire response for catclaw acacia is provided below [153]:

Fire in conjunction with other disturbances: The following studies involve use of fire and other disturbances as a means of reducing woody vegetation. The prescribed fire timing for these studies often differs from presettlement fire regimes for the areas. In the Rolling Plains and Edwards Plateau regions of Texas, sites chained then burned reduced catclaw acacia cover by 40%. Chaining occurred 4 to 5 years prior to a late winter prescription fire, and coverage change measurements occurred 2 years postfire [156].

In the San Simon Valley of southeastern Arizona, researchers assessed the effects of grazing and fire in a shrub-invaded grassland. The average ground cover (number of counts/500 census locations) for catclaw acacia on all plots was 3.7% prior to any treatments. Fires occurred on the 20th or 21st of June 1993. Catclaw acacia coverage decreased on burned and grazed plots. Coverage initially decreased on unburned grazed plots but decreases were short lived. The resulting changes in ground cover for catclaw acacia are presented below (note: Burned, B; Unburned, UB; Grazed, G; Ungrazed, UG) [161]:

Repeated fires: Another method used to control woody vegetation is repetitive burning. Catclaw acacia seems tolerant of repeated fires that allow for at least a year between fires; however, fires that burn within the same year resulted in decreased catclaw acacia cover and density. In the Rio Grande Plains of Texas, researchers annually and biennially burned mesquite-acacia savannahs during the dormant (January-February) and growing (July-August) seasons. Growing season fires burned when air temperatures were between 95 °F and 104 °F (35 °C-40 °C), wind speeds were 2.2 to 5.4 m/s, and relative humidity was 20% to 50%. Dormant season fires burned when air temperatures were 44.6 °F to 64.4 °F (7 °C-18 °C), winds were 1.3 to 4.5 m/s, and relative humidity was 65% to 80%. For the biennial burning schedule, a total of 2 fires burned during the study. The dormant season annual fires occurred for 4 consecutive years while the growing season annual fires burned for 3 consecutive years. Regardless of burn prescription, catclaw acacia coverage was greater on burned sites. The changes in catclaw acacia cover are provided below [115]:

In the western South Texas Plains, some sites were burned for 2 consecutive winter seasons (winter burn). Other sites were burned in the winter and burned again the following summer (winter-summer burn), while other sites were unburned. Catclaw acacia cover and density increased following the winter burn and decreased following the winter-summer burn treatment. The longevity of these changes is unknown. The changes in catclaw acacia given different patterns of burning are given below [136]:

Using fire to decrease shrub cover, increase herbaceous cover, and/or alter stream flows requires repetitive burning and integrated management. Hibbert and others [55] suggest prescription burns in chaparral-dominated brush communities alone do not often significantly reduce shrub cover. Many shrubs in this community, including catclaw acacia, sprout following fire, and likely only fire-sensitive species are killed. A combination of fire and other control methods is necessary to substantially reduce the shrub component from chaparral communities [55]. Humphrey [62] suggests that fires every 5-10 years in desert grasslands could control woody vegetation encroachment [62].

The effectiveness of fire as a tool to combat increases in nonnative species is unknown for many desert areas. In saguaro-paloverde dominated Sonoran Desert communities, postfire rehabilitation measures are necessary following any prescription fires designed to control nonnative species, as these communities are not fire adapted [1]. In southeastern Arizona, hawk's eye (Euryops multifidus) displaced native grasses and shrubs (including catclaw acacia). The response of hawk's eye monocultures to fire or other natural disturbance processes is unknown [123].

When considering the postfire response of vegetation, postfire utilization is important. In Anza-Borrego Desert State Park of California, researchers assessed the utilization of catclaw acacia by herbivores following a July fire. The number of catclaw acacia sprouts per hectare browsed by wildlife varied by season. For the number of sprouts produced postfire, see the Fire alone section above. The utilization of new sprouts was greatest in the fall and winter months. Sprout browsing results are provided below [153]:

MANAGEMENT CONSIDERATIONS

• IMPORTANCE TO LIVESTOCK AND WILDLIFE
• VALUE FOR REHABILITATION OF DISTURBED SITES
• OTHER USES
• OTHER MANAGEMENT CONSIDERATIONS

Livestock: Catclaw acacia is typically grazed in the spring or when new growth is available, but animal densities and availability of other forage also affect livestock use of catclaw acacia. Humphrey [58] considered catclaw acacia marginal cattle forage. Utilization of catclaw acacia is typically restricted to spring when young twigs and leaves are available. Humphrey [58] considered mature pods "worthless as feed." In areas of the Kofa National Wildlife Refuge in Yuma County, Arizona, browsing of Acacia spp. occurred in areas where cattle numbers were high [139]. In Coahuila, Mexico the diets of goats were monitored for 3 years. Utilization was highest by goats in the summer and fall. The percentage of their diets constituting catclaw acacia is shown below [87]:

In another northeastern Mexico study, goat grazing of catclaw acacia followed no seasonal pattern [128].

Deer: The utilization of catclaw acacia by both mule and white-tailed deer varies with year, season, and climate conditions. In a 4-year-long study of mule deer and white-tailed deer diets in southeastern Arizona, researchers found that only mule deer fed on catclaw acacia. Catclaw acacia was approximately 4% of mule deer diets from February through April and about 18% in May, June, and July. The disproportionate usage between deer species was likely because white-tailed deer inhabited higher elevations where catclaw acacia was rare [5]. In the Tonto National Forest of south-central Arizona, both white-tailed deer and mule deer fed on catclaw acacia. Stomach content analyses revealed catclaw acacia usage was greatest (14% average volume) for 11 mule deer taken in mid-summer. For white-tailed deer, catclaw acacia usage was greatest (16% average volume) for 5 deer taken in late December. Utilization of catclaw acacia in all other seasons was low (0%-2%) by both white-tailed and mule deer [95]. In the Belmont Mountains of Arizona, mule deer utilized catclaw acacia most in the winter months, but high utilization rates occurred in only 1 of 3 sampling years [75]. In the Sonoran Desert south of Tucson, catclaw acacia made up 17.9%, 1.9%, 11.2%, and 3.9% of mule deer diets in the spring, summer, fall, and winter, respectively [143]. However, in the Coconino National Forest of Arizona, catclaw acacia made up just 0.05%, 0.2%, and 0.04% of trained mule deer diets in the winter, spring, and summer, respectively [109].

Mule deer browsing increased with drought conditions in south-central Arizona. Mule deer diets when precipitation levels were 6 inches (154 mm) below average contained 6 times more catclaw acacia than during a normal precipitation year. The percent volume of catclaw acacia eaten from March through July during a normal precipitation year was 2.1 ±1.1 and during the drought was 12.3±4.4 [4]. Many factors could account for the variable use of catclaw acacia by deer. Past disturbances, availability of other vegetation, and/or herbivore population density fluctuations may affect utilization rates.

Other ungulates: Catclaw acacia is an important food for both collared peccaries and feral asses. In southern Arizona, Eddy [32] observed collared peccaries feeding, and based on time-spent-feeding data, he established that catclaw acacia beans constituted 3%-5% of the collared peccary diet from July through September. Researchers described catclaw acacia beans as "relished" by collared peccaries [32]. Feral asses in the Mohave Desert consistently utilize catclaw acacia. The highest levels of use occur from October through January when catclaw acacia makes up about 10% of the feral ass diet [14].

Carnivores: The following studies indicate that carnivores may utilize catclaw acacia. Murie [108] found a single coyote scat comprised primarily of catclaw acacia, which was a rare component of the area's vegetation. In central Arizona, mountain lions buried 2 of 9 pronghorn kills under catclaw acacia and shrub live oak brush thickets [112].

Small mammals: Rodents and rabbits commonly feed on catclaw acacia. In southeastern Arizona and southwestern New Mexico, researchers recovered catclaw acacia flowers, leaves, and empty seed pods from western white-throated woodrat dens [102]. Gullion [48] reports that a conservation officer in Nevada observed beaver eating catclaw acacia when Lake Mohave flooded more preferred vegetation. Mature catclaw acacia is not preferred by desert cottontails and jackrabbits, but nonetheless is important. Rabbits browsed newly planted catclaw acacia in Riverside county, California [37]. Turkowski [154] found Acacia spp. (catclaw and whitethorn) comprised a majority of desert cottontail diets in March and April during an exceptionally dry season (0 precipitation from January to April). Vohries and Taylor [165] similarly report the utilization of large stem bark, small diameter branches (.06-.33 inches), and leaf buds by both antelope jackrabbits and black-tailed jackrabbits during dry seasons.

Game birds: Catclaw acacia provides nesting habitat, roosting sites, and food for several game birds. In southern Arizona, 11 of 87 Gambel's quail roosting sites were in Acacia spp., while 1 of 3 located nests were under Acacia spp. [46]. Scaled quail also nest under Acacia spp. [169]. Catclaw acacia is an important year-round food source for both Gambel's and scaled quail [48,167]. In Brewster County, Texas, a region considered the geographic center of the scaled quail's range, catclaw acacia fruits were in more than 10% of 71 crops analyzed throughout the year, and catclaw acacia was the 8th most frequently consumed food by scaled quail [167]. White-winged doves also feed on catclaw acacia seeds [48].

Other birds: The use of catclaw acacia for nesting and foraging by southwestern birds is extensive. In southern Nevada, catclaw acacia received 19% relative use as nesting sites by breeding desert birds [8]. In southeastern New Mexico, cactus wren and loggerhead shrike breeding pairs chose catclaw acacia for nesting sites, in an area where catclaw acacia was uncommon [26]. Two of 12 cactus wren nests studied in the Chihuahuan Desert of Arizona and New Mexico were found in catclaw acacia shrubs. Catclaw acacia was used as nest material in another cactus wren nest [100]. Black-throated sparrows used catclaw acacia greater than 6.6 feet (2 m) tall for nesting [152]. Lesser nighthawks nested under Acacia spp. [169]. In Arizona's Organ Pipe National Monument, verdins used Acacia spp. (whitethorn and catclaw) most when foraging; phainopeplas used Acacia spp. second to mesquite when foraging. Black-tailed gnatcatchers, ash-throated flycatchers, and Gila woodpeckers also used Acacia spp. for foraging, but usage was much less [116].

In other studies, many birds preferred catclaw acacia habitats. Black-chinned hummingbirds, ladder-backed woodpeckers, ash-throated flycatchers, verdins, cactus wrens, mockingbirds, black-tailed gnatcatchers, brown-headed cowbirds, pyrrhuloxias, and house finches utilize desert shrub habitats where catclaw acacia is common in the Chisos Mountains of Texas [169]. Habitat used by the endangered ferruginous pygmy owl includes communities where catclaw acacia is common. Sonoran desert scrub vegetation dominated by mesquite, palo verde, desert hackberry, and catclaw acacia may connect pygmy owl habitats and populations [21].

Palatability/nutritional value: Many have studied the chemical composition of catclaw acacia. Compositional differences may reflect climate, region, soil, and/or collection differences.

In the Edward Plateau region of Texas, researchers assessed the nutritional value of leaves collected from April through July and twigs collected in July. As a general trend, the highest values came from plant material collected earliest, while the lowest values corresponded to the later collections. The nutritional contents are provided below [64]:

Catclaw acacia and other leguminous shrubs in the area are considered an important summer protein source for mule deer [157]. The chemical composition of catclaw acacia fruits collected in late June from Arizona chaparral and desert habitats is provided below. The in vitro digestibility was 32% for mule deer and 29% for white-tailed deer [158].

For catclaw acacia foliage collected in the fall from the Tamaulipas shrubland in Nuevo Leon, Mexico, the chemical composition was [127]:

Several other chemical composition studies involved the collection and analysis of plant material throughout the year. The range of catclaw acacia leaf nutrient contents as seasons change is provided below for northeast Mexico [126]:

In several regions of Arizona (Picacho Mountain lowlands, King Valley, and the Harquahala Mountains) researchers analyzed the nutritional composition of catclaw acacia. The results are given below [76,130,140]:

Cover value: Catclaw acacia provides shelter, protection, and shade to a diversity of desert mammals and birds. Trees or large shrubs (≥6.6 feet (2 m)) provide thermal cover for bighorn sheep. Catclaw acacia normally reaches this height or greater, allowing bighorn sheep to avoid direct sunlight and moderate high daytime temperatures [45]. Catclaw acacias are important cover for collared peccaries and shade for cattle as well [61]. The western white-throated woodrat uses catclaw acacia for den protection [102]. Similarly in the Santa Rita Range of Arizona, 66% of catclaw acacia shrubs inspected had Merriam's kangaroo rat burrows beneath them [132]. Catclaw acacia is also one of many desert shrubs thought to provide protection to rabbits and rodents from coyote predation on the San Carlos Reservation in Arizona [108]. In the Mohave Desert, catclaw acacia provides patches of cover for Gambel's quail as they move across inhospitable areas [47].

VALUE FOR REHABILITATION OF DISTURBED SITES:
Catclaw acacia is valuable in reclaiming asbestos, mining, and other disturbed sites. The use of catclaw acacia seedlings predominates in revegetation efforts, but catclaw acacia was in a seed mixture used to successfully revegetate a pipeline corridor in Arizona. Using tillage, mulch, and site-adapted seed, the revegetated site closely resembled nearby undisturbed sites 10 years after planting [65]. On an abandoned asbestos milling site in Globe, Arizona, catclaw acacia transplants were 100% successful even given rodent herbivory in the area [121]. Catclaw acacia seedlings survived on a gold mine spoils site in the Mohave Desert. Survival rates were not reported [39]. Catclaw acacia was one of many species used to revegetate disturbed sites (road side cuts, mining sites, eroded hillsides, and gullies) by the Utah Division of Wildlife Resources and other cooperators. In southern desert shrubland areas, catclaw acacia established well when transplanted, spread well by seed, and survived on alkaline or acidic soils. In categories of natural vegetative spread, growth rate, soil stability, and disturbance tolerance, catclaw acacia received mid level ratings [124].

As transplants are favored over seed, the following insights regarding catclaw acacia seedling production may prove useful. When growing catclaw acacia seed in containers, a tall container is recommended to house the rapidly developing root system [37]. Heydari and others [54] found the root length of catclaw acacia seedlings was greater than 23.6 inches (60 cm) 4-5 months after planting on watered sites. Fidelibus and Bainbridge [39] found seedling growth and survival were not compromised when bareroot seedlings were transported to the field site in moist fabric rather than in greenhouse containers.

OTHER USES:
Indigenous people found several uses for catclaw acacia. The Akimel O'odham or Gila River Pima ate catclaw acacia seeds when better foods were not available; the author considered catclaw acacia a "starvation food" [131]. The Chauilla Native Americans of southern California utilized catclaw acacia wood as fuel and ate catclaw acacia beans. The pods were eaten fresh, dried, or ground into powder; the bitter taste of the pods suggests catclaw acacia was not preferred. However, all Chauilla interviewed recalled catclaw acacia as a food source [11].

Moore [103] suggests several other catclaw acacia medicinal properties. Pods are used to make an eyewash to treat conjunctivitis. Leaves and pods when ground into powder will stop small amounts of bleeding and soothe chafed skin or diaper rash. When this powder is made into a tea, it can be used as an antimicrobial wash or drunk to treat diarrhea and dysentery. Native Americans used catclaw acacia to soothe sore flank and back muscles of their horses. The flowers and leaves in tea can treat nausea, vomiting, and hangovers. The thick, sticky catclaw acacia root when made into tea treats sore throats, mouth inflammations, and coughs [103].

Wood Products: Catclaw acacia wood is strong, hard, tight grained, and heavy [52,74,164]. It is used for cabinets, turnery, and fencing [52]. The contrasting reddish brown heart wood and yellow sapwood makes it valuable for making souvenirs [85].

OTHER MANAGEMENT CONSIDERATIONS:
Catclaw acacia is able to withstand heavy grazing pressure. Defoliated plants showed significantly more shoots (p=0.05), greater branch length (p<0.01), and leaf density (p=0.02) in the current year's growth than did control plants. Following defoliation treatments, plants were undisturbed for 1 year. Branch length of these previously defoliated plants was significantly (p=0.03) less than control plants. Spine density was significantly (p=0.04) greater on defoliated mature plants compared to undisturbed controls [22].

Many have researched the control of catclaw acacia in once grassland-dominated ecosystems. Mechanical control [23,137], chemical control  [70,104,105,117,163], and combined control measures are described [99].

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