Grasslands of the World.pdf - Disasters and Conflicts - UNEP

Australian grasslands 355
Figure 9.3
Extent of grasslands in Australia .
in the northern Kimberley region of Western Australia, the “Top End” of the
Northern Territory, and northern Cape York Peninsula in Queensland. In
contrast, the tropical (northeastern Queensland) and subtropical (southeastern
Queensland) tall -grass communities have a less defined and more unreliable
rainfall pattern, and usually less than 750 mm annual rainfall.
Within the monsoon tall -grass communities , those dominated by perennial
grasses (Themeda triandra (Plate 9.1), Chrysopogon fallax , Sorghum plumosum ,
Sehima nervosum , Heteropogon contortus and Aristida spp. ) occur on texture
contrast and earth soils, and communities dominated by annuals (Sorghum spp. ,
Schizachyrium fragile ) grow on sands and skeletal soils. Heteropogon contortus
is an important species in the tropical and subtropical tall -grass communities
in eastern Queensland. Originally, Themeda triandra was commoner, and in
some areas Heteropogon contortus is decreasing and the stoloniferous grasses
Bothriochloa pertusa and Digitaria didactyla are increasing. Other important
genera are Bothriochloa, Dichanthium , Chrysopogon and Aristida. Treeless
grasslands dominated by Dichanthium and Bothriochloa spp. occur on
cracking clays. Tree clearing to increase herbage growth has been widespread in
the subtropical tall -grass, but less important in the tropical and monsoon areas,
where the yield responses are less (Mott et al., 1985).
Brigalow
Brigalow (Acacia harpophylla ) forest and woodlands extend from central
Queensland to northern New South Wales on medium to high fertility clays