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Abstract:
We present a new stage-structured model, called SHRUBPOP, for projecting potential impacts of grazing and rainfall (drought) over periods of up to 500 years on populations of trees and shrubs in the Australian chenopod rangelands. Created in Microsoft Excel®, the model is based on functional groups rather than species so that it can be used, with or without modification, for any species of tree or shrub. It includes the effects of grazing pressure of four herbivore species: sheep, rabbits, goats and kangaroos. Rainfall (either modelled or real rainfall records) can be included as another variable. Model runs can be repeated in series, with different herbivore intensities, using the end population numbers of the previous run as the starting numbers for the next run, to model the effects of management interventions such as spelling of paddocks and control of feral herbivores. By using different rainfall data, various climate-change scenarios may also be created. It is simple to adjust the parameter files to model populations of species from other regions and for different climate conditions, or for the effects of grazing by other herbivores, such as cattle.
