The interactive effects of fire and herbivory on understorey vegetation and its dependent fauna Claire Foster A thesis submitted for the degree of Doctor of Philosophy of The Australian National University August 2015 © Copyright by Claire Foster 2015 ii Declaration This thesis is my own work, except where otherwise acknowledged (see Preface and Acknowledgements) Claire Foster August 2015 iii iv Preface This thesis is structured as a series of connected papers that have been published in, or were submitted to, peer reviewed journals at the time of thesis submission. These papers are listed at the end of this preface and are referred to in the text by their roman numerals. All papers were intended as stand-alone pieces of work. For this reason, there is some unavoidable repetition between chapters, for example in the background material, and the description of the study area and experimental design. Due to journal copy-editing there may be minor differences between the papers presented here and their published versions. The formatting and content of this thesis complies with The Australian National University’s College of Medicine, Biology and Environment guidelines for ‘Thesis by Compilation’. In line with these guidelines, an Extended Context Statement has been provided at the beginning of the thesis. The Extended Context Statement is not intended to be a complete literature review, but rather a framework for understanding the relationships between all aspects of the research. Paper I provides a detailed review of literature concerning the effects of large herbivores on other animals, and Papers II, III, IV and V each present a review of the literature relevant to the focus of the paper. I performed the majority of the work for the papers that form this thesis. This included developing research questions and experimental designs, data collection and analysis, and writing manuscripts. My supervisors (Philip Barton, Chloe Sato and David Lindenmayer) and collaborators provided advice on conceptualisation, experimental design, data analysis, and manuscript revisions. The addition of different co-authors to each paper reflects contributions from collaborators, which are detailed below. The author contribution statements below have been agreed to in writing by all authors. Other assistance is acknowledged in the acknowledgments section at the end of each paper. v Paper I: Foster, C.N., Barton, P.S. and D.B. Lindenmayer (2014) The effects of large native herbivores on other animals. Journal of Applied Ecology. 51, 929-938. Conceptualisation & design: CNF, DBL, PSB; Data extraction and analysis: CNF; Manuscript drafting: CNF; Manuscript revision: CNF, PSB, DBL. Paper II: Foster, C.N., Barton, P.S., Sato, C.F., Wood, J.T., Macgregor, C.I., and D.B. Lindenmayer (2016) Herbivory and fire interact to affect forest understory habitat, but not its use by small vertebrates. Animal Conservation. 19, 15-25. Conceptualisation & design: CNF, DBL, CIM, PSB, JTW; Data collection: CNF, CIM; Data analysis: CNF, JTW, CFS; Manuscript drafting: CNF; Manuscript revision: CNF, PSB, DBL, CFS, CIM, and JTW. Paper III: Foster, C.N, Barton, P.S, Sato, C.F, Macgregor, C.I, and D.B. Lindenmayer (2015) Synergistic interactions between fire and browsing drive plant diversity in a forest understory. Journal of Vegetation Science. 26, 1112-1123. Conceptualisation & design: CNF, DBL, CIM, PSB; Data collection: CNF, CIM; Data analysis: CNF, CFS; Manuscript drafting: CNF; Manuscript revision: CNF, PSB, DBL, CFS, CIM. Paper IV: Foster, C.N, Barton, P.S., Wood, J.T. and D.B. Lindenmayer (2015) Interactive effects of fire and large herbivores on web-building spiders. Oecologia. 179, 237-248. Conceptualisation & design: CNF, DBL, PSB, JTW; Data collection: CNF, Data analysis: CNF, PSB, JTW; Manuscript drafting CNF, Manuscript revision: CNF, PSB, DBL, JTW. Paper V: Foster, C.N, Sato, C.F., Lindenmayer, D.B., and P.S. Barton (Accepted) Integrating theory into disturbance interaction experiments to better inform ecosystem management. Global Change Biology, doi:10.1111/gcb.13155. Conceptualisation & design: CNF, PSB, CFS, DBL; Data extraction: CNF; Manuscript drafting: CNF, Manuscript revision: CNF, PSB, CFS, DBL. vi Acknowledgements Thank you to my supervisors David Lindenmayer, Chloe Sato, and Philip Barton for their support and guidance during my candidature. David’s confidence in me was pivotal for allowing me to get my experiments up and running within a few months of commencing. The freedom David allowed me in my topics and approach enabled me to complete a PhD that I have found both interesting and thoroughly enjoyable. Chloe’s advice on analyses, discussions on applied management, and general assistance with the whole PhD process has been invaluable. Philip’s advice, constructive feedback and patience with trawling through every first draft have been fantastic. Our regular meetings have helped me stay focussed, and turn my disjointed rambles into something worth writing about. My PhD would have been a very different experience without your advice and encouragement. I would also like to thank Chris MacGregor, Peter Lane and Jeff Wood for their assistance and advice at various times during my candidature. In particular, Chris MacGregor’s cheerful company, willing assistance and ongoing advice made my fieldwork, and especially the dreaded fence construction, so much more enjoyable. Chris was always happy to keep an eye on my experiments, chainsaw a tree from exclosure fences or help identify a difficult specimen. John Evans also provided invaluable assistance with sorting and identifying invertebrate collections. All of my supervisors and collaborators have been outstanding in providing constructive and timely feedback on my written work, for which I am very grateful. I would like to thank the Department of Environment and the landowners and co- managers of Booderee National Park, the Wreck Bay Aboriginal Community, for allowing me to conduct this study in Booderee National Park and providing in-kind support. I would particularly like to thank Nick Dexter and Martin Fortescue for their ongoing support, advice and interest in this project, and making the burning of my experimental plots a reality. Thank you also to all the staff of Booderee National Park who were involved in conducting the prescribed burns, especially Stuart James, who gave me training so I could participate myself. vii Much of my field work would not have been possible without the assistance of a band of willing volunteers. Thank you to Angela, Stuart, Darren, Dylan, Helen, Emily, Xiying, Laura, Kevin, Daniela, Anna and Luke for cheerfully putting up with the early starts, leeches and ticks and wrestling with all the gates. Thank you to the Long Term Ecological Research Network, the Australian Academy of Science (Margaret Middleton Fund) and the Normal Wettenhall Foundation for granting financial support to this project. Thank you also to the ANU College of Medicine and Biology for providing me with a supplementary scholarship. My fellow students and the staff at the Fenner School created an environment of encouragement, active discussion and constructive feedback that made my candidature so much more enjoyable. In particular, thank you to Ben Scheele for great discussions, good company, and reading drafts, and Karen Ikin for your friendship, encouragement and the morning coffee run. I would also like to thank Nélida Villaseñor, Darren Le Roux, Will Batson, Laurence Berry, Nick Engerer, John Evans, Geoff Kay, Miles Kieghley, Megan Evans, Stephanie Pulsford, Laura Rayner, Chloe Sato, Philip Barton, Ingrid Stirnemann, Martin Westgate, Alessio Mortelliti, Jenny Pierson and Crid Fraser for numerous instances of assistance and encouragement, as well as many great lunchtime discussions. Thank you also to Claire Shepherd and Tabitha Boyer for your assistance with navigating the university administration jungle. Thank you to my family for their love and support throughout this experience. In particular to my partner Stuart, who has provided love, good humour and positivity over the last 3.5 years. Thank you for continuing to visit during long periods of field work, even when I made you get up at five, or count poo for your trouble, and for putting things in perspective when I needed it. Finally, thank you to my Mum, for making the effort to understand what I do, correcting my grammar, and encouraging my curiosity from the very beginning. viii Abstract Interactions between multiple disturbances have been shown to have unexpected, and often undesirable effects on ecosystems and biodiversity. Improving our ability to predict and manage the outcomes of multiple disturbances is therefore an important research priority. In this thesis, I focussed on the interaction between fire and grazing (or browsing) by large herbivores. Evidence of the individual effects of fire and large herbivores is substantial, but there has been little quantitative synthesis of the effects of native herbivores on biodiversity. Using a systematic review and meta-analysis, I found that high densities of large herbivores usually have negative effects on other animals. However, I found that interactions between large herbivores and episodic disturbances, such as fire, remain poorly understood. I therefore designed a field experiment to test the interactive effects of prescribed fire and large herbivores on forest flora and fauna. I used full and partial exclosure fences to create a gradient of herbivore pressure across both burnt and