Acacia loderi Shrublands - Determination to make a minor amendment to Part 3 of Schedule 1 of the Threatened Species Conservation Act

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Determination to make a minor amendment to Part 3 of Schedule 1 (Endangered ecological communities) of the Act by inserting the Acacia loderi Shrublands (as described in the determination of the Scientific Committee under Division 5 Part 2) and as a consequence to omit reference to the Acacia loderi Shrublands (as described in the final determination to list the ecological community) which was published on pages 10955 to 10959 in the NSW Government Gazette No. 131 dated 6 October 2000. Minor amendments to the Schedules are provided for by Division 5 of Part 2 of the 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. The Acacia loderi Shrublands is the name given to the plant community that is dominated by the tall shrub/small tree  Acacia loderi (commonly known in some parts of its range as nelia). Other tree species that may occur in association with  Acacia loderi are  Acacia aneura,  Acacia oswaldii,  Callitris gracilis,  Casuarina pauper and  Flindersia maculosa. The mistletoes  Amyema quandang and  Lysiana exocarpi frequently occur on  Acacia loderi. Understorey species within the  Acacia loderi Shrublands include:

2. The community has a naturally open structure of individual shrubs to small trees (to 8 m high) with a low, diverse understorey dominated by chenopod subshrubs, herbs and grasses. The community is often interspersed by woodlands of Casuarina pauper (belah),  Alectryon oleifolius (rosewood) or  Flindersia maculosa. Fox (1993), Pickard and Norris (1994) and Westbrooke and Miller (1995) discuss floristic composition, distribution, and structure of the  Acacia loderi Shrublands.

3. The total species list of the community is considerably larger than that given in 1 (above), with many species present in only one or two sites or in very small abundance. In any particular site not all of the assemblage listed in 1 may be present. At any one time, there may only be seeds of some species present in the soil seed bank with no above-ground individuals present. This is particularly the case for the large ephemeral floral component of the community. Species composition will vary between sites depending on geographical location and local conditions. The species composition of a site will be influenced by the size of the site and by its recent disturbance history and in particular the pattern (season, magnitude) of recent rainfall.

4. The Acacia loderi Shrublands are known from the Broken Hill Complex, Murray-Darling Depression, Cobar Peneplain, Riverina, Mulga Lands and Darling Riverine Plains Bioregions. Bioregions are defined in Thackway and Cresswell (1995). They occur from south western New South Wales (NSW) to north western Victoria and eastern South Australia. In NSW, the community is mainly confined to south western NSW extending east to Hillston and north to White Cliffs. The major stands of the community occur between Broken Hill, Ivanhoe and Wilcannia, while only isolated stands occur beyond these areas.

5. The Acacia loderi Shrublands are found on solonized brown and duplex soils on level to undulating plains or on calcareous red earths. Typical habitat has a rainfall range of 240mm to 280mm.

6. Most remnant stands of the community are located on pastoral leases although small patches occur in conservation reserves including Mungo and Kinchega National Parks.

7. Most current stands of Acacia loderi Shrublands have an understorey modified by grazing and include unpalatable natives and a range of exotic weeds. Many examples of the community exist as isolated and degraded patches. Threats to the community include clearing and a lack of regeneration of tree species through heavy grazing pressure, particularly from stock and rabbits. Although there is some limited regeneration by vegetative means (suckering) in the dominant  Acacia loderi, most existing stands consist of old age cohorts. Even within conservation reserves such as Kinchega National Park, rabbit grazing pressure has severely limited regeneration of the community dominant  Acacia loderi (Auld 1995) and flooding from over-filling of the Menindee Lakes has resulted in destruction of several stands of the community. A number of former stands now consist of only rings of dead trees.

8. In view of the fragmented nature of many stands, the widespread lack of regeneration in the dominant tree (Acacia loderi), the continued threat of heavy grazing pressure and further clearing, the Scientific Committee is of the opinion that Acacia loderi Shrublands are likely to become extinct in nature unless factors threatening its survival or evolutionary development cease to operate and that listing as an endangered ecological community is warranted.

Dr Richard Major
Chairperson
Scientific Committee

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

References:

Auld, T.D. (1995) The impact of herbivores on regeneration in four trees from arid Australia. The Rangeland Journal 17, 213-227.

Fox, M. (1993) Acacia shrublands of western New South Wales. Unpublished National Estate Programme report.

Pickard, J. and Norris, E. H. (1994) The natural vegetation of north-western NSW: notes to accompany the 1:1000000 vegetation map sheet. Cunninghamia 3, 423-465.

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.)

Westbrooke, M. E. and Miller, J. D. (1995) Vegetation of Mungo National Park, western NSW. Cunninghamia 4, 63-81.