Edge Effects in Fire-Prone Landscapes: Ecological Importance and Implications for Fauna
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EDGE EFFECTS IN FIRE-PRONE LANDSCAPES: ECOLOGICAL IMPORTANCE AND IMPLICATIONS FOR FAUNA KATE ANNA PARKINS orcid.org/0000-0002-0882-638X Submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy June 2018 School of Ecosystem and Forest Sciences Faculty of Science University of Melbourne i ii ABSTRACT The overarching aim of this thesis was to investigate the ecological importance of fire edges, focusing on the influence of fire-induced edge effects on fauna in forested landscapes. Edges are ubiquitous environmental features, occurring in a wide range of ecosystems and across multiple spatial scales. Edges have been extensively researched in some contexts, particularly agricultural and urban landscapes. Accordingly, much of our understanding about how edges influence animals comes from highly modified ecosystems. Fire is an agent of edge creation and a globally important driver of biome distribution and community composition, yet little is known about how fire edges affect ecological processes in flammable ecosystems. In this thesis I review the literature on fire, fauna and edge effects to summarise current knowledge of faunal response to fire edges and identify knowledge gaps (Chapter 2). I developed a conceptual model for predicting edges effects in fire-prone landscapes, combining several drivers of faunal-fire responses. Fire-generated edge effects were found to differ from edges in modified systems, being temporally dynamic, spatially complex and characterised by the strength of the interaction between components of the disturbance regime and other biophysical factors. In Chapter 3 I investigated the response of ground-dwelling mammals to burnt/unburnt edges created by prescribed burning. I used a space-for-time substitution design to explore how species use of fire edges changes over time as the burnt side of the edge regenerates. I found that understorey complexity was reduced on the burnt side of edges for the first two years after fire. Larger animals with generalist resource requirements were more active at burnt edges immediately after fire, whereas small mammals were generally less active on burnt edges for up to 3 years. Species were not following patterns of temporal change in vegetation structure, with high usage during times of reduced understorey complexity and low usage when complexity was high. This suggests that habitat change is not a good predictor of animal use at fire edges and that other important processes are likely occurring. For example, foxes and cats were using the burnt side of edges immediately after fire, which may have important implications for the long- term persistence of native fauna if changes in habitat structure at fire edges cause predation rates to increase. In Chapter 4 I assessed the trade-off between deploying more detection units or extending the length of the sampling period on two frequently assessed variables in camera trapping studies – iii species richness and detection probability. The trade-off between these two factors is expected to affect data quality, but there is little information about their relative influence. I examined the trade-off between increasing deployment time or increasing the number of detection units on species richness and detectability (Chapter 4). I found that that increasing the number of cameras deployed per site was an effective method for increasing the detection of ground-dwelling mammals. Multiple cameras and longer deployment times were necessary to detect a high proportion of species present. Increasing the number of cameras or increasing deployment length resulted in high overall detectability for the more detectable species, but multiple cameras were required to achieve high detectability in a reasonable time frame (<50 days) for less detectable species. In Chapter 5 I investigated resource selection of a semi-arboreal mammal eight years after a major wildfire using GPS telemetry. Survival and persistence of animals after fire is largely driven by the abundance and distribution of remaining resources and the rate at which key habitat components regenerate or re-accumulate. I found that resource selection for the mountain brushtail possum (Trichosurus cunninghami) often depended on the sex of the animal and forest type, suggesting that considering spatial changes in resource availability and demographic class may be necessary to accurately determine patterns of resource selection after a major wildfire. This thesis adds to the body of knowledge on the ecological importance of fire edges and their implications for fauna, while providing several important conceptual and methodological advances in the study of ecology. Edges are pervasive and important environmental features that require further attention. Mechanistic approaches based on the strength of habitat associations and resource availability may help to clarify the nature and strength of edge effects in fire-prone landscapes and improve predictive models. A better understanding of fire edges will enable land managers to integrate the needs of biodiversity in to future fire management planning. iv DECLARATION This is to certify that: I. The thesis comprises only my original work towards the PhD except where indicated in the preface. II. Due acknowledgement has been made in the text to all other material used. III. The thesis is fewer than 100,000 words in length, exclusive of tables, maps, bibliographies and appendices. Kate Parkins June 2018 v PREFACE This thesis comprises four papers that present my PhD research (Chapters 2 - 5). The General Introduction (Chapter 1) outlines the key concepts and themes underlying the research. The Synthesis (Chapter 6) summarises key results, discusses implications for management and highlights areas for future research. The data chapters have been prepared as stand-alone papers for publication in collaboration with co-authors. One of the chapters has been published (Chapter 2), and two are in preparation (Chapters 3 & 4). As such, this thesis does not contain a chapter describing the study area, study species and common methods. There is also some overlap in chapter content particularly with regards to descriptions of study areas. The pronoun ‘we’ is used instead of ‘I’ in recognition of the co-authors’ contributions. A comprehensive review of relevant literature is provided in Chapter 2. Some assistance was provided by an electronics engineer (Kean Maizels) with the development and construction of the circuit boards used in the GPS collars as part of Chapter 5. Field work was conducted under the National Parks Act (Research Permit Number 10007387). Faunal surveys were conducted with ethics approval from the University of Melbourne Animal Ethics Committee (Research Permit Numbers 1413324 and 1513673). The chapters, co-authors and my contributions are as follows: vi Thesis Manuscript title My contribution chapter Chapter 2 Parkins K, York A, Di Stefano J. (2018) Edge effects in K Parkins 80% fire-prone landscapes: ecological importance and implications for fauna. Ecol Evol. 00:1-12. http://doi.org/10.1002/ece3.4076 Contributions: KP, JD and AY conceived the ideas and developed the structure. KP led the writing of the manuscript with editorial guidance from JD and AY. Chapter 3 Parkins K, Scott A, Swan M, Sitters H, Di Stefano J, York K Parkins 70% A. (In prep). Habitat use at fire edges: Do animals follow temporal patterns of habitat change? Contributions: KP led the fieldwork, with assistance from AS, MS, HS and JD. KP analysed the data with assistance from JD. KP wrote the manuscript with editorial assistance from JD, AY, HS, MS. Chapter 4 Parkins K, Penman T, Di Stefano J, York A. (In prep). K Parkins 80% Increasing detectability in camera trap surveys: more cameras, more days, or both? Contributions: KP, JD, AY conceived and designed the study. KP conducted the fieldwork, with assistance from AS, MS, HS and JD. KP analysed the data with assistance from TP and JD. KP wrote the manuscript with editorial assistance from JD, AY and TP. Chapter 5 Parkins K, Maizels K, Di Stefano J, York A. The devil is in K Parkins 85% the detail: Forest type and sex influence post-fire resource selection in a semi-arboreal mammal. Contributions: KP, JD, AY conceived and designed the study. KM assisted with the design and construction of the GPS devices. KP conducted the fieldwork, with assistance from JD and volunteers. KP analysed the data with assistance from JD and Bronwyn Hradsky. KP wrote the manuscript with editorial assistance from JD and AY. vii I contributed to the following manuscript during my candidature: Fischer M, Parkins K, Maizels K. J, Sutherland D. R, Allan B. M, Coulson G, Di Stefano J. (2018) Biotelemetry marches on: A cost-effective GPS device for monitoring terrestrial wildlife. PLoS One, 13, e0199617 I also prepared a manuscript during my candidature relating to research conducted prior to my PhD: Parkins K, Moloney P, Cheers G, MacHunter J. (In prep). Powerful owls in a peri-urban environment: testing habitat suitability models and detectability. The theses of the two Masters students who worked on collaborative projects are: Scott A. (2015). Edge effects in fire-prone landscapes: Influence of species traits and resource distribution on ground-dwelling mammal responses to fire edges. Masters thesis. University of Melbourne. Langmaid K. (2017). Fire severity and vegetation diversity interact to influence range size in the mountain brushtail possum Trichosurus Cunninghami. Masters thesis. University of Melbourne.