Late quaternary vegetation of the Atherton Tableland, north-east Queensland, Australia

Abstract

The vegetation of north-east Queensland is composed of a number of isolated rain-forest patches, which show great variation with respect to altitude, rainfall and soil parent material, surrounded by a great expanse of open eucalypt woodland. In order to attempt to explain this vegetation pattern it was decided to undertake a study of one rain-forested area. The Atherton Tableland was selected as it contains a number of volcanic craters with accumulated organic sediments suitable for pollen analytical investigation and it lies within a topographically and climatologically diverse area where the presence of a variety of rain-forest types and eucalypt woodland suggested that any past changes would be clearly indicated in pollen records. To assist in the interpretation of results from pollen analysis of sediment cores, stratigraphic and aquatic vegetation investigations of the crater sites were undertaken (Chapter 3) and studies were made on the relationship between the modern vegetation and modern pollen deposition in a number of dry land and aquatic environments that could have been represented in the pollen diagrams (Chapter 4). Five pollen diagrams from four crater sites were prepared and radiocarbon dated (Chapter 5). Four of these diagrams provide details of vegetation through the last 11,000 years while the fifth, from Lynch's Crater, extends back from near present to about 60,000 B.P. Interpretation of vegetation changes, evidenced from the pollen records, is largely in terms of climate though the possible effects of aboriginal man are also considered (Chapter 6). Detailed interpretations of vegetation and climate change for diagrams covering the last 11,000 years, are suggested from statistical comparisons between modern and fossil pollen spectra. The results indicate that subtropical rain-forest dominated by Araucaria, was present on the Atherton Tableland from before 60,000 B.P. to about 38,000 B.P. and existed under about half the present annual rainfall. This was replaced by open eucalypt woodland, between 38,000 and 27,000 B.P., as a result of either a decrease in precipitation or burning by aboriginal man. From about 8500 to 7000 B.P. the open woodland was replaced by 'temperate' rain-forest as a result of an increase in precipitation. Rain-forest then remained dominant over the Tableland for the next 4000 years or so but changed from the initial 'temperate' to a subtropical or tropical kind with an increase in temperature. At about 2500 B.P., the rain-forest became drier and allowed a partial return of the open eucalypt woodland. The extension of this sequence of vegetation and climatic change, indicated for the Atherton Tableland, over the last 60,000 years to north-east Queensland in general (Chapter 7) provides a basis for the interpretation of many problematical features of present day vegetation distributions. Show more