The Flinders Ranges South Australia: Evidence from Leporillus Spp
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University of Wollongong Research Online University of Wollongong Thesis Collection University of Wollongong Thesis Collections 1999 A holocene vegetation history of the Flinders Ranges South Australia: evidence from Leporillus spp. (stick-nest rat) middens Lynne McCarthy University of Wollongong Recommended Citation McCarthy, Lynne, A holocene vegetation history of the Flinders Ranges South Australia: evidence from Leporillus spp. (stick-nest rat) middens, Doctor of Philosophy thesis, School of Geosciences, University of Wollongong, 1999. http://ro.uow.edu.au/theses/1962 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] A HOLOCENE VEGETATION HISTORY OF THE FLINDERS RANGES SOUTH AUSTRALIA: EVIDENCE FROM LEPORILLUS SPP. (STICK-NEST RAT) MIDDENS A thesis submitted in fulfilment of the requirements for the award of the degree DOCTOR OF PHILOSOPHY from UNIVERSITY OF WOLLONGONG by LYNNE MCCARTHY B.Env.Sc. BSc (Hons.) SCHOOL OF GEOSCIENCES 1999 This work has not been submitted for a higher degree at any other University or Institution and, unless acknowledged, is my own work. Lynne McCarthy i ABSTRACT Palaeoecological records for semi-arid and arid environments of Australia are limited due to poor preservation of material in this environmental setting. As a consequence, a Holocene vegetation and climatic record for a large part of the continent is incomplete. Leporillus spp. (stick-nest rat) middens provide a wealth of palaeoecological information for Holocene environments in areas where such records are rare. Eighteen middens from three key sites in the Flinders Ranges (Arkaroola-Mount Painter Sanctuary, Mount Chambers Gorge and Brachina Gorge), were investigated in this project to provide a thorough spatial and temporal coverage of palaeoecological sites. Issues of midden taphonomy, temporal resolution of pollen and macrofossil evidence, refining the interpretation of palaeoecological records from middens, and reconstructing palaeovegetation and climates during the Holocene, are dominant themes of this research. Modern pollen rain at study sites was investigated to provide the foundation for interpretation of palaeoecological evidence from the stick-nest rat middens. A study of the regional modern pollen rain along a west-east transect in the central and northern Flinders Ranges reflected the high spatial variability in vegetation communities from semi-arid rocky upland environments. Local environmental conditions at individual midden sites (aspect and degree of exposure at cave sites and local vegetation cover) were significant factors in determining the composition of the modern pollen rain at individual midden sites . Accelerator Mass Spectrometry (AMS) radiocarbon dating was used to examine the taphonomy of middens and refine the temporal resolution of these deposits. The majority of middens were found to have been deposited rapidly. Temporal resolution of middens can be complex, however in most instances, there were contemporaneous ages of different components in the middens (leaves, pollen concentrates and faecal pellets). AMS dating provided reliable ages for individual middens. Vegetation taxa were better represented by pollen rather than macrofossils in the midden assemblages as evidenced by MacrofossihPollen Index values. Macrofossils are regarded as a secondary line of evidence in these midden records. They can verify the local occurrence of a taxon, whose source (local or regional) may not be distinguished solely in the pollen record. Pollen and macrofossil records suggest that woodland and shrubland communities with an understorey of herbaceous taxa and grasses were dominant around 7 000-5 000 yrs B.P in the northern ranges, and shrublands with an understorey of herbaceous taxa and chenopods were dominant in the central ranges. This is indicative of wetter and warmer ii conditions than present during this part of the Holocene. Shrubland communities declined in the central ranges while persisting in the north from 4 000-2 000 yrs B.P, to be replaced by chenopod shrublands with a less diverse herbaceous component in the understorey with increasing aridity into the Late Holocene. Chenopod shrublands continued to increase from 1 000 yrs B.P to the present in the central ranges. Midden records have provided evidence for a shift between transitional shrubland communities to chenopod shrublands in the central ranges. To the north, woodland and shrublands remained throughout the Holocene. Topographically buffered vegetation in the northern ranges is more resilient than central ranges vegetation to climate change. Change in vegetation communities was more visible in the central ranges, as a result of different environmental conditions more sensitive to changes in effective precipitation. This highlights the complexity of factors that affect plant distributions in semi-arid environments. Underlying the climatically driven response is the role of biogeographic parameters that influence the diversity and structure of different vegetation communities. In sheltered rugged topography, in the northern ranges, plant communities are more stable as evidenced by the occurrence of relict species and maintenance of woodland and shrubland communities throughout the Holocene even as conditions were becoming increasingly arid. The same climatic scenario of increasing aridity in the central ranges resulted in less stable vegetation communities that responded to cooler and drier conditions by shifting from dominantly shrublands to an extensive cover of chenopod shrublands. Present spatial variability in the vegetation being a feature of the last 1 000 yrs (and possibly longer in the central ranges), compared with more homogeneous conditions across the ranges from 7 000-5 000 yrs B.P, is certainly consistent with the argument that climatic parameters such as ENSO have become more variable during the Late Holocene. iii ACKNOWLEDGEMENTS Many thanks to Lesley Head for constant support, encouragement, patience and guidance during different stages of the PhD. Thankyou for the generous amount of time invested into reading draft chapters, useful discussions, and providing thoughtful and constructive comments about this work, especially during the writing stage. Thankyou to a team of people who provided invaluable assistance and expertise in their contributions to different aspects of this thesis. Graham Medlin for his enthusiasm and generosity in providing assistance with bone macrofossil identifications, locations of middens and helpful discussions. Helen Vonow, Martin O'Leary and staff at the Adelaide State Herbarium for plant and macrofossil identifications. Professor Michael Tyler for frog bone identifications. Greg Martin for assistance in finding middens. Trevor Nasmith and Eric Dahl from the South Australian Parks and Wildlife for assistance in the field. Botanists from the Department of NSW Agriculture Seed Laboratory for identifications of fossil seeds. BETA Analytic and ANSTO for AMS radiocarbon dates. Sue Pritchard, David Martin and Richard Miller for drafting wonderful diagrams and maps. Robert McCarthy and Lesley Head for proof reading final drafts of the thesis. Judy McCarthy, Jan McCarthy, Jenny Atchison, Vanessa Allen, Terry Lachlan, Jeannette Mangan and Lesley Head for help and plenty of laughs during the hunt for amberat, pollen traps and vegetation surveys during field trips to the Flinders Ranges. The study was funded by the ARC (Grant no. A19530447), AINSE (Grant no. 94/188 and 97/116R) and the Quaternary Environments Research Centre, University of Wollongong. I am grateful to Julio Betancourt, Tom Van Devender and families, for their generosity and hospitality during my visit to Tucson. The opportunity to work with, and exchange ideas and information with such respected researchers in the field of midden analysis was valuable. Thankyou to great friends Jenny, Maria, Laurie, Filiz, David, Gordon and John who have kept me sane and have been a source of strength and happiness, especially during the final stages of putting this thesis together. Special thanks to Brendan for love and support right from the beginning and for always seeing great things ahead for me. Thank you to Dad, Judy, Jan, Robert, Gerry and Dawn for always believing that I could do this and finish it! IV TABLE OF CONTENTS Abstract i Acknowledgements iii Table of Contents iv List of Plates ix List of Figures x List of Tables xv CHAPTER 1: INTRODUCTION: THESIS AND AIMS 1.1 Palaeoecology of the Semi-Arid Zone: the issues, questions and problems 1 1.2 The Evidence 1 1.3 The Thesis: Methodological and Taphonomic Issues 3 1.4 Thesis Objectives 3 1.5 Chapter Outline 5 CHAPTER 2: THE RESEARCH CONTEXT 2.1 Introduction 7 2.2 Midden Analysis 7 2.2.1 Neotoma Midden Analysis: the beginnings 8 2.2.2 Contributions of Neotoma Midden Studies to the Palaeoecology of Desert Areas in the USA 9 2.2.3 Midden Studies in South Africa and the Middle East 11 2.2.4 Methodological and Taphonomic Issues in Midden Analysis 13 2.2.5 Australian Midden Studies 18 2.3 Holocene Palaeoenvironments of Australia 22 2.3.1 Overview of Holocene Climate 23 2.3.2 Lake Level and Pollen Records 24 2.3.3 Dune and Fluvial Records 27 2.3.4 Evidence for Seasonality in Holocene Climates 27 2.3.5 Contradictions Between Holocene Climate Reconstructions 28 2.4 Contribution of Leporillus spp. Midden Records 30 2.5 Conclusion 31 CHAPTER 3: THE FLINDERS RANGES: A REGIONAL PERSPECTIVE 3.1 Introduction