Impact Assessment - Italian buckthorn (Rhamnus alaternus) in Victoria
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Assessment of plant invasiveness is done by evaluating biological and ecological characteristics such as germination requirements, growth rate, competitive ability, reproduction methods and dispersal mechanisms. Assessment of plant impacts, however, is determined by the extent to which a plant affects a land manager’s environmental, economic and social resources.
The relative importance of these resources varies depending upon the value people place on them and, as such, the assessment process is subjective. For example, a farmer is likely to place a higher emphasis on the impact of a plant on production (economic resource) than its impact on areas of natural vegetation occurring on the farm. Conversely, a Landcare or Friends group would value environmental or social resources more than economic resources.
Recognising that the value of resources vary between different land tenures, plant impact assessments allow a prioritisation of resources by land managers. Assessments can apply at a local, regional or state level, and the relative values of each resource identified may differ at each level.
The impact assessment method used in the Victorian Pest Plant Prioritisation Process uses three broad resource categories: social, environmental and agricultural, each with a number of related attributes. For example, social resources include such attributes as how the plant affects human access for recreation, or if it creates a health risk due to toxicity or by producing allergens.
| Each resource attribute, or criterion, is assessed relative to a list of intensity ratings. Depending upon information found in relation to each criterion, a rating of Low, Medium Low, Medium High or High is assigned. Descriptions of the impact criteria and intensity ratings used in this process can be viewed here. |
The following table provides information on the impact of Italian buckthorn
A more detailed description of the methodology of the Victorian Weed Risk Assessment (WRA) method can be viewed below:
Victorian Weed Risk Assessment (WRA) method (PDF - 630 KB)
Victorian Weed Risk Assessment (WRA) method (DOC - 1 MB)
To view the information PDF requires the use of a PDF reader. This can be installed for free from the Adobe website (external link).
Common Name: Italian Buckthorn
Scientific name: Rhamnus alaternus
| Question | Comments | Rating | Confidence |
| Recreation | |||
| 1. Restrict human access? | Rhamnus alaternus is a fast growing shrub, able to grow to 6 m and form dense stands. Used as a hedge it could therefore pose a major physical barrier (Blood 2001; Muyt 2001; Weber 2003). The plants ability to sucker could also impose on tracks and is reportedly difficult to control requiring significant works with follow up (Blood 2001; Weber 2003). | H | MH |
| 2. Reduce tourism? | Unknown. | M | L |
| 3. Injurious to people? | R. alaternus’ branches have traditionally been used in Spain to make a decoction for high blood pressure (Akerreta et al 2007). There is no evidence however of the plant causing injury. | L | M |
| 4. Damage to cultural sites? | Unknown. | M | L |
| Abiotic | |||
| 5. Impact flow? | The species can occur in riparian vegetation, there is no evidence however of it occurring in flowing water and obstructing flow. | L | M |
| 6. Impact water quality? | The species can occur in riparian vegetation, there is no evidence however of it occurring in water and affecting water quality. | L | M |
| 7. Increase soil erosion? | As reported by Blood (2001) the species is fast growing, has a strong root system and readily suckers therefore providing good vegetation cover for the soil surface and support to the soil structure, reducing the risk of erosion. | ML | M |
| 8. Reduce biomass? | The species is reported to displace the existing vegetation creating a dense species poor stand (Weber 2003). The species ability to prevent regeneration of trees and shrubs as reported by Muyt (2001) may stop the biomass accumulating beyond a certain point, overall however invasion by R. alaternus is considered to cause direct replacement of biomass. | ML | MH |
| 9. Change fire regime? | Unknown. | M | L |
| Community Habitat | |||
| 10. Impact on composition (a) high value EVC | EVC= Escarpment Shrubland (E); CMA= Glenelg Hopkins; Bioreg= Glenelg Plain; VH CLIMATE potential. The species vigorous growth shades out ground flora altering the floral composition and can prevent regeneration of shrubs and trees and lead to species poor stands (Muyt 2001; Weber 2003). The species therefore may cause major displacement of species within a layer. | MH | MH |
| (b) medium value EVC | EVC= Hills Herb-rich Woodland (D); CMA= Glenelg Hopkins; Bioreg= Goldfields; VH CLIMATE potential. The species vigorous growth shades out ground flora altering the floral composition and can prevent regeneration of shrubs and trees and lead to species poor stands (Muyt 2001; Weber 2003). The species therefore may cause major displacement of species within a layer. | MH | MH |
| (c) low value EVC | EVC= Rocky Outcrop Herbland (LC); CMA= Glenelg Hopkins; Bioreg= Greater Grampians; VH CLIMATE potential. The species vigorous growth shades out ground flora altering the floral composition and can prevent regeneration of shrubs and trees and lead to species poor stands (Muyt 2001; Weber 2003). The species therefore may cause major displacement of species within a layer. | MH | MH |
| 11. Impact on structure? | The species vigorous growth shades out ground flora altering the floral composition and can prevent regeneration of shrubs and trees and lead to species poor stands (Muyt 2001; Weber 2003). The species therefore may eventually have a major effect on all layers. | H | MH |
| 12. Effect on threatened flora? | Not specifically reported, however its general impact of floral composition could impact threatened species. | MH | L |
| Fauna | |||
| 13. Effect on threatened fauna? | Not specifically mentioned, however the alteration of vegetation composition could impact threatened fauna by altering habitat structure and food supply. | MH | L |
| 14. Effect on non-threatened fauna? | Not specifically mentioned, however the alteration of vegetation composition could impact fauna by altering habitat structure and food supply. It is unknown however to what extent this would impact fauna. | M | L |
| 15. Benefits fauna? | Fruit is eaten by birds and possible by possums (Muyt 2001). | MH | MH |
| 16. Injurious to fauna? | There is no evidence of this. | L | M |
| Pest Animal | |||
| 17. Food source to pests? | Berries possibly eaten by foxes (Muyt 2001). | MH | MH |
| 18. Provides harbour? | Used as an ornamental hedge the species is capable of forming dense stands (Blood 2001). Muyt (2001) reports that the species may be a food source for foxes, therefore the dense vegetation it forms may also provide shelter. | MH | M |
| Agriculture | |||
| 19. Impact yield? | Reported to invade plantations (Webb, Sykes & Garnock-Jones 1988). It is unknown however if the species reduces yield by any significant amount. | M | L |
| 20. Impact quality? | Reported to invade plantations (Webb, Sykes & Garnock-Jones 1988). It is unknown however if the species impacts the quality of the produce by any significant amount. | M | L |
| 21. Affect land value? | Unknown | M | L |
| 22. Change land use? | Reported to invade plantations (Webb, Sykes & Garnock-Jones 1988). It is unknown however if invasion by the species results in any change to land use. | M | L |
| 23. Increase harvest costs? | Reported to invade plantations (Webb, Sykes & Garnock-Jones 1988). It is unknown however if invasion by the species results in any change to cost of production. | M | L |
| 24. Disease host/vector? | While considered rare the species can be a host of Alfalfa mosaic virus, a disease that effects lucerne (Cardin 2006; Garran & Gibbs 1982). Is reported as a host of Pseudomonas savastanoi a bacterium that causes olive knot disease (Temsah, Hanna & Saad 2007). | M | H |
Impact Assessment Record - Italian buckthorn (PDF - 61KB)
Impact Assessment Record - Italian buckthorn (DOC - 57KB)
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