Mapping the vegetation of Hobart : the application of synusiae-based analysis for the purpose of conservation management

The utility of synusiae-based mapping has been demonstrated for conservation management in the Tasmanian World Heritage Area. To test its usefulness in a pen-urban environment, the Municipality of Hobart was chosen. Hobart contains substantial areas of remnant bushland. In total 4100 ha or 53% of the city is remnant bushland. The bushland areas are owned by government or quasi-government authorities or are privately held. Management of these areas is largely restricted to fuel-reduction burning with the aim of protecting lives iind property from major bushfires. The vegetation of Hobart was mapped using this synusiae-based approach with the aid of a Geographic Information System. Plant communities, identified using aerial photographs and ground surveys, were divided into one to four layers. Each layer corresponds to one or an association of two synusiae. Maps were created using a system of notation which readily identifies the communities present on the basis of the synusiae present. The dominant or tallest stratum/synusia(e) was always included. Synusiae present in other strata were only identified if their cover was significant. A total of twenty-three synusiae for the dominant layer were identified based on structural tree/shrub forms, growth forms or according to their situation (that is, environmental parameters or species associations). The second stratum was seldom significant and was simply coded according to the tree species. The understorey (third stratum) was identified according to either a synusiae based on a growth forms or their situation. Six of these were identified. The ground layer (forth stratum) was coded according to synusiae based on growth form and/or an additional code describing the surface features. A total of 600 communities were distinguished using this system of notation. For analysis, communities were grouped according to the dominant synusiae and if appropriate either the understorey or ground layer synusiae. This resulting 84 'mapping units' were then grouped again according to their dominant strata synusia(e) and/or their location in Hobart. Each group formed a separate map. Mapping units were then analysed according to environmental parameters (aspect, slope, altitude and geological substrate), fire history and land tenure. This information was used to make recommendations for future conservation management, with particular emphasis on fire management practices. Each mapping unit was also classified according to pre-existing vegetation classifications. The conservation status of some of these communities was upgraded as a result of this work. Nine communities of high conservation value were identified, mapped and described. Recommendations are made for their future management and preservation. In addition to the synusiae-based analysis mentioned above a list of 59 rare or threatened species was tabulated and mapped from existing sources. Of these 16 are also unreserved (that is, not known to exist in a secure reserve in Tasmania). These are included only to further highlight the significance of bushland areas in Hobart. General recommendations for future management of the bushland areas include the establishing of buffer zones and vegetation corridors to protect areas of high conservation value and areas of bushland where rare or threatened plants are present. Other recommendations include the preservation of bushland areas with centres more than 400 m from the nearest urban development. Amendments to the Hobart Planning Scheme or State Government legislation and greater cooperation between various authorities may be necessary to implement these recommendations. The maps prepared are an important database which can be used by both managers and planners to preserve the integrity of the bushland in Hobart.