Two systems or one? Vegetation dynamics in Australia’s Wet Tropics Photos: L.Warman Laura Warman Thesis submitted for the degree of Doctor of Philosophy Evolution and Ecology Research Centre School of Biological, Earth and Environmental Sciences University of New South Wales March 2011 PLEASE TYPE THE UNIVERSITY OF NEW SOUTH WALES Thesis/Dissertation Sheet Surname or Family name: Warman First name: Laura Other name/s: Abbreviation for degree as given in the University calendar: School: School of Biological, Earth and Environmental Sciences Faculty: Science Evolution and Ecology Research Centre Title: Two systems or one? Vegetation dynamics in Australia’s Wet Tropics Abstract 350 words maximum: (PLEASE TYPE) Around the world tropical rainforests intergrade with open, fire-dependent (pyrophytic) vegetation forming landscape- scale mosaics. However, rainforests and open vegetation are mostly studied independently from each other. This has been the case in the Australian Wet Tropics. This thesis begins by arguing that the vegetation of north-eastern Queensland can be considered as a complex system where rainforests and pyrophytic vegetation represent alternative stable states. This is important because it creates a new context for understanding the region’s biological dynamics. It allows us to move forward from an understanding where only abiotic factors determine the distribution of vegetation, to one in which the vegetation itself plays an important and active role at several scales. Globally, studies of abrupt boundaries between closed forests and pyrophytic vegetation focus on the contrast between abiotic factors on either side of the boundaries. I used a novel approach considering controls in non-boundary vegetation and comparing them to parameters across boundaries at a regional scale. My results show that contrasts in soil chemistry across boundaries are not greater than the variance found within either vegetation type, and that the vegetation itself can change soil chemistry remarkably quickly. This highlights the active, rather than passive, role of vegetation in the region. In contrast to other systems presenting alternative stable states (such as coral reefs, savannas or kelp forests), I found herbivory in the Wet Tropics was similar across vegetation types. I also show for the first time that the advantages of compound vs. simple leaves do not lie in leaf construction or herbivore avoidance, addressing a long debated topic to which there is still no satisfying answer. Lastly, a computer model compares the effects on landscape-scale vegetation patterns of changing species interactions under varying environmental conditions. The model evaluates the outcome of obligate rainforest and pyrophytic “species” competing with pioneers and ‘traitors’ and proposes long-term hypotheses that may be tested in the field. In conclusion, using ideas about alternative stable states as a starting point has allowed me to make contributions towards understanding the interaction between different factors involved in large-scale vegetation dynamics in the Australian Wet Tropics. Declaration relating to disposition of project thesis/dissertation I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all property rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstracts International (this is applicable to doctoral theses only). ………………………………………………………… ……………………………………..…………… ……….……………………...… Signature Witness Date The University recognises that there may be exceptional circumstances requiring restrictions on copying or conditions on use. Requests for restriction for a period of up to 2 years must be made in writing. Requests for a longer period of restriction may be considered in exceptional circumstances and require the approval of the Dean of Graduate Research. FOR OFFICE USE ONLY Date of completion of requirements for Award: COPYRIGHT STATEMENT ‘I hereby grant the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstract International (this is applicable to doctoral theses only). I have either used no substantial portions of copyright material in my thesis or I have obtained permission to use copyright material; where permission has not been granted I have applied/will apply for a partial restriction of the digital copy of my thesis or dissertation.' Signed …………………………………………….............. Date …………………………………….……….............. AUTHENTICITY STATEMENT ‘I certify that the Library deposit digital copy is a direct equivalent of the final officially approved version of my thesis. No emendation of content has occurred and if there are any minor variations in formatting, they are the result of the conversion to digital format.’ Signed …………………………………………….............. Date …………………………………….……….............. i ORIGINALITY STATEMENT ‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.’ Signed …………………………………………….............. Date …………………………………….……….............. ii Statement of contributions of co-authors and declarations of permission to publish All publishers and co-authors have granted permission for the following publications to be submitted and published as a thesis. No other authors will be submitting this work as part of their thesis submissions. The contribution of each author to the respective publications is stated at the start of each chapter. All photographs were taken by Laura Warman. Warman, L. and Moles, A.T. 2009. Alternative stable states in Australia's wet tropics: a theoretical framework for the field data and a field case for the theory. Landscape Ecology 24: 1-13. DOI: 10.1007/s10980-008-9285-9 Reproduced with kind permission from Springer Science+Business Media: Landscape Ecology, Alternative stable states in Australia's wet tropics: a theoretical framework for the field data and a field case for the theory, 24, 2009, 1-13, Warman, L. & Moles A.T, © Springer Science+Business Media B.V. 2008. Warman L., Moles A.T and Edwards W. 2011. Not so simple after all: Searching for the ecological advantages of compound leaves. Oikos 120:813-821. DOI: 10.1111/j.1600-0706.2010.19344.x Reproduced with kind permission from Oikos and Wiley-Blackwell. Oikos grants authors the right to reproduce their article in a new publication of which they are the author, editor or co-editor, including a thesis or dissertation. Warman L., Bradford M.G. and Moles A.T. A broad approach to abrupt boundaries: Looking beyond the boundary at soil attributes within and across tropical vegetation. In review at Journal of Biogeography Warman L., Fletcher C.S. and Moles A.T. Traitors on the landscape? A model of interactions between rainforests and fire-prone forests. In preparation for Journal of Ecology iii Acknowledgements The first acknowledgement must go to Professor Des Cooper; if not for him and the MConBio program I might not have returned to science. With humour and encouragement, Des let me convince myself that I wanted to pursue a PhD (and tried to pass the blame later). For all of this, the sav blanc and proper introduction to Melbourne Cup Day: Thank you again Des! If Des opened the door to the PhD, then Angela Moles lay down the welcome mat and invited me in. For all her good intentions, she has since been saddled with nagging questions, endless discussions on soil, many e-mails sent at the wee hours of dawn and never-ending first chapter drafts. Angela: my most heartfelt thanks. I seriously don’t believe I could have started, let alone finished a PhD without your constant support and faith in me (both personally and as a scientist). Admittedly, the hard-lines probably helped as well. Thank you so much for all you’ve taught me. Thank you for all the carrots and the sticks, the slaps-upside the head, the encouragement, the hugs, cups of tea, and especially the ever-important smiley-faces on manuscript drafts. I’m looking forward to climbing trees with you again! Will Edwards literally opened the door to me and, in return, promptly had his car filled with mud, leeches and leaves (more than once). Thank you for giving me an anchorage in the Far North and the foothold I needed to get going. Thank you as well for all those hours in the forest tagging leaves, all the advice, comments and all those discussions late into the tropical night. Special thanks to Paul Adam for asking me hard questions in kind ways and answering all my questions. Thank you as well for all of the relevant reading material that appeared magically on my desk throughout my candidature.