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The effect of exotic pasture development on floristic diversity in central Queensland, Australia

Fairfax, RJ & Fensham, RJ 2000, Biological Conservation, vol. 94, pp. 11-21.

The establishment of exotic pasture following tree clearance can negatively impact the floristic composition of vegetation in brigalow (Acacia harpophylla), gidgee (A. cambagei) and eucalypt (Eucalyptus populnea, E. melanophloia) dominated woodlands and forests in semi-arid central Queensland. 

  The authors of this study examined how floristic richness and diversity fare between uncleared pastures, native pastures and exotic pastures across three different land types (brigalow, gidgee and eucalypt) within the Brigalow Belt biogeographic region.  In native and exotic pastures, overall species richness, native species richness and native species diversity were significantly lower than in uncleared pastures across all three land types. In brigalow and eucalypt land, the depletion in the diversity and richness of species and lifeforms in cleared pastures was particularly pronounced. The authors also noticed that the exotic perennial grass, buffel grass (Cenchrus ciliaris), was extremely high in abundance in cleared pastures.  These findings all highlighted the adverse impacts of exotic pasture introduction on the floristic diversity and richness in the Brigalow Belt region. 

  Quality habitats are essential for maintaining biodiversity; therefore, changes in vegetation structure of ecologically important woodlands and forests can have serious implications for local wildlife.  The introduction of exotic grasses following vegetation clearance is a common practice seen in livestock husbandry.  Most exotic grasses exhibit great colonising ability and high drought and grazing tolerance. Exotic grasses are also typically more palatable to livestock than most native pasture species, which allows them to compete with native vegetation and thrive in semi-arid regions of Australia. 

  Although the colonising capability of exotic pastures has been realised, the rate and extent of their expansion in much of Australia is still unclear.  Moreover, the impacts of exotic pasture on local biodiversity have not fully been identified and quantified.  Many Australian wildlife species, particularly arboreal marsupials, are already subjected to threats posed by habitat loss and invasive species. The indirect impact of exotic grass invasion is, therefore, likely to add pressure to the survival and conservation of these animals.

 

Summarised by Cherie Chan

 

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