Eremaean (Central Australian) 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. vesicaria.  Atriplex 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.

Littoral salt lake vegetation (Lake Lefroy, Western Australia)

In this semi-arid zone annual evaporation is about ten times that of rainfall. The salt lake recieves water from various streams but dries up completely for about a quarter of the year. The shorelines soils are highly saline and classed as hypersaline in some cases. Four shorelines have been recognised: siliciclastic dunes, dune swales, gypsum dune beds and scree slopes.

Siliciclastic Dune Vegetation
These large dunes usually above 5 m included both littoral and foredune components. The littoral zone was found to be hypersaline with some of the highest levels of salinity recorded. Consequently it provided difficult condition for plant colonisation and supported just two species: Gunniopsis septifraga and Halosarcia syncarpa. The foredunes were less saline but their combination of salinity and acidity again making them a harsh environment for most plants. The few species recorded included Calandrinia granulifera, Darwinia diosmoides, Jacksonia spinosa and Melaleuca thyoides.

Dune Swale Vegetation
Included here are small interdune swales and hindshore dunes. The charactersitic species included Disphyma crassifolium and Frankenia setosa in the swales and Jacksonia spinosa in the hind dunes areas. Acidity varied but was more pronounced in the hind dunes.  Other species found in this zone include Angianthus preissianus, Atriplex nana, Calandrinia polyandra, Calotis hispidula, Centrolepis polygyna, Crassula sieberiana, Disphyma crassifolium, Dodonaea viscosa, Eragrostis dielsii, Eragrostis falcata, Frankenia pauciflora, Gnephosis angianthoides, Gnephosis tenuissima, Grevillea acuaria, Gunniopsis quadrifida, Gunniopsis rodwayi, Gunniopsis septifraga, Halosarcia halocnemoides,  Halosarcia indica, Hemichroa diandra, Hyalochlamys globifera, Lepidium phlebopetalum, Maireana amoena, Maireana eriosphaera, Maireana glomerifolia, Scaevola spinescens, Stenopetalum sphaerocarpum, Triglochin calcitrapa, Triglochin cristata and Wurmbea dioica.

Gypsum Dune Bed Vegetation
Lake shores with relict gypsum beds are common in places producing distinctly alkaline conditions. The main species here are Atriplex nana and Disphyma crassifolium. Others include Atriplex codonocarpa, Frankenia desertorum, Rhodanthe floribunda, Senecio glossanthus and the introduced species Hordeum leporinum, Mesembryanthemum nodiflorum and Pentzia suffruticosa.

Scree Slope Vegetation
In places the shoreline is composed of broken fragments of duricrust (Tertiary sediments) ranging in size from gravel to small boulders. The main scree species is Halosarcia lylei with Frankenia pauciflora occurring in the transition zone between scree and the lake surface.  The few other species found in this zone include Centrolepis polygyna, Gunniopsis septifraga and Maireana carnosa. 

References

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