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Landscape Connectivity: a Key to Effective Habitat Restoration in Lowland Agricultural Landscapes

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Landscape Connectivity: a Key to Effective Habitat Restoration in Lowland Agricultural Landscapes UNIVERSITY OF READING Landscape connectivity: a key to effective habitat restoration in lowland agricultural landscapes Grace Twiston-Davies Thesis submitted for the degree of Doctor of Philosophy School of Biological Sciences March 2014 I Abstract Landscape scale habitat restoration has the potential to reconnect habitats in fragmented landscapes. This study investigates landscape connectivity as a key to effective habitat restoration in lowland agricultural landscapes and applies these findings to transferable management recommendations. The study area is the Stonehenge World Heritage Site, UK, where landscape scale chalk grassland restoration has been implemented. Here, the ecological benefits of landscape restoration and the species, habitat and landscape characteristics that facilitate or impede the enhancement of biodiversity and landscape connectivity were investigated. Lepidoptera were used as indictors of restoration success and results showed restoration grasslands approaching the ecological conditions of the target chalk grassland habitat and increasing in biodiversity values within a decade. Restoration success is apparent for four species with a broad range of grass larval host plants (e.g. Melanargia galathea, Maniola jurtina) or with intermediate mobility (Polyommatus icarus). However, two species with specialist larval host plants and low mobility (Lysandra bellargus), are restricted to chalk grassland fragments. Studies of restoration grassland of different ages show that recent grassland restoration (1 or 2 years old) may reduce the functional isolation of chalk grassland fragments. A management experiment showed that mowing increases boundary following behaviour in two species of grassland Lepidoptera; Maniola jurtina and Zygaena filipendulae. Analysis of the landscape scale implications of the grassland restoration illustrates an increase in grassland habitat network size and in landscape connectivity, which is likely to benefit the majority of grassland associated Lepidoptera. Landscape and habitat variables can be managed to increase the success of restoration projects including the spatial targeting of receptor sites, vegetation structure and selection of seed source and management recommendations are provided that are transferrable to other species-rich grassland landscape scale restoration projects. Overall results show restoration success for some habitats and species within a decade. However, additional management is required to assist the re-colonisation of specialist species. Despite this, habitat restoration at the landscape scale can be an effective, long term approach to enhance butterfly biodiversity and landscape connectivity. II Acknowledgements I would first and foremost like to thank my supervisors, Jonathan Mitchley and Simon Mortimer. Their positivity, support and guidance has been crucial in assisting me through these challenging four years. I have especially appreciated their underlying guidance whilst giving me the independence to develop and direct my own research. For the funding that has made this research possible, I would like to thank the Natural Environment Research Council and the National Trust (CASE PhD Studentship F3776000). I would also like to thank Lynneth Brampton and David Rymer for their financial support during the final 9 months of the PhD. I would additionally like to thank the British Ecological Society and Royal Entomological Society for financial assistance to attend a training course and a conference. I would particularly like to thank Christopher Gingell and the tenant farmers at the National Trust Stonehenge Landscape; Rob Turner, Hugh Morrison, Billy King and Phillip Sawkill for their invaluable practical assistance, cooperation and advice. I would also like to thank the current and former staff and volunteers of the Stonehenge Landscape, mainly Lucy Evershed, Carole Slater, Ben Cooke, Ramona Iacoban and Katherine Snell for their help and humour which made for an enjoyable and eventful three years of field work. I would like to also thank Rangers Mike Dando and Clive Whitbourn for their cooperation. On a personal note, I would like to thank my current and former fellow PhD students who have provided friendship and support. In particular I would like to thank Mel Orros, Heather Campbell and Becky Thomas who have been invaluable in providing support through the creation and consumption of baked goods. I would especially like to thank David Rymer for his unfaltering love and patience through the last two and a half years that were an emotional and mental challenge. I would like to give final and special thanks to my mother, Lynneth Brampton, for her unconditional, love, support and sacrifices. I would have not made it this far without her humour, generosity and strength and I dedicate this work to her. III I acknowledge the following people for their cooperation, assistance and contributions to the following thesis chapters: Jonathan Mitchley and Simon Mortimer as my supervisors are acknowledged for their supervision and authors on the paper and book chapter included in Appendix A. Overall: the following people have helped me to expand and develop my plant identification skills; Jonathan Mitchley, Lucy Evershed, Nigel Cope and courses run by Dominic Price for the Species Recovery Trust. Advice from my supervisory committee from Graham Holloway and Simon Potts and additional advice from Christopher Gingell and Mark Fellowes. Tim Shreeve provided access to Lepidoptera ecological associations data. The previous work of MSc students has provided the botanical information for Chapter 2 and in the discussion sections; Rachel Craythorne, Hannah Campbell and Clare Pemberton. The course from the Field Studies Council on the identification of butterflies and moths of SE England and run by Ken Willmott was funded by a grant from the British Ecological Society and helped to develop my Lepidoptera identification skills. My use of ArcMap ESRI© was assisted by a course on Geographical Information Systems for Ecologists and Conservation Practitioners, by the University of Reading and run by Graham Holloway. Digital maps were from Ordnance Survey, Natural England and English Heritage and edited with the assistance of maps from the National Trust, English Heritage and Google maps. Dudley Stamp Map from EDINA. Proof reading of the Chapters were provided by Mel Orros and David Rymer. Chapter 3: advice on the statistical analysis of my data using CANOCO 5 was provided by Jan Lepš and Petr Šmilaur and moral support and discussion regarding understanding CANOCO 5 from Jess Neumann during the Multivariate Analysis of Ecological data using CANOCO course at the University of South Bohemia. Statistical advice was from the University of Reading, Statistical Advisory Service. Chapter 4: cooperation from Rob Turner, Hugh Morrison, Billy King and Phillip Sawkill in accessing the chalk grassland fragments for the survey. Chapter 5: Ben Cooke mowed the sections for the experiment in the Seven Barrows field and Ramona Icoban assisted with collecting the data for the plant surveys. The experiment fencing was set up and the removal of hay was by Hugh Morrison and Billy King. Chapter 6: access to data and advice on matrix permeability from Amy Eycott, Kevin Watts and the Forestry Commission. Lepidoptera distribution data in the wider landscape were provided from the IV Butterflies for the New Millennium recording scheme, courtesy of Butterfly Conservation and the Wilshire and Swindon Biological Records Centre. Other: the data from MSc projects by Clare Pemberton and Claire Ryan were used in the book chapter in Appendix A. Cooperation and practical assistance in fencing off an experimental area and creating enclosures for a pilot study was from Ben Cooke and Rob Turner and assistance in collecting data during the pilot study and in looking for and recording Adonis Blue (Lysandra bellargus) eggs from Ramona Iacoban. Additionally, cooperation from the MSc students who I worked alongside; Fiona Campbell, Clare Pemberton, Claire Ryan and the National Trust Rangers, Mike Dando and Clive Whitbourn. Finally I have used photos with the permission of Lucy Evershed and Nigel Cope for conference posters and presentations. Declaration I confirm that this is my own work and the use of all material from other sources has been properly and fully acknowledged. Grace Twiston-Davies, September 2014 V Contents Abstract .................................................................................................................................................. II Acknowledgements ............................................................................................................................... III Declaration ............................................................................................................................................. V Contents ................................................................................................................................................. VI Chapter 1 Introduction ........................................................................................................................... 1 1.1 Ecological networks and landscape connectivity .......................................................................... 1 1.1.1 Why we need ecological networks; habitat fragmentation and climate change .................. 1 1.1.2 What are ecological networks ..............................................................................................
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