Triodia Mallee, western nsw sa (Photo: B. Pellow)



Yüklə 0,65 Mb.
tarix02.09.2017
ölçüsü0,65 Mb.



MVG 14 - Mallee Woodlands anD SHrublands



Triodia Mallee, western NSW SA (Photo: B. Pellow)

Overview

    • Mallee Woodlands and shrublands are semi-arid systems dominated by eucalypt species that produce multiple stems from an underground rootstock known as a lignotuber.

    • Some vegetation in non-arid regions also supports eucalypts with mallee growth forms, but these are not part of MVG 14 or MVG 32.

    • Eucalypts are the most widespread tree component of this MVG however species of Callitris, Melaleuca, Acacia and Hakea may co-occur as trees at varying densities and may co-dominate mallee communities.

    • An open tree layer (notionally 10 -30% projective foliage cover, 20-50% crown cover) distinguishes MVG 14 from MVG32 (Mallee Open Woodlands and Sparse Mallee Shrublands), which has a sparser tree layer (notionally <10% foliage projective cover, <20% crown cover), However, this distinction is largely artificial, as tree cover varies spatially at fine scales and temporally with fire regimes, while the occurrence of tree, shrub and ground layer species shows little relationship to variations in eucalypt cover.

    • Understorey composition is strongly influenced by rainfall, soil types and fire regime and can be dominated by hummock grasses (spinifex), chenopods or other woody shrubs.

    • Some mallee woodlands are among the most fire prone of all plant communities in semi-arid and arid zones (Keith 2004).

Facts and Figures

Major Vegetation Group

MVG 14 - Mallee Woodlands and Shrublands

Major Vegetation Subgroups

(number of NVIS descriptions)

61. Chenopod Mallee NSW, SA, VIC. (111)

55. Shrubby Mallee NSW, SA, VIC. (37)

27. Triodia Mallee NSW, SA, VIC. (150)

29. Heathy Mallee SA, VIC. (280)



xx. Western Mallee WA (XX)

Typical NVIS structural formations

Mallee woodland (mid, low)

Open mallee woodland (mid, low)



Open mallee shrubland (mid, low)

Number of IBRA regions

40

Most extensive in IBRA region

Est. pre-1750: Murray Darling Depression (NSW, SA and Vic)


Estimated pre-1750 extent (km2)

387 230

Present extent (km2)

271 529

Area protected (km2)

99 969

Structure and physiognomy

  • Woodlands and shrublands dominated by low, multi-stemmed, sclerophyllous eucalypts and occasionally small trees from other genera with a spares to dense understorey.

  • Height of eucalypt canopy varies from 2 to 10 m (Bradstock and Cohn 2002).

  • Tree canopy cover varies with rainfall, topographic position, soil characteristics and particularly fire history, but projective foliage cover is notionally within the range 10 -30% and crown cover is notionally within the range 20 – 50%.

  • Understorey structure also varies with rainfall, topographic position, soil characteristics and particularly fire history, and may be dominated by sclerophyllous or non-sclerophyllous shrubs, hummock grasses, chenopods or tussock grasses.

  • Ground layer is strongly influenced by recent rainfall and fires. In drought the ground layer is spares while following heavy rainfall a prominent cover of ephemeral herbs with tussock grasses occurs.

  • A soil crust forms on flat areas and local depressions, comprising cyanobacteria, lichens and mosses, but is largely absent from dune crests and slopes.

  • The major vegetation subgroups of this MVG differ in terms of canopy dominants, understorey composition, soil characteristics and topographic position (Haslem et. al 2010)

Indicative flora

    • Eucalypts of the semi-arid mallee woodlands belong almost entirely to sections Bisectaria and Dumaria within the subgenus Symphyomyrtus, although a few species belong to sections Adnataria, also within Symphyomyrtus (Hill 1989). See further discussion in Notes below. Widespread mallee tree species include Eucalyptus dumosa, Eucalyptus socialis, Eucalyptus gracilis, Eucalyptus oleosa, and Eucalyptus calycogona.

    • Distinctions between the five Major Vegetation Subgroups are based mainly on the perennial components of the understorey.

    • Chenopod mallee subgroup understorey includes species of Maireana, Sclerolaena, Enchylaena, Chenopodium and Zygophyllum. Eucalyptus oleosa, Eucalyptus gracilis, Eucalyptus dumosa and Eucalyptus calycogona are the most commonly occurring trees, while Callitris verrucosa and Triodia are essentially absent. It occurs on shallow sandplains with heavier textured soils associated with shallow calcrite subsoils across New South Wales, Victoria and South Australia (Cheal and Parkes 1989; Sparrow 1989; Haslem et al. 2010).

    • Shrubby mallee subgroup includes a range of mostly non-sclerophyll shrubs from genera such as Senna, Acacia, Dodonaea, Myoporum, Eremophila, Enchylaena, Sclerolaena, Melaleuca, Grevillea, Hakea, and Westringia. Triodia and Callitris are very uncommon in these communities and biological soil crusts are typical except where disturbed by livestock. Any of the major mallee eucalypts may be locally dominant in Shrubby mallee, It occurs where calcite subsoils are below moderate depths of red loamy sand in dune swales and flat sandplains across New South Wales, Victoria and South Australia (Sparrow 1989; Keith 2004; Haslem et al. 2010).

    • Triodia mallee subgroup has an understorey dominated by hummock grasses (Triodia scariosa and Triodia irritans) interspersed with small trees or shrubs of genera such as Acacia, Callitris, Eremophila and Beyeria. The principal eucalypts are Eucalyptus costata, Eucalyptus socialis and Eucalyptus dumosa. It typically occurs over the summits and slopes of dunes across the lower Murray and Eyre districts of New South Wales, Victoria and South Australia (Keith 2004; Haslem et. al. 2010).

    • Heath mallee subgroup is typified by more sclerophyllous shrub genera, with Callitris verrucosa often prominent in either the tree or shrub layer. Typical shrub genera include Acacia, Aotus, Baeckea, Leptospermum, Melaleuca, Beyeria, Brachyloma, Hibbertia, Cryptandra, Spyridium and Phebalium. Eucalyptus costata is the most common tree, but other species occur frequently. Triodia may occur sparsely among the shrubs. Heathy mallee is typically found on white sandplains in south western Victoria and the adjoining area of south eastern South Australia, as well as the Eyre Peninsula (Sparrow 1989; Cheal & Parkes 1989; Haslem et al. 2010). There is a transition to true heathlands within increasing rainfall to the south (Cheal & Parkes 1989).

    • Western mallee subgroup is characterised by several eucalypts some of which are endemic to Western Australia, including Eucalyptus eremophila, Eucalyptus moderata, Eucalyptus oleosa, Eucalyptus incrassata, Eucalyptus foecunda, Eucalyptus redunca and Eucalyptus uncinata (Beard et. al 2013). The understorey is predominantly shrubby with species of Melaleuca and Acacia, and occasional Triodia. It is widespread in the southern goldfield regions, extending eastward to the coast of the Great Australian Bight (Beard et al. 2013).

    • Ephemeral herbs from a wide range of plant families are abundant after rain including the Poaceae (mainly Austrostipa), Asteraceae, Goodeniaceae, Solanaceae, Apiaceae, Brassicaceae and Zygophyllaceae.


Photo: M. Fagg
mvg14a

Western Mallee, near Lake Grace, WA (Photo: M. Fagg)

Environment

  • Typically semi-arid Mediterranean with cool winters and hot dry summers, and annual rainfall of between 200 – 500 mm per annum occurring predominately in winter.

  • Occurs on calcareous sandplains, predominantly with lateritic soils in western Australia and on Aeolian landscapes in eastern Australia (Bradstock and Cohn 2002).

  • Different geomorphic processes have shaped these mallee regions with much of the central and south-eastern mallee characterised by sand dune and swale systems (Hill 1989).

  • In many areas the variation in the thickness of surface sand above clay or calcareous hard pan affects the structural and floristic composition of mallee (Bradstock and Cohn 2002).

  • Soils associated with mallee of arid Australia include solonized brown soils, siliceous sands, calcareous sands, solodized solonetz, soloths, earthy sands and calcareous red earths (Blackburn and Wright 1989).

Geography

  • Located in the semi-arid areas of southern Australia in southwest New South Wales, northwest Victoria, southern South Australia and southern Western Australia.

  • Largest area occurs in South Australia (126 804 km2).

  • In the east mallee is largely restricted to the sandplains and sand dunes of the western part of the Murray Basin with small areas occurring on landforms of Aeolian origin further north (Wassan 1998).

  • In the west mallee occurs on three main land forms the Yilgarn Plateau, the Stirling coastal zone and the Nullarbor Plain (Wassan 1998).

  • Centrally, in South Australia mallee occurs on extensive dunefields of the Eyre Peninsula, the lower Murray and in the Gulf Ranges provinces (Wassan 1998).

  • Make up the most arid of the eucalypt-dominated communities of temperate Australia (Parsons 1994).

Change

  • Approximately 30% of the estimated pre-1750 extent cleared accounting for 11.4% of total clearing in Australia including large areas of southern Western Australia and South Australia and northern Victoria.

  • Losses have been disproportionate, and greatest by far in the Chenopod mallee subgroup (Sparrow 1989; Cheal & Parkes 1989).

  • Approximately 116 000 km2 cleared since European settlement. Clearing for crops is ongoing, albeit at reduced rates. Legacies of fragmentation continue to degrade ecological functions.

  • Removed from many cereal cropping and sheep grazing lands in the southern and eastern parts of Australia over the last 100 years, most recently irrigated vineyards and orchards.

  • Clearing of the mallee in South Australia commenced in approximately 1900 following the widespread introduction of the stump-jump plough.

  • Most of the South Australian Murraylands, Yorke and Eyre Peninsula areas were cleared before World War II. Tops of sandhills were cleared later in the 1960s as part of the rabbit control program.

  • The Kangaroo Island mallee community was cleared following World War II with the soldier settlement scheme.

  • Overgrazing associated with pastoral activities and feral herbivores (notably rabbits and goats) have modified mallee in the inland and more arid areas of Australia beyond the rainfall limits of cropping and within the cropping region.

  • Fire regimes involving short intervals between successive fires and fire events followed by droughts and/or overgrazing are greatly reducing plant diversity and the capacity of mallee to support its avian and mammal fauna (Bradstock & Cohn 2002; Watson et al. 2012).

  • Threats include fragmentation of remaining areas, inappropriate fire regimes (e.g. fires too regular and/or too intense) and grazing impact on understorey.

  • Associated issues in understanding and managing mallee areas for multiple values are yet to be fully explored.

Tenure

Important areas of mallee occur in conservation reserves on the border of South Australia and Victoria, south-western New South Wales and in eastern Western Australia.

Mallee Woodlands and Shrublands occur on a range of land tenures.

New South Wales:

leasehold land, freehold land, protected areas and little in state forests and reserved crown land







South Australia:

freehold land, protected areas, leasehold land, defence land

Victoria:

protected areas, state forests and freehold land

Western Australia:

protected areas, other and reserved crown land, leasehold land, small and isolated areas on freehold land

Key values


  • Many species of plants, birds, reptiles and invertebrates not found in any other ecosystems.

  • Uniquely Australian form of semi-arid woodland.

  • Remnant populations of many rare and endangered species of vertebrate and invertebrates (e.g. the Black-eared Miner and the Mallee Fowl).

  • Significance to Indigenous communities.

  • Conservation and tourism.

List of key management issues

  • Control of vegetation clearing for mining, cropping and other transient uses.

  • Weed control in remnant vegetation within agricultural landscapes.

  • Management of total grazing pressure (including domestic, native and feral animals).

  • Rising water tables in cropping areas affected by dryland salinity.

  • Destruction of soil crusts by non-native hard hooved animals.

  • Wind erosion of soils exposed by overgrazing or cropping.

  • Fire frequency and interactions between fires and droughts.

  • Livestock grazing and feral animal activity in recently burnt areas.

  • Declining rainfall, especially in western and southern Australia.

  • Many forms of mallee vegetation remain primarily in private ownership or under leasehold.

  • Increased stewardship and multi-value management in response to pastoralist and mining access to natural resources.

  • 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

Blackburn G. and Wright M.J. (1989) Soils. In Mediterranean Landscapes in Australia: Mallee Ecosystems and their Management (ed. Noble J.C and Bradstock R.A.) pp. 34 - 53. CSIRO, Canberra

Bradstock R.A. and Cohn J.S (2002). Fire regimes and biodiversity in semi-arid mallee ecosystems. In Flammable Australia. The fire regimes and biodiversity of a continent. (ed Bradstock R.A., Williams J.E and Gill A.M.) pp. 238 - 258. Cambridge University Pres, Cambridge

Brooker M.I.H. and Kleinig D.A. (1999) Field guide to Eucalypts, South-eastern Australia, Volume 1, 2nd edition. Bloomings Books, Melbourne, 353pp.

Brooker M.I.H. and Kleinig D.A. (2001) Field guide to Eucalypts, South-western and Southern Australia, Volume 2, 2nd edition. Bloomings Books, Melbourne, 428pp.

Cheal D.C. and Parkes D.M.(1989) Mallee vegetation of victoria. In Mediterranean Landscapes in Australia: Mallee Ecosystems and their Management (ed. Noble J.C and Bradstock R.A.) pp. 125 - 140 CSIRO, Canberra

Haslem A., Callister K. E., Avitabile S. C. Griffioen P. A., Kelly, L. T. Nimmo D. G., Spence Bailey L. M., Taylor R. S., Watson S. J., Brown L., Bennett A. F., Clarke M. F. (2010) A framework for mapping vegetation over broad spatial extents: A technique to aid land management across jurisdictional boundaries. Landscape and Urban Planning, 97, 296-305.

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

Hill K.D. (1989) Mallee Eucalypt communities: their classification and biogeography In Mediterranean Landscapes in Australia: Mallee Ecosystems and their Management (ed. Noble J.C and Bradstock R.A.) pp. 93 – 108. CSIRO, Canberra

Noble J.C and Bradstock R.A., eds. (1989) Meditrerranean Landscapes in Australia, Mallee ecosystems and their management. CSIRO, Melbourne, 485pp.

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.

Parsons R.F. (1994) Eucalyptus scrubs and shrublands. . In: Australian Vegetation (ed. R.H. Groves) pp. 291-319. Cambridge Univ. Press, Cambridge.

Sparrow A. (1989) Mallee vegetation of South Australia. In Mediterranean Landscapes in Australia: Mallee Ecosystems and their Management (ed. Noble J.C and Bradstock R.A.) pp. 109 - 124. CSIRO, Canberra

Wardell-Johnson G.W., Williams J.E., Hill K.D. and Cumming R. (1997) Evolutionary biogeography and contemporary distribution of eucalypts. In: Eucalypt Ecology. Individuals to ecosystems (eds J.E. Williams and J.C.Z. Woinarski) pp. 92-128. Cambridge Univ. Press, Cambridge.

Wasson R.J. (1989) Landforms. In Mediterranean Landscapes in Australia: Mallee Ecosystems and their Management (ed. Noble J.C and Bradstock R.A.) pp. 13 - 34. CSIRO, Canberra

Watson SJ, Taylor RS, Nimmo DG, Kelly LT, Haslem A, Clarke MF, Bennett AF. (2012). Effects of time-since-fire on bird species: how informative are generalized fire-response curves for conservation management? Ecological Applications 22, 685-696.

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 3.0.

1996/97 Land Use of Australia, Version 2.

Collaborative Australian Protected Areas Database – CAPAD 2004 – Terrestrial.



Notes

  • Many authors take a broad interpretation of ‘mallee woodland’ to include any vegetation dominated by multi-stemmed eucalypts. That concept encompasses additional vegetation types including woodlands on rocky hills and other stony substrates in semi-arid landscapes at temperate and subtropical latitudes that incorporate mallee growth forms from sections Exsertaria or Adnataria. It may also include mallee heaths in temperate humid or semi-humid climates on rocky or sandy substrates with multi-stemmed eucalypts from subgenus Monnocalyptus or Eudesmia .All of these vegetation types are excluded from MVGs 14 and 32, and instead referred to woodland and heathland groups. The ‘true’ mallee woodlands and shrublands included within MVGs 14 and 32 encompass those in semi-arid, winter-rain, temperate climates on sandy duplex substrates, dominated by eucalypts in sections Bisectaria and Dumaria.

  • Some vegetation types in previous versions of NVIS, the Northern Territory and Queensland have now been re-interpreted to other MVGs.

  • See the Introduction to the MVG fact sheets for further background on this series.



Chenopod Mallee, near Balranald, NSW (Photo: B. Pellow)



Yüklə 0,65 Mb.

Dostları ilə paylaş:




Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur ©azkurs.org 2020
rəhbərliyinə müraciət

    Ana səhifə