NORTHERN AUSTRALIAN SAVANNAS - MANAGEMENT FOR PASTORAL PRODUCTION

Annual variability of rainfall is high, resulting in uncertainty in management decisions. Systems analysis models of pastoral enterprises are being constructed which predict the response of savannas to management alternatives against a background of annual climatic variation as well as expected long-term global climate change. In N Australia, El Nino/Southern Oscillation events account for over half the major ecologically significant droughts. The seasonal persistence of the Southern Oscillation phase allows forecasts to be made before the onset of summer rains. The potential of such forecasts is examined with respect to savanna management. Models of soil water budgeting, grass production, pasture utilization and annual production are being developed for each savanna community in N Australia. The key processes in these models are plant growth as a function of climate inputs and the effect of grazing on plant survival and production. Periods of overgrazing can be identified when model output is combined with regional animal number statistics; and management decisions such as burning can be improved when ENSO based forecasts are used. -from Authors