MVG 11 Eucalypt Open Woodlands DRAFT

MVG 11 - Eucalypt Open Woodlands

Desert eucalypt woodlands Hamersley Region, WA (Photo: B. Pellow)

Overview

• Characterised by broad spacing between canopy trees often resulting in a parkland appearance with a prominent ground layer.
• Overstorey is dominated by drought-tolerant eucalypts close to the arid limits of trees.
• Understories are characterised by xeromorphic plants that vary between depositional and upland landforms
• Occur in a central band across semi-arid Australia from Western Australia to western New South Wales.
• Replaced by MVGs 5 and 12 in more humid climates.
• Prone to occasional fires in upland areas.
• Used primarily for broad scale pastoralism.

Facts and figures

Semi-arid floodplain and wadi woodlands (Eucalyptus largiflorens) western NSW (Photo: B. Pellow)

Structure and physiognomy

• Dominated by a sparse overstorey of eucalypts typically with less than 20% canopy cover (<10% foliage projective cover) canopy 6 – 15 m tall.
• Tree canopies are composed of sclerophyllous, vertically oriented notophyll (20 – 45 cm2) to mesophyll (45-150 cm2) foliage.
• In upland woodlands, the understorey typically comprises an open layer of xeromorphic shrubs with hummock or tussock grasses and ephemeral forbs. In depositional plains and channels, the understorey includes tussock grasses and chenopod shrubs and forbs that vary in cover with rains and floods.

Indicative flora

• Species composition varies with landform and rainfall seasonality.
• Dominated by box eucalypts in depositional zones that retain subsoil moisture and upland sites in higher rainfall areas. In contrast bloodwood eucalypts (genus Corymbia) and snappy gums dominate dry upland sites.
• Species of Acacia, Eremophila and Dodonaea are common shrubs on uplands and peneplains, while chenopod shrubs and forbs may occur on in depositional areas.
• Represented by three subgroups.
• Semi-arid floodplain and wadi woodlands (also represented in MVG 5) are dominated by species of Eucalyptus in sections Adnataria and Exsertaria within subgenus Symphyomyrtus. Eucalypts such as Eucalyptus coolabah, Eucalyptus microtheca, Eucalyptus vitrix, Eucalyptus largiflorens, Eucalyptus populnea, Eucalyptus tereticornis and Eucalyptus camaldulensis are widespread. The understorey may consist of a shrub layer of species from the genera Acacia, Dodonaea, Eremophila, Muehlenbeckia, and Rhagodia and the groundlayer has an abundance of forbs, chenopods, graminoids and tussock grass (Keith 2004; Victoria Department of Sustainability and Environment 2004; Beard et. al 2013, Neldner et. al 2014).
• Semi-arid upland woodlands (also represented in MVG 5) include species such as Eucalyptus intertexta, Eucalyptus populnea, Eucalyptus melanophloia, Eucalyptus siderophloia (all in section Adnataria of subgenus Symphyomyrtus) and Callitris glaucophylla (Keith 2004). In rocky locations Eucalyptus viridis and Eucalyptus vicina occur. The understorey typically has a shrub layer of genera such as Acacia, Allocasuarina, Dodonaea, Eremophila, Hakea, Myoporum and chenopods (Keith 2004; Neldner et. al 2014). The groundlayer is rich in forbs and graminoids including species of Aristida, Astrebla Austrostipa, Chloris, Dichanthium, Enteropogon, Heteropogon, Panicum, Rytidosperma, Abutilon, Alternanthera, Brunoniella, Evolvulus, Fimbristylis, Goodenia, Sida and a range of chenopods (Keith 2004; Neldner et. al 2014).
• Desert eucalypt woodlands are a variable and poorly known group of communities dominated by a sparse layer eucalypts over hummock grasses, with tussock grasses in locally moist sites. At tropical latitudes, Eucalyptus leucophloia and Corymbia dichromophloia are widespread with Eucalyptus leucophylla, Eucalyptus pruinosa, Corymbia capricornia and Corymbia aspera in Queesland (Neldner et. al 2014), while Eucalyptus brevifolia, Eucalyptus gamophylla and Eucalyptus kingsmillii occur in Western Australia (Beard et. al 2013). Corymbia terminalis is widespread across the central and northern deserts, Corymbia aparrerinja is characteristic of central Australia and Eucalyptus gonglyocarpa occurs across the Great Victoria Desert region, sometimes with smaller mallee trees such as Eucalyptus youngiana. The shrub layer is generally sparse and represent by species from the genera such as Acacia, Atalaya, Callitris, Dodonaea, Grevillea, Hakea and Senna. Hummock grasses are typically abundant and include Triodia pungens thoughout, and Triodia brizoides, Triodia longiceps, Triodia schinzii and Triodia wiseana in different parts of the range. Tussock grasses include Aristida, Enneapogon and Thyridolepis (Keith 2004; Beard et. al 2013; Neldner et. al 2014).

Environment

• Occur in warm arid climates where mean annual rainfall is generally in the range of 200 – 450 mm, at the limit of eucalypt distribution, except where run-on enhances soil moisture in drier locations.
• Soils range from clay loams on ephemeral semi-arid floodplains to sandy loams on rocky uplands or outcrops.
• Occasionally fire prone, especially in tropical latitudes and uplands, but rarely fire prone on arid floodplains.

Geography

• Extensive, particularly in the semi-arid interior and the tropics and cover many dry inland plains and undulating landscapes (the “downs”) and some rocky outcrops.
• Largely across northern Australia and eastern Australia, with scattered occurrences across the central and Great Victoria Desert region of Western Australia.
• Largest areas are in Northern Territory (222 030 km2) and Queensland (167 557 km2).

Change

• Approximately 8% of the estimated pre-1750 extent cleared accounting for 3.9% of total clearing in Australia, although clearing has occurred preferentially on the inland floodplains and is limited on the uplands.
• Approximately 40 000 km2 cleared since European settlement.
• Cleared for cereal cropping and sheep grazing in the south-east and south-west of Australia and for mining in the Pilbara region of Western Australia.
• Remnant occurrences have been extensively modified. In the northern parts of Australia they have been modified by pastoral activities and changes to fire regimes. In Queensland and New South Wales pasture improvement and tree thinning have been extensively employed and the shrubby understorey has often been removed to increase pasture growth.
• Due to their presence in pastoral areas or proximity to intensive agricultural areas, fire regimes have been modified leading to many Eucalypt Open Woodlands being impacted by invasive species, especially aggressive introduced plant species, notably buffel grass.
• Threats include clearing for cropping, pastoral development or mining, overgrazing and altered fire regimes.

Tenure

Eucalypt Open Woodlands occur on a range of land tenures.

Key values

• Biodiversity at the arid limits of eucalypt woodland distribution.
• Remnant populations of a wide range of vertebrate and invertebrate species.
• Ecotourism and scenic landscapes, particularly on arid ranges such as the MacDonnell’s, Hamersley and Flinders.
• Resources and cultural sites valued by Indigenous communities.

List of key management issues

• Control of clearing and other threats on the edges of remnants.
• Regional planning and design of mining projects.
• Fire management, particularly the effects of increased fuel loads from introduced grasses and grazing land management practices.
• Weed control.
• Total grazing pressure from domestic, feral and native animals.
• Long term monitoring to inform future management strategies.

References

Australian Surveying and Land Information Group (1990) Atlas of Australian Resources. Volume 6 Vegetation. AUSMAP, Department of Administrative Services, Canberra, 64pp. & 2 maps.

Beadle N.C.W. (1981) The Vegetation of Australia. Cambridge Univ. Press, Cambridge, 690pp.

Beard J.S., Beetson, G.R, Harvey J.M. Hopkins A.J.M and Shepherd D.P. (2013) The Vegetation of Western Australia at 1:3,000,000 Scale. Explanatory Memoir. Second Edition. Science Division, Department of Parks and Wildlife, Western Australia

Brooker M.I.H. and Kleinig D.A. (1994) Field guide to Eucalypts, Volume 3, Northern Australia. Inkata Press, Sydney, 383pp.

Fox I.D., Neldner V.J., Wilson G.W., et al. (2001) The Vegetation of the Australian Tropical Savannas. Env. Prot. Agency, Qld and Tropical Savannas CRC, 2 map sheets and 1 legend; online at URL: http://savanna.ntu.edu.au/information/ .

Hobbs R.J. and Yates C.J., eds. (2000) Temperate Eucalypt Woodlands in Australia. Biology, conservation management and restoration. Surrey Beatty & Sons, Sydney, 430pp.

Keith D. (2004) Ocean Shores to Desert Dunes. The native vegetation of New South Wales and the ACT. Department of Environment and Conservation (NSW), Hurstville.

National Land and Water Resources Audit (2001) Australian Native Vegetation Assessment 2001. National Land and Water Resources Audit, Canberra, 332pp.

Neldner, V.J., Niehus, R.E., Wilson, B.A., McDonald, W.J.F. and Ford, A.J. (2014). The Vegetation of Queensland. Descriptions of Broad Vegetation Groups. Version 1.1. Queensland Herbarium, Department of Science, Information Technology, Innovation and the Arts.

Victoria Department of Sustainability and Environment (2004). EVC Bioregion Benchmark for Vegetation Quality Assessment. http://www.depi.vic.gov.au/environment-and-wildlife/biodiversity/evc-benchmarks [Accessed June 2015]

Data sources

Interim Biogeographic Regionalisation for Australia (IBRA), Version 6.1.

Land Tenure in Australia's Rangelands (1955 to 2000), National Land and Water Resources Audit.

National Vegetation Information System, Version 4.1.

1996/97 Land Use of Australia, Version 2.

Collaborative Australian Protected Areas Database – CAPAD 2004 – Terrestrial.

Species Profile and Threats (SPRAT) database Australian Government Department of the Environment and Heritage; online at URL: http://www.deh.gov.au/cgi-bin/sprat/public/sprat.pl .

Notes

• With new descriptions for Western Australia’s vegetation types, some areas previously treated as Eucalypt Open Woodlands (MVG 11) were allocated to Eucalypt Woodlands (MVG 5) in NVIS 3.0.
• Vegetation types where Sorghum spp. are the dominant understorey grasses to eucalypts with an open woodland structure have been assigned to Tropical Eucalypt Woodlands/Grasslands (MVG 12).
• Larger areas of this group have been identified in Queensland, based on improved NVIS data.
• A large area in South Australia’s far west derived from gap-filling (non-NVIS) data requires improved vegetation mapping.
• See the Introduction to the MVG fact sheets for further background on this series.

Semi-arid upland woodlands, near Hillston, NSW (Photo: B. Pellow)