Grizzlybear Pricklypear (Opuntia erinacea)

Present distribution

Scientific name:	Opuntia erinacea Engelm. & Bigelow ex Engelm.
Common name(s):	Grizzlybear Pricklypear

This weed is not known to be naturalised in Victoria

Habitat:

Native to North America. Reported in various habitat from grassland and desert to montane forest, shrubland and riparian areas.

Potential distribution

Potential distribution produced from CLIMATE modelling refined by applying suitable landuse and vegetation type overlays with CMA boundaries

Map Overlays Used

Land Use:
Forest private plantation; forest public plantation; pasture dryland; pasture irrigation

Broad vegetation types
Coastal scrubs and grassland; coastal grassy woodland; heathy woodland; lowland forest; heath; box ironbark forest; inland slopes and plains; sedge rich woodland; dry foothills forest; montane dry woodland; sub-alpine woodland; grassland; plains grassy woodland; valley grassy forest; herb-rich woodland; sub-alpine grassy woodland; montane grassy woodland; riverine grassy woodland; rainshadow woodland; mallee; mallee heath; boinka-raak; mallee woodland; wimmera / mallee woodland

Colours indicate possibility of Opuntia erinacea infesting these areas.

In the non-coloured areas the plant is unlikely to establish as the climate, soil or landuse is not presently suitable.

map showing the potential distubution of grizzlybear pricklypear

Red= Very high	Orange = Medium
Yellow = High	Green = Likely

Impact

QUESTION	COMMENTS	RATING	CONFIDENCE
Social
1. Restrict human access?	Low growing clumping cactus, may slow movement but no completely prevent it (Benson 1982).	ml	m
2. Reduce tourism?	No reported evidence, may have negative influence on aesthetics.	ml	ml
3. Injurious to people?	Does have spines (Benson 1982).	mh	m
4. Damage to cultural sites?	No reports of structural damage, may have a negative influence on aesthetics.	ml	ml
Abiotic
5. Impact flow?	Is found in some riparian areas, however it forms clumps and is only low growing would not pose a serious impediment, fast flowing water may also break up the plant and aid vegetative dispersal (Benson 1982).	l	m
6. Impact water quality?	No reports of such.	l	m
7. Increase soil erosion?	Forms clumps with up to 1m diameter (Benson 1982), also the presence of its prickles prevent the overgrazing of grass/herb species in the immediate vacinity (Mueller, Shoop & Laycock 1994), reducing net soil exposure.	l	m
8. Reduce biomass?	Biomass is noted to have increased were it is the dominant plant species (Hart. & Ashby 1998).	l	m
9. Change fire regime?	Due to its spines O.erinacea reduces grazing pressure of grass and herb species, increasing net biomass and therefore fuel loads and fire intensity.	mh	m
Community Habitat
10. Impact on composition (a) high value EVC	EVC= Damp Sands Herb-rich Woodland (V); CMA= Mallee; Bioreg= Murray Mallee; H CLIMATE potential. Competitive in the ground layer, forming clumps.	ml	mh
(b) medium value EVC	EVC= Riverine Grassy Woodland (D); CMA= Mallee; Bioreg= Murray Mallee; H CLIMATE potential. Competitive in the ground layer, forming clumps.	ml	mh
(c) low value EVC	EVC= Loamy Sands Mallee (LC); CMA= Mallee; Bioreg= Murray Mallee; H CLIMATE potential. Competitive in the ground layer, forming clumps.	ml	mh
11. Impact on structure?	Competitive in the ground layer, forms clumps of up to 1m in diameter (Benson 1982), however also noted for protecting sensitive species from over grazing so must have space within clump for other grass and herb species (Rebollo etal 2002).	ml	m
12. Effect on threatened flora?	Noted for protecting sensitive species from over grazing (Rebollo etal 2002).	ml	m
Fauna
13. Effect on threatened fauna?	No specific data, noted to be eaten by rodents in native range may be a valuable alternate food source (Benson 1982).	m	ml
14. Effect on non-threatened fauna?	Its presence in a grassland may provide a shrubby refuge where previously there wasn't one (Benson 1982).	l	ml
15. Benefits fauna?	Is edible may also provide shelter within its spines (Benson 1982).	mh	m
16. Injurious to fauna?	Does have spines (Benson 1982).	mh	m
Pest Animal
17. Food source to pests?	Eaten by rodents (Benson 1982).	ml	m
18. Provides harbor?	May provide shelter within its spines.	m	ml
Agriculture
19. Impact yield?	Has been noted to reduce grazing pressure in its immediate area due to its spines (Rebollo etal 2002). My be eaten by stock but spines need to be removed from the edible flesh of o.erinacea, therefore it is not readily available for stock to eat (Mueller, Shoop & Laycock 1994).	ml	m
20. Impact quality?	No evidence of such.	l	m
21. Affect land value?	If control deemed necessary may have some negative influence on land values.	m	m
22. Change land use?	Present in rangeland systems, if dominant in an area may reduce stocking rates, but not change practises.	l	m
23. Increase harvest costs?	If impede stock movement may increase mustering times.	mh	m
24. Disease host/vector?	No evidence of this.	l	m

Invasive

QUESTION	COMMENTS	RATING	CONFIDENCE
Establishment
1. Germination requirements?	No specific data on seed germination, like most opuntia species presumed vegetative propagules can set root when ever there is sufficient water.	h	ml
2. Establishment requirements?	Reportedly present in woodland, therefore able to tolerate a degree of shading (Benson 1982).	mh	m
3. How much disturbance is required?	Reported present in woodland and grassland (Benson 1982).	mh	m
Growth/Competitive
4. Life form?	Low growing clumping cactus (Benson 1982).	l	m
5. Allelopathic properties?	none described	l	m
6. Tolerates herb pressure?	All varieties have large spines that resist grazing by cattle and reduce herbivory by rodents (Hubert 1980).	mh	m
7. Normal growth rate?	Low growing cacti, only to 1m high forming a clump, would grow as fast as some other cactus species (Hubert 1980).	ml	ml
8. Stress tolerance to frost, drought, w/logg, sal. etc?	A low growing cacti, of high altitudes (450m+) (Frost tolerant) (O.polyacantha reported to withstand temperatures of -40C) (Ishikawa & Gusta 1996 and Rebollo etal 2002). Commonly found in deserts (Drought tolerant) (Benson 1982). Reported along waterways may be tolerant of some degree of waterlogging.	mh	mh
Reproduction
9. Reproductive system	Produces fruit with many seeds, broken segments may also spread vegetatively (Benson 1982 and Hubert 1980).	h	mh
10. Number of propagules produced?	Each fruit contains numerous seeds, fruit production not known (Benson 1982).	mh	m
11. Propagule longevity?	Not reported.	m	l
12. Reproductive period?	The species can reportadly live for 100+ years (Bowers, Webb & Rondeau 1995).	h	mh
13. Time to reproductive maturity?	Unknown how long until plants can bear fruit, may produce vegetative propagules within one year.	h	m
Dispersal
14. Number of mechanisms?	Fruit eaten by rodents, also described along riparian zones water may be an important dispersal agent for vegetative propagules (Benson 1982).	mh	m
15. How far do they disperse?	Water may disperse propagules many kilometres.	h	m

References

Benson. L. (1982) The Cacti of the United States and Canada. Stanford University press, Stanford, California.

Bowers. J.E., Webb. R.H. & Rondeau. R.J. (1995) Longevity, recruitment and mortality of desert plants in Grand Canyon, Arizona, USA. Journal of Vegetation Science. 6: 551-564.

Hart. R.H. & Ashby. M.M. (1998) Grazing intensities, vegetation, and heifer gains: 55 years on shortgrass. Journal of range management. 51: 392-398.

Hubert. E.W. (1980) Cacti of the Southwest : Arizona, western New Mexico, southern Colorado, southern Utah, southern Nevada, eastern California. Rancho Arroyo

Ishikawa. M. & Gusta. L.V. (1996) Freezing and heat tolerance of Opunti cati native to the Canadian prairie provinces. Canadian Journal of Botany. 74: 1890-1895.

Mueller. D.M., Shoop. M.C. & Laycock. W.A. (1994) Mechanical harvesting of plains pricklypear for control and feeding. Journal of range management. 47: 251-254.

Rebollo. S., Milchunas. D.G., Noy-Meir. I. & Chapman. P.L. (2002) The role of a spiny plant refuge in structuring grazed shortgrass steppe plant communities. Oikos. 98: 53-64.

Global present distribution data references
Australian National Herbarium (ANH) 2006, Australia’s Virtual Herbarium, Australian National Herbarium, Centre for Plant Diversity and Research, viewed Aug 29 2006, http://www.anbg.gov.au/avh/

Calflora: Information on California plants for education, research and conservation. [web application]. 2006. Berkeley, California: The Calflora Database [a non-profit organization]. Available: http://www.calflora.org/ . (Accesses: Aug 29, 2006)

Global Biodiversity Information Facility (GBIF) 2006, Global biodiversity information facility: Prototype data portal, viewed Aug 29 2006, http://www.gbif.org/

Missouri Botanical Gardens (MBG) 2006, w3TROPICOS, Missouri Botanical Gardens Database, viewed Aug 29 2006, http://mobot.mobot.org/W3T/Search/vast.html

Rebollo. S., Milchunas. D.G., Noy-Meir. I. & Chapman. P.L. (2002) The role of a spiny plant refuge in structuring grazed shortgrass steppe plant communities. Oikos. 98: 53-64.

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