THE IMPACT OF GRAZING BY MACROPODS ON COASTAL FOREDUNE VEGETATION IN SOUTHEAST QUEENSLAND

The extent of grazing by two macropodids, the agile wallaby (Macropus agilis) and the swamp wallaby (Wallabia bicolor) on coastal foredunes on South Stradbroke Island in southeast Queensland was investigated to determine potential impacts on the principal sand colonizing species, sand spinifex grass (Spinifex sericeus). Grazing on spinifex grass on the foredunes of South Stradbroke island can be attributed principall y to agile wallabies. Foraging activity by wallabies was higher in are as of high spinifex abundance, however, grazing intensity and impact o n spinifex was only important on foredunes with low spinifex abundance . Spinifex consumption by wallabies was also related to a number of fa ctors, especially composition and structure of vegetation in adjacent habitats. Spinifex consumption increased when the abundance of ground cover components (grasses, sedges, forbs) in adjacent habitats was low and structural complexity was high. Grazing on foredunes by wallabies significantly affects the species composition of the foredune communi ty by excluding the establishment of a number of perennial foredune pl ant species. This may have implications for community succession in co astal ecosystems.