Botany in Australia - Vegetation Types

Vegetation Types

Australia's terrestrial flora can be collected into characteristic vegetation groups. The most important determinant is rainfall, followed by temperature which affects water availability. Several schemes of varying complexity have been created, the most recent scheme developed by the Natural Heritage Trust divides Australia's terrestrial flora into 30 Major Vegetation Groups, and 67 Major Vegetation Subgroups.

According to the scheme the most common vegetation types are those that are adapted to arid conditions where the area has not been significantly reduced by human activities such as land clearing for agriculture. The dominant vegetation type in Australia is the hummock grasslands that occur extensively in arid Western Australia, South Australia and the Northern Territory. It accounts for 23% of the native vegetation, the predominant species of which are from the genus Triodia. Zygochloa also occurs in inland sandy areas like the Simpson Desert.

A further 39% of native vegetation is covered by a combination of:

• Eucalypt woodlands found at the transition between hummock grasslands and higher rainfall areas where conditions still limit tree growth; the woodland may have a grass or shrubby understory. The largest area is in Queensland.
• Acacia forests and woodlands that occur in semi-arid areas where tree growth is stunted. The dominant Acacia species varies with the location, and may include lancewood, bendee, mulga, gidgee and brigalow. The largest area is in Western Australia.
• Acacia shrublands in semi arid and arid regions. The most common are mulga shrublands; the largest area is in Western Australia.
• Tussock grasslands that occur in semi-arid and some temperate parts of Australia; they host a large variety of grasses from more than 10 genera. The largest area is in Queensland.
• Chenopod/samphire shrubs and forblands that are widespread in the near-estuarine, arid and semi-arid areas. Species in chenopod communities are drought and salt tolerant and include the Sclerolaena, Atriplex, Maireana, Chenopodium and Rhagodia genera while samphire representatives include Tecticornia, Salicornia, Sclerostegia and Sarcocornia. Both South and Western Australia have large areas with this vegetation type.

Other groups with restricted areas of less than 70,000 square kilometres include tropical or temperate rainforest and vine thickets, tall or open eucalypt forests, callitris and Casuarina forests, and woodlands and heath.