Experiments on the capacity of present sheep flocks to extinguish some tree populations of the South Australian arid zone

Abstract

Since the inception of pastoralism in South Australian arid zone vegetation last century, successive seedling inputs of some native tree species have been extinguished over most of their range. This has happened even in places that have not been overtly overstocked. Populations of the affected species are in consequence gerontologic and much woodland over thousands of km 2 will vanish unless the situation alters. Hypotheses are that introduced sheep or rabbits or both are responsible. We report experiments in which the capacity of present sheep flocks to extinguish simulated seedlings was evaluated. These demonstrated that a typical flock was able easily and consistently to suppress such inputs to a 4050 ha paddock at a rate and scale that would extinguish most in a few weeks. The pattern of suppression appeared to be stable for the flock and paddock studied, regardless of year or season.