Native Vegetation on Cracking Clay Soils of the Liverpool Plains - Determination to make a minor amendment to Part 3 of Schedule 1 of the Threatened Species Conservation Act

The Scientific Committee is of the opinion that the amendment is necessary or desirable to correct minor errors or omissions in the Determination in relation to the Thackway and Cresswell (1995) reference.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Native Vegetation on Cracking Clay Soils of the Liverpool Plains is characterised by the assemblage of species discussed in paragraphs 3 to 5. The community occurs on cracking clay soils (vertosols - including soils referred to as Black Earth) and is within the Liverpool Plains Catchment. The Mooki River, Coxs Creek and their tributaries drain this catchment into the Namoi River. This catchment occurs in the Brigalow Belt South and Nandewar Bioregions. Bioregions are defined in Thackway and Cresswell (1995).

2. Native Vegetation on Cracking Clay Soils of the Liverpool Plains is generally grasslands which are often dominated by Austrostipa aristiglumis, Dichanthium sericeum or Panicum queenslandicum but can include shrubs and trees which are generally sparse but may be locally common.

3. Native Vegetation on Cracking Clay Soils of the Liverpool Plains is characterised by the following assemblage of species.

4. The total flora list for the community is considerably larger than that given above, with many species present in only one or two sites or in very small quantity. In any particular site not all of the assemblage listed above will be present. At any one time, seeds of some species may only be present in the soil seed bank with no above-ground individuals present. The species composition of the site will be influenced by the size of the site, recent rainfall or drought conditions and by its disturbance history. The community is an important habitat for a diverse fauna (vertebrate and invertebrates), but detailed fauna records are not available.

5. In wetter locations the Native Vegetation on Cracking Clay Soils of the Liverpool Plains may contain a number of species that are not common in drier areas. Such species include Agrostis avenacea, Cyperus spp., Eleocharis spp., Juncus spp., Rumex dumosus and Rumex tenax. Tree species such as Eucalyptus melliodora, Eucalyptus populnea subsp. bimbil, Eucalyptus conica and Angophora floribunda and shrub species such as Acacia pendula may be scattered to locally common in the Native Vegetation on Cracking Clay Soils of the Liverpool Plains.

6. Native Vegetation on Cracking Clay Soils of the Liverpool Plains is known to occur in the Coonabarabran, Gunnedah, Murrurundi, Narrabri, Parry and Quirindi Local Government Areas. This community occurs over an altitude range (above sea level) varying from 750 m in the south to 210 m in the north. Change in altitude is gradual and areas often remain waterlogged for some time after heavy rainfall or floods.

7. Native Vegetation on Cracking Clay Soils of the Liverpool Plains has largely been modified as a result of cropping, grazing and alteration of disturbance regimes. Salinity is also considered to be an increasing problem to this vegetation. Erosion, particularly of recently cultivated areas, following flooding results in deposition of soil over native vegetation and movement of plant propagules both native and exotic. Saline perched water tables are also left closer to the surface after removal of surface soil and this affects recolonisation of these areas by native species.

8. Native Vegetation on Cracking Clay Soils of the Liverpool Plains now occupies only a small proportion of its original range. Sim and Unwin (1983) reported that by 1978 approximately 85% of the Black Earth Alluvial Plains Land System of the Liverpool Plains was under cultivation and this proportion has increased further.

9. Most of the surviving remnants of this community are found on travelling stock routes through the plains. These may be wide but if next to roads they are often used by diverted traffic while roadworks are being carried out.

10. Invasion by exotic species is also a threat to this community. The most common weeds are Ammi majus and Aster subulatus but thistles, annual grasses and exotic legumes may also be locally common. A few weeds such as Phalaris paradoxa, Myagrum perfoliatum and Scorzonera laciniata are generally only found on clay soils, including vertosols.

11. Native Vegetation on Cracking Clay Soils of the Liverpool Plains is not known to be conserved in any area managed by the National Parks and Wildlife Service.

12. In view of the small area of most existing remnants, and the threat of further clearing, disturbance and degradation, the Scientific Committee is of the opinion that Native Vegetation on Cracking Clay Soils of the Liverpool Plains is likely to become extinct in nature in NSW unless factors threatening its survival or evolutionary development cease to operate.

Dr Richard Major
Chairperson
Scientific Committee

Proposed Gazettal date: 02/12/11
Exhibition period: 02/12/11 – 03/02/12

Reference

Sim, I & Unwin, N. (1983) The natural grasslands of the Liverpool Plains New South Wales. Report based on research by J.A. Duggin and P.N. Allison. Department of Environment and Planning, Sydney.

Thackway R, Cresswell ID (1995) An interim biogeographic regionalisation for Australia: a framework for setting priorities in the National Reserves System Cooperative Program. (Version 4.0. Australian Nature Conservation Agency: Canberra.)