Restricted in the Mallee and Wimmera CMAs. Habitat: Temperate regions on a wide range of soils in moderately warm, unshaded situations. They occur as weeds of cereal crops, lucerne, degraded pastures, roadsides, lowland grassland and grassy woodlands, particularly in dry, sandy areas.
1. Germination requirements? “In the field Amsinckia germinates with the autumn rains (April onwards), and by winter the seed produced in the preceding spring is highly germinable.” Requires autumn temperature and rainfall to germinate. (Connor, 1965, p.55)
2. Establishment requirements? Connor (1965) found that, given suitable moisture, seed germination was consistently high under both light and dark conditions (66% and 62% germination respectively). Seed can thus germinate whether buried or exposed. (Connor, 1965, p.54)
3. How much disturbance is required? While it does occur in lowland grassland & grassy woodland population densities are small. Predominantly, it is a weed of highly disturbed areas such as cereal crops, lucerne, degraded pastures and roadsides. (Carr et al., 1992; Parsons and Cuthbertson, 2001)
6. Tolerates herb pressure? While one sp. of Amsinckia is toxic particularly to cattle, it is nonetheless grazed. Germination and seed production are staggered through the life cycle of the plant. “Four separate germinations have been noted during this period [autumn].” Seed production is high. This indicates that, while the plant may be eaten, its staggered seed production ensures that plants will continue to flower and to persist through subsequent years.(Parsons and Cuthbertson, 1992)
7. Normal growth rate? “Early germination and rapid growth give yellow burrweed seedlings a competitive advantage over other species.” Rapid growth rate exceeds that of species of similar life form. (Parsons and Cuthbertson, 1992)
8. Stress tolerance to frost, drought, w/logg, sal. etc? “Plants die with the onset of summer temperatures in late spring or early summer.” Not drought tolerant. Resistance to other stresses not documented. Consider a tender herb. (Parsons and Cuthbertson, 1992)
REPRODUCTION
9. Reproductive system? An annual herb. Reproduces sexually. “The species of Amsinckia… belong to the section* Muricatae. Self-pollination is a common feature of reproduction within the Muricatae. Combined with cross-compatibility, this places the group in a very aggressive position.” Self and cross-pollination. (Connor, 1965, pp. 50-51)
10. Number of propagules produced? “Amsinckia spp. are prolific seeders producing up to 1600 seeds per plant.” Produces more than 1,000 seeds. (Parsons and Cuthbertson, 2001)
11. Propagule longevity? “The longevity of seed is not known but, stored indoors, they live for more than 2 years but probably not as long as this in the field.” Seeds survive less than 5 years. (Parsons and Cuthbertson, 2001)
13. Time to reproductive maturity? “Seeds germinate… in autumn. The seedling develops into a rosette from which a flowering stem is produced in mid-winter. Growth is still rapid and flowering commences in August, continuing for about 2 months.” Less than 12 months to produce propagules. (Parsons and Cuthbertson, 2001)
DISPERSAL
14. Number of mechanisms? “The bristly calyx facilitates dispersal on wool, fur and hair of animals including foxes. Human activities are most important, resulting in spread through the movement of contaminated harvesting equipment, hay balers and seed graders, and the dispersal of contaminated seed, fodder and stock.” Propagules spread by attaching to animals and through normal harvesting activities. (Parsons and Cuthbertson, 2001)
15. How far do they disperse? As human activities are most important in spreading the seed, it is likely that contaminated produce or machinery will disperse propagules more than 1 kilometre. (see comment above). (Parsons and Cuthbertson, 2001)
Impact Assessment
RECREATION
1. Restrict human access?Amsinckia is an erect annual herb that grows to a height of 70 cm. While infestations can be of the order of 90 plants per square metre, it is not likely to impede human traffic.(Parsons and Cuthbertson, 2001)
3. Injurious to people? No recorded affect on humans, but the stiff hairs or bristles on the leaves and stems may cause some discomfort for a person on foot. (Parsons and Cuthbertson, 2001)
4. Damage to cultural sites? Presence of the plant is quite noticeable during flowering. It would have a moderate negative visual effect. (Parsons and Cuthbertson, 2001)
9. Change fire regime? No known to affect fire regime.
COMMUNITY HABITAT
10(a) Impact on composition of high value EVC? EVC=Plains grassland (E); CMA=North Central; Bioreg=Victorian Riverina; VH CLIMATE potential. It occurs on a wide range of soils, particularly dry, sandy soils, in moderately warm, unshaded situations. Annual; competes with annual grasses/forbs. Occurs rarely in small populations. (Parsons and Cuthbertson, 2001)
10(b) Impact on medium value EVC? EVC=Broombush mallee (D); CMA=Goulburn Broken; Bioreg=Northern Inland Slopes; VH CLIMATE potential. As above. (Parsons and Cuthbertson, 2001)
10(c) Impact on low value EVC? EVC=Sand heathland (LC); CMA=Glenelg Hopkins; Bioreg=Victorian Volcanic Plains; VH CLIMATE potential. As above. (Parsons and Cuthbertson, 2001)
11. Impact on structure? Not known as a problem in environmental situations. It occurs in lowland grassland and grassy woodland vegetation, but its distribution is rare and it occurs in small populations. Minor effect on > 20% of the floral strata. (Carr et al., 1992)
12. Effect on threatened flora?
FAUNA
13. Effect on threatened fauna?
14. Effect on non-threatened fauna? No recorded effects on habitat or food source of non-threatened fauna. Predominantly a weed of cropping; few if any fauna co-existing in situation. (Carr et al., 1992; Parsons and Cuthbertson, 2001)
15. Benefits fauna? “Birds are known to eat the seed.” But bird spp. not specified (native or introduced). “Bristles on the leaves and stems make the plant unattractive to stock and it is generally unpalatable.” Annual spp. dying back in summer; no harbor. Very limited benefit, if at all. (Faithfull, 1998; Parsons and Cuthbertson, 2001)
16. Injurious to fauna? Not evident, though “…one spp. causes liver disease which killed 2000 cattle in the United States, but deaths have not be recorded in Australia.” Generally unpalatable; limited potential to injure to fauna. (Parsons and Cuthbertson, 2001)
PEST ANIMAL
17. Food source to pests? “Birds are known to eat the seed.” Not known if native or introduced species. Not known to provide a significant source of food. (Parsons and Cuthbertson, 2001; DNRE, 1998)
18. Provides harbor? An erect, annual herb that dies back in late spring or early summer. Not likely to provide harbor. (Parsons and Cuthbertson, 2001)
AGRICULTURE
19. Impact yield? Very competitive in cereal crops. Recorded instance of 48% reduction in wheat yield in NSW. (Parsons and Cuthbertson, 2001)
20. Impact quality? It is claimed Amsinckia seed imparts a peculiar taint to flour and fragments of the black seedcoat discolour flour. The “bristly calyx becomes an impurity in wool.”
21. Affect land values? Considering its potential impact on both yield and quality, the presence of this weed would reduce land value. It can be controlled with appropriate mechanical and chemical treatments. (Parsons and Cuthbertson, 2001)
22. Change land use? See above. No chemicals are registered for use against Amsinckia in broad-leaved cereal crops. Therefore, farmers wishing to cultivate broad-leaved winter crops in lieu of winter cereals may have to temporarily change land use. (Parsons and Cuthbertson, 2001)
23. Increase harvest costs? “Human activities are most important [in dispersal] resulting in spread [of seed] through the movement of contaminated harvesting equipment, hay balers and seed graders.” Farm machinery used on affected properties must be thoroughly cleaned to eliminate the presence and subsequent dispersal of the seed. This could increase harvesting costs. (Parsons and Cuthbertson, 2001)
24. Disease host/vector? None evident.
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Article: wra893 (permalink) Date: 8 September 2009; 12:22:15 PM AEST