Eremaean Acacia Woodland and Scrubland

Something like half of all acacias in Australia occurs in the arid and semi-arid zones. Their success in dry conditions is thought to be partly attributable to their ability to fix atmospheric nitrogen through a symbiotic relationship with rhizobia in their root nodules and the ability of their xeromorphic phyllodes to conserve water. In Eremaea several acacia alliances have been described. Woodland dominated by Acacia cambagei covers vast areas of the wetter eastern zones and extends westward in to the Simpson Desert. This tree can reach heights of 5-10 m and is notorious for the sewer-like smell it gives off when its phyllodes are damp. A shrub layer is usually absent but may include Eremophila mitchellii, Santalum laceolatum and the endemic or near endemic Apophyllum anomalum (Capparaceae) and Capparis lasianthos (Capparaceae). The herbaceous layer, if present, is usually dominated by grasses, which in the dry zones include the endemic or near endemic Astrebla pectinata and Triodia pungens (Poaceae). Acacia aneura woodland extends over vast tracts of the arid and semi-arid zones despite the fact that it seems to need at least some winter and summer rain. It is however well adapted to dry conditions with taproots that can penetrate several metres. Soils are also important as far as its distribution is concerned since it is mainly confined to Red Earths and Lithosols. Tree height varies according to conditions and ranges from 3-10 m, but the species can live for at least two centuries. Acacia aneura is often the sole dominant but a few other trees occur locally as co-dominants. These include the endemic or near endemic eucalypts Eucalyptus gamophylla, E. kingsmillii and E. striaticalyx (Myrtaceae). A less common associate is the endemic or near endemic Acacia pruinocarpa (Fabaceae). Under storey assemblages also vary from place to place with clear changes occurring from east to west. Among these are many endemic or near endemic shrubs such as Acacia adsurgens (Fabaceae), Capparis lasiantha (Capparaceae), Myoporum deserti (Scrophulariaceae) and several species of Eremophila such as E. abietina, E. bowmanii, E. cuneifolia, E. fraseri, E. freelingii, E. margarethae, E. miniata, E. paisleyi and E. platycalyx (Scrophulariaceae).

The herbaceous layer is usually dominated by grasses and again including a number of endemic or near species such as Paractenium novae-hollandiae, Plagiosetum refractum, Plectrachne schinzii, Stipa eremophila, Triodia clelandii, T. irritans and T. spicata (Poaceae). The endemic or near endemic Acacia pachycarpa (Fabaceae) replaces A. aneura in the north-west and is the dominant species throughout the Great Sandy Desert and on to the north-west coast. It can reach 8 m in height but often only achieves 3 m in dryer areas. Associated trees include Acacia impressa, Bauhinia cunninghamii, Dolichandrone heterophylla, Erythrophleum chlorostachys and Gyrocarpus americanus. The shrub layer often contains the endemic or near endemic Acacia translucens (Fabaceae) and Jacksonia aculeata (Fabaceae), while the ground layer comprises grasses such as Eragrostis eriopoda, Plectrachne schinzii and Triodia pungensAcacia lonophyllum and A. ramulosa co-dominate woodland mainly in Western and South Australia and in the Northern Terratories. They occur on deep unconsolidated sand and sand plains including the Red Sands around Shark Bay and northwards. Other associated trees include Acacia coriacea, Eucalyptus oleosa and the endemic or near endemic Eucalyptus oldenfieldii (Myrtaceae) and Grevillea stenobotrya (Proteaceae). Understory shrubs include Adriana tomentosa, Calytrix murcata, Crotalaria cunninghamii, Hibiscus pinonianus and the endemic or near endemic Pityrodia loxocarpa (Lamiaceae) and Stylobasium spathulata (Stylobasidaceae). Grass such as Aristida browniana and Plectrachne schinzii dominate the ground layer. Finally the endemic or near endemic Acacia grasbyi (Fabaceae) is often the dominated species in limestone areas including the Nullabor Limestones. Under shrubs here include Solanum lasiphyllum and the endemic or near endemic Eremophila clarkei (Scrophulariaceae), but when these woodlands or scrubland traverse subsaline depressions Atriplex becomes the main under storey taxa with species such as Atriplex hymenotheca, A. nummularia and the endemic or near endemic A. bunburyana (Chenopodiaceae). Other acacia that dominate parts of Eremaea include Acacia acuminata, A. calcicola, A. catenulata, A. ligulata, A. sowdenii, A. transluscens and A. xiphophylla.


Eremaean Casuarina Woodland

In Eremaea these forests are dominated by either Casuarina cristata or the endemic C. decaisneana (Casuarinaceae). They grow surprisingly tall for such dry conditions but unlike species found in wetter climates they do not produce nitrogen-fixing nodules. Woodland dominated by C. cristata is not exclusive to Eremaea. It also occurs in wetter areas where trees can reach heights of 13 m. In Eremaea it is mainly confined to the Nullarbor regions. Here Eremophila scoparia often dominates the shrub layer. Other associated shrubs include the endemic or near endemic Eremophila miniata (Scrophulariaceae) and Maireana carnosa (Chenopodiaceae). Much better adapted to the arid zone is the amazing Casuarina decaisnena. It occurs over wide areas of the arid zone and despite the extremely dry conditions it is one of the tallest of the casuarinas and possibly the tallest tree in the arid zone. Heights of 20 m have been recorded and it is renowned for its extremely hard wood. In the Tanami Desert Eremophila longifolia is the common under shrub, while other species include Cassia nemophila, Solanum orbiculatum and the endemic or near endemic Canthium latifolium (Rubiaceae). In the Great Sandy Desert, the under shrubs include Acacia salicine, Carissa lanceolata, Gyrostema tepperi and the endemic or near endemic Eucalyptus pachyphylla (Myrtaceae). In both deserts, the herbaceous layer is dominated by endemic hummock grasses such as Plectrachne schinzii and Triodia pungens (Poaceae). Groves of Casuarine decaisneana are occasionally interspersed with open stands of other trees such as the endemic or near endemic Brachychiton gregorii (Sterculiaceae) and Eucalyptus gongylocarpa (Myrtaceae). The associated shrubs include the endemic or near endemic Exocarpus sparteus (Santalaceae) and Grevillea juncifolia (Proteaceae).


Eremaean Mallee

Mallee is an aboriginal word for eucalypts of shrub proportions with many stems arising from a large lignutuber. Vegetation dominated by mallee tends to occur in scattered patches but these may be relicts of more extensive formations in the past. Precise seasonal incidence of rain appears to be a subsidiary factor as far as their distribution is concerned. Soils, on the other hand, play a more significant role with most mallee communities occurring on well-drained soils of coarse texture. Under story species also vary with soils types and can be broadly divided into calcicole, halophyte and xerophyte assemblages. The dominant mallee eucalypts in the Eremaean BioProvince include Eucalyptus diversifolia, E. dumosa, E. foecunda, E. gracilis, E. incrassata, E. loxophlebia, E. oleosa, E. pyriformis, E. socialis and the endemic or near endemic E. concinna, E. eremophila, E. leptopoda and E. oldenfieldii (Myrtaceae). Mallee dominated by E. diversifolia is mainly confined to wetter areas in South Australia including the Eyre Peninsula and Kangaroo Island. Among the associated species are a number of endemic or near endemic eucalypts such as E. cneorifolia (mainly Kangaroo Island), E. remota (confined to Kangaroo Island) and E. lansdowniana (southern part of Eyre Peninsula). The under storey is largely composed of xerophytic species but composition varies. On Kangaroo Island, Hakea ulicina and Olearia teretifolia are the most abundant shrubs, but members of the Epacridaceae such as Acrotriche fasciculiflora, Astroloma conostephioides and Epacris impressa are also common. This assemblage is also unique in the presence of various species endemic to the island such as Adenanthos sericea (Proteaceae) and Petrophila multisecta (family?). Mallee dominated by Eucalyptus foecunda is mainly confined to the west where it can be found in association with Eucalyptus gracilis and E. oleasa on low dunes and around salt lakes. Shrubs of Meloleuca uncinata occasionally form a dense under storey, but in deep white sand adjacent to the coast Acacia cyclops becomes the principal under storey species. Other shrubs may include the endemic or near endemic Brachychiton gregorii (Sterculiaceae) and Eucalypus leptopoda (Myrtaceae). In the east, including the Nullarbar region, the main mallee type is dominated by E. dumosa, E. gracilis, E. oleosa and E. socialis, but may also include various other eucalypts such as the endemic or near endemic E. socialis (Myrtaceae).

The under storey can be divided into two main types. In the wetter areas the characteristic shrubs are Acacia oswaldii, Callitris preissii, Exocarpus aphyllus, Eucarya accuminata, Geijera linearifolia and Pittosporum phylliraeoides. In dryer areas species such as Eremophila scoparia, Heterodendron oleifolium, Myoporum platycarpum and the endemic Codonocarpus cotonifolius (Gyrostemonaceae) become more conspicuous components. A sporadic herbaceous layer is usually present chiefly composed of grasses such as Danthonia setacea and the endemic or near endemic Triodia scariosa (Poaceae). Also confined to Western Australia is mallee dominated by the endemic or near endemic Eucalyptus eremophila. Associated eucalypts may include E. anceps, E. calycogona, E. celastroides, E. erythronema, E. flactonia, E. fourestiana, E. leptocalyx, E. merrickae, E. ovularis or E. pileataEucalyptus forestiana is the distinctive ‘fuchsia mallee’ with its four angled, orange-scarlet buds. Mallee dominated by Eucalyptus pyriformis and the two endemic or near endemic species E. leptopoda and E. oldenfieldii, sometimes referred to as sand plain mallee, stretches across the northern fringes of western areas virtually from the Indian Ocean to the arid central South Australia. Among the associated eucalypts are various endemic or near endemic species like Eucalyptus pimpiniana (Myrtaceae). However, this is a very loose association with many of the associated species having varying distributions. The under storey also comprises a varying assemblage of species such as Acacia longispinea, Anthrotroche myoporoides, Hakea buculenta, Micromyrtus peltigera, Verticordia ethleliana and the endemic or near endemic Plectrachne desertorum (Poaceae). Finally in the Kalgoorle area at the fringes of the arid zone mallee dominated by the endemic or near endemic Eucalyptus concinna can be found. It also extends into the Victoria Desert. Associated eucalypts include the endemic or near endemic Eucalyptus comitae-vallis, while at ground level there are scattered hummocks of Triodia scariosa and the annual herb Ptilotus exaltatus. Other eucalypts largely confined to the arid zone include Eucalyptus carnei, E. gamophylla, E. gillii, E. gongylocarpa, E. kingsmillii, E. lucasii, E. odontocarpa, E. pachyphylla and E. striaticalyx, but none of these form well defined alliances and their under storey species vary from place to place. Nevertheless, the ground layers often include members of the Australian endemic grass Triodia such as Triodia basedowii, T. concinna, T. longipes, T. pungens, and shrubs of the genus Eremophila (a genus largely confined to Eremaea) such as Eremophila leucophylla.


Eremaean Halophytic Shrubland

Also known as shrub steppe or saltbush these formations are mainly confined to sub saline or saline soils in the southern half of Eremaea. They are all dominated by members of the Chenopodiaceae; a plant family that is well represented in Australia with about 21 genera, 11 of which are endemic, and most of these are found in the arid or semi-arid zones. All of the species have capacity to accumulate salt a feature that is often associated with succulence. These formations can be broadly divided types dominated by the genus Atriplex and those dominated by the endemic genus Maireana. The main Atriplex species are A. hymenotheca, A. nummularia, A. rhagodioides and A. vesicariaAtriplex nummularia is widely distributed in the arid and semi-arid zones including the fringes of the Simpson Desert and the Nullarbor Plain, and can reach heights of up to 2 m. Under storey species may include Rhogodia spinescens and the endemic Maireana sedifolia together with various annual species of Atriplex and Bassia. Atripex vesicaria (bladder saltbush) is also widely distributed and distinguished by the presence of bladders on the bracteoles although these may be absent in some ecotypes. Its distribution ranges from New South Wales to Western Australia. Associated species include various endemic chenopods such as Atriplex spongiosa, Babbagia acroptera and Maireana astrotricha (Chenopodiaceae), while species from other families include Ixiolaena leptolepis and the endemic or near endemic Abutilon halophilum (Malvaceae) and Erodium cygnorum (Geraniaceae). Atriplex rhagodioides replaces A. vesicaria in the driest parts of the arid zone and A. hymenotheca occurs as a local dominant on the Nullarbor Plain. Maireana is the dominant taxa of at least three saltbush communities. The main dominants are M. astrotricha, M. pyramidata and M. sedifolia and all are endemic to the arid or semi-arid zones. However, these are fairly loose alliances and two or all three species can often be found growing together. Maireana sedifolia is the most common dominant on the limestone of the Nullarbor Plain. Common associates include Angianthus brachypappus, Bassia patenicuspis, B. uniflora, Gnephosis skirrophora and Stipa nitida together with a large number of annuals.


Eremaean Desert Heath

Heaths are rare in the arid zone but can be found, for example, in parts of the Great Victoria Desert. They occur on the flanks and lower slopes of dunes, where it sometimes replaces the more typical hummock grass of Plectrachne and Triodia. They can grow to heights of about 30 cm and here they are dominated by Thryptomene maisonneuvii. Associated species include Calytrix longiflora and the endemic or near endemic Micromyrtus flaviflora (Myrtaceae). On the summits of dunes, heaths becomes more sparse and taller species occur such as Acacia salicina, Crotalaria cunninghamii, Gyrostemon ramulosus together with endemic or near endemic taxa like Callitris preissii subsp. verrucosa (Cupressaceae), Eucalyptus gongylocarpa (Myrtaceae) and Grevillea stenobotrya (Proteaceae).


Eremaean Astrebla Grassland

Grass of the genus Astrebla is largely endemic to the arid and semi-arid zones of Australia. Four Astrebla grassland alliances have been identified based on the dominance of A. clymoides, A. lappaceae, A. pectinata or A. squarrosa. However, these often intergrade and have many associated species in common. Astrebla squarrosa is the most abundant species on the Carpentaria plains where it intergrades with Dichanthium grassland. It is also the tallest species reaching heights of up to 2 m. Other species rarely exceed 1 m. Astrebla lappaceae is probably the most common species overall extending over large areas, while A. pectinata is only dominant in the wetter areas. Astrebla elymoides is possible the least common, but sometimes forms monospecific stands in A. pectinata grassland. Associated species vary, but it is reckoned up to 100 species can be found in association with A. lappaceae. Among the many associated grasses are Aristida latifolia, Eriachne nervosa, Panicum decomposition and the endemic or near endemic Eragrostis xerophila and Spathia nervosa (Poaceae).


Eremaean Eragrostis Grassland

These grasslands can be broadly divided in to three communities dominated by Eragrostis dielsii or E. setifolia or the endemic E. xerophila(Poaceae). The latter dominates tussock grassland on clay in the arid zone from western Queensland through Central Australia and westwards to the Indian Ocean. In central areas, it is associated with Astrebla pectinata, while on the western coastal plains species such as Chloris ruderalis, Dichanthium humilis, Enneapogon planifolius, Eragrostis lacunaria, Sporobolus actinocladus and Triraphis mollis are common associates. The occasional tree may include the endemic or near endemic Melaleuca lasiandra (Myrtaceae). Eragrostis dielsii is usually only dominant in waterlogged areas and E. setifolia is typically dominant on shallow soils on limestone. The later is abundant throughout the arid zone and extends on to the Nullarbor Plain.


Eremaean Plectrachne schinzii Spinifex Grassland

Grassland dominated by the endemic Plectrachne schinzii (Poaceae) extends over vast tracts from the northwest through the Great Sandy Desert and into Central Australia. It is often associated with Triodia basedowii and T. pungens together with other grasses such as Danthonia bipartita and Eragrostis eropoda. Shrubs or small trees, such as the endemic or near endemic Acacia inaequilatera (Fabaceae) and Hakea macrocarpa (Proteaceae), are often scattered throughout these grasslands and should possibly, therefore, be described as savanna.


Eremaean Triodia Spinifex Grassland

Four Triodia dominated grasslands have been identified. The dominant species are T. basedowii, T. irritans, T. mitchellii and T. pungens. The latter occurs across the arid interior from western Queensland to the Indian Ocean. In addition to a number of other grasses, associated species may include a number of endemic forbs such as the Euphorbia australis (Euphorbiaceae), and many annual species occur in the spaces between hummocks. Triodia basedowii often dominates hummock grasslands in the south. Again large numbers of associated annual species occur such as Calandrina balonensis, Cleome viscosa, Erodium crinitum, Euphorbia drummondii, Haloragis gossei, Lepidium rotundum, Podolepis canscens and the endemic or near endemic Euphorbia eremophila (Euphorbiaceae), Plychosema trifoliatum (family?) and Trachymene glaucifolia (Apiaceae). Triodia irritans is often found associted with the endemic Triodia scariosa (Poaceae) and occurs mainly in the south with possibly the largest stands occurring in the Musgrave Ranges in South Australia, while Triodia mitchellii is confined to semi-arid areas of Queensland and northern New South Wales.


Eremaean Zygochloa paradoxa Grassland

Hummock grassland dominated by the endemic Zygochloa paradoxa (Poaceae) is centred on the Simpson Desert where it is mainly confined to the crests of sand dunes. The hummocks are often spaced at distances of 2-6 m apart. Associated herbaceous flora is entirely ephemeral with species such as Aristida arenaria, Citrullus lanatus, Crotalaria dissitiflora, Myriocephalus stuartii, Salsola kali, Tribulus hystrix, Tetrogonia expansa, Trichinium alopecuroideum, Trichodesma zeylanicum, Zygophyllum howittii and the endemic Blennodia pterosperma (Brassicaceae).

Further information required.



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