Fire-stimulated rainforest seedling recruitment and vegetative regeneration in a densely grassed wet sclerophyll forest of north-eastern Australia

Details of plant regeneration, combined with soil seedbank data, are docume nted for a densely grassed wet sclerophyll forest in north-eastern Australi a. The following two hypotheses were tested: (1) that established individua ls of rainforest pioneer species are killed by low to moderate intensity fi res and (2) that seedling recruitment of these species is evenly distribute d throughout the intervals between fires. Both the sclerophyll and rainforest pioneer species displayed strong regene rative abilities as a response to low or moderate intensity fires. Most of the rainforest pioneer species were not killed by two recent fires but vege tatively regenerated. Alstonia muelleriana showed fire-enhanced vegetative expansion via root suckering. Both the sclerophyll and rainforest pioneer s pecies were found to recruit seedlings primarily as a pulse in the first ye ar or two after a fire, with limited recruitment after longer intervals bet ween fires. This is consistent with suggestions that grass competition may limit tree recruitment. The germinable soil seedbank was dominated by rainf orest pioneers, herbs and grasses, with heat treatment of the seedbank enha ncing seed germination of two rainforest pioneer species. These results dem onstrate the ability of rainforest pioneers to exploit the post-fire enviro nment and indicate the complex nature of rainforest boundary dynamics. Furt her research into tropical rainforest expansion is required to examine the effects of fire regimes on vegetative and seedling regeneration across rang e of sites.