Australia
AustraliaPlant Life
Although only a dozen plant families are unique to Australia, there are 530 unique genera and many unique species within these genera. As the Australian fragment of prehistoric Gondwanaland drifted north, its ancient flora became the basis for the present plant systems. Increasing aridity modified this vegetation, giving much of it hardened, pointed leaves of reduced size--a condition called scleromorphy.
Australia's native vegetation is divisible into seven types. The first type of vegetation consists of remnants of Gondwanan rain forests, with primitive flowering plants, palms, and laurels. These occur where high rainfall and high temperatures coincide with fertile, often volcanic soils, mainly in coastal north Queensland. In climax rain forests, three layers of trees appear, entangled with shrubs, lianas, and epiphytes. Closest to original Gondwanan conditions are the temperate rain forests of Tasmania, dominated by the myrtle beech and swathed in tree-ferns and mosses--called moss forests.
The second type of vegetation, communities dominated by the tall, straggly eucalyptus trees, is the most ubiquitous, forming a wide, concentric band around the desert core. Of the 500 species, two or three typically form a mosaic in one locality and intermingle with other plant associations. Eucalyptus trees are classified according to their bark types--hence the names stringybark, ironbark, bloodwood, and smoothbark (the gums that shed their outer bark annually). The most widespread is the river red gum. Mallee eucalypts survive in semiarid regions by growing multiple stems (lignotubers) from a common rootstock. The world's tallest flowering plant is a southern eucalyptus, the mountain ash. Its height can exceed 325 feet (100 meters). Building timbers are obtained in Victoria from alpine ash and mountain ash, in New South Wales and Queensland from blackbutt, spotted gum, bluegum, and ironbark, and in Western Australia from jarrah and karri, another type of eucalypt.
A third type of plant community is dominated by wattles (the genus Acacia of the Mimosa family) and advances beyond the last eucalyptus trees into the desert. Although more than 900 species are known, vast regions are dominated by just a few, including brigalow, mulga, and gidgee. Their tannin-rich bark is used in tanning leather. One of the less attractive of the varieties of acacia is the mulga. This small tree grows on thousands of square miles of arid inland Australia. The slang term "out in the mulga" refers to the distant outback areas. Aborigines had a number of uses for this tree. Its wood provided a slow-burning fuel for cooking fires, and it was also used to make spear blades.
The golden wattle is the acacia most familiar to natives. It is the floral symbol of Australia. There is even a Wattle Day, which may be celebrated on August 1 or September 1. Eucalyptus or acacia trees are dominant over 75 percent of the continent.
Three other types of vegetation are...
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