Dynamics of some Western Australian ligneous formations with special reference to the invasion of exotic species

Invasion of natural vegetation in Australia by exotic species has become pronounced in the last 150 years of European settlement. Changes in the frequency and type of fire have been a major disturbance to the dynamics of natural vegetation, and this disturbance has allowed rapid spread of exotics, particularly in urban and semi-rural regions. Less obvious disturbances include changes in nutrient levels and hydrological regimes, which also allow exotic species to establish and spread, at the expense of native species. Permanent plots established in various vegetation types show a decline in diversity which is associated with an increase in invasion by exotic species. Possible management strategies, designed to maintain the natural vegetation, which can be postulated include control and change of fire regime, removal of exotic species before seed-set, and the active introduction of native plants adapted to disturbance