Eremaean (Central Australian) Acacia 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 pungens.  Acacia 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 (Central Australian) 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. pileata.  Eucalyptus 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 (Central Australian) 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).

Cape York Heath and Scrub

Sometimes referred to as ‘wet desert’ because of the low stature of this vegetation but occurring in a climate where you would normally expect to find rain forest. However, the soils are nutrient poor and have particularly low levels of phosphorus. The vegetation forms a mosaic of open and closed communities. In open areas there are patches of scrub mainly dominated by Banksia dentata and the endemic Melaleuca saligna (Myrtaceae) and Thryptomene oligandra (Myrtaceae). In other areas they comprise a form of closed heath no more than about 2 m tall dominated by Fenzlia obtusa and Leptospermum fabricia, but also including shrubs like Choriceras tricorne, Jacksonia thesioides, Sinoga lysicephala and the endemic Acacia calyculata (Fabaceae), Boronia bowmanii (Rutaceae), Morinda reticulata (Rubiaceae) and Neoroepera banksii (Picrodendraceae). In the herbaceous layer Schoenus sparteus and Xanthorrhoea johnsonii are the most common species, but also noteworthy is the presence of the three insectivorous plants Byblis liniflora, Nepenthes mirabilis and Utricularia chrysantha. Heath and scrub also replaces rain forest on mountains such as Mount Bellenden-Kev and Mount Finnegan. Here the characteristic species include Agapetes meiniana, the endemic Dracophyllum sayeri (Epacridaceae), Leptospermum wooroonooran (Myrtaceae) and Rhododendron lochae (Ericaceae), together with species of Austromyrtus, Balanops, Bubbia, Drimys, Orites and Quintinia. The two members of Ericaceae (Agapetes and Rhododendron) provide affinities with the floras of New Guinea and Asia, while Dracophyllum provides links with southeastern Australia and New Zealand. Banksia dentata is the only species of Banksia to occur in the tropics and extends into New Guinea. 

Southwest Australian Bush of Southern Sand Plains

This region includes the undulating plains along the south coast from Pallinup River to Israelite Bay and extends inland to Lake Grace. Two of the more prominent shrubs of these southern bush lands are Hakea crassifolia and the endemic Lambertia inervis (Proteaceae). The latter represents a near endemic genus with all but one species endemic to the southwest. Another widespread endemic shrub found here is the unusual Franklandia fucifolia (Proteaceae), while other important shrubby species are the so-called bottlebrushes Beaufortia micrantha, B. orbifolia and B. schaueri, and the wax flowers Chamelaucium axillare and C. megalopetalum (Mrytaceae).  Both genera are endemic to the southwest, with some 15 species of Chamelaucium. Among the endemic herbs are species of the endemic genus Anthotium (Goodeniaceae) including Anthotium humile and A. rubiflorum. Both have perennial rootstocks and rosetted linear leaves.

Southwest Australian Bush of Northern Sand Plains

These sandy plains occur north of Perth between Moore River and Shark Bay. Like their southern counterpart two of the most prominent families are Proteaceae and Myrtaceae. In the former there are at least 20 species of Banksia including the endemic B. burdettii and many species of the endemic Dryandra such as D. nana, D. carlinoides, D. kippistiana, D. shuttleworthiana and D. speciosa. Most dryandras and banksias produce abundant nectar and although birds and insects are attracted to this, it seems that small marsupials are the main pollinators. Other conspicuous members of the Proteaceae include the grevilleas, such as the spectacular white plume grevellea (Grevillea leucopteris) and the endemic smokebush Conospermum stoechadis.  Of the Myrtaceae, the intriguing genus Darwinia, with its great diversity of inflorescences, is well represented with some 30 species endemic to the southwest. Two of the more common of these are Darwinia neildiana and D. speciosa.  Other indigenous members of this family include various species of the genus Calothamnus.   All 25 species of this genus are endemic to the southwest but only about 10 occur on the northern sand plains including Calothamnus blepharospermus, C. homalophyllus and C. quadrifidus.  Also present are many poisonous plants of the endemic genus Gastrolobium, such as Gastrolobium oxylobioides, which have caused problems for pastoralists since the early days of settlement.  Flowers of many colours are seen in the family Goodeniaceae and even in the genus Lechenaultia with about 25 species, flowers may be blue, white, yellow, red, orange or green. One of the more common of these is the endemic blue lechenaultia (Lechenaultia biloba).  In areas of deep sand are various members of the enigmatic, endemic genus Anigozanthos, including Anigozanthos manglesii and A. pulcherrimus (Haemodoraceae), while other endemic members of this family are the so-called cotton-heads such as Conostylis aurea, C. candicans and C. stylidioides.  Other endemic genera that are well represented in this area are Beaufortia, Hypocalymma and Scholtzia. Apart from Xanthorrhoea preissii, moncots are not a dominant feature of these sand plains, but the allied Kingia australis is found in a few areas. Orchids are also rarely found but members of the genera Caladenia, Diuris and Thelymitra may be encountered including the endemic Caladenia crebar and C. flava (Orchidaceae).  Finally several species of native conifer grow in the area include the endemic sand plain cypress (Actinostrobus arenarius) and its smaller relative the endemic dwarf cypress (A. acuminatus).

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