KEY PERIODS IN THE EVOLUTION OF THE CENOZOIC VEGETATION AND FLORA IN WESTERN TASMANIA - THE LATE PLIOCENE

摘要

Fossil pollen and spores in organic-rich sediments in a side gully in the Linda Valley, western Tasmania, preserve one of the most detailed records of a Late Pliocene flora and vegetation available to date in Australia. This includes Araucariaceae, Beauprea Brongn. & Gris. and a number of sub-canopy broadleaf trees now confined to warm temperate-tropical habitats. Changes in community dominance are interpreted in terms of alluvial events and point to the existence of altitudinally zoned plant communities in western Tasmania-Microstrobos J. Garden & L. Johnson heathland on the higher slopes and Nothofagus (Brassospora) Hill & Read-Lagarostrobos franklinii (J.D.Hook.) Quinn evergreen rainforest with or without Dacrydium Sol. ex Lamb. emmend. de Laub. at lower elevations. The evidence demonstrates the survival of Nothofagus (Brassospora) spp in western Tasmania at a time when other published data imply the taxon was virtually eliminated from the south-eastern mainland. It is proposed that increasingly seasonal climates drove an 'ecological wedge' into a former continuum of wet forest types along the east coast of Australia, with Plio-Pleistocene glaciation being ultimately responsible for the demise, of what had become relict populations, of Brassospora spp. in western Tasmania.