Murray Mallee

The Murray Mallee as recognised by Conn (1993) includes the Murray MalleeMurray Scroll Belt and Robinvale Plains regions in the current sytem of bioregions of Victoria.

The physiographic province described by the general term 'Mallee' refers to those semi-arid plains of south-eastern Australia characterized by extensive sand-ridges on which eucalypts with a particular growth habit (see 'The malice habit' below) form the dominant cover (Bowler & Magee 1978). This Mallee province is here divided into two regions, namely the Murray Malice and the Lowan Malice Regions.

Location

Murray Mallee in VictoriaThe southern limits of the Murray Malice Region forms a narrow zone in the Dimboola and Gerang Gerung area that separates the western and eastern parts of the Wimmera Region. The Little Desert of the Lowan Malice Region isolates a small disjunct area of the Murray Mallee to the west of Horsham. The region extends beyond the Murray River (into New South Wales and South Australia) in the north to about the 3308 meridian of latitude, with more scattered occurrences extending towards Menindee (latitude about 32o30'S). In New South Wales this region occurs mainly to the east of the Darling River and then to the west of the Silver City Highway. In South Australia the northern limits approximate the northern boundary of the Dangalli Conservation Park, north of Renmark. Although no attempt has been made to map the exact extent of this region in South Australia, it extends north into the southern (particularly, south-western) part of the South Olary Plains environmental region of the Eastern province (Laut et al. 1977a, 1977b). The eastern boundary (in Victoria) is formed by the western limit of the cl Irrent floodplain of the Avoca River, with the western boundary adjoining the eastern limits of the Lowan Malice (the Big Desert and the southern parts of the Sunset Country). At latitude about 34o40'S the region extends westerly, from Victoria to just north of Nildottie on the Murray River in South Australia. It then includes the area between the eastern edge .of the Mt Lofty Ranges escarpment and the Murray River as far south as Langhorne Creek in the Bleasdale environmental association of the south-east malice environmental heathlands region in South Australia of Laut ct al. (1977a, 1977b) and as far north as a latitude of about 3408. There are several outliers, particularly in New South Wales.

This suggests that the malice communities have expanded and contracted with changes in climate (Beadle 1981). In Victoria outliers occur north of Bendigo in the _Whipstick Maliee', and near Melton (Myers 1986).

In South Australia this region includes part of the Murray Malice of Laut et al. (1977a, 1977b). However, a large part of that province is here included in the Lowan Mallee Region (see beiow). In New South Wales this region approximates to vegetation region _3A (Camcron, L. M. 1935), includes the southern part of the Far Western Plains (Anderson 1947, 1961) or South Far Western Plains (Jacobs & Pickard 1981). Although the boundary between the Far Western Plains and the (near) Western Plains is somewhat arbitrary, the southern limits of this boundary arc a reasonable approximation to the eastern boundary of the Murray Malice Region. Within Victoria the boundary between this region and the Wimmera is somewhat arbitrary because the vegetation has been extensively cleared for wheat cultivation.

For a summary of the information available on this region, refer to Cottington and Harris (1987).

Major grids A-C, E-H. Approximate area 32 044 km2 .

Major landforms

The major landforms include an extensive undulating, mainly reddish clay to sandy plain that is often locally overlain by linear west-east aligned, stabilized sand dunes (Woorinen Formation, refer to Wasson in Noble and Bradstock 1989). In the eastern part of this plain, the surface is gently undulating with north-south to NNW-SSE aligned ridges (Hills 1939; Rowan & Downes 1963). It is thought that some of these are stranded coastal dunes formed during the retreat of the Tertiary Murray Sea (Blackburn 1962).

In general, malice occurs on well-drained soils of coarse texture (see Gibbons and Rowan, this volume). Soils of hue texture, frequently associated with river systems, usually support woodlands rather than malice. The only notable riverine landforms occur along the Darling, Murray and Murrumbidgee Rivers in the northeast part of this region (e.g. in Victoria, the Lake Hattah-Kulkyne area). All streams arise outside the region. The major riverine systems include the Darling, Murray, Murrumbidgee, Wimmera, Yarriambiac, Tyrrell and Lalbcrt. The last three creeks arise as effluents (outside the region) of the Wimmera River (Yarriambiac) and the Avoca River (Lalbert and Tyrrell). Freshwater lakes include Lakes Hindmarsh and Albacutya. There are several salt lakes, the largest of these being Lake Tyrrell.

The topography of the region is character ized by loosely compacted surface formations, all of which are below 200 mctres altitude. A useful summary of the geology and physiology of this region is provided in Anon, (1987) and Wasson (in Noble & Bradstock 1989).

Climate

The region is characterized by a semi-arid cli mate with a mean annual rainfall of between about 400 mm in the southern parts and 220 mm in the extreme north. The small area that experiences a cool, relatively moist coastal climate in South Australia is characterized by a higher mean annual rainfall of about 500 mm. Since the region has a generally low relief with only minor topographical variation, little cli matic change occurs across it. The wettest month is generally October, with the central and southern parts of the region having a high incidence of heavy summer thunderstorms, particularly during February. Droughts are a natural feature of the northern parts.

Much of the region experiences hot dry sum mers and mll~ d winters, with temperatures slightly higher throughout the year in the northern parts. Frosts are common between May and September.

The winds usually are from the northern, western and southern sectors (see also _Climate of Victoria, this volume).

Vegetation

The complexity of the vegetation in this region is illustrated by the floristic vegetation map in Anon. (1987, map 10) and Cheal and Parkes (in Noble & Bradstock 1989, figs 8.2 and 8.3). Fre quently, the communities occur as complex mosaics. A summary of the vegetation commu nities is presented in the above two publications.

The mallee habit

Large areas of this region, extending into South Australia and New South Wales, are dominated by _malice eucalypts. The term _malice refers to a growth form, not to a particular eucalypt spe cies (Specht 1972). These eucalypts are small (3-10 metres high), highly drought-tolerant trees that have a large underground lignotuber (_malice roots'). This lignotuber gives rise to sev eral slender spreading branches or _trunks that terminate in a cluster of smaller branches with relatively sparse foliage. The largely buried lignotuber is protected from fires (Parsons in Groves 1981; Gill, this volume) and frosts (O'Brien et al. 1986). The importance of ligno tuber regrowth, rather than regeneration from seed after burning or severe frost damage, is characteristic of many genera in the several families that occur in this region (Gardner 1957). Xanthorrhoea, a common component of the malice-heath alliance (see below), has flower buds in apex and subterranean buds that are activated after fire (Gill, this volume).

Mallee communities

The most common mallee species in the region are Eucalyptus costata, E, dumosa, E. gracilis, E. leptophylla, E. oleosa and E. socialis. The canopy resulting from dense malice communities is usually very even, and often approximately horizontal. Most malice communities are structuf ally dehned as open-scrubs (Specht 1970)~ Other small trees and shrubs that are frequently associated with this community include Acacia ligulata, A. rigens (both restricted to this region in Victoria), A. wilhelmiana, Callitris verrucosa, Dodonaea viscosa subsp. angustissima, Exocarpos aphyllus, Melaleuca uncinata, Olearia pimeleoides, Phebalium bullatum and Senna spp, All the Victorian species of Eremophila occur in this region. The herbaceous layer is usually discontinuous and is dominated by Triodia scariosa in the drier areas on infertile soils. Fertile soils support a ground-layer richer in grasses and herbs (e,g. Actinobole uliginosum, Danthonia setacea, Dianella revoluta, Goodenia willisiana, G. pinnatijida, Lepidosperma laterale and Stipa species). Ajuga Australis is locally common under tall mallee or on sandy lake banks (e.g. Lake Hattah). With increasing aridity, salinity and/or calcium (limestone) content, semi-succulents (e.g. Crassula, Zygophyllum apiculatum and Chenopodiaceae) become progressively more important (`Chenopod malice' sensu Anon. 1987). Short-lived annual herbs (ephemeral forbs) are often briefly common after rain. Eucalyptus gracilis, E. oleosa and E. socialis chiefly occur on brown loamy soils in relatively Hat areas, whereas the other malice eucalypts are more common on the white sandy dunes of the _Desert areas of the Lowan Malice Region (see below). For a generalized summary of the mallee communities which occur on the aeolian soils, refer Hill (in Noble & Bradstock 1989). Soil texture and the often related availability of water has a signihcant influence on thc composition of the species in stands (Willis 1943; Rowan & Downes 1963; Parsons & Rowan 1968; Noy-Meir 1974).

Eucalyptus dumosa, E. gracilis, E. oleosa and E. socialis characterize the most common malice alliance which forms a mosaic with Acacia, Callitris (Adams 1985) and A/ectryon Oleolius shrublands and low woodlands, and halophytic Chenopodiaceae-dominated shrub|ands.

Chenopod mallee

This community is common in the Sunset Country dunefields of the Woorinen Formation. It occurs in the red-brown soils of the swales. The overstorey is dominated by Eucalyptus gracilis and E. oleosa. The very openunderstorey is characterized by members of the Chenopodiaceae (e.g. Maireana pentatropis) and Zygophyllaceae (e.g. Zygophyllum aurantiacum, Z. apiculatum). The open ground-layer includes Chenopodium cupicatum, C. desertorum, Enchylaena tomentosa, Maireana erioclada, M. radiata, M. sc/erolaenoides, Omphalolappula concava, Ptilotus seminudus, Scleroleana diacantha, S. obliquicuspis and Stipa e/egantissima (Anon. 1987).

East/west dune mallee

This community is common to the west of the Raak Plain and to the northern Sunset Country. It occurs on dunes with compact sandy-clay cores that are overlain by pale-orange sands. The overstorey is dominated by Eucalyptus costata E. dumosa, E. /eptophylla and E. socia/is (Plate 6A). The open shrub-layer is characterized by Acacia rz.gens, A. wilhe/miana, Callitris verrucosa, Phebalium bullatum and/or Prostanthera serpyllifolia subsp. microphylla. The ground-layer consists of a more or less continuous sward of Triodia scariosa, and other herbs, particularly members of the Asteraceae.

Anon. (1987) and Cheal and Parkes (in Noble & Bradstock 1989) recognize a _shallow-sand malice community which is intermediate between the Chenopod malice of the swales and the east/west dune malice and deep-sand malice of the dunes.

Murray Malle, east-west dune mallee

Murray Mallee; east-west dune mallee. Eucalyptus socialis and E. leptophylla with Callitris verrucosa, Cryptandra amara, Melaleuca lanceolata, Phebalium bullatum. Werrimull South, Sunset Country.

Red-swale malice

This community characterizes the heavy soils of the swales and plains that arc strongly influenced by underlying sandstone. The overstorey is dominated by Eucalyptus calycogona, E. dumosa and/or E. socia/is. The first two eucalypts commonly form a _whipstick subcommunity over large areas. The very open understorey commonly consists of Beyeria opaca, Dodonaea bursario1ia, Melaleuca lanceolata and Westringia rigida. The very open ground-layer characteristically includes Erodium cn`nitum, Maireana enchylaenoides, Plantago drummondii and Sclero/aena diacantha.

Big malice

A community characterized by large, tall, malice eucalypts (typically Euca/yptus behriana, E. porosa, and sometimes E. ca/ycogona and E. dumosa) often occurs with red-swale malice or on the margin of isolated grassy clearings. These eucalypts are also distinct because they have one or only a few thick trunks. The community occurs on heavy soils that have a strong underlying sandstone influence. The very open understorey is dominated by various chenopods (e .g. Chenopodium desertorum, Einadia nutans, Enchy/aena tomentosa, Maireana enchylaenoides and Sc/ero/aena diacantha). Carpobrotus modestus and Senecio /autus are common components of the ground-layer.

Belah woodland

communlt~ y on the deeper, red-brown sandy soils of prominent old beach ridges. Associated species include Eremophila opposiOlia, Exocarpos aphyllu, Hakea, leucoptera, H, tephrosperma, Myoporum platy. carpum, Pittosporum phylliraeoides, Santalum acuminatum and S. murrayanum. A small shrub-layer, about one metre high, is characterized by Chenopodium cupica(urn, Eremophila glabra, Olearia muelleri, O. pime/eoides, Scaevola spinescens and Senna artemisioides. The ground-layer consists of sub-shrubs, perennial tussock grasses and other herbs. This community is best developed in the Yarrara Block of the Murray-Sunset National Park, a few kilometres north of the Sunset Country (Plate 6B). There is a smaller occurrence at Robinvale.

Unlike the malice eucalyps, Callitris species are killed by fire and regenerate solely from seed. Extensive grazing of Callitris seedlings by rabbits and the deaths by fire have severely reduced the amount of regeneration of these species.

Murray Mallee, Belah woodland

Murray Mallee; Belah woodland. Casuarina pauper woodland with Myoporum platycarpum, and understorey species Hakea leucoptera, Olearia muelleri, Senna artemisioides, Scaevola spinescens. Yarrara, Sunset Country

Pine Buloke woodland

This community is dominated by Ca/litris preissii (Pine) and/or A//ocasuarina /uehmannii (Buloke) . It occurs on lunettes associated with lake beds and creek systems. Although the former species typically occurs on deep sands and the latter species on heavier loams, both also occur together over broad areas (Anon. 1987). All examples of this community are disturbed to a greater or lesser extent. The open understorcy is characterized by Acacia oswaldii, Pittosporum phy//iraeoides and Santa/um acuminatum. The ground cover was apparently once dominated by perennial tussock grasses and herbs (Anon. 1987). These have been largely replaced by several introduced species, for example, *Brasica tournefortii, *Hypochoeris glabra, *Medicago minima, *Silene spp., *Trifolium spp. and * Vulpia bromoides. This community occurs in the Hattah-Kulkyne National Park.

In the far north-west of the region, near the Murray River, Callitris g/aucophylla replaces C. preissii as the dominant tree species on lunettes. However, this community is very z are ill Victoria.

Grassy woodland and grassy malice

These communities are often inappropriately referred to as Savannah woodland and savannab malice, respectively; however, the word _Savannah refers to tropical grassland with scattered trees and palms, and so is not used here. Typically, these communities are very disturbed. The overstorey may be scattered or absent. These communities may be anthropogenic rather than `natural (Anon. 1987) because both occur in heavily grazed areas (e.g. in evaporation basins and the fringing area of the alluvial plain).

Woodlands with a grassy ground-layer have an overstorey of scattered Ca//itris preissii and Alecton Oleolius. The overstorey of this malice community consists of scattered Eucalyptus graCi\is and E. socialis. The ground flora consists of alien plants. These include *Brassica tournefortii, *Critesion murinum subsp. g/aucum, *Medicago mim'ma, *Schismus barbatus, *Sonchus oleraceus, *Urtica urens and *Vulpia spp.

Floodplain woodlands and forests

The floodplains of the more significant river systems support a Eucalypins camaldulensis (River Red-gum)-E. largillorens woodland to open" forest. The latter species usually occurs on the Hat plains at a slightly higher level than E. camaldulensis. The soil is characterls.tically a grey clayey loam, usually with a well-contrasted profile differentiation (essentially duplex in structure). This community is also described for the Lowan Malice and Riverina Regions.

Black Box-chenopod woodland

The Murray River floodplain is characterized by a Eucalyptus largorens (Black Box) woodland with a Chenopodiaceae understorey (e.g. Chenopodium m"h'ariaceum, Enchylaena tomentosa and Rhagodia spinescens). The understorey is frequently dominated by Muehlenbeckiaflorulenta (e.g. at the southern edge of Lake Hindmarsh). Chenopods also dominate the ground-layer.

Black Box wetland

In areas of alkaline gilgai soils (see Gibbons & Rowan, this volume) that arc periodically Hooded (e.g. Yarriambiac Creek floodplain, Connor 1966a), the Eucalyptus largi,|lorens (Black Box) alliance typically lacks shrubs. However, a dense herbaceous ground-layer of rushes and sedges is common. The common species include E/eocharis acuta, E. pusilla and ]uncusflavidus. Danthonia duttom~ana, Enteropogon acicularis and Eragrostis lacunaria are more common on the drier sites.

River Red-gum forest

Eucalyptus camaldulensis (River Red-gum) dominates an open-forest, often with an open understorey of Acacia salt.ct.nu or A. stenophyIla. The ground-layer commonly includes Alternanthera denticulata, Centipeda cunninghamii, Chamaesyce drummondii, ez.us  nocaulos, Paspalidium juborum and Wahlenbergia fluminalis.

Good examples of this forest occur along much of the Murray River in the north-west of the state.

Grasslands

Natural grassland areas are poorly developed. Bromus arenan.us and species of Chloris, Danthonia, Eragrostis and Stipa are common. Many of these communities have been invaded by alien species.

Sandplain grassland

Examples of this community occur in the sandy soil of old evaporation basins of the Sunset Country. Grazing by sheep has resulted in the establishment of several alien species. Tlle dominant grasses of this grassland are Aristida contorta, Stipa drummondii and S. eremohila. The other common herbaceous species include Hyalosperma semisterile, H. stuartianum, Leptorhndzos waitzia, Minuria leptophylla, Podolepzs' canescen.s and RhodantFze pygrnaea.

Gypseous plains grassland/gypseous rise woodland

The grassland communities that occur on the gypseous plains (copi) of the far north-west of the Sunset Country are heavily grazed by sheep. All examples of these communities in Victoria are extremely disturbed, and their original composition can only be inferred. Anon. (1987) suggests that the semi-arid woodland present in South Australia may approximate to the gypseous rise woodland. The common herbaceous species include Brach.yscome Linear.iloba, *Bromus rubens, Daucus glocFzidiatus, *Erodium cnnitum, Goodenia pusilli]lora, *Hypochoeris glabra, *Medicago minima, *Sonchus oleraceus and Stipa scraba group. The low shrubs of Sclerolaena diacantha and S. obliquicuspis are the last shrubs to disappear from heavily grazed areas (Anon. 1987).

Halophytic shrubland

With the exception of the Darling-MurrayMurrumbidgee river system, the rivers in this region terminate in inland _lakes that are usually dry and are referred to as _playas. The playa bed is either clayey (clay flats) or saltencrusting (salt pans). Small playas and those that are regularly flushed out by floodwaters have a saline or subsaline clay substrate, usually overlying gypscous clays.

Many salt lakes (e.g. Lake Tyrrell), salt pans, gypsum (copi) and clay Hats occur throughout this region, with the greatest development in the north of the state (between Mildura and Boundary Point) and adjoining the floodplain forest of the Murray. The northern plains support bluebush shrubland (Maireana ramidataM. sedOlia) on sandy soil that has a reasonably high lime content.

Large copi deposits occur near Cowangie (north-east of Murrayville), on the South Australian-Victorian border south of the Sturt Highway, and to the west of Lake Hattah in the Raak Plain. These are the sites of old lakes that have dried up (Hills 194O).

The type and density of vegetation on saline playas is determined by the salt concentrations, which, in part, is determined by the season. When crystalline salt is visible on the surface, the vegetation is retricted to the surrounding higher land. The most salt-tolerant species belong to the Chenopodiaceae, particularly the samphires or glassworts (namely Halosarca, Packycorna and Sclerostea), but also Atn`/ex, Maireana and Sclerolaena. Other salt-tolerant plants include Franhenia, Dishyma crassolium subsp. clavellatum and ZygophyIlum (Plate 6C). Several annual Asteraceae are also common.

Murray Mallee, halophytic shrubland

Murray Mallee; halophytic shrubland, Melaleuca halmaturorum (Salt Paperbark) with low succulent shrubs and herbs, including Disphyma, Frankenia, Halosarcia, Sarcocornia. Dune mallee upslope from halophytic shrubland margin. Pink Lakes.

Alluvial-plain shrubland

The broad alluvial terraces that occur along the Murray River to the west of Mildura, support an alluvial-plain shrubland. This area is also devoid of trees.

The dominant low shrub-layer is predominantly composed of members of the Chenopodiaceae. The common species include Atlex vesicaa, Sclerolaena divaricata and S. tricusis. The ground-layer is characterized by Dhyma crassolium subsp. clavellatum and several native and introduced herbs (e.g. Brachyscome Iineariloba, Crassula colorata, Pogonolepis muelleana and Senecio glossanthus). Areas that are more affected by saline groundwater usually support Halosarcia pergranulata and *Parahol incuTVa. Most areas are subject to sheep-grazing.

A more diverse Chenopodiaceae-dominated shrubland (the _Alluvial-rise Shrubland, sensu Anon. 1987) occurs on the red-brown sandyloam rises that are scattered on the alluvial plain. The shrub-layer is usually dominated by Maireana pyramidata to about one metre high. Occasionally Atrip/ex nummu/aria or Maireana sedolia are also present. The ground-layer includes scattered A/ex /ind/eyi, Ma/acocera trz-~ corn Sclero/aena brachtera and S. tc. This shrubland is usually more degraded by grazing than the alluvial-plain shrubland.

Lake-bed communities

The type of community that is present on lake beds is dependent upon the soil type and the time since inundation (Anon. 1987). In the first few seasons after a flood, the dried-out lake beds arc usually dominated by tall native herbs (e.g. Agrost avenacea, Glycyrrhza acanthocarpa and Lavatera plebeia). Increased grazing pressure between flood periods usually results in the introduction and establishment of alien species (e.g. *Bromus spp., *Critesion spp., *Hypochoe glabra, *Medicago spp. and *Tolium spp.) (Anon. 1987).

Land use

This region has been extensively cleared for the cultivation of cereal crops and grazing. Much of the region receives additional supplies of water via the gravitational-feed channel system. Approximately half of the water for the Wimmera-Malice domestic and stock water supply originates in the Grampians (Calder, J. 1987). Irrigation along the Murray River has enabled the establishment of orchards and vineyards in the Mildura-Red Cliffs area. The other additional supply of water, other than rainfall, is from artesian bores. The National and State Parks ensure the conservation of the remaining native flora and fauna.

National Parks

Hattah-Kulkyne (in part)48 000 ha;

Murray-Sunset (in part)633 000 ha.

Source: Conn, B.J. (1993) Natural regions and vegetation of Victoria, in: Foreman, D.B. and N.G. Walsh (eds), Flora of Victoria Volume 1, pp. 79–158, Inkata Press.