Title: Nassella trichotoma (Nees) Hack. Ex Arechav.

Scientific Name: Nassella trichotoma (Nees) Hack. Ex Arechav. (Synonym; Stipa trichotoma)

Common Names: serrated tussock, nassella tussock



Source & more images (via ALA)

Habitat: Plants require relatively cool conditions for growth and survival; the optimum temperature range is 10oC to 15oC. The plant is also capable of surviving severe droughts. Serrated tussock can be found growing on soils derived from granite, basalt, shale, slate or sandstone. While adapted to nutrient-deficient soils it also responds to higher soil fertility. It is highly tolerant of acidic soils, and will also grow on basalt soils with higher pH. It is not often found in wet swampy areas, heavily shaded areas or areas affected by salinity, but is well adapted to rocky terrains. In the absence of competition from other vegetation, serrated tussock establishment is not restricted by shallow soils.

Distribution:



Original source via CABI


Invasiveness Assessment

ESTABLISHMENT


1. Germination requirements? “Seeds germinate at any time of the year but mostly in autumn and winter” (Parsons & Cuthbertson 1992 p. 112).


2. Establishment requirements? “Occurring as a weed in open pastures and lightly timbered areas” (Parsons & Cuthbertson 1992 p. 112).

3. How much disturbance is required? “Invades nature grasslands, grassy woodlands, drier forests and rocky shrublands” (Muyt 2001 p. 75).


GROWTH / COMPETITIVE


4. Life form? Perennial tussock-forming grass (Parsons & Cuthbertson 1992 p. 112).

5. Allelopathic properties? No Allelopathic properties described.

6. Tolerates herb pressure? “The plant is eaten by sheep and cattle only if nothing else is available” (Parsons & Cuthbertson 1992 p. 113).

7. Normal growth rate? “Most seedlings that establish in a dense strand of N. trichotoma or in a vigorous improved pasture are killed by competition in the first or second spring or summer”. Seedlings not killed by competition will grow as fast as comparable grasses in the surrounds (Campbell & Vere 1995 p. 194).


8. Stress tolerance to frost, drought, w/logg, sal. etc? “Tolerates, fire, drought and frost” (Blood 2001 p. 208).


REPRODUCTION


9. Reproductive system? “Reproduction is by seed” (Parsons & Cuthbertson 1992 p. 112).

10. Number of propagules produced? “Seed production is prolific and a hectare of dense tussock growth is estimated to produce more that 2 tonnes of seed per year” (Parsons & Cuthbertson 1992 p. 114). “Large vigorous plants can produce 100,000 seeds annually” (Muyt 2001 p. 75).

11. Propagule longevity? “Some seeds remain dormant in the soil for up to 15 years, possibly more” (Parsons & Cuthbertson 1992 p. 114). “Soil in a forest that had no fresh seed added for 13 years had a germination capacity of 8%”. (Campbell & Vere 1995 p. 194).

12. Reproductive period? “Tussocks persist for many years producing new flowering stems and some new leaves each year” (Parsons & Cuthbertson 1992 p. 113).

13. Time to reproductive maturity? “Plants rarely flower in the first year but continue vegetative growth until the second summer when flowers and seeds are usually produced” (Parsons & Cuthbertson 1992 p. 112).

DISPERSAL


14. Number of mechanisms? See ‘dispersal’ section.

15. How far do they disperse? “The seed head breaks off near the base of the plant and may be blown considerable distances, even up to several kilometres” (Parsons & Cuthbertson 1992 p. 113).


Impact Assessment

RECREATION


1. Restrict human access? “A perennial tussock-forming grass to 50 cm high and 25 cm diameter at the base.” Leaf spread is about 50 cm. Would not hinder human access (Parsons & Cuthbertson 2001; Groves et al. 1995).


2. Reduce tourism? Tussocks are noticeable, but would not restrict recreational activities (Parsons & Cuthbertson 2001).

3. Injurious to people? Not toxic to humans (Parsons & Cuthbertson 2001).

4. Damage to cultural sites? “Tussocks persist for many years. Roots are diffuse and fibrous, mostly in top 20 cm of soil, and even seedlings are difficult to pull from the soil.” Not likely to contribute to soil erosion (Parsons & Cuthbertson 2001).

ABIOTIC


5. Impact flow? Terrestrial species.

6. Impact water quality? Terrestrial species.

7. Increase soil erosion? “Tussocks persist for many years. Roots are diffuse and fibrous, mostly in top 20 cm of soil, and even seedlings are difficult to pull from the soil.” Not likely to contribute to soil erosion (Parsons & Cuthbertson 2001).


8. Reduce biomass? “It dominates pastures and invades natural areas forming dense swards.” Replaces biomass (Blood 2001).


9. Change fire regime? “N. trichotoma burns readily in winter. A dense mature infestation of N. trichotoma generally has 5 – 20 tussocks per square metre.” “Dense stands produce a serious fire hazard.” Dense infestations would moderately change the frequency and intensity of fire risk. CFA trials (at Melton 1998) have indicated serrated tussock burns with an intensity up to seven times greater than grasslands. Seed heads create additional hazards where they build up against housing, sheds, roadsides, fencelines etc. This is a particular hazard in the rural/urban interface areas of outer west Melbourne (Groves et al. 1995)


COMMUNITY HABITAT


10(a) Impact on composition of high value EVC? EVC=Plains grassland (E); CMA=Corangamite; Bioreg=Victorian Volcanic Plain; VH CLIMATE potential. Prolific seeder. Each plant can cover a large area leading to almost complete cover in dense infestations and eliminating most other species. Serious impact on grasses/forbs. 3 fold effect, competitiveness, water usage high, allelopathy Monoculture – if up to 20% or greater ST infestation – cannot save grassland (Parsons & Cuthbertson 2001; Colin Hocking pers comm).


10(b) Impact on medium value EVC? EVC=Grassy dry forest (E); CMA=Port Phillip; Bioreg=Central Victorian Uplands; VH CLIMATE potential. Also grows in lightly timbered areas. Impact as in 10(a) above (Parsons & Cuthbertson 2001).


10(c) Impact on low value EVC? EVC=Heathy dry forest (E); CMA=Glenelg Hopkins; Bioreg=Goldfields; VH CLIMATE potential. Impact as in 10(b) above (Parsons & Cuthbertson 2001).

11. Impact on structure? “In dense stands foliage of N. trichotoma completely covers the soil surface, thereby suppressing competitors" (Groves et al. 1995) “Mature plants develop a drooping, smothering form eventually excluding other ground-flora” (Muyt 2001).


12. Effect on threatened flora? From serrated tussock establishment it takes only seven years to dominate a pasture or native grassland Effects on Danthonia threatens ANZECC rated rare or threatened native plant species (Groves et al. 2003).


FAUNA


13. Effect on threatened fauna? Hotter burns impact on striped legless lizard, and other ground dwelling species. Loss of flora biodiversity as serrated tussock displaces desired species impacts on adequate food supply. Golden sun moth, needs Danthonia – displaced by ST – only occurs basalt plains – Golden sun moth management plan ACT (Clark & Spier 2004).


14. Effect on non-threatened fauna? “Plants are unpalatable and infestations commonly expand as other species are selectively grazed out. The smothering form eventually excludes other ground-flora.” Reduction in habitat for native fauna. Or habitat changed dramatically ? Possible local extinction Wombats foraging in Monaro plains – foraging limited by ST infestations – forced to raid rubbish bins (Muyt 2001).


15. Benefits fauna? No documented benefits for fauna.

16. Injurious to fauna? “Sheep will not graze it unless forced to and they lose weight and die due to a rumen full of undigested leaves.” May have similar impact on fauna (Blood 2001).

PEST ANIMAL


17. Food source to pests? Not known as a food source to pests.

18. Provides harbor? Across the basalt plains rabbits are the greatest vertebrate environmental pest and serrated tussock provides harbour ... permanent harbour – Rowsley Valley.


AGRICULTURE


19. Impact yield? “Even moderate infestations reduce carrying capacity by about 40% and up to 100%.” Serious impact on quantity of produce (Parsons & Cuthbertson 2001).


20. Impact quality? Animals forced to eat the plant lose condition. “Even a moderate loss of condition results in lowered wool quality because of loss of crimp and breaks in the fleece. Seeds also contribute to vegetable fault in wool" (Parsons & Cuthbertson 2001). Major impact on quality. Canola crop contaminated by seed contaminant by wind, civil court case - $60,000 damage.


21. Affect land values? As a serious weed of pasture with significant impact on carrying capacity and reduction in agricultural return, its presence would seriously affect land value. Seven (7) Local Govt councils have introduced rebate schemes to arrest the decline in land value (Parsons & Cuthbertson 2001).

22. Change land use? In New Zealand, “considerable effort to control [N. trichotoma], involving government purchase of heavily infested farms, clearing the weed at government expense, and reselling the land for farming, has been expended over many years” (Parsons & Cuthbertson 2001). Without government intervention, the land would have had no use for pastoral activities. Significant change in land use.

23. Increase harvest costs? Not a weed of cropping in Australia. In uncultivated areas serrated tussock dominates but can be controlled with cropping regimes. In very heavy infestation areas continuous cropping is the only control option and creates another set of problems with soil health. However the impact of seeding tussock blown onto preharvested crops have resulted in downgraded quality of produce and has seen one civil case against neighbouring polluters. More seed testing carried out. Time taking in harvest and post harvest testing. Also need to continually cultivate each year to prevent re-establishment.

24. Disease host/vector? None evident. Unknown.

NON-CHEMICAL MANAGEMENT



Link to non-chemical management methods from the Victorian Serrated Tussock Working Party




Feedback

Do you have additional information about this plant that will improve the quality of the assessment? If so, we would value your contribution.


Assessment ratings originally made by the Victorian Department of Primary Industries.
The entry of this assessment was made possible through the generous support of the Victorian Serrated Tussock Working Party.






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Date: 12 January 2012; 11:41:56 AM AEDT

Author Name: David Low
Author ID: adminDavid