Influence of climate and community composition on the population demography of pasture species in semi-arid Australia

Substantial recruitment of Callitris glaucophylla in woodland, Sclerolaena birchii in cleared woodland, and Astrebla lappacea in grassland is related to catastrophic events of the past century in the form of interactions between climate, the impact of European land use (sheep, cattle, rabbits) and the rabbit myxoma epizootic. The direct effect of rainfall on the demography of these species and its indirect effect through competition via suites of accompanying plant species are examined. Major long-term changes in plant populations are generated by extreme sequential events rather than by random isolated events. One of the most potent climatic agents for change in eastern Australia is the El Niño/Southern Oscillation phenomenon.