THE AUSTRALIAN NATIONAL UNIVERSITY THESES, SIS/LIBRARY R.G. MENZIES BUILDING H02 Telephone: +61 2 6125 4631 Australian National University Facsimile:+61 2 6125 4063 Canberra ACT 0200 Australia Email: [email protected] USE OF THESES This copy is supplied for purposes of private study and research only. Passages from the thesis may not be copied or closely paraphrased without the written consent of the author. EARLY HOLOCENE VEGETATION DYNAMICS OF LAKE BARRINE BASIN NORTHEAST QUEENSLAND AUSTRALIA Yinshuo Chen Thesis submitted for the degree of Doctor of Philosophy at the Australian National University October 1986 Except where otherwise acknowledged, this thesis represents my own work. \^AS*-^ [nM-~-~y Yinshuo Chen Frontispiece. Lake Barrine, northeastern Queensland, Australia .11:H I ACKNOWLEDGEMENTS Research for and writing of this thesis were undertaken during four years in the Department of Biogeography and Geomorphology, Australian National University, during tenure of an A.N.U. postgraduate scholarship. A great many people assisted from the inception to the completion of the project; brief mentions here are hardly adequate to express my gratitude to them. Firstly, I extend ray heartiest thanks to my supervisor, Professor Donald Walker who initiated palynological investigation in tropical Australia, aided in the selection and definition of this Ph.D. subject, gave continuous enthusiastic encouragement and provided invaluable criticism throughout the entire research period. He has also been my best English teacher; from giving the first English test when we first met in Beijing to the final correction of even minor English errors in my thesis, I have benefitted greatly from his patience and kindness. The hospitality of his family has made my stay in Australia a very pleasant one. I am grateful to my advisors, Drs Jim Bowler and David Green for helpful and stimulating discussions. Dr Green's knowledge and experience in statistics and computing have been a major source of help in data analysis and final preparation of the thesis. My sincere thanks must go to Mr Jim Neale who provided principal assistance in field work and has been a reliable friend during the four years I spent in a foreign country. I would like to thank Judy Owen, Joan Guppy, Gill Jemmett, Daphne MOSS, Keith Fitchett, Jim Caldwell and John Magee for their help in the laboratory and Alan McDonell, Marcia Murphy and Caroline Twang in dealing with many administrative matters. For permission to work at Lake Barrine and kind help ir. the field, 1 am indebted to ii Queensland National Parks and Wildlife Service, particularly to Mr G. Wieden and the staff of the Lake Eacham office. I am grateful to Drs John Chapell, Gurdip Singh and Maureen Longmore for their constructive suggestions and criticism on the mid-term report of the project. I owe a particular debt to Drs Green and Singh for their time and patience in reading an early draft of the thesis and making invaluable comments on it. I can not forget all the help I have received from my fellow students in the department. Alan House, in particular, provided useful information about modern rainforest-sclerophyll woodland boundaries on the Atherton Tableland. Three Chinese professors must be thanked: Professor Xu Ren, Professor Liu Dongsheng and Associate Professor Sun Xiangjun who helped me in various ways before and during the course. Finally, my deepest thanks should be extended to my wife, Wei Chen, for being tolerant of my long absences from China before she came to Australia and for her consistent encouragement and assistance throughout the whole period. iii ABSTRACT This thesis presents the results of an investigation of vegetation dynamics and the related environmental changes at a crater lake, Lake Barrine, near the modern rainforest sclerophyll woodland boundary in tropical Australia during the early Holocene (ca 10 000 - 3 500 B.P.), using fine resolution pollen analysis techniques such as small interval radiocarbon dating, "absolute" pollen frequency, and various statistical techniques (e.g. sequence splitting, time series analysis, model fitting, etc.). A bathymetric survey was carried out on Lake Barrine in 1983 and several sediment cores were taken from various water depths to reveal the general stratigraphy of the lake sediment. Three cores were used in the pollen analytical study. The sedimentation rate during the period concerned has been estimated to be constant at 0.6 mm per year from 22 radiocarbon dates of the three cores. The within-sample interval is 17 years and between-sample interval 34 years in the master core. Thirty-three selected pollen taxa and charcoal particles were counted and a sequence-splitting treatment was applied to each individual taxon. The numbers of significant splits at each sample level were used to zone the pollen diagrams. The results show that the major vegetation change from sclerophyll woodland to rainforest took place about 6800 B.P. During the sclerophyll woodland period, charcoal influx rate was very high, indicating that fire was an important environmental factor. Time series analysis was used to analyze fire frequencies and the response of various sclerophyll taxa to the fire. The results show "that before 9300 B.P. the fire frequency was high (less than 50-year intervals) after which it dropped to a 230-year iv interval probably as the result of an increase in rainfall. Some rainforest trees invaded the area during that period, but the fire prevented the £^ trier development of forest. By 6800 years B.P, perhaps due to further increase in rainfall or perhaps purely by chance, fire was absent from the area for a sufficient period to allow rainforest trees to expand and to replace the sclerophyll woodland as the dominant vegetation type. During early rainforest development different rainforest tree taxa expanded at different times. The processes of population expansion of several taxa have been successfully fitted to one of two population growth models, namely, the exponential model and the logistic model. Doubling time for each taxon was calculated and varied from less than 100 years to more than 300 years. The secondary trees had shortest doubling time, while the gymnosperra canopy trees had the longest. By comparison with modern analogues, it is suggested that the early rainforest experienced three major climatic periods: wet-cool (6800 - 6100 B.P.); wet-warm (6100 - 5000 B.P.); and dry-warm (after 5000 B.P.). The results of the investigation show that fine resolution pollen analysis can not only reveal general changes in vegetation and environment, but also provide ecologically important information on vegetation dynamics. TABLE OF CONTENTS ACKNOWLEDGEMENTS I ABSTRACT iii TABLE OF CONTENTS v LIST OF TABLES vii LIST OF FIGURES viii CHAPTERS 1 INTRODUCTION 1.1 Development of Quaternary pollen analysis 1 1.2 Palynological studies in tropical regions 5 1.3 Population ecology 9 1.4 Aims of this project and the structure of 11 the thesis 2 STUDY AREA 13 2.1 The Atherton Tableland and its neibourhood 13 2.1.1 Physiography and geology 13 2.1.2 Climate 17 2.1.3 Soils 20 2.1.4 Vegetation 21 2.1.5 Quaternary vegetation history 25 2.2 Lake Barrine 27 3 FIELD AND LABORATORY METHODS 29 3.1 Bathymetric survey and sediment sampling 29 3.2 Sediment analysis 33 3.3 Pollen preparation 33 3.4 Counting and identification 36 3.5 Radiocarbon dating 38 4 BASIC DATA 39 4.1 Chronology 43 4.2 Sediment cores 48 4.2.1 Pollen and charcoal sequence-splitting 48 4.2.2 Pollen diagrams 58 4.2.3 Sediment analysis 75 5 POLLEN AND SEDIMENT DISTRIBUTION IN LAKE BARRINE 79 5.1 General review 79 5.2 Pollen and sediment distribution at present 83 5.2.1 Sediment analysis 83 vi 5.2.2 Pollen sources 95 5.2.3 Pollen distribution 99 5.3 Pollen and sediment distribution in the past 113 5.3.1 Sediment analysis 113 5.3.2 Pollen distribution 116 5.4 Implication of the results 119 6 FIRE AND THE SCLEROPHYLL-RAINFOREST TRANSITION 122 6.1 Fire in present Australian vegetation 122 6.2 FossiJ charcoal and fire history 127 6.3 Time series analysis 132 6.4 Fire in the sclerophyll woodland stage at 139 Lake Barrine 6.4.1 Two different fire regimes 141 6.4.2 Plant response to fire 148 6.4.3 Implication for climate change 160 6.5 Fire and rainforest establishment 164 7 EARLY RAINFOREST DEVELOPMENT 168 7.1 Two simple population growth models 168 7.2 Population growth of rainforest tree taxa 174 7*3 Major stages in early rainforest development 202 8 FINAL DISCUSSION 209 REFERENCES 214 APPENDICES 231 I Pollen counts 231 II Ecological information on selected taxa 244 vii LIST OF TABLES Table 3-1 Location of mud-water interface samples 31 Table 4-1 Radiocarbon dates 44 Table 4-2 Comparion of high splits levels 60 Table 5-1 Major parameters of mud-water interface 89 sediment size Table 5-2 Comparison of ratio over Casuarina between surface 98 mud and pollen traps Table 5-3 Comparison of mean pollen concentrations in 108 surface mud beneath shallow and deep water Table 5-4 Major parameters of core B7A sediment size 115 Table 5-5 Comparison of pollen influx between cores 117 B7A, B68 and B9 Table 7-1 Comparison of two model fittings 177 Table 7-2 Result of model fitting 179 Table 8-1 Comparison of Holocene palynological results 210 on the Atherton Tableland viii LIST OF FIGURES Figure 2-1 Physiography and geology of the Atherton- 14 Cains-Innisfail area Figure 2-2 Rainfall vegetation and land use of the 19 Atherton-Cains-Innisfail area Figure 2-3 Vegetation of the eastern Atherton region 22 Figure 3-1 Bathymetric