A scenario calculator for effects of grazing land management on carbon stocks in Australian rangelands

Management of grazing lands has been included in land-based mechanisms for reduction of greenhouse gas emissions. This paper describes a spatial system for scenario analysis of the effect of changes in grazing management on rangeland carbon balances. The system is based on identification of alternative biophysical carbon states and incorporates the effects of management changes and socio-economic and cultural barriers to changes. The management factors include grazing pressure, fire management, control or spread of woody weeds and introduction of browse shrubs. The impact of these factors may be influenced by frequency of good and poor growth years, frequency of droughts and be discounted due to social and economic barriers to adoption. The system appeared to plausibly represent the rangeland responses to management when tested for responses to climate variability and changes in stocking rate, and the impact of prescribed burning in the Tropical Woodlands. Responses are highly sensitive to the knowledgebased estimates of proportion of area in zones for each carbon state and the value of the relative carbon index for each state. A complete and ecologically sound representation of this simple model of carbon state dynamics and climate/vegetation interactions is needed to ensure that scenario analysis is useful and valid for scoping studies.