Mj Brown

The nature of the transition from sedgeland to alpine vegetation in south-west Tasmania. I: Altitudinal vegetation change on four mountains

The results of contemporary research suggest that vegetation varies continuously with environment, except where dominants create new habitats. However, phytosociological and distributional data from the treeless parts of mountains in the south-west of Tasmania indicate the existence of a sharp vegetation boundary at 700-900 m above sea level, despite an apparent climatic, geologic, edaphic and topographic continuity of environment. This boundary cannot be attributed to the interactions between species, because it occurs within sparsely vegetated gravel as well as within continuous vegetation cover on peat. The boundary might have originated as a result of the local extinction of lowland species during the climatic vicissitudes of the Quaternary. However, there is a possibility that the boundary correlates with a persistent cloud ceiling, and more climatic data are needed from the region before historical explanations become necessary.

Stand structure, reproductive activity and sex expression in Huon pine (Lagarostrobos franklinii (Hook L.) Quinn.)

The nature and variability of stand structure, reproductive activity and sex expression were investigated in natural populations throughout the geographic and ecological range of Lagarostrobos franklinii, a Tasmanian endemic rainforest tree in the family Podocarpaceae. Size-class distributions adn tree densities were variable among sites. Overall, 30% of trees produced cones, but several populations deviated significantly from this percentage. Larger trees were more likely to produce cones than smaller trees. Stand structure and light availability appeared to have an effect on the proportions of trees producing cones. Cone-producing trees tended to be clumped within stands. Overall there were equal proportions of male and female trees, and approximately 4% of cone-producing trees were monoecious. There were however some populations with greater proportions of one sex. Similarity in the proportions of females in populations was correlated with similarities in their floristic composition. Trees of like gender tended to be clumped at short distances within populations.

Selection and design of Phytophthora management areas for the conservation of threatened flora in Tasmania

Abstract In Tasmania Phytophthora cinnamomi can cause serious disease in heaths, dry sclerophyll forests, moorlands and disturbed rainforests growing below 600 m and receiving more than 600 mm rainfall annually. Before the current research 136 native plant species were known to be hosts for P. cinnamomi . Very few of these plant species are considered threatened by its activities. However, susceptible rare and threatened plants are at the greatest risk. Management areas were selected and designed for the purpose of safeguarding 44 species that appear on state and national lists of rare and threatened plants and are susceptible to and potentially at risk from P. cinnamomi . The selection process and criteria used for selecting management areas are presented. Of the 101 areas surveyed 74 were selected based on their diversity and the aim of selecting three management areas, when possible, for each species. The 61 areas finally selected were based on landscape management criteria as well as species criteria; they contained all 44 target species. There were 109 inclusions of target species in the 61 management areas selected out of a possible 136 in the original 101 areas.