Weed invasion of the tropical Mackay coast, Queensland, Australia

George N. Batianoff and Andrew J. FranksA

Queensland Herbarium, Department of Environment, Mt. Coot-tha Road, Toowong, Queensland 4066, Australia.

A Present address: Department of Botany, The University of Queensland, St. Lucia, Queensland 4072, Australia.


Summary

A three to five kilometre wide section of the tropical central Queensland coast around Mackay was studied. Naturalized exotic plants comprise 28% of the total flora. The naturalized flora includes 311 species belonging to 64 families and 203 genera. Herbaceous lifeforms (66.8%) dominate weed flora of the tropical Mackay coast. The changes in species composition and vegetation structure are viewed in terms of succession. Analysis of weed species occurrence indicated that 78% of species are either infrequent or rare in their present distribution reflecting secondary successional influences in disturbed habitats. Weed cover >35% was found to reduce native species richness in coastal Casuarina woodlands. Under current land-use practises weeds are not only naturalizing in ever increasing numbers but also have the potential to expand their present vegetation cover to thresholds that will reduce native species diversity over the long term.

We identified 56 species (18% of the total flora) of environmental weeds that are considered seriously invasive within this study area. The most susceptible vegetation types to environmental weed invasions are; riparian forest (44 species), open forest (32 species) and beach scrub (30 species). Disturbed habitats support approximately 95% of the environmental weeds. Priority control measures are required for Brachiaria mutica, Bryophyllum spp., Dalbergia sissoo, Panicum maximum, Psidium guajava, Sporobolus spp., Syzygium cumini and Themeda quadrivalvis.

Local authorities are responsible for the condition of native vegetation and as a result are encouraged to allocate resources to maintain the natural environment. Education of Mackay coastal managers and residents is urgently required to discourage unnecessary disturbance including the dumping of garden refuse into native vegetation.

 

Plant Protection Quarterly (1998) 13 (3) 123-130.