1
MVG 6—ACACIA FORESTS AND WOODLANDS
• Acacia is the dominant tree component. (A. melanoxylon). The most widespread species • Although the trees are stunted (often less than are mulga and brigalow. 10 m), in some areas they can grow to heights • Dominance is controlled by climatic conditions of 25 m. and soil factors. • Dominant species include lancewood (Acacia • Eucalypts occur in some places shirleyi), bendee (A. catenulata), mulga (A. aneura), as occasional emergents. gidgee (A. cambagei), brigalow (A. harpophylla), • Understorey species are generally low shrubs western myall (A. papyrocarpa) and blackwood or herbaceous. oto: M. Fagg Ph Acacia aneura woodland near Yenloora, Qld 2
MVG 6—ACACIA FORESTS AND WOODLANDS
Facts and figures
Major Vegetation Group MVG 6—Acacia Forests and Woodlands Major Vegetation Subgroups Brigalow (Acacia harpophylla) forests and woodlands (32) (number of NVIS descriptions) Other Acacia forests and woodlands (160) Mulga (Acacia aneura) woodlands with tussock grass (56) Arid and semi-arid acacia low open woodlands and shrublands with chenopods (29) Arid and semi-arid acacia low open woodlands and shrublands with hummock grass (11) Arid and semi-arid acacia low open woodlands and shrublands with tussock grass (36) Mulga (Acacia aneura) woodlands and shrublands with hummock grass (3) Typical NVIS structural Tall closed forest formations Open forest (tall, mid and low) Tall woodland Mallee woodland (tall and mid) Open woodland (mid and low) Number of IBRA regions 71 Most extensive in IBRA region Est. pre–1750 and present: Murchison (WA) Estimated pre–1750 extent (km2) 495 059 Present extent (km2) 408 632 Area protected (km2) 36 064
Species
Co-dominants include Eucalyptus, Callitris, Casuarina Southern Queensland and Terminalia. Theg round layers are generally Dominated by A. aneura, A. cambagei (gidgee), herbaceous. Associated species include shrub species A. harpophyllaa (brigalow) with casuarina and both such as Eremophila, Dodonaea, chenopods such as forb and grassy understoreys; A. catenulata, A. shirleyi Atriplex, Maireana, Sclerolaena and grasses such with eucalypt species, A. microsperma, A. rhodophloia, as Triodia, Plectrachne, Aristidaa and Austrostipa. A. melvillei, A. rhodoxylon with an A. aulacocarpa mix Northern Australia on coastal dunes. Dominated by A. shirleyii with grassy understorey Northern central and west of New South Wales and A. crassicarpaa on coastal dunes in Cape York Contain A. pendulaa (myall), A. harpophylla Peninsula. (brigalow), A. melvillei, A. excelsaa and A. cambagei Central and central west Queensland (gidgee) across to South Australia with A. salicina Dominant species are A. cambageii (gidgee), A. shirleyi with E. camaldulensis; A. aneura, A. victoriaee and with eucalypt species, A. harpophyllaa (brigalow) A. papyrocarpaa mixed overstorey with acacia and with casuarina, A. catenulata (bendee) with grassy chenopod shrubs. understorey, A. argyrodendron with shrubland; A. aneura with eucalypt species, A. rhodophloia, A. rhodoxylon, A. crombiei, A. tephrinaa (boree), A. georginae, A. excelsa and A. cyperophylla with grassy understorey. 3
MVG 6—ACACIA FORESTS AND WOODLANDS
South Australia Low woodlands of A. papyrocarpaa occur west of a sedge understorey woodland in the eastern half Port Augusta and surrounding the Nullarbor Plain. of the State. Also A. longifoliaa and A. implexa. Tasmania Western Australia Very restricted areas with A. melanoxylon and A large area of this group covers the central area A. dealbata (silver wattle), with larger areas as including A. aneura, A. coriacea, A. eremaea, a co-dominant or subdominant with eucalypt species. A. victoriae, A. ramulosa, A. linophylla, A. sclerosperma, Victoria A. rostelliferaa and A. papyrocarpaa—some mixed with callitris and eucalypt species. Very restricted with A. melanoxylon, A. dealbata, A. mearnsiii swampy/riparian communities; A. silvestris mixed community; A. pycnanthaa with 4
MVG 6—ACACIA FORESTS AND WOODLANDS
Geography
• Climatic conditions are generally dry, • Extensively cleared for agriculture (particularly hot summers, with cool to warm winters. the brigalow and mulga communities). Rainfall is variable although maximum falls •Modified by pastoral and (in localised areas) occur in summer. mining activities. • Occur in New South Wales, Northern Territory, • As the pastoral industry has faced restructuring Queensland, South Australia, Tasmania, in recent years, some areas have been purchased Victoria and Western Australia primarily for conservation (e.g. some pastoral stations in semi-arid regions. in Western Australia and Queensland). • Largest areas are in Western Australia • Foremost threats are changes in fire regime and (232 09 1km2). over-grazing (including cattle, sheep and feral animals) (NLWRA, 2001b). Recent changes Change in land management policies have resulted in a • Approximately 17.5% of the estimated shift to use of native pasture grasses, restrictions pre–1750 extent cleared accounting for 8.5% on clearing and a search for more sustainable of total clearing in Australia. management of rangeland pastures. • Approximately 86 000 km2 cleared since European settlement.
Tenure Acacia Forests and Woodlands mainly occur on leasehold land.
New South Wales: protected areas, leasehold and freehold land Northern Territory: leasehold land, some freehold land, protected areas Queensland: freehold and leasehold land, protected areasand some state forests South Australia: leasehold land, protected areas Tasmania: protected areas, state forests, freehold land Victoria: state forests and protected areas Western Australia: leasehold land, protected areas, crown land, reserved crown land
Key values
• Biodiversity (ecological communities and • Ecotourism (including bushwalking and endangered species). landscapes in remote areas). • Remnant populations of a wide range Key values are mainly associated with biodiversity of vertebrate and invertebrate species. and ecotourism values, ecological communities and • Timber values (e.g. craft products such protection of endangered species. as sandalwood). 5
MVG 6—ACACIA FORESTS AND WOODLANDS
Management considerations Beadle N.C.W. (1981) The Vegetation of Australia. Cambridge Univ. Press, Cambridge, 690pp. • Clearing, especially in Queensland. Beard J.S. (1976) Murchison. Vegetation Survey • Grazing pressure from both domestic stock of Western Australia, 1:1 000 000 series. Explanatory and feral animals. notes to sheet 6. Univ. of Western Aust. Press, • Fire regimes (recognising that some introduced Nedlands, 141pp. & map grasses such as buffel grass (Cenchrus ciliariss) Johnson R.W. and Burrows W.H. (1994) Acacia and gamba grass (Anropogon gayanuss) burn with open forests, woodlands and shrublands. In: a hotter fire than native pasture grasses, thereby Australian Vegetation (ed. R.H. Groves) pp. 257–290. altering regeneration opportunities of trees Cambridge Univ. Press, Cambridge. and shrubs). Morgan G. (2001) Landscape Health in Australia. • Weed control (a major issue with pastoralists A rapid assessment of the relative condition of Australia’s is the level of investment able to be made given bioregions and subregions. Environment Australia and the low profitability of the land). National Land & Water Resources Audit, Canberra, 109pp. References National Land & Water Resources Audit (2001a) Australian Native Vegetation Assessment 2001. National Australian Surveying and Land Information Group Land & Water Resources Audit, Canberra, 332pp. (1990) Atlas of Australian Resources. Volume 6 Vegetation, AUSMAP, Department of Administrative National Land & Water Resources Audit (2001b) Services, Canberra, 64pp. & 2 maps. Rangelands—Tracking Changes, National Land and Water Resources Audit, Canberra. gg Photo: M. Fa Photo: Acacia harpophylla (brigalow) forest, 60km east of Tambo, Qld 6
MVG 6—ACACIA FORESTS AND WOODLANDS
Data sources Notes Interim Biogeographic Regionalisation for Australia • The areap rotected has increased by 23 000 km2 (IBRA), Version 6.1. since NVIS 1, reflecting improved reservation Land Tenure in Australia’s Rangelands (1955 to in the arid and semi-arid zones. 2000), National Land and Water Resources Audit. • This increase is despite a decrease in estimated National Vegetation Information System, Version 3.0. area of the group due to many NVIS vegetation 1996/97 Land Use of Australia, Version 2. types in Western Australia being reassigned to other MVGs on the basis of improved vegetation Collaborative Australian Protected Areas Database —CAPAD 2004—Terrestrial. descriptions. Species Profile and Threats (SPRAT) database • See the Introduction to the MVG fact sheets Australian Government Department of the for further background on this series. Environment and Water Resources;