Tropical Forests in Australia

Along the east coast of Queensland, where precipitation is most abundant, are scattered tracts of Malayan or tropical rainforest. Among the characteristic trees are red cedar (Cedrela), rosewood (Synoum), hoop and bunya pines (Araucaria), Kauri pine (Agathis), and Queensland maple (Flindersia). All are useful as cabinet woods, and they support an important lumber industry. Vines, ferns, and orchids are abundant in these mixed tropical forests. Certain members of the tropical forest association, such as cabbage palms (Livistona australis), are also found along the New South Wales coast.

Open Forests

Inland from the principal coastal forests are stands of open stunted forests of eucalyptus and acacia species. The eucalypts occupy the western slopes of the Eastern Highlands as well as a wide belt along the north coast. Not only are all these trees able to stand a low average rainfall but they also survive severe droughts extending over several successive seasons. On the western flanks of the highlands of New South Wales and Queensland are extensive growths of cypress pine (Callitris). It grows in open stands and reproduces rapidly. In recent years it has been milled extensively, in part because it resists termites.

Acacia Species

There are more than 600 species of acacia in Australia, and most of them are found in the hotter and drier interior regions. Acacias usually appear as scattered trees in grass- and shrub-covered areas and are low, spreading trees with relatively thin foliage. They are of little commercial significance because of their small size. They are commonly called mulga, brigalow, or wattle by Australians. The seed pods of acacias are an important type of fodder for sheep, and in times of drought even the foliage is utilized. The golden bloom of the acacia provides much color for the interior plains and hills and for desert stream courses during late winter and spring months. One species of acacia, known as blackwood (Acacia melanoxylon), grows to log size in Tasmania and provides excellent cabinet wood.

Shrub Growth

Among the best-known and most valuable types of shrub growth in Australia are saltbush (Atriplex) and bluebush (Kochia). They are common along the south coast from New South Wales to western Australia. Considerable amounts of annual forage are available between the perennial shrubs, but in times of drought sheep feed on the succulent foliage of both saltbush and bluebush. These growths resemble the sage brush of the United States in many respects.

Native Grasses

One of the most valuable native grasses is Mitchell grass (Astrebla), which covers considerable areas in central Queensland and adjacent portions of New South Wales and Northern Territory. It occurs in scattered perennial clumps, and after rains much ephemeral forage grows on the intervening ground. The uncertain nature of rainfall, however, results in wide variations in the amount of vegetation from season to season. Growth takes place after the brief period of summer rains, and a long dormant period occurs during the drier winter season.

Desert Vegetation

The native vegetation of the desert regions consists entirely of drought-resisting plants and trees. Acacias (mulga and brigalow) are most common, but dwarf eucalypts appear near the margins. Stream courses are defined by lines of tree growths, such as the she oak (Casuarina). Spinifex (Triodia) is a tough spiny grass that grows in large clumps in sandy desert areas. Spinifex and mulga provide most of the feed for sheep in some of the driest pastoral areas of the continent.