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

ABBREVIATION:

OPUPOL

SYNONYMS:

No entry

NRCS PLANT CODE [98]:

OPPO

COMMON NAMES:

plains prickly-pear
hairspine cactus

TAXONOMY:

The fully documented scientific name of plains prickly-pear is Opuntia polyacantha Haw. (Cactaceae) [6,30,42,51,69]. Infrataxa are as follows [69,70,71]:

Opuntia polyacantha var. arenaria (Englm.) Parfitt
Opuntia polyacantha var. erinacea (Englm.) Parfitt
Opuntia polyacantha var. hysricina (Engelm.) Parfitt
Opuntia polyacantha var. nicholii (L. Benson) Parfitt
Opuntia polyacantha. var. polyacantha

Grizzleybear prickly-pear (Opuntia × columbiana Griffiths) is a plains prickly-pear × little prickly-pear (O. fragilis) hybrid [69].

LIFE FORM:

Cactus

FEDERAL LEGAL STATUS:

No special status

OTHER STATUS:

No entry

AUTHORSHIP AND CITATION:

Johnson, Kathleen A. (2000, December). Opuntia polyacantha. In: Remainder of Citation

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

GENERAL DISTRIBUTION:

Plains prickly-pear grows in the northern and southern Great Plains, the shrub- and woodlands of the Great Basin, the eastern Sierra Nevada, the borders of the Rocky Mountain forest regions, and the northern Chihuahuan Desert. It occurs from British Columbia to Manitoba southward through the Dakotas and Missouri to Texas and every state westward [6,30,42]. A distributional map of plains prickly-pear is available on the PLANTS database.  Distribution of infrataxa is as follows [70]:

Opuntia polyacantha var. arenaria - in sandy soils near the Rio Grande of southeastern New Mexico, extreme western Texas, and northern Chihuahua
Opuntia polyacantha var. erinacea - Arizona
Opuntia polyacantha var. hysricina - eastern Utah and western Colorado
Opuntia polyacantha var. nicholii - Arizona and New Mexico
Opuntia polyacantha. var. polyacantha - Alberta and Saskatchewan south to western Texas, New Mexico, and southeastern Utah

ECOSYSTEMS [29]:

FRES21 Ponderosa pine
FRES29 Sagebrush
FRES30 Desert shrub
FRES32 Texas savanna
FRES33 Southwestern shrubsteppe
FRES34 Chaparral-mountain shrub
FRES35 Pinyon-juniper
FRES36 Mountain grasslands
FRES38 Plains grasslands
FRES40 Desert grasslands

STATES:

BLM PHYSIOGRAPHIC REGIONS [8]:

5 Columbia Plateau
6 Upper Basin and Range
7 Lower Basin and Range
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountain Piedmont
14 Great Plains
15 Black Hills Uplift
16 Upper Missouri Basin and Broken Lands

KUCHLER [55] PLANT ASSOCIATIONS:

K011 Western ponderosa forest
K016 Eastern ponderosa forest
K017 Black Hills pine forest
K023 Juniper-pinyon woodland
K024 Juniper steppe woodlands
K031 Oak-juniper woodlands
K037 Mountain-mahogany-oak scrub
K038 Great Basin sagebrush
K039 Blackbrush
K040 Saltbush-greasewood
K043 Paloverde-cactus shrub
K051 Wheatgrass-bluegrass
K053 Grama-galleta steppe
K054 Grama-tobosa prairie
K055 Sagebrush steppe
K056 Wheatgrass-needlegrass shrubsteppe
K057 Galleta-threeawn shrubsteppe
K058 Grama-tobosa shrubsteppe
K059 Trans-Pecos shrub savanna
K060 Mesquite savanna
K063 Foothills prairie
K064 Grama-needlegrass-wheatgrass
K065 Grama-buffalo grass
K066 Wheatgrass-needlegrass
K067 Wheatgrass-bluestem-needlegrass
K068 Wheatgrass-grama-buffalo grass
K070 Sandsage-bluestem prairie
K085 Mesquite-buffalo grass
K088 Fayette prairie

SAF COVER TYPES [26]:

68 Mesquite
220 Rocky Mountain juniper
237 Interior ponderosa pine
238 Western juniper
239 Pinyon-juniper
242 Mesquite

SRM (RANGELAND) COVER TYPES [83]:

101 Bluebunch wheatgrass
104 Antelope bitterbrush-bluebunch wheatgrass
105 Antelope bitterbrush-Idaho fescue
107 Western juniper/big sagebrush/bluebunch wheatgrass
301 Bluebunch wheatgrass-blue grama
302 Bluebunch wheatgrass-Sandberg bluegrass
303 Bluebunch wheatgrass-western wheatgrass
314 Big sagebrush-bluebunch wheatgrass
315 Big sagebrush-Idaho fescue
316 Big sagebrush-rough-fescue
317 Bitterbrush-bluebunch wheatgrass
318 Bitterbrush-Idaho fescue
319 Bitterbrush-rough fescue
323 Shrubby cinquefoil-rough fescue
324 Threetip sagebrush-Idaho fescue
401 Basin big sagebrush
402 Mountain big sagebrush
403 Wyoming big sagebrush
405 Black sagebrush
408 Other sagebrush types
412 Juniper-pinyon woodland
413 Gambel oak
414 Salt desert shrub
415 Curlleaf mountain-mahogany
416 True mountain-mahogany
501 Saltbush-greasewood
502 Grama-galleta
503 Arizona chaparral
504 Juniper-pinyon pine woodland
505 Grama-tobosa shrub
506 Creosotebush-bursage
507 Palo verde-cactus
508 Creosotebush-tarbush
509 Transition between oak-juniper woodland and mahogany-oak association
604 Bluestem-grama prairie
605 Sandsage prairie
606 Wheatgrass-bluestem-needlegrass
607 Wheatgrass-needlegrass
608 Wheatgrass-grama-needlegrass
609 Wheatgrass-grama
610 Wheatgrass
611 Blue grama-buffalo grass
612 Sagebrush-grass
613 Fescue grassland
614 Crested wheatgrass
615 Wheatgrass-saltgrass-grama
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
712 Galleta-alkali sacaton
713 Grama-muhly-threeawn
714 Grama-bluestem
715 Grama-buffalo grass
718 Mesquite-grama
727 Mesquite-buffalo grass
729 Mesquite

HABITAT TYPES AND PLANT COMMUNITIES:

In the Great Plains of southern Alberta and Saskatchewan, the western Dakotas, and eastern Montana, Wyoming and Colorado, common associated grasses include blue grama (Bouteloua gracilis), western wheatgrass (Pascopyrum smithii), thickspike wheatgrass (Elymus lanceolatus), green needlegrass (Nassella viridula), needle-and-thread grass (Hesperostipa comata), buffalo grass (Buchloe dactyloides), prairie junegrass (Koeleria macrantha), Prairie sandreed (Calamovilfa longifolia), Sandberg bluegrass (Poa secunda), and threadleaf sedge (Carex filifolia). Associated shrubs and forbs may include big sagebrush (Artemisia tridentata), plains silver sagebrush (A. cana ssp. cana), fringed sagewort (A. frigida), rubber rabbitbrush (Chrysothamnus nauseosus), black greasewood (Sarcobatus vermiculatus), broom snakeweed (Gutierrezia sarothrae), shadscale (Atriplex confertifolia), Gardner's saltbush (A. gardneri), fourwing saltbush (A. canescens), winterfat (Krascheninnikovia lanata), and little clubmoss (Selaginella densa). Plains prickly-pear occurs infrequently in the understory of open stands of ponderosa pine (Pinus ponderosa) [4,19,40,43,44,57,61,79,83].

In the cold desert grasslands and shrublands of the northern interior, including southern British Columbia, eastern Washington and Oregon, Idaho, and western Montana, plains prickly-pear occurs with blue grama, western wheatgrass, thickspike wheatgrass, green needlegrass, needle-and-thread grass, Sandberg bluegrass, prairie junegrass, threadleaf sedge, bluebunch wheatgrass (Pseudoroegneria spicata), and Idaho fescue (Festuca idahoensis). Common associated shrubs are big sagebrush, fringed sagewort, gray low sagebrush (A. arbuscula spp. arbuscula), rubber rabbitbrush, green rabbitbrush (C. viscidiflorus), gray horsebrush (Tetradymia canescens), and broom snakeweed. Exotics include cheatgrass (Bromus tectorum) and spotted knapweed (Centaurea maculosa) [,49,60,66,72,79,83]. A bluebunch wheatgrass/plains prickly pear habitat type has been described for west-central Idaho [25,95,96].

In montane Utah, Nevada, and western Colorado, common plant associates are Colorado pinyon (Pinus edulis), Utah juniper (Juniperus osteosperma), true mountain-mahogany (Cercocarpus montanus), Gambel oak (Quercus gambelii), Utah serviceberry (Amelanchier utahensis), big sagebrush, black sagebrush (A. nova), budsage (A. spinescens), spiny hopsage (Grayia spinosa), shadscale, winterfat, Gardner's saltbush, green rabbitbrush, Hood's phlox (Phlox hoodii), and white sage (Kochia americana). Grasses include Indian ricegrass (Achnatherum hymenoides), bottlebrush squirreltail (Elymus elymoides), saline wildrye (Leymus salinus), and mutton grass (Poa fendleriana) [3,25,31,78].

In the southern Great Plains region of northern Texas, western Oklahoma, and eastern New Mexico, common plant associates include blue grama, buffalo grass, western wheatgrass, threeawn (Aristida spp.), lovegrass (Eragrostis spp.), sideoats grama (Bouteloua curtipendula), tobosa (Pleuraphis mutica), galleta (P. jamesii), and vine mesquite (Panicum obtusum). Dominant woody plants are broom snakeweed, sand sagebrush (A. filifolia), sand shinnery oak (Quercus havardii), cholla (Opuntia imbricata), soapweed yucca (Yucca glauca), and mesquite (Prosopis glandulosa) [28,83].

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

IMPORTANCE TO LIVESTOCK AND WILDLIFE:

Plains prickly-pear is an important seasonal food of the black-tailed prairie dog, composing up to 58% of its winter diet [10,16,27,53,90].

Pronghorn rely on plains prickly-pear [4,92], notably after fire [19,88]. Fires burn the spines off the plants, providing a source of preferred forage.

Other animals reported to eat plains prickly-pear include:

northern pocket gopher [100]
bushy-tailed woodrat [50]
Nuttall cottontail [50,60]
black-tailed jackrabbit [60]
white-tailed jackrabbit [23]
desert cottontail [34]
least chipmunk [39]
bison [73,74]
white-tailed deer [32,33]
collared peccary [33,59]
northern bobwhite [33]

Plains prickly-pear is regarded as an important emergency forage for livestock. Although the moisture content of aboveground tissues of plains prickly-pear is high, nutrient content is low [32,33].

PALATABILITY:

The palatability of plains prickly-pear to livestock and wildlife is generally considered poor to fair, because spines deter grazing [21]. When spines are singed off by wildfires not severe enough to destroy the plants, plains prickly-pear becomes a desirable food source [19,88]. Cattle ranchers in the southwestern U.S. burn plains prickly-pear plants to remove spines and rendering them fit for livestock consumption [32,84].

NUTRITIONAL VALUE:

Prickly-pear in the genus Opuntia have been utilized as a forage substitute for grazing livestock in Texas and Mexico for at least a century. It is highly variable in nutrient content, depending on species or variety, age, and plant part. Most research indicates that Opuntia prickly-pear are low in protein and phosphorus but high in energy, water, fiber, and ash [32].

Singed plains prickly-pear was evaluated as a cattle forage in Colorado. Plains prickly-pear increased total dry matter consumption and weight gain in cattle. Chemical analyses indicated that digestibility of plains prickly-pear was at least equal to that of alfalfa (Medicago sativa) hay. Plains prickly-pear contained about 40% more soluble carbohydrates than alfalfa hay, but only about 3.4% digestible protein. The authors concluded that singed plains prickly-pear was palatable and nutritious, but should be supplemented with protein [84].

COVER VALUE:

In Texas, northern bobwhite quail rely on plains prickly-pear for cover while traveling and escape from predators. Many other small birds and mammals rely on prickly-pear species for protective cover [33,59].

VALUE FOR REHABILITATION OF DISTURBED SITES:

No entry

OTHER USES AND VALUES:

Many species of Opuntia prickly-pear are used as food by humans [32,33,35,67]. Native Americans ate plains prickly-pear fruit raw, dried, or cooked. Fruit was piled on the ground and stirred with branches, rolled or singed with hot coals to remove spines, then split and dried in the sun. The flesh of plains prickly-pear was used as a binding agent in garment and weapon making. Ripe fruits were used for dye [15,24,36].

MANAGEMENT CONSIDERATIONS:

Land managers often view prickly-pear cacti as a mixed blessing. In some places dense stands of plains prickly-pear compete with more desirable forage species and grass production is reduced. However, plains prickly-pear grows in sites that will not support a high level of grass production (e.g. drought stricken and dusty, saline, or shallow and gravelly) [32,33,79,103]. Abundant plains prickly-pear is sometimes cited as an indicator of poor range condition.

The presence of plains prickly-pear can reduce both the production and availability of forage [87]. Hyde and others [47] reported forage production doubled where mechanical beaters had been used to control plains prickly-pear. In the Colorado plains, Bement [5] measured percent cover of plains prickly-pear after 25 years of light, moderate, and heavy cattle grazing and observed little effect on the abundance of plains prickly-pear. He concluded, "The illusion that prickly-pear abundance in this area is associated with heavier grazing is because the prickly-pear in the more lightly-used pastures is camouflaged by the ungrazed grass." The cactus was more visible in the heavily grazed areas, thus appearing to be increasing as a result of grazing. He reported no increase in blue grama production after plains prickly-pear control (hand clipping at the root crown) but did report that more forage was physically available for grazing.

Plains prickly-pear is susceptible to damage by several insects, including a moth (Melitara dentata), the blue cactus borer (Olycella subumbrella), and the cactus bug (Chelinidea vittiger) [80,102]. These insects are favored by moist conditions and can be an effective means of natural control during wet periods [17]. Both the cactus bug and the blue cactus borer prefer burned cactus pads (stems) to unburned pads [58,80]. This preference may help to increase prickly-pear mortality after prescribed fire [101].

Because plains prickly-pear colonies can survive and even increase during drought, they provide structural protection for more desirable species, usually grasses, to grow and produce seed. Where soil drifting and blowing occurs, the clusters of plants become microsites where topsoil, moisture and litter collect [5,45,103]. The ecology of prickly-pears during the drought of the 1930's was closely observed by Weaver and Alberston [103], along with other Great Plains species. Their summary comments about the cacti are excerpted here:

"Interrelations of the short grasses to cactus, especially the opuntias which form large clumps, are of interest and importance. During the years of desiccation when the cactus increased so greatly, it furnished a haven for relict blue grama. It could not be grazed and consequently afforded oases for seed production. With the return of a more favorable environment for the enemies of cactus, their death began...Since the more drought resistant blue grama was often the sole survivor in or near the place where the cactus had grown, the ratio of this species to buffalo grass was often higher in soil formerly occupied by the cactus."

• GENERAL BOTANICAL CHARACTERISTICS
• RAUNKIAER LIFE FORM
• REGENERATION PROCESSES
• SITE CHARACTERISTICS
• SUCCESSIONAL STATUS
• SEASONAL DEVELOPMENT

GENERAL BOTANICAL CHARACTERISTICS:

Plains prickly-pear is a perennial, typically reaching 4 to 12 inches (10-30 cm) in height and rarely growing more than 16 inches (40 cm) tall [42]. The glabrous, flattened stems are 2 to 4 inches (5-12 cm) broad, 2 to 5 inches (5-13 cm) long, and about 0.4 inches (1 cm) thick. Spines of these stems are only slightly barbed. The species tends to form clumps or mats that extend several yards in diameter [6,42]. Mats up to 12 feet (3.7 m) in width and 30 feet (9.15 m) long were observed in the Great Plains [104].

The fruits are dry at maturity and are covered with barbed spines. Fruits develop on stem lobes. An examination of 550 randomly selected branches revealed fruit on 32% of the stem lobes, varying from none to 5 fruits per lobe. The most fruit is produced on stem branches that are 6 to 8 years old. The number of seeds varies from none to more than 70 per fruit [97]. Seeds are flat, and about 1.5 to 3.5 mm thick [70].

Plains prickly-pear has a shallow, laterally extensive root system that takes advantage of rainfall as scant as 2.5 mm. Its high water retention capability in aboveground tissues allows it to survive drought. A clump 1 foot (0.3 m) in diameter may have a root system 4 to 6 feet (1.2-1.8 m) in diameter [17,22,71,97].

Opuntia plants usually live less than 20 years, but vegetative propagation can ensure a very long life span for the clonal colony [93].

RAUNKIAER [75] LIFE FORM:

Stem succulent

REGENERATION PROCESSES:

Plains prickly-pear reproduces by seeds, layering, and sprouting from segments mechanically separated from the parent plant. Stem die-back in mature clumps can separate the plant into several individuals [56,97]. Detached stems buried in soil or litter may grow horizontally before sprouting [6,38,62,71,97,103]. Root sprouting has been documented in diploid populations of Opuntia polyacantha var. polyacantha in New Mexico [38,70]. Root sprouting may occur in other Opuntia polyacantha populations and  infrataxa, but is poorly documented in the literature and in herbaria specimens [70].

Following a severe July hailstorm in northeastern Colorado, researchers quantified the number of plants that established from the many broken and scattered stem segments. In a pasture with an original plains prickly-pear ground cover of 1.2%, the hail detached an estimated 1,660 segments/acre (4,100 segments/ha). In another pasture that had 3.3% plains prickly-pear ground cover, 7,700 segments/acre (19,100 segments/ha) were detached by the storm. By August of the following year, 1,400 and 2,400 of the segments had rooted, respectively, in the 2 pastures [56].

Seeds of plains prickly-pear fall near the parent plant or are dispersed by mammals that consume the fruits. They are also dispersed when barbs on the fruits or lobes attach to a passing large mammal [45,48,93,97,103,104]. Information on seed longevity was not found.

Seedling growth was measured for 3 years in 22 field plots in northeastern Colorado. By the end of the 3rd growing season plains prickly-pear seedlings were only 2.5 to 3 inches (6-8 cm) in length. The diameter of well-developed clumps may increase 3 inches (8 cm) annually. Plains prickly-pear clusters 3 feet (0.9 m) in diameter may take as much as 15 years to develop [97].

SITE CHARACTERISTICS:

Plains prickly-pear occurs on dry sites in 22 central and western states and provinces. It is common in the Great Plains, Great Basin, and Southwest [,6,45]. Plains prickly-pear occurs both on grazed ranges and in areas not used by livestock [38,97]. It occurs in disturbed roadside areas [63] and in old, relict, pre-agricultural plant communities [3,25]. It is found on clay loam and sandy loam soils but is infrequent on sand dunes. In grasslands, prickly-pear does not occur in areas characterized by abundant soil moisture, such as swales and depressions. Its frequency decreases in wet years. Precipitation is a primary determinant of the distribution and abundance of plains prickly-pear [76,97].

Plains prickly-pear was classified in a Utah salt-gradient study as having a low tolerance to salt [86], but a survey of saline areas (visible salt crystals on the soil surface) in southern Alberta and Saskatchewan revealed that plains prickly-pear was present on more than 11% of the sites [11].

Throughout its range, plains prickly-pear occurs from as low as 1,000 feet (300 m) in the Great Plains [83] to at least as high as 8,000 feet (1,600 m) in the southern Great Basin [6].

Elevations reported in the literature are as follows:

4,300 to 7,500 feet (1,310-2,285 m) in Colorado [25,40]
2,250 to 5,700 feet (685-1,735 m) in Montana [61,83]
4,920 to 6,560 feet (1,500-2,000 m) in Utah [31]
1,000 to 5,000 feet (300-1,525 m) in the northern Great Plains [83]
1,000 to 8,000 feet (300-2,440 m) in the southern Great Plains [6,83]

SUCCESSIONAL STATUS:

Although plains prickly-pear is present and often abundant in climax or late-successional communities throughout its range [3,25,37,103], it is often regarded a disturbance-adapted, early seral species [83]. It increases in number in response to disturbances such as drought [103], grazing pressure [79], and severe hailstorms [56]. Plains prickly-pear cover decreases as precipitation normalizes following drought [45,97,103].

SEASONAL DEVELOPMENT:

Fruits ripen approximately 2-1/2 months after flowering [70]. The phenology of plains prickly-pear over a 1-year period in northern Colorado was as follows [64]:

• FIRE ECOLOGY OR ADAPTATIONS
• POSTFIRE REGENERATION STRATEGY

FIRE ECOLOGY OR ADAPTATIONS:

Plains prickly-pear plants are vulnerable to fire [49,93,106]. Plants regenerate by sprouting from the root crown, by layering of unburned or partially burned stem pieces that contact soil, and from seedling establishment [1,13,56,93,97]. 

Many succulents, including plains prickly-pear, live in fire-prone habitats with fire frequencies ranging from 1 to 3 years (Canadian prairies), to more than 250 years (Sonoran Desert). Succulent mortality after a fire is often greater than 50%, but rarely total. Authors speculate that increased fire severity causes increased succulent mortality, but data are lacking [46,93].

Fire regimes for plant communities and ecosystems in which plains prickly-pear is likely to occur are summarized below. For further information regarding fire regimes and fire ecology of communities and ecosystems where plains prickly-pear is found, see the `Fire Ecology and Adaptations' section of the FEIS species summary for the plant community or ecosystem dominants listed below.

Community or Ecosystem	Dominant Species	Fire Return Interval Range (years)
bluestem prairie	Andropogon gerardii var. gerardii-Schizachyrium scoparium	< 10 [12,54]
sagebrush steppe	Artemisia tridentata/Pseudoroegneria spicata	20-70 [12]
basin big sagebrush	A. t. var. tridentata	12-43 [81]
Wyoming big sagebrush	A. t. var. wyomingensis	10-70 (40)** [30,108]
saltbush-greasewood	Atriplex confertifolia-Sarcobatus vermiculatus	< 35 to < 100
desert grasslands	Bouteloua eriopoda and/or Pleuraphis mutica	5-100
plains grasslands	Bouteloua spp.	< 35
blue grama-needle-and-thread grass-western wheatgrass	B. gracilis-Hesperostipa comata-Pascopyrum smithii	< 35
blue grama-buffalo grass	B. gracilis-Buchloe dactyloides	< 35
grama-galleta steppe	Bouteloua gracilis-Pleuraphis jamesii	< 35 to < 100
blue grama-tobosa prairie	B. gracilis-Pleuraphis mutica	< 35 to < 100
cheatgrass	Bromus tectorum	< 10
paloverde-cactus shrub	Cercidium microphyllum/Opuntia spp.	< 35 to < 100 [12]
curlleaf mountain-mahogany*	Cercocarpus ledifolius	13-1000 [2,82]
mountain-mahogany-Gambel oak scrub	C. l.-Quercus gambelii	< 35 to < 100
blackbrush	Coleogyne ramosissima	< 35 to < 100
western juniper	Juniperus occidentalis	20-70
wheatgrass plains grasslands	Pascopyrum smithii	< 35
pinyon-juniper	Pinus-Juniperus spp.	< 35 [12]
Mexican pinyon	P. cembroides	20-70 [65,91]
Rocky Mountain ponderosa pine*	P. ponderosa var. scopulorum	2-10
galleta-threeawn shrubsteppe	Pleuraphis jamesii-Aristida purpurea	< 35 to < 100
mesquite	Prosopis glandulosa	< 35 to < 100
mesquite-buffalo grass	P. g.-Buchloe dactyloides	< 35
Texas savanna	P. g. var. glandulosa	< 10
oak-juniper woodland (Southwest)	Quercus-Juniperus spp.	< 35 to < 200
little bluestem-grama prairie	Schizachyrium scoparium-Bouteloua spp.	< 35 [12]

*fire return interval varies widely; trends in variation are noted in the species summary
**(mean)  

POSTFIRE REGENERATION STRATEGY [89]:

Geophyte, growing points deep in soil

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

IMMEDIATE FIRE EFFECT ON PLANT:

Moderate or even low-severity fires can top-kill prickly-pear species [7,93,99,106]. Aboveground tissues of Opuntia spp. are easily killed by fire, but some fleshy stem segments usually survive low- to moderate-severity fire and resume growth, even when burned off the parent plant [7,46,49,93,106]. Prickly-pears are vulnerable to mortality from heat generated by fires as well as by actual burning [99]. Hotter fires probably lead to higher mortality, but data are needed [46,93]. 

DISCUSSION AND QUALIFICATION OF FIRE EFFECT:

No entry

PLANT RESPONSE TO FIRE:

The succulent stems of prickly-pear species are not combustible and without sufficient fuel may suffer little damage from fire [46]. However, it is reported that a related species, brownspine prickly-pear (O. phaecantha), is easily killed by fire if the plant's height is less than 1 foot (0.3 m) [107]. In west Texas, Heirman and Wright [41] also reported that brownspine prickly-pear less than 2 feet (0.61 m) tall were easily killed by fire because flames readily engulfed the plants. Plains prickly-pear postfire mortality may be delayed for 3 or more years. Secondary effects of fire include insect infestation of weakened plants and increased grazing pressure when spines are burned off [,13,14,77,101,105,107]. Studies in Texas showed that the cactus bug and the blue cactus borer prefer burned cactus pads to unburned pads [20,80,85,101]. This preference may increase prickly-pear mortality after burning [80]. In Wyoming, Smith and others [87] attributed mortality of plains prickly-pear to dehydration following the burn rather than from fire-caused heat damage.

Brownspine prickly-pear experienced high die-off following low-severity fire in Texas. Initial mortality was 20%. Insects entered surviving plants through fire-scarred tissue, spreading bacterial and fungal infections. New sprouts appeared within a few weeks following the fire, but many sprouting plants lost their vascular connection to the root because of insect damage and decay. By the end of the 3rd year, mortality exceeded 70%. Most plants surviving through postfire year 3 had sprouted from the root crown. The authors observed that mortality of both burned and unburned plants of brownspine prickly-pear increased during years of below average precipitation [13].

DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:

No entry

FIRE MANAGEMENT CONSIDERATIONS:

Frequent fire reduces populations of low-growing Opuntia species like plains prickly-pear [7]. Plants that survive in unburned refugia provide parents for regenerating burned areas. Observations of 1,665 plants from 19 succulent species on burned areas Arizona showed that 13% were in unburned refugia [93]; the spatial extent of the refugia was not described.

Fire has been used as a tool to increase the edibility of plains prickly-pear and related species for livestock by burning off spines [32,84]. Wildlife consumption of burned plains prickly-pear is also a consideration. In southern Alberta, pronghorn were attracted to burned areas to graze on plains prickly-pear when spines were singed off green plants [19,88].

Although prescribed burning may effectively control plains prickly-pear in some cases, in dry years desirable forage is lost [105,106]. In a 1965 Wyoming study, burning was among 4 treatments tested for controlling plains prickly-pear. The other 3 methods were chemical, bulldozer blading over frozen ground, and beating with a tractor attachment. Burning was found to be unsatisfactory because, though cactus kill was estimated to be 70%, an unacceptable amount of preferred vegetation was damaged. At that time, the most successful method was thought to be blading, despite vegetation and soil damage [47].

Opuntia polyacantha: References

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Related categories for SPECIES: Opuntia polyacantha | Plains Prickly-Pear