Comparative population dymatics of Eucalyptus caldocalyx in its native habitat and as an invasive species in an urban bushland in south-western Australia.

Eucalyptus cladocalyx F. Muell., is a tree with a restricted distribution in the Southern Flinders Ranges, South Australia. It was originally introduced into the urban bushland of Kings Park, Perth, Western Australia in 1932 as an ornamental. Since its planting, E. cladocalyx has become invasive, spreading into the bushland up to 70 m away from planting sites. Anecdotal evidence suggests that the E. cladocalyx population is increasing at a greater rate than the two principal native tree species, E. gomphocephala DC. and E. marginata Donn ex Smith, but little is known about the factors influencing its invasion, or its biology. This study describes the population structure of E. cladocalyx, E. gomphocephala and E. marginata in Kings Park and the role of fire in the recruitment process. The study indicated that the three species have characteristics common to temperate Eucalyptus species that mass recruit seedlings following fire, with high numbers of seedlings found in recently burnt areas and low numbers in unburnt areas. Seedling survival in E. cladocalyx was higher than either of the native species. Furthermore, E. cladocalyx adults showed higher rates of canopy recovery following fires. It is argued that although fire in Kings Park is providing opportunities for E. cladocalyx, E. gomphocephala and E. marginata recruitment, the E. cladocalyx population is more resilient in an environment frequently disturbed by fire compared with the native populations.