Grassland Natural History
The Dictates of History
Themeda australis (Kangaroo Grass) was once considered to be distinct from Themeda triandra of Africa and Asia. Found in all of the mainland states as well as Tasmania, it is probably the most widely-distributed native grass species on our continent. The renaming of the Australian species as “T. triandra,” identified a more direct vegetation link between Australia and the old world of Gondwanaland.
Volcanic activity has maintained the fertility of Themeda-dominant tropical grasslands such as the Serengeti on the African continent. In contrast much of the Australian landscape has lost its fertility and become significantly drier throughout its post- Gondwanaland history. The wetter climate and richer volcanic soils of the extreme north of Australia currently produce our best examples of luxuriant Themeda triandra grasslands. Although the Chloris genus is common to both continents, Chloris gayana appears to have a more significant role in the fertile native pastures of Africa than does Chloris truncata that is confined to Australia’s temperate zones. Today, C. truncata appears to struggle to find a natural niche in southern regions that have long dry summers. It tends to colonize bared sites that are occasionally wet during the warmer seasons. In recent years, this native grass has suffered the ignominy of becoming a significant weed in zero tillage cereal crops due in part to its tolerance of glyphosate.
While the imminent extinction of any plant species is readily given high status, the dysfunction brought upon many species by a separation from their original geological and biological environments is a matter that deserves more attention.
Grassland communities have never been static. From the slow changes of tectonic plate movement, through the faster changes that resulted from the land-management techniques of the First Australians, to the much more rapid vegetation changes that followed European settlement and agriculture, Australian grasslands have always been a product of these ever-changing conditions. Most of Australia’s native grass communities now contain many introduced grassland species. (See our listing of common and scientific names of native and introduced grasses.)