Impact Assessment - Dolichos pea (Dipogon lignosus) 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 Dolichos pea.
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: Dolichos Pea
Scientific name: Dipogon lignosus
| Question | Comments | Rating | Confidence |
| Recreation | |||
| 1. Restrict human access? | It is reported to grow over existing vegetation building up enough biomass so that the supporting plant collapses. It can from dense masses of dead stems and other biomass more than 1 m thick, including in riparian areas (Blood 2001). As this growth would be worst where the plant has something existing to grow over it is unlikely to cause track closure. | MH | MH |
| 2. Reduce tourism? | Reported to be the second most noticed species to Buddleja in a public survey of seven weeds in New Zealand, due to its substantial floral displays (McCluggage 2004). Unknown if the species effect on access would also impede any recreational activities. | M | L |
| 3. Injurious to people? | There is no reported evidence of the species causing injury. | L | M |
| 4. Damage to cultural sites? | Reported to be the second most noticed species to Buddleja in a public survey of seven weeds in New Zealand, due to its substantial floral displays (McCluggage 2004). The species ability to build up so much biomass that it causes the supporting plants to collapse as reported by Blood (2001) may imply that the species would also be possible of collapsing infrastructure. | M | L |
| Abiotic | |||
| 5. Impact flow? | The species is reported to invade riparian vegetation but no impact on water flow is reported (Blood 2001). | L | MH |
| 6. Impact water quality? | The species is reported to invade riparian vegetation but no impact on water flow is reported (Blood 2001). | L | MH |
| 7. Increase soil erosion? | The thick mat of vegetation the species forms protects the soil surface from wind and water erosion (Gandhi 1957). Muyt (2001) describes the species root system as woody occasionally branched taproot which can be several metres long. A well developed root system would reduce the probability of large scale erosion. | L | H |
| 8. Reduce biomass? | The species is able to build up so much biomass that the supporting plants collapse due to the weight (Blood 2001). This would be a short term gain, however Muyt (2001) describes the species invading gaps and margins where it can the bring down trees and preventing regeneration will continue to invade with the increased light levels which would lead to a significant decrease in biomass. | H | MH |
| 9. Change fire regime? | There is no specific data presented on this species effect on fire regime, fire kills mature plants and stimulates mass germination of seedling (Muyt 2001). The plant forms dense masses which contain dead material (Blood 2001). The alteration of biomass and the creation of fire ladders as the species can grow up trees and accumulate dead material could alter the fire intensity. It is unknown however the flammability of the living material and there for its effect on fire frequency. | M | M |
| Community Habitat | |||
| 10. Impact on composition (a) high value EVC | EVC= Damp Sands Herb-rich Woodland (V); CMA= Glenelg Hopkins; Bioreg= Glenelg Plain; VH CLIMATE potential. Highly invasive in heathland and woodlands Dolichos pea is reported to be able to ‘smother all ground flora”, bring down shrubs and trees and prevent regeneration (Muyt 2001). Being able to smother all species in the lower strata it is effectively forming a monoculture. | H | MH |
| (b) medium value EVC | EVC= Sand Heathland (R); CMA= Glenelg Hopkins; Bioreg= Glenelg Plain; VH CLIMATE potential. Highly invasive in heathland and woodlands Dolichos pea is reported to be able to ‘smother all ground flora”, bring down shrubs and trees and prevent regeneration (Muyt 2001). Being able to smother all species in the lower strata it is effectively forming a monoculture. | H | MH |
| (c) low value EVC | EVC= Heathy Woodland (LC); CMA= Glenelg Hopkins; Bioreg= Glenelg Plain; VH CLIMATE potential. Highly invasive in heathland and woodlands Dolichos pea is reported to be able to ‘smother all ground flora”, bring down shrubs and trees and prevent regeneration (Muyt 2001). Being able to smother all species in the lower strata it is effectively forming a monoculture. | H | MH |
| 11. Impact on structure? | Highly invasive in heathland and woodlands Dolichos pea is reported to be able to ‘smother all ground flora”, bring down shrubs and trees and prevent regeneration (Muyt 2001). The species is having a major effect on all layers by smothering all “ground flora” species and felling shrubs and trees. | H | MH |
| 12. Effect on threatened flora? | Listed as threatening competitor to Villarsia calthifolia a rare species in Western Australia (Gilfillan & Barrett 2004). There is no evidence of its effect on threatened species in Victoria however. | MH | L |
| Fauna | |||
| 13. Effect on threatened fauna? | There is no data reported on the species effect on threatened species. | MH | L |
| 14. Effect on non-threatened fauna? | Significant alteration of the vegetation and therefore habitat for species it is likely to affect fauna species, however there is no reported data. | M | L |
| 15. Benefits fauna? | The plant is eaten by possums and wallabies (Wotherspoon & Wotherspoon 2002). Birds disperse the seed (Muyt 2001). Unknown which species. Produces prolific flowers (Blood 2001). Likely to be visited by insects. | MH | H |
| 16. Injurious to fauna? | There is no evidence of the species injuring fauna species. | L | M |
| Pest Animal | |||
| 17. Food source to pests? | The species is edible as it was suppressed by possums and wallabies (Wotherspoon & Wotherspoon 2002). Therefore it may be eaten by species such as rabbits or goats but there is no evidence of this reported. | M | L |
| 18. Provides harbor? | Grows over existing vegetation creating dense mats of biomass (Blood 2001). This may provide shelter for species such as rabbits or foxes but there is not evidence of this reported. | M | H |
| Agriculture | |||
| 19. Impact yield? | Not reported as a weed of agriculture. | L | M |
| 20. Impact quality? | Not reported as a weed of agriculture. | L | M |
| 21. Affect land value? | Not reported as a weed of agriculture. | L | M |
| 22. Change land use? | Not reported as a weed of agriculture. | L | M |
| 23. Increase harvest costs? | Interfered with harvesting in an organic soybean crop when trailed as a cover crop as it twined around the soybean plant (Hively and Cox 2001). However it is not reported as a weed of agriculture. | L | M |
| 24. Disease host/vector? | There is no evidence reported of this species being host to a pest or disease of an agricultural crop. | L | M |
This table can also be viewed as a PDF document (printer friendly).
Impact Assessment Record - Dolichos pea (PDF - 88KB)
Impact Assessment Record - Dolichos pea (DOC - 60KB)
To view the information PDF requires the use of a PDF reader. This can be installed for free from the Adobe website (external link).
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