Honey locust (Gleditsia triacanthos)

Present distribution

Scientific name:	Gleditsia triacanthos L.
Common name(s):	honey locust

Map showing the present distribution of this weed.

Habitat:

Tolerant of drought and salinity, can grow in saline soils (Simons et al. 2005). In its native environment occurs in woodland, on rocky slopes and floodplains. It can however invade forest, grassland, riparian areas including freshwater wetlands and where zero tillage is practiced areas of cropping (Ghersa et al. 2002 and Weber 2003). Alluvial flats and bottomlands. Ample soil moisture. Tolerant of frost. Winter dormant (Bulloch 1986). Climates: Summer rainfall (temperate & sub-tropical) (Wells et al. 1986). Tolerating most soil types, including soils which are moderately saline. Most prolifically on fertile, alluvial soils. Along rivers in Queensland (Csurhes & Kriticos 1994). Shade intolerant (Simons et al. 2005).

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:
Broadacre cropping; forestry; horticulture perennial; horticulture seasonal; pasture dryland; pasture irrigation

Ecological Vegetation Divisions:
Coastal; swampy scrub; freshwater wetland (permanent); treed swampy wetland; lowland forest; foothills forest; forby forest; damp forest; riparian; wet forest; high altitude shrubland/woodland; granitic hillslopes; rocky outcrop shrubland; alluvial plains grassland; semi-arid woodland; alluvial plains woodland; ironbark/box; riverine woodland/forest; freshwater wetland (ephemeral); saline wetland

Colours indicate possibility of Gleditsia triacanthos 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 distribution of honey locust

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

Impact

QUESTION	COMMENTS	RATING	CONFIDENCE
Social
1. Restrict human access?	Forms dense thickets with thorns impeded access to areas (Ghersa et al. 2002), which include areas of wetlands and waterways (Weber 2003). While there are thornless varieties in cultivation, the plant is naturally armed with 5-10 cm three pronged spines (Bulloch 1986). Major impediment to access waterways or machinery. Significant works required to provide reasonable access, tracks closed or impassable.	h	mh
2. Reduce tourism?	Can change grassland to dense woodland and impair visibility along roadsides (Ghersa et al. 2002). While there are thornless varieties in cultivation, the plant is naturally armed with 5-10cm three pronged spines (Bulloch 1986). Visitors are not likely to be comfortable visiting an area that potentially has a dense thicket of extremely spiny trees. Major impact on recreation. Weeds obvious to most visitors, with visitor response complaints AND a major reduction in visitors.	h	mh
3. Injurious to people?	While there are thornless varieties in cultivation, the plant is naturally armed with 5-10cm three pronged spines (Bulloch 1986).	h	h
4. Damage to cultural sites?	Can create problems with visibility along roadsides, especially at intersections and bridges (Ghersa et al. 2002). Moderate visual effect.	ml	mh
Abiotic
5. Impact flow?	Reported to invade riparian areas and fresh water wetlands (Weber 2003). Impacts for this species have not been quantified, presumed impact on flow by extensive root lateral system.	ml	m
6. Impact water quality?	Reported to invade riparian areas and fresh water wetlands (Weber 2003). Has a well developed lateral root system (Bulloch 1986 and Csurhes & Kriticos 1994). Is deciduous therefore altering light and temperature relationships and food-webs similar to that of Salix sp.	m	ml
7. Increase soil erosion?	Has a well developed lateral root system which was identified as a value to soil conservation (Bulloch 1986 and Csurhes & Kriticos 1994) Low probability of large scale soil movement; or decreases the probability of soil erosion.	l	mh
8. Reduce biomass?	Invading grassland G. triacanthos creates a dense woodland (Ghersa et al. 2002). Biomass may increase.	l	h
9. Change fire regime?	Most abundant in areas with an intermediate to low fire frequency in comparison to the high fire frequency of grasslands (Briggs, Knapp & Brock 2002). Minor change to either frequency or intensity of fire risk.	ml	mh
Community Habitat
10. Impact on composition (a) high value EVC	EVC = Red Gum Wetland (V); CMA =North Central; Bioregion =Wimmera; VH CLIMATE potential. Can completely dominate vegetation turning grassland into a dense woodland (Ghersa et al. 2002). Monoculture within a specific layer; displaces all spp. within a strata/layer	h	h
(b) medium value EVC	EVC = Grassy Dry Forest (D); CMA =North East; Bioregion =Central Victorian Uplands; VH CLIMATE potential. Can completely dominate vegetation turning grassland into a dense woodland (Ghersa et al. 2002). Monoculture within a specific layer; displaces all spp. within a strata/layer	h	h
(c) low value EVC	EVC = Lowland Forest (LC); CMA =East Gippsland; Bioregion =East Gippsland Lowlands; VH CLIMATE potential. Can completely dominate vegetation turning grassland into a dense woodland (Ghersa et al. 2002). Monoculture within a specific layer; displaces all spp. within a strata/layer	h	h
11. Impact on structure?	Can completely dominate vegetation turning grassland into a dense woodland (Ghersa et al. 2002). Minor effect on >60% of the layers or major effect on < 60% of the floral strata.	mh	mh
12. Effect on threatened flora?	Predicted to cause some localised extinctions in the Pampa grasslands of Argentina (Ghersa et al. 2002). Can completely dominate vegetation turning grassland into a dense woodland (Ghersa et al. 2002). There is no direct link to any VROT species.	m	l
Fauna
13. Effect on threatened fauna?	Can completely dominate vegetation turning grassland into a dense woodland (Ghersa et al. 2002). Predicted to cause some localised extinctions in the Pampa grasslands of Argentina (Ghersa et al. 2002). There is no direct link to any threaten fauna.	m	l
14. Effect on non-threatened fauna?	Can completely dominate vegetation turning grassland into a dense woodland (Ghersa et al. 2002). Predicted to cause some localised extinctions in the Pampa grasslands of Argentina (Ghersa et al. 2002). Habitat changed dramatically, leading to the possible extinction (extirpation) of non-threatened fauna.	h	m
15. Benefits fauna?	Dense thickets provides shelter of dense thorny thickets, seed pods and foliage edible (Ghersa et al. 2002) Provides some assistance in either food or shelter to desirable species.	mh	m
16. Injurious to fauna?	Possesses large (5-10cm) sharp spines (Bulloch 1986). Large spines or burrs dangerous to fauna. Toxic, and/or causes allergies.	h	h
Pest Animal
17. Food source to pests?	Seed pods eaten by rabbits (Csurhes & Kriticos 1994). Supplies food serious pest (e.g. rabbits and foxes), but at low levels (e.g. foliage).	mh	mh
18. Provides harbour?	Perceived as habitat for species such as foxes, but not quantified (Ghersa et al. 2002). Capacity to provide harbour and permanent warrens for foxes and rabbits throughout the year.	h	ml
Agriculture
19. Impact yield?	When managed, can form part of a silvo-pastoral system (Bruno-Soares & Abreu 2003). However as a weed changes pasture into dense thickets effectively reducing the area of productivity and therefore yield (Csurhes & Kriticos 1994). Major impact on quantity of produce (e.g. 5-20%).	mh	m
20. Impact quality?	No impact of quality reported.	m	l
21. Affect land value?	There is a perception in Argentina that thickets of this species are habitat for pest plants and animals and can harbour diseases (Ghersa et al. 2002). Decreases in land value <10%.	m	m
22. Change land use?	When managed, can form part of a silvo-pastoral system (Bruno-Soares & Abreu 2003). However as a weed changes pasture into dense thickets effectively reducing the area of productivity and therefore yield (Csurhes & Kriticos 1994). Major detrimental change and significant loss for agricultural usage (e.g. complete change to different ag use e.g. farm forestry.)	h	m
23. Increase harvest costs?	Dense thickets restrict movement and impedes access to fences especially near water ways (Csurhes & Kriticos 1994 and Ghersa et al. 2002). Minor increase in cost of harvesting – e.g. slightly more time or labour is required.	m	m
24. Disease host/vector?	Pest free in Australia (Csurhes & Kriticos 1994).	l	ml

Invasive

QUESTION	COMMENTS	RATING	CONFIDENCE
Establishment
1. Germination requirements?	Hard seed requires some scarification to break dormancy, which can be achieved by passing through the gut of a grazing mammal sp. (Weber 2003).	ml	mh
2. Establishment requirements?	In its native environment occurs in woodland. It can invade forest (Ghersa et al. 2002 and Weber 2003). Shade intolerant, requires open spaces for establishment (Simons et al. 2005). May prefer open areas to establish in but could also establish under moderate canopy/litter cover.	mh	ml
3. How much disturbance is required?	Invades grassland and woodland (Summerville, Steichen & Lewis 2005). It can invade forest (Ghersa et al. 2002 and Weber 2003). Establishes in healthy AND undisturbed natural ecosystems (eg. mallee, alpine, heathland).	h	mh
Growth/Competitive
4. Life form?	Leguminous shrub (Parissi, Papachristou & Nastis 2005).	mh	h
5. Allelopathic properties?	None described.	m	l
6. Tolerates herb pressure?	Foliage and seed pods used as a fodder source, able to form coppice regrowth. However this is poor for young plants (Simons et al. 2005). Consumed and recovers slowly. Reproduction strongly inhibited by herbivory but still capable of vegetative propagule production (by rhizomes or tubers); weed may still persist.	ml	mh
7. Normal growth rate?	Found to be faster growing than Juniperus virginiana, Populus sp. and Phalaris arundinacea (Patterson, Hulet & Bates 2006). Rapid growth rate that will exceed most other species of the same life form.	h	h
8. Stress tolerance to frost, drought, w/logg, sal. etc?	Tolerant of drought (Simons et al. 2005). Tolerant of salinity, can grow in saline soils (Simons et al. 2005). Tolerant of frost (Bulloch 1986). Resprouts vigorously after being damaged by fire or cutting (Briggs, Knapp & Brock 2002). In its native environment occurs in floodplains. It can invade grassland, riparian areas including freshwater wetlands and where zero tillage is practiced areas of cropping (Ghersa et al. 2002 and Weber 2003). Highly tolerant of waterlogging and possibly highly tolerant of salinity. Tolerant of frost, fire and drought. Highly tolerant of at least two of drought, frost, fire, waterlogging, and salinity, AND MAY be tolerant of another. Susceptible to at least one.	mh	mh
Reproduction
9. Reproductive system	Dioecious plant some individuals can have male and female flowers can also possess perfect flowers (Simons et al. 2005). Sexual (self AND cross-pollination).	ml	mh
10. Number of propagules produced?	Capable of producing 20-75 kg of seed pods per tree, with an average of 5200 seeds per kilogram. (Simons et al. 2005). Above 2000.	h	mh
11. Propagule longevity?	Seed has hard seed coat which needs to be scarified in some way before germination, some seeds found to germinate after 50 years (Simons et al. 2005). Greater than 25% of seeds can survive over 20 years in the soil.	h	mh
12. Reproductive period?	The best cropping trees are reported to be between 25 and 75 years old (Bulloch 1986). Reported not to be reproductively active until a minimum of 10 years (Schnabel, Nason & Hamrick 1998). 75yrs-10yrs= 65years. Mature plant produces viable propagules for 10 years or more.	h	ml
13. Time to reproductive maturity?	Reported not to be reproductively active until a minimum of 10 years (Schnabel, Nason & Hamrick 1998). Greater than 5 years to reach sexual maturity.	l	mh
Dispersal
14. Number of mechanisms?	Seed pods fall to the ground and are eaten by grazing animals (Bruno-Soares & Abreu 2003 and Schnabel, Nason & Hamrick 1998). Secondary dispersers include mammals and floodwater (Weber 2003). Has edible fruit that is readily eaten by potentially highly mobile animals.	h	mh
15. How far do they disperse?	Secondary dispersers include mammals and floodwater (Weber 2003).Seed pods fall to the ground and are eaten by grazing animals (Bruno-Soares & Abreu 2003 and Schnabel, Nason & Hamrick 1998). Very likely that at least one propagule will disperse greater one kilometre.	h	mh

References

Briggs. J.M., Knapp. A.K. & Brock. B.L. (2002) Expansion of Woody Plants in Tallgrass Prairie: A Fifteen-year Study of Fire and Fire-grazing Interactions. The American Midland Naturalist. 147: 287-294.

Bruno-Soares. A.M & Abreu. J.M.F. (2003) Merit of Gleditsia triacanthos pods in animal feeding, Chemical composition and nutritional evaluation. Animal Feed Science and Technology. 107: 151-160.

Bulloch. B.T. (1986) Management and Uses of Gleditsia triacanthos (Honey Locust). Plant Materials for Soil Conservation Technical Note No. T8. in Water & Soil Miscellaneous Publication No. 94, Plant Materials Handbook for Soil Conservation. Volume 2: Introduced Plants (ed) Van Kraayenoord. C.W.S. & Hathaway. R.L. Soil Conservation Centre, Aokautere, Ministry of Works and Development, Palmerton North, Wellington.

Csurhes. S.M. & Kriticos. D. (1994) Gleditsia triacanthos L. (Caesalpiniaceae), another thorny, exotic fodder tree gone wild. Plant Protection Quarterly. 9: 101-105.

Ghersa. C.M., de la Fuente. E., Suarez. S. & Leon. R.J.C. (2002) Woody species invasion in the Rolling Pampa grasslands, Argentina. Agriculture, Ecosystems and Environment. 88: 271-278.

Parissi. Z.M, Papachristou. T.G. & Nastis. A.S. (2005) Effect of drying method on estimated nutritive value of browse species using an in vitro gas production technique. Animal Feed Science and Technology. 123-124: 119-128.

Patterson. P.H., Hulet. R.M. & Bates. R.M. (2006) Growth and foliar nitrogen status of four plant species exposed to atmospheric ammonia. Journal of Environmental Science and Health. Part B, Pesticides, Food Contaminants, and Agricultural Wastes. 41:
1001-1018.

Schnabel. A., Nason. J.D. & Hamrick. J.L. (1998) Understanding the population genetic structure of Gleditsia triacanthos L.: seed dispersal and variation in female reproductive success. Molecular Ecology. 7: 819-832.

Simons. A.J., Salim.A.S., Orwa. C., Munjuga. M. & Mutua. A. (2005) Agroforestre database. A tree species reference and selection guide. Version 3.0.

Summerville. K.S., Steichen. R.M. & Lewis. M.N. (2005) Restoring Lepidopteran Communities to Oak Savannas: Contrasting influences of habitat quantity and quality. 13: 120-128.

Van Kraayenoord C.W.S & Hathaway R.L. (1986) Plant Materials Handbook for Soil Conservation, Volume 2: Introduced Plants. Soil Conservation Centre, Aokautere; Ministry of Works and Development, Wellington.

Weber. E. (2003) Invasive Plant Species of the World. A Reference Guide to Environmental Weeds. CABI Publishing, Wallingford, Oxon OX108DE, UK.

Wells M.J; Balsinhas A.A; Joffe H; Engelbrechst V.M; Harding G & Stirton C.H. (1986) A Catalogue of Problem Plants in Southern Africa Incorporating the National Weed List of Southern Africa. Memoirs of the Botanical Survey of South Africa, vol. 53.

Global present distribution data references

Global Biodiversity Information Facility (GBIF) (2009) Global biodiversity information facility, Available at http://www.gbif.org/ (verified 29 May 2009).

Australian National Herbarium (ANH) 2006, Australia’s Virtual Herbarium, Australian National Herbarium, Centre for Plant Diversity and Research, http://www.anbg.gov.au/avh/ (viewed 03 June 2009).

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