Carex divisa Huds.

Title: Carex divisa Huds.

Scientific Name:

Carex divisa Huds.

Common Names:

divided sedge

Source & more images

Habitat: Native to Europe, Asia & Northern Africa. Introduced in Australia, New Zealand, North America & South Africa (eflora 2007). Occurs in brackish situations, grassland, marshes, damp pasture, coastal & lake shores, along streams/ irrigation channels, gardens, rice fields, in mountains to 2600m & often in inorganic soils (Aich et al 1980, Jermy & Tutin 1982, eflora 2007). In Australia occurs in WA, SA, Tasmania & Victoria. In Victoria, naturalised along creek flats in North-central region & some Melbourne suburbs (Walsh & Entwisle 1994). Near Sunbury, inhabits wetland & creek edges & tussock grass communities (K. Roberg pers. com.). Near Castlemaine invades herb-rich woodland, creekline grassy woodland, riparian woodland & pasture (I. Higgins pers.com.). In southern WA occurs in brackish wetlands, swamps, winter-wet depressions & in sandy clay & black peaty sand (Marchant et al. 1987, Florabase 1993, Walsh & Entwisle 1994).

Distribution:

Original source via GBIF

Invasiveness Assessment

ESTABLISHMENT

1. Germination requirements? No information on the germination requirements of Carex divisa was found documented.

2. Establishment requirements? It is recorded as inhabiting creekline grassy woodland and herb-rich woodland communities, (pers.com.) an indication that it may be able to establish under a moderate canopy cover.

3. How much disturbance is required? Naturalised along creek flats in Victoria (Walsh & Entwisle 1994) and documented as invading grassland, (Richardson et al 2006, K. Roberg pers.com.) and riparian and creek line grassy woodland (I. Higgins pers.com.). Establishes in minor disturbed natural ecosystems eg. grassland, riparian vegetation.

GROWTH / COMPETITIVE

4. Life form? Tufted sedge to 80 cm with long creeping rhizomes (Richardson et al 2006; Walsh & Entwisle 1994, eflora 2007). Lifeform: geophyte.

5. Allelopathic properties? No information was found documented to indicate C. divisa possesses any allelopathic properties, however, literature on this species is limited.

6. Tolerates herb pressure? There is information from France indicating that C. divisa is a species of grasslands and is grazed by sheep (Aich, O’Rourke & Bourbouze 1980). Observations in Victoria indicate it is rarely grazed unless animals are forced through starvation (I. Higgins pers.com.). It appears that this species is consumed, but it is not preferred by grazing animals.

7. Normal growth rate? A rapid rhizome spreading species that can be difficult to control (Walsh & Entwisle 1994). Has rapidly invaded adjacent pasture and grassland areas (Richardson et al 2006). Growth rate in comparison to species of the same life-form was not found documented.

8. Stress tolerance to frost, drought, w/logg, sal. etc? ‘The frequent flooding of permanent pastures in winter, favours the development of Carex divisa…’ (Jeannin & Lafon 1975). Known to occur on coastal marshes (Aich et al 1980), ‘halophytic meadows’ (Vanden Berghan 1965) and often found in brackish situations (Richardson et al 2006). Known to occur in the Atlas mountains with a mean minimum Winter temperature of -2oC and precipitation mostly falling as snow from December to March. Possesses thick, woody rhizomes (Jermy & Tutin 1982). Likely to be tolerant of frost, salt and water logging and the presence of thick rhizomes may indicate some tolerance to fire.

REPRODUCTION

9. Reproductive system? Inflorescence is a spike containing both male and female flowers and the seed is a dark yellow-brown nut (Walsh & Entwisle 1994). Spreads by rhizomes (Walsh & Entwisle 1994). Reproduces both sexually and vegetatively.

10. Number of propagules produced? No information was found on the number of propagules produced by C. divisa.

11. Propagule longevity? No information was found on the longevity of propagules produced by C. divisa

12. Reproductive period? ‘Theoretically, clones of many [Carex] species may survive for many hundreds of years by growing at one end and dying at the other…’ (Bernard 1990). Examples of documented life-spans of some Carex species include: C. flava more than 10 years, C. comosa, more than 20 years and C. pilosa & C. stricta, more than 50 years. From this information on Carex as a genus, it appears likely that mature C. divisa plants would continue to produce propagules for at least 10 years. It has also been described as being a ‘long lived’ species (I. Higgins pers.com.).

13. Time to reproductive maturity? Described as being able to produce seed ‘by two years post-germination’ (I. Higgins pers.com.).

DISPERSAL

14. Number of mechanisms? Introduced for Stream bank stabilisation but has rapidly invaded adjacent pasture and grassland areas (Richardson et al 2006, Walsh & Entwisle 1994). In Victoria recorded growing in riparian situations with spread being via soil movement and probably water flow (I. Higgins pers.com.). Viable seeds of C. divisa have been found in the dung of red deer (Malo & Suarez 1995). Dispersal is most likely by water and soil movement and potentially by animals.

15. How far do they disperse? Although no information was found on the dispersal distance of propagules, through water and potentially animal dispersal, it is possible that propagules could travel at least 200m.

Impact Assessment

RECREATION

1. Restrict human access? Described as a tufted sedge or as a creeping perennial herb with slender and wiry stems arising singly along a creeping rhizome, to 80cm/1m (Marchant et al 1987, Richardson et al 2006; Walsh & Entwisle 1994). Likely to have minimal impact on human access.

2. Reduce tourism? Described as being very similar in appearance to the rare native sedge Carex chlorantha, so it is probable that this weed would not be obvious to the ‘average’ visitor.

3. Injurious to people? No information was found to suggest this species is injurious to people.

4. Damage to cultural sites? Possesses thick, woody creeping rhizomes (Jermy & Tutin 1982), but no information was found documented to suggest that this species causes damage to cultural sites or infrastructure.

ABIOTIC

5. Impact flow? Described as occurring adjacent to aquatic habitats but ‘rarely in the water’ (Jermy & Tutin 1982), and as a lower growing herbaceous monocot it is unlikely to have much affect on water flow.

6. Impact water quality? Described as occurring adjacent to aquatic habitats but ‘rarely in the water’ (Jermy & Tutin 1982). No information was found to suggest this species impacts on water quality.

7. Increase soil erosion? Has been deliberately introduced in some areas for the stabilization of stream banks (Walsh & Entwisle 1994; Richardson et al 2006). Rhizomes, thick woody, some-times far creeping and branched (Jermy & Tutin 1982). Likely to decrease the probability of soil movement.

8. Reduce biomass? Described as smothering a Poa grass community in Sunbury, Victoria (K. Roberg pers. com.) and because it grows to a similar height as many Poa and other grass species (80-100cm), it is probable that almost direct replacement of biomass by C. divisa may occur rather than a noticeable increase.

9. Change fire regime? In Victoria, C. divisa has been observed forming a monoculture and completely smothering a Poa grass community (K. Roberg pers. com.). With Poa spp. having high flammability foliage (Chladil & Sheridan 2006) the replacement by C. divisa, with broader foliage that does not dry out as intensely as that of Poa spp., is likely to reduce fuel flammability and may cause some reduction to the intensity of fire in grassland situations.

COMMUNITY HABITAT

10(a) Impact on composition of high value EVC? EVC= Creekline Tussock Grassland (BCS= E); CMA= Glenelg Hopkins; Bioreg= Victorian Volcanic Plain; CLIMATE potential=VH. Inhabits wetland areas and creek edges displacing Poa and Bolboschoenus spp. ‘It formed monocultures; overtaking all native vegetation….it completely smothered what was once a productive Poa seed collection site’ (K. Roberg pers.com.). Monoculture within a specific layer; displaces all species within a strata/layer.

10(b) Impact on medium value EVC? EVC= Sedgy Riparian woodland (BCS= D); CMA= North Central; Bioreg= Central Victorian Uplands; CLIMATE potential=VH. Inhabits wetland areas and creek edges displacing Poa and Bolboschoenus spp. ‘It formed monocultures; overtaking all native vegetation….it completely smothered what was once a productive Poa seed collection site’ (K. Roberg pers.com.). Monoculture within a specific layer; displaces all species within a strata/layer.

10(c) Impact on low value EVC? EVC= Seasonally Inundated Shrubby Woodland (BCS= LC); CMA= Glenelg Hopkins; Bioreg= Wimmera Plain; CLIMATE potential=VH. Inhabits wetland areas and creek edges displacing Poa and Bolboschoenus spp. ‘It formed monocultures; overtaking all native vegetation….it completely smothered what was once a productive Poa seed collection site’ (K. Roberg pers.com.). Monoculture within a specific layer; displaces all species within a strata/layer

11. Impact on structure? Inhabits creek and wetland edges displacing Poa and Bolboschoenus spp. (pers.com.). ‘It formed monocultures; overtaking all native vegetation….it completely smothered what was once a productive Poa seed collection site’ (K. Roberg pers.com.). It is described as forming a ‘monoculture’ but no information was found specifically of its specific on recruitment of upper strata species. However, the above information indicates it is likely to have at least a major affect on < 60% of the floral strata.

12. Effect on threatened flora? Inhabits creek and wetland edges displacing Poa and Bolboschoenus spp. (pers.com.). ‘It formed monocultures; overtaking all native vegetation….it completely smothered what was once a productive Poa seed collection site’ (K. Roberg pers.com.). It is likely to have similar impacts on threatened flora, however, no information specific to threatened flora was found documented.

FAUNA

13. Effect on threatened fauna? C. divisa has been observed forming monocultures, displacing native vegetation and more specifically smothering Poa tussock grass communities in the western outskirts of Melbourne (K. Roberg pers.com.). It is also described as invading grasslands in general as well as woodland and riparian communities (Richardson et al 2006, I. Higgins pers. com). Tussock grassland provides important feeding and nesting habitat to small mammals, birds and insects (EWR 2007, MV 2005, Prober & Thiele 2005). The displacement of Poa grass communities by C. divisa would likely lead to reduced habitat and potential decrease in associated faunal populations. No information specific to threatened fauna was found documented, but species for which tussock grasslands are important habitat, such as the endangered Eastern barred bandicoot, could potentially be affected. (EWR2007).

14. Effect on non-threatened fauna? C. divisa has been observed forming monocultures, displacing native vegetation and more specifically smothering Poa tussock grass communities in the western outskirts of Melbourne (K. Roberg pers.com.). It is also described as invading grasslands in general as well as woodland and riparian communities (Richardson et al 2006, I. Higgins pers. com). Tussock grasslands provide important feeding and nesting habitat to small mammals, birds and insects (EWR 2007, MV 2005, Prober & Thiele 2005). The displacement of Poa grass communities by C. divisa would likely lead to reduced habitat and potential decrease in associated faunal populations.

15. Benefits fauna? Described as being low in palatability and rarely grazed unless animals are forced through starvation (I. Higgins pers. com.). Other information suggests that in Europe it is grazed by sheep and by red deer in low quantities (Aich et al 1980, Malo & Suarez 1995). Small numbers of seeds were found cached by mole rats in Israel (Heth, Golenberg & Nevo 1989). No information was found in the literature to suggest C. divisa benefits desirable native fauna, but there is potential for it to provide some assistance to native grazers and rodents.

16. Injurious to fauna? Although the literature is limited, no information was found to indicate that C. divisa possesses any properties injurious to fauna.

PEST ANIMAL

17. Food source to pests? Seeds of C. divisa were found cached by mole rats in Israel (Heth, Golenberg & Nevo 1989) and in the dung of red deer in Spain (Malo & Suarez 1995) suggesting that C. divisa may provide some food source to one or more minor pest species, such as deer or rodents.

18. Provides harbor? The habit of C. divisa to form substantial monocultures to 1m high adjacent to riparian systems (Walsh & Entwisle 1994; Richardson 2006, K. Roberg pers.com.), gives it the potential capacity to provide some harbour to pest animals, however, no information in relation to pest harbour was found documented.

AGRICULTURE

19. Impact yield? C. divisa is known to invade pasture (Richardson 2006, Walsh & Entwisle 1994) and has been observed colonising entire paddocks’ on creek flats near Castlemaine, Victoria. It is also described as being rarely grazed, having low palatability and disliked by farmers (I. Higgins pers. com.). Its ability to ‘colonise entire paddocks’ could lead to significant yield loss (>5%) because of reduced stocking potential due to low quality grazing land.

20. Impact quality? Although literature on this species is limited, it is described as being invasive in pasture (Richardson 2006, Walsh & Entwisle 1994) and has been observed ‘colonising entire paddocks’ (I. Higgins pers.com.), but no information was found to suggest C. divisa reduces agricultural quality.

21. Affect land values? Documented as being invasive in pasture (Richardson 2006, Walsh & Entwisle 1994) and observed ‘colonising entire paddocks’ (pers.com.). It is also described as being rarely grazed, having low palatability and disliked by farmers (I. Higgins pers. com.). However, no information was found documented to indicate that this species would affect land value.

22. Change land use? Documented as invading pasture (Richardson 2006, Walsh & Entwisle 1994), ‘observed’ colonising entire paddocks’ near Castlemaine (I. Higgins pers. com.), and described as being rarely grazed, having low palatability and disliked by farmers (I. Higgins pers. com.). Although no information was found documented that C. divisa specifically causes a change in land use, it is documented as grazed by sheep in Europe (Aich et al 1980) and it is possible that a downgrading of land use priority, for example to a grazing species with less agricultural return, but that will eat C. divisa, may be necessary on invaded grazing land.

23. Increase harvest costs? Although C. divisa is documented as invading pasture, being rarely grazing and having low palatability to stock (Richardson 2006, Walsh & Entwisle 1994, I. Higgins pers. com.), there is no information to suggest this specie would cause an increase in harvest costs in grazing situations.

24. Disease host/vector? No information was found documented to indicate this species acts as a host or vector for diseases of agriculture

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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 Weed's Network.

Attachments:

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commented on by (1)

wra3745: re: Carex divisa Huds.

referenced by (1)

wra998: Common Name - D (via divided sedge)

Article: wra2892 (permalink)
Categories: :wra:c, :wra:inv1, :wra:invm, :wra:inv2, :wra:invmh, :wra:inv3, :wra:inv4, :wra:invml, :wra:inv5, :wra:inv6, :wra:inv7, :wra:inv8, :wra:inv9, :wra:invh, :wra:inv10, :wra:inv11, :wra:inv12, :wra:inv13, :wra:inv14, :wra:inv15, :wra:imp1, :wra:impl, :wra:imp2, :wra:imp3, :wra:imp4, :wra:imp5, :wra:imp6, :wra:imp7, :wra:imp8, :wra:impml, :wra:imp9, :wra:imp10a, :wra:imph, :wra:imp10b, :wra:imp10c, :wra:imp11, :wra:impmh, :wra:imp12, :wra:imp13, :wra:imp14, :wra:imp15, :wra:imp16, :wra:imp17, :wra:imp18, :wra:impm, :wra:imp19, :wra:imp20, :wra:imp21, :wra:imp22, :wra:imp23, :wra:imp24
Date: 26 October 2009; 4:46:00 PM AEDT

Author Name: Fariba Moslih
Author ID: moslih