The vegetation ecology of Tasmanian dry closed-forest

The subject of this study is a poorly known closed-forest community that occurs as small, disjunct stands in eastern Tasmania. This community has affinities with dry rainforest, a formation that occurs extensively in mainland Australia. There is ongoing debate as to what constitutes Australian rainforest, with most definitions based on the regeneration requirements of the constituent species. A species must be capable of self-replacement in the absence of exogenous disturbance to qualify as a rainforest species. The present study aims to answer the questions: 1. Where does dry closed-forest occur in Tasmania and what environmental factors influence this distribution? 2. How does the floristic composition of this community vary across its range? 3. What are the modes ofregeneration of the major tree species of this community and why is Eucalyptus absent? 4. What are the conservation management and reservation requirements of the community? Additionally, an overarching aim concerns whether the study community can be considered rainforest. To achieve these aims the study: documents the geographic variation of dry closedforest stands and test the hypothesis that distributional characteristics are related to fire-avoidance by mapping the location and characteristics of stands and measuring variables of the local stand environment; documents the floristic variation of dry closed-forest in relation to environmental variables by conducting a survey of the vascular plant species composition and stand environment; determines if this community requires exogenous disturbance for perpetuation, by studying the spatial arrangement and regeneration-characteristics of major canopy species within stands; and investigates why Eucalyptus is absent from this community by conducting experiments of the germination and growth of Eucalyptus and some comparative dry closed-forest species in a number of soil treatments. One hundred and eighty three stands were mapped. Stands occupied a number of different topographic and edaphic situations that afford protection from fire. Six floristic sub-communities were differentiated, and a number of environmental variables shown to significantly influence this variation. Floristic similarities were shown to exist between this community and other Australian rainforest and wetforest communities. Stands not recently disturbed proved to be dominated by selfreplacing species, while early-successional stands consisted mainly of species requiring exogenous disturbance for regeneration. There was no significant segregation of individuals either within or between species, however seedlings of bird-dispersed species were clustered around large trees. The germination experiments indicated that limitations on Eucalyptus establishment are related to soil properties (particularly damping-off fungi) and competition with dry closedforest species. Tasmanian dry closed-forest appears to be a community that has some affinity with rainforest in terms of distribution, floristic composition, structural attributes and regeneration strategy. However, the identification of a number of successional stages of this vegetation type, that require fire for the establishment of a number of key species, brings into question the status of this vegetation as rainforest. This only highlights the challenges present in attempting to define Australian rainforest vegetation.