Holocene vegetation and climate change from near Lake Pedder, south-west Tasmania, Australia
To use surface pollen and vegetation relationships to aid the interpretation of a Holocene pollen record. Location
South-west Tasmania, Australia. Methods
A survey was undertaken of surface-pollen samples from the major regional vegetation types: alpine, rain forest and moorland. Relationships between vegetation type and surface-pollen representation were analysed usingtwinspanclassification and ordination. A core was retrieved from moorland vegetation, and interpretation of the fossil pollen sequence was aided using relationships detected in our surface-pollen analysis. Results
Regional vegetation types are reflected in the pollen rain of south-west Tasmania, despite the over-representation of important rain forest tree species in samples from non-forest sites.twinspanclassification of the surface-pollen samples identified the following indicator pollen taxa for each vegetation type: Astelia alpina (alpine); Lagarostrobos franklinii (rain forest); Leptospermum and Melaleuca (moorland). Detrended correspondence analysis of the surface-pollen samples clearly separates samples from each vegetation type. Correlation of the ordination axes with environmental data identified a dominant temperature/altitudinal gradient in the surface-pollen data (R = 0.852/0.844). Application of the results of the surface-pollen analysis to the fossil sequence revealed that fire-promoted moorland has dominated the local environment around the core site for the entire Holocene. Changes in fossil pollen composition also suggest that temperatures increased through the Late Glacial to peak in the mid-Holocene and declined thereafter, a trend consistent with other sites in the region. Main conclusions
Pollen spectra can successfully be used to predict local vegetation in south-west Tasmania. At least this part of inland south-west Tasmania has remained forest-free throughout the Holocene, conflicting with the dominant palaeoecological paradigm of a mid-Holocene dominated by rain forest. A comparison with pollen records from moorland vegetation across the region suggests that fire-promoted moorland has dominated the landscape since the Late Glacial. We suggest that burning by people through the Late Glacial (if not earlier) facilitated the spread of moorland throughout the region, greatly restricting the expansion of rain forest. The continued influence of fire throughout the Holocene in this perennially wet landscape argues for a revision of the dominant human-occupation model that depicts an abandonment of the interior of south-west Tasmania in the Late Glacial in response to the expansion of rain forest.