A Vegetation History and Quantitative Estimate of Holocene Climate from Chapple Vale, in the Otway Region of Victoria, Australia

Abstract

A well-dated pollen record from Chapple Vale in the north of the Otway region provides a detailed history of vegetation and environments through the last c. 7000 years. From the commencement of the record, a stand of cool temperate rainforest, dominated by Nothofagus cunninghamii (Hook.) Oerst., grew on or around the site and was surrounded by eucalypt-dominated tall open forest. Between c. 5200 and 4600 years BP (before present), the rainforest declined and tall open forest predominated. Some time after 4400 years BP there was a major and consistent increase in charcoal values, suggesting an increase in burning, the progressive development of scrub–heath vegetation on site and the replacement of tall open forest vegetation by eucalypt woodland surrounding the site. The fossil evidence for N. cunninghamii on the site and its present restriction to wetter areas and gullies of the Otway Ranges indicate, from the application of the present bioclimatic range of the species, a mean annual temperature and winter temperatures that were c. 1˚C cooler than present, and summer temperatures that were possibly slightly cooler than present, together with a much higher effective precipitation from the commencement of the record until c. 4600 years BP. These climatic estimates are in accord with those derived from a similar study of changing distributions of N. cunninghamii in the Central Highlands of lower mean annual and cooler summer temperatures and higher effective precipitation over this time span. However, for winter, the evidence is equivocal. While the Otway estimates suggest lower temperatures, the Central Highlands findings show slightly higher temperatures. Taking into account additional present-day records for N. cunninghamii, it is likely that the Otway estimates are the most reliable.