Territory Environments
Riparian Forests, Woodlands and Shrublands of the Arid Zone
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Strictly speaking, riparian communities are those situated on the banks of watercourses. In central Australia, where watercourses are usually dry, riparian communities often extend across the bed of the creek or river.
The most common riparian communities in central Australia are Teatree (Melaleuca spp.) shrublands, River Red Gum (Eucalyptus camaldulensis) and Coolabah (Eucalyptus coolabah) forests and woodlands. Riparian communities are some of the most species-rich communities in central Australia with a diversity of forbs, grasses and sedges
The Teatree shrublands are composed primarily of M. glomerata, however M. bracteatra, M. trichostachya, M. dissitiflora, M. viridiflora and M. nervosa also occupy river or creek banks and may co-exist in various combinations. In the steeper, upper reaches of watercourses Teatree shrublands predominate. The understorey of these shrublands is usually mixed grasses.
Once the watercourse reaches flatter ground River Red Gum forests and woodlands with grass understorey dominate although areas of Teatree shrublands are by no means uncommon. No central Australian river reaches the sea, instead the water disperses into low lying areas or basins called "floodouts". These floodouts are usually dominated by Coolabah (E. coolabah) woodlands. Under natural conditions these forests and woodlands have an understorey of various short lived shrubs and grasses.
Riparian Melaleuca shrubland communities may be as little as 10 metres wide. Forest and woodland communities are usually no more that a few hundred metres, however, the Finke Floodout Forest is approximately 20 km long and 6 km at its widest covering the whole floodout basin and Lake Surprise is an open Coolbah woodland with grass understorey some 10 km long and 5 km at its widest.
Threats
The major threats to riparian communities are the introduced weeds Athel Pine (Tamatix aphylla), Couch Grass (Cynodon dactylon) and Buffel Grass (Cenchrus ciliaris).
Athel Pine is infesting long reaches of the Finke River and is moving up some tributaries. Athel Pine along the banks may be very dense, excluding all native plant species. Buffel Grass is widespread throughout the pastoral areas and many reserves in central Australia and, along with Couch Grass, has invaded many watercourses, outcompeting native plant species.
Fire is a threat to the riparian communities invaded by Buffel Grass as it is very flammable. Buffel Grass is also fire tolerant and recovers quickly after being burnt so that the frequency of fires may be beyond the capacity of native species to recover.
In the river beds Athel Pines, Couch and Buffel Grasses are colonising and stablilsing otherwise unstable sand "islands". This may lead to choking of the river channel and an increase in flooding of the surrounding plains.
Floodouts are often degraded by grazing and contain many introduced weeds (Latz 1996).
The effect of these weeds species on the riparian fauna is unknown.
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Further reading
- Latz, P.K. 1996. Bushfires and Bushtucker: Aboriginal plant use in central Australia. Alice Springs: IAD Press.
