Commonwealth of Australia

Inclusion of ecological communities in the list of threatened ecological communities under section 181 of the Environment Protection and Biodiversity Conservation Act 1999

I, TONY BURKE, Minister for Sustainability, Environment, Water, Population and Communities, pursuant to paragraph 184(1)(a) of the Environment Protection and Biodiversity Conservation Act 1999, hereby amend the list referred to in section 181 of that Act by:

including in the list in the endangered category

Arnhem Plateau Sandstone Shrubland Complex

as described in the Schedule to this instrument.

Dated this…............11th .........................day of…..........November ...............2011.

signed

TONY BURKE

Minister for Sustainability, Environment, Water, Population and Communities

SCHEDULE

Arnhem Plateau Sandstone Shrubland Complex

The Arnhem Plateau Sandstone Shrubland Complex ecological community occurs predominantly on the Arnhem Plateau massif and outliers such as Ubirr Rock, Nawurlandja (Little Nourlangie Rock) and Burrunggui (Nourlangie Rock – Mt Brockman). The ecological community is particularly associated with substrates of quartzose sandstone and occurs on rock pavements, through to shallow tenosols (skeletal to shallow sandsheets), typically with major rocky components. The ecological community also occurs on laterised Cretaceous mudstone and greywacke sediments on the Marawal Plateau.

The Arnhem Plateau Sandstone Shrubland Complex represents heathlands and shrublands that are dominated by an understorey of diverse, evergreen sclerophyllous shrubs and herbaceous taxa. The ecological community contains a naturally large proportion of obligate seeder taxa along with some resprouter plant species.

The tree canopy is not the dominant vegetation layer for this ecological community and is typically absent or sparse, with various tree species as scattered emergents above the diverse shrub stratum. The species composition of the sparse tree canopy, many of which are endemic to the ecological community, can be variable and may include genera such as Acacia, Banksia, Callitris, Corymbia, Eucalyptus, Ficus and Pandanus. Near rainforest zones, emergent trees such as Allosyncarpia and/or Xanthostemon, may also be present.

Most of the plant diversity of the ecological community occurs in the mid layer of medium to tall shrubs. Obligate seeder shrubs comprise a large proportion of the woody mid layer taxa in the ecological community. Typical shrub genera present in the ecological community include: Acacia, Boronia, Calytrix, Gardenia, Grevillea, Hibbertia, Hibiscus, Jacksonia, Lithomyrtus, Petraeomyrtus punicea, Pityrodia and Tephrosia.

The composition of the ground layer will varies depending on past and present fire regimes, water availability and seasonal conditions. The ground layer consists of a diverse range of low shrubs, herbs and grasses, with ferns and vines being uncommon. Annuals typically comprise the most common ground layer component during the wet season. Perennial native grasses such as hummock (“spinifex”) grasses (e.g. Triodia spp.) and mat-forming (Micraira spp.) grasses may be interspersed or become dominant in patches. The ground layer can be sparse, depending on the presence of bare rock. In bare sandstone pavement habitats Micraira spp. may be the dominant plant.

The key diagnostic characteristics for the Arnhem Plateau Sandstone Shrubland Complex ecological community are:

• Distribution mostly occurs within the Arnhem Plateau bioregion. The community may extend marginally to neighbouring bioregions including Arnhem Coast, Central Arnhem, Darwin Coastal, Daly Basin, Gulf Fall and Uplands, and Pine Creek where outlying and isolated sandstone outcrops occur away from the main plateau.
• The ecological community is mainly restricted to the Buldiva and Bedford land systems. It occurs along the closely spaced joints and crevices of rock pavements and also on low-nutrient acid soils usually derived from the quartz-rich substrates such as skeletal and shallow sandsheets with major rocky components e.g. boulders and pinnacles. Localised patches also occur on laterised Cretaceous mudstone sediments such as on the Marrawal Plateau.
• It typically occurs on substrates that range from rock pavements, shallow tenosols (skeletal to shallow sandsheets) which generally contain major rocky components. Bare rock is heavily prevalent (50% or greater of total area at typical sites, sometimes more than 70%).
• It typically occurs at elevations of 200 to 400 metres above sea level on the main Arnhem Plateau massif but may occur lower (down to 100 metres) on outlying rock outcrops.
• The tree canopy, when present, is typically absent to sparse and shows the following features:
  • Species composition is variable, typically comprising members of the genera Acacia, Blepharocarya, Corymbia, Callitris, Eucalyptus, Ficus, Gardenia, Terminalia, Owenia, Xanthostemon and/or Persoonia; and
  • The trees are generally widely spaced emergents with a canopy cover typically less than 5%.
• The mid layer shows these features:
  • Obligate seeder species present include the genera: Acacia, Boronia, Calytrix, Corchorus, Cryptandra, Dicarpidium, Grevillea, Hibbertia, Hibiscus, Jacksonia, Leptosema, Lithomyrtus, Petraeomyrtus punicea, Pityrodia, Tephrosia, Thryptomene and/or Triumfetta;
  • Obligate seeder taxa comprise at least 10% of the shrub species present, but more usually comprise >50% of the shrub species present; and
  • Shrub species are predominantly sclerophyllous.
• The ground layer contains a variety of herbaceous and grass species, depending on seasonal conditions and site characteristics.
  • During the dry season the ground layer is generally dominated by perennial grasses such as hummock grasses (Symplectriodia spp., Triodia spp.) and mat-forming grasses (Micraira spp.);
  • During the wet season, the most common ground layer vegetation typically comprises annual herbs.