NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. Themeda grassland on seacliffs and coastal headlands in NSW is an ecological community described by Adam et al. (1989). The community is found in the NSW North Coast, Sydney Basin and South East Corner Bioregions, on seacliffs and coastal headlands. The structure of the community is typically closed tussock grassland, but may be open shrubland or open heath with a grassy matrix between the shrubs. The community belongs to the Maritime Grasslands vegetation class of Keith (2004).
2. The community is characterised by the following assemblage of species.
- Acacia sophorae
- Banksia integrifolia subsp. integrifolia
- Commelina cyanea
- Glycine clandestina
- Glycine microphylla
- Hibbertia scandens
- Isolepis nodosa
- Kennedia rubicunda
- Lepidosperma spp.
- Leptospermum laevigatum
- Lomandra longifolia
- Monotoca elliptica
- Opercularia aspera
- Pimelea linifolia
- Poranthera microphylla
- Sporobolus virginicus
- Themeda australis
- Viola banksii
- Westringia fruticosa
3. The total species list of the community is considerably larger than that given above, with many species present at only one or two sites, or in low abundance. The species composition of the site will be influenced by the size of the site, recent rainfall and drought conditions and by its disturbance history (including fire, grazing and land clearing). At any one time, above ground individuals of some species may be absent, but the species may be represented below ground in soil seed banks or as dormant structures such as bulbs, corms, rhizomes, rootstocks or lignotubers. The list of species given above is of the vascular plant species, the community also includes micro-organisms, fungi, cryptogamic plants and a diverse flora. These components of the community are poorly documented.
4. Themeda australis is the dominant species in the community. Themeda australis is an extremely widespread species, but in this community may have a distinctive appearance, being prostrate and having glaucous leaves. These features are retained in cultivation and the form is believed to be genetically distinct (SWL Jacobs, pers. comm.). Scattered shrubs occur in many stands, most frequently Pimelea linifolia, Banksia integrifolia and Westringia fruticosa. These and other woody species often have dwarf growth forms. Although a number of woody species are listed as part of the community, these are usually sparsely distributed and may be absent from some stands. Tussocks of Poa poiformis may be found in some stands of the community, but Poa poiformis-dominated tussock grassland is generally found lower on cliffs (closer to the sea and more exposed to spray) and on steeper slopes.
5. A number of threatened species occur in some stands of the community, including Diuris sp. aff. chrysantha, Pultenaea maritima, Rutidosus heterogama, Thesium australe (Cohn 2004) and Zieria prostrata (Hogbin 2001). The endangered population of the low growing form of Zieria smithii at Diggers Head is found in this community. The community is the major habitat for a number of other species, including Chamaecrista maritima, Plectranthus cremnus and Stackhousia spathulata. The presence of threatened species is a matter which will need to be addressed, on a stand by stand basis in management plans, but the presence of threatened species is not required for definition of the community.
6. The community is found on a range of substrates, although stands on sandstone are infrequent and small. Larger stands are found on old sand dunes above cliffs, as for example at Cape Banks and Henry Head in Botany Bay National Park (Adam et al. 1989), and on basalt headlands, as for example at Damerals Head in Moonee Beach National Park. Occurrences of the community in northern NSW are discussed by Griffith et al. (2003).
7. Individual stands of the community are often very small, a few square m, but at some sites larger stands of up to several hectares or tens of hectares occur. Overall, the community therefore has a highly restricted geographic distribution comprising small, but widely scattered patches.
8. Themeda grassland on seacliffs and coastal headlands has been affected by pasture improvement to accommodate livestock grazing to varying degrees throughout its range (e.g. in the Coffs Harbour and Shellharbour-Kiama districts). More recently, the distribution has been depleted by coastal development. While some stands are protected from further land use change, a major threat to the community is posed by invasion by shrubs, both introduced species such as Chrysanthemoides monilifera and Lantana camara, and native species including Acacia sophorae, Banksia integrifolia and Westringia fruticosa. Although native shrubs are a feature of the community, invasion and conversion to dense shrubland has occurred at a number of sites in recent years and this may threaten the persistence of grassland elements in the community. This may reflect changed fire regimes and reduced grazing pressure (including by rabbits). A further major threat is associated with recreational use, with weed invasion and erosion occurring adjacent to footpaths and from use of off-road vehicles. Collectively, these processes may result in a large reduction of the ecological function of the community.
9. In view of the highly restricted distribution, small patch size and ongoing threats to the community, the Scientific Committee is of the opinion that Themeda grassland on seacliffs and coastal headlands in the NSW North Coast, Sydney Basin and South East Corner Bioregions is likely to become extinct in nature in New South Wales unless the circumstances and factors threatening its survival cease to operate.
Dr Lesley Hughes
Proposed Gazettal date: 21/10/05
Exhibition period 21/10/05 - 16/12/05
Adam P, Stricker P, Wiecek BM, Anderson DJ (1989) The vegetation of seacliffs and headlands in New South Wales, Australia. Australian Journal of Ecology 14, 515-547.
Cohn JS (2004) Effects of slashing and burning on Thesium australe R Brown (Santalaceae) in Coastal grasslands of NSW. Proceedings of the Linnean Society of New South Wales 125, 57-65.
Griffith SJ, Bale C, Adam P, Wilson R (2003) Wallum and related vegetation on the NSW North Coast: description and phytosociological analysis. Cunninghamia 8, 202-252.
Hogbin PM (2001) Conservation outcomes arising form research into the population genetics, taxonomy and reproductive ecology of the endangered plant Zieria prostrata PhD, the Australian National University, Australia.
Keith DA (2004) 'Ocean shores to desert dunes: The native vegetation of New South Wales and the ACT.' NSW Department of Environment and Conservation. Sydney.