Exotic grass invasion in the tropical savannah of northern Australia: ecosystem consequences

N. Rossiter, S. Setterfield, M. Douglas, L. Hutley and G. Cook
Weeds Society of New South Wales, 6-9 September 2004

Introduced African grasses are invading the tropical savannahs of northern Australia and displacing native grasses. A study aimed to quantify the effect of introduced gamba grass (Andropogon gayanus) invasion on nitrogen availability and soil water dynamics over the wet season in a tropical savannah. It was found that, compared with sites dominated by native grasses, sites invaded by gamba grass had: greatly increased fire intensities, reduced available soil nitrate levels, trebled grass water use, and more than halved deep drainage of water. Gamba grass therefore has the ability to out-compete native grasses and alter catchment hydrology to the detriment of wetlands and streams.