Impact Assessment - Whiskey grass (Andropogon virginicus) 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 Whiskey grass.
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: Whiskey grass
Scientific name: Andropogon virginicus
| Question | Comments | Rating | Confidence |
| Recreation | |||
| 1. Restrict human access? | As a grass species that only grows to 1 m and with no reported barbs or sharp edges, it is thought unlikely that the species would impose any restriction on access (Edgar & Connor 2000; Parsons & Cuthbertson 2001). | L | MH |
| 2. Reduce tourism? | The species is reported to be a weed mainly of roadsides, railway lines and other disturbed places (Edgar & Connor 2000; Parsons & Cuthbertson 2001). It is therefore thought that any impact on tourism and recreation is unlikely. | L | MH |
| 3. Injurious to people? | There is no evidence of this reported. | L | M |
| 4. Damage to cultural sites? | The species is reported to be a weed mainly of roadsides, railway lines and other disturbed places (Edgar & Connor 2000; Parsons & Cuthbertson 2001). It is therefore thought that any impact on cultural sites or infrastructure is unlikely. | L | MH |
| Abiotic | |||
| 5. Impact flow? | The species can occur in riparian and wetland 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 affecting water quality. | L | M |
| 7. Increase soil erosion? | The species is a clumping grass species (Parsons & Cuthbertson 2001). It is therefore thought that areas invaded by this species would have a moderate probability of large scale soil movement. | ML | M |
| 8. Reduce biomass? | Unknown; as the species is less palatable and therefore able to accumulate more biomass, this may be viewed as increasing biomass (Parsons & Cuthbertson 2001). In Hawaii however the species is associated with reducing overall biomass through alteration of the fire regime (Freifelder & Vitousek 1998). | M | L |
| 9. Change fire regime? | As the species is less palatable, dried material remains over summer and a potential fire hazard (Parsons & Cuthbertson 2001). Therefore the species has the potential to moderately increase the fuel load and therefore the fire intensity. | M | MH |
| Community Habitat | |||
| 10. Impact on composition (a) high value EVC | EVC= Riverine Grassy Woodland (V); CMA= Goulburn Broken; Bioreg= Murray Fans; VH CLIMATE The species is reported to be able to dominate within the grass layer (Sorenson 1991). | MH | H |
| (b) medium value EVC | EVC= Montane Grassy Woodland (D); CMA= North East; Bioreg= Highlands-Northern Fall; VH CLIMATE The species is reported to be able to dominate within the grass layer (Sorenson 1991). | MH | H |
| (c) low value EVC | EVC= Montane Grassy Woodland (D); CMA= North East; Bioreg= Victorian Alps; VH CLIMATE The species is reported to be able to dominate within the grass layer (Sorenson 1991). | MH | H |
| 11. Impact on structure? | The species is reported to be able to dominate within the grass layer (Sorenson 1991). In Hawaii it is reported to have less impacts on native species than two other grass species (D’Antonio, Tunison & Loh 2000). As the species largely invades grassland, the grass layer is the only one present and so if the species is able to dominate that layer, it is thought to impact upon more than 60% of the flora strata. | MH | H |
| 12. Effect on threatened flora? | Unknown. | MH | L |
| Fauna | |||
| 13. Effect on threatened fauna? | Unknown. | MH | L |
| 14. Effect on non-threatened fauna? | Unknown | M | L |
| 15. Benefits fauna? | Grass species that grow to 1 m, may provide limited and short term shelter for species. | MH | M |
| 16. Injurious to fauna? | There is no evidence of this reported. | L | M |
| Pest Animal | |||
| 17. Food source to pests? | Reported to be unpalatable and of low fodder value to stock (Griffin, Watson & Strachan 1988). It may therefore by eaten by grazing pest species however this is thought to be minimal. | L | MH |
| 18. Provides harbor? | Grass species that grow to 1 m, may provide limited and short term shelter for pest species. | M | M |
| Agriculture | |||
| 19. Impact yield? | Has little fodder value, reducing the carrying capacity however as the species is reported to invade poorly managed and or marginal areas of pasture, the impact is thought to be minor (Griffin, Watson & Strachan 1988; Parsons & Cuthbertson 2001). | ML | H |
| 20. Impact quality? | Seeds can catch in wool and may therefore be recognised as minor contamination (Parsons & Cuthbertson 2001). | ML | MH |
| 21. Affect land value? | The species is reported to invade poorly managed and or marginal areas of pasture (Griffin, Watson & Strachan 1988; Parsons & Cuthbertson 2001). Therefore the value of the property is likely to be devalued for other reasons and therefore the presence of this species is likely to have little impact. | L | M |
| 22. Change land use? | In changes to management is likely to be limited, such as replacing pasture to more vigorous species instead of native grasses (Parsons & Cuthbertson 2001) | ML | MH |
| 23. Increase harvest costs? | In forestry control or suppression of this species, may be necessary to enable the establishment of the plantation species (Groninger et al 2004). | M | H |
| 24. Disease host/vector? | There is no evidence of this reported. | L | M |
Impact Assessment Record - Whiskey grass (PDF - 98KB)
Impact Assessment Record - Whiskey grass (DOC - 58KB)
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