Action Oak Knowledge Review An assessment of the current evidence on oak health, identification of evidence gaps and prioritisation of research needs May 2019 Christopher Quine, Nick Atkinson, Sandra Denman, Marie- Laure Desprez-Loustau, Robert Jackson, Keith Kirby Acknowledgements The Panel would like to thank all those involved in drawing together knowledge for this review against a very tight timetable – contributors are listed on the following page and at the start of each chapter. Claire Holmes provided comprehensive support. We are also grateful to Defra for financial support, for reviewers who provided comments which honed the content, and to the many stakeholders who provided insights and knowledge along the way. Please cite this publication as - Quine, C.P., Atkinson, N., Denman, S., Desprez-Loustau, M-L., Jackson, R., Kirby, K. (eds) 2019. Action Oak Knowledge review: an assessment of the current evidence on oak health in the UK, identification of evidence gaps and prioritisation of research needs. Action Oak, Haslemere, UK. ISBN 978-1-5272-4193-0 Version number: 1.2 Date: May 2019 ii Contributors Editorial Panel Nick Atkinson Marie-Laure Desprez-Loustau Keith Kirby Woodland Trust INRA, Bordeaux Oxford University Sandra Denman Robert Jackson Chris Quine Forest Research University of Reading Forest Research Authors Bianca Ambrose-Oji Peter Crow James McDonald Forest Research Forest Research Bangor University Frank Ashwood Ben Ditchburn Ruth Mitchell Forest Research Forest Research James Hutton Institute Nadia Barsoum David Edwards Jake Morris Forest Research Forest Research Defra Sue Benham Alison Dyke Liz O’Brien Forest Research SEI, York University Forest Research Martin Bidartondo Hilary Geoghegan Richard O’Hanlon Imperial College London Reading University Agri-Food & Biosciences Inst. Mike Birkett Robin Gill Ana Perez-Sierra Rothamsted Research Forest Research Forest Research Emma Bonham Clare Hall Suzanne Perry Harper Adams University Forest Research Natural England Samantha Broadmedow Jeanette Hall Michael Petr Forest Research Scottish Natural Heritage Forest Research Alice Broome Daegan Inward Katy Reed Forest Research Forest Research Forest Research Nathan Brown Mike Jeger Laura Suz Rothamsted Research Imperial College, London Royal Botanic Gardens Kew Paul Brown Anparasy Kajamuhan Julie Urquhart Fera Forest Research Gloucester University Joan Cottrell Gary Kerr Elena Vanguelova Forest Research Forest Research Forest Research Rob Coventry Mariella Marzano Jozsef Vuts Forest Research Forest Research Rothamsted Research Bridget Crampton Bangor University iii Executive Summary Oak is a much-loved and essential component of British landscapes in settings from woodlands to urban parks. There are concerns over its health and prospects for the future given a growing range of threats. A knowledge review was commissioned to identify what is known and not known about oak health. In particular, the evidence relating to the two native oak species in the British landscape, Quercus robur and Q. petraea, the functions performed and threats faced, and the interactions with a range of social, economic and environmental factors. The aim is to provide a framework to prioritise future research on these native oak species in the UK. Teams of authors, 41 in all from institutes in Britain and abroad, reviewed relevant published literature and consulted with stakeholders to ascertain the state of expert knowledge. Findings are summarised in ten main chapters which focus on a particular topic (e.g. pests; diseases; monitoring), provide relevant sources and references, and identifiy specific gaps in the knowledge. A panel of six senior scientists reviewed the findings, reflected on the broader knowledge requirements and incorporated them into a broad conceptual framework. Six grand challenges emerged from the synthesis of the topics that provide a focus for future research, integrating the contribution of many disciplines. These are -: 1. Securing long-term commitment - Tackle the dearth of long-term records through a renewed commitment to existing monitoring, trials and sustained commitment to exploration of new methods. 2. Understanding oak demography and its dynamics - Tackle the lack of understanding of demography, especially in non-woodland settings. 3. Uncovering the functioning of tree systems - Tackle the lack of holistic studies of oak health (and that of other tree species) 4. Profiling the threats - Tackle uncertainty over the magnitude of the future health problem from pests and diseases, those already in Britain and those yet to arrive, to understand the single and compound nature of threats. 5. Fostering management and engagement - Tackle the lack of management of (oak) woodlands and lack of engagement of owners and publics in tree health. 6. Establishing the nature of interactions and complexity - Tackle the inherently complex and uncertain nature of the health problems associated with oak. iv Contents Page Acknowledgements ii Contributors iii Executive summary iv Chapter 1 Oak Health Knowledge Review 1 Introduction and Synthesis 2 Environmental factors stressing oak trees 17 2.1 Oak health and functional diversity of mycorrhizas 25 3 Pest threats to UK oak health 39 4 Pathogen threats to native oaks in the UK 65 5 Oak health and biodiversity 95 6 Fundamental knowledge of genetics and implications for health of oak trees 117 7 Monitoring oak health 141 8 Land managers and publics: knowledge, attitudes and actions associated 159 with threats to oak trees 9 Management of oak tree health 175 10 Semiochemical-based strategies 189 Figures 1.1 Oak health conceptual framework. 6 2.1 Distribution of published relevant research in the UK across the main 30 environmental factors, expressed as percentage of total number of publications consulted in this review. 2.2 Distribution of published relevant studies in the UK across main research and 30 experimental approaches, expressed as percentage of total number of publications consulted in this review. 2.3 Number of publications (hits) on Web of Science using different search terms 31 for oak declines. v 5.1 Impacts of biodiversity under five alternative oak futures produced under 104 current drivers of change for high forest oak ecosystems. 5.2 Impacts on biodiversity under five alternative oak futures produced under 105 current drivers of change for open oak ecosystems. 7.1 Distribution of historic (1987-2007) Forest Condition Survey (FCS) oak plots 151 and their status in 2018. 84 sites have been revisited and monitoring could continue at these sites. 9.1 Schematic stages of stand development following major disturbances. 180 Tables 1.1 Chapter structure of knowledge review. 7 1.2 Terminology relating to weight of evidence. 8 1.3 Glossary of terms. 8 1.4 Summary of prominence of oak in Britain 9 1.5 Main chapter specific knowledge gaps. 11 1.6 Interactions contributing to oak health. 13 1.7 Six grand challenges for oak health derived from the knowledge review. 14 2.1 Type and form of N deposition and associated risk areas. 31 2.2 Search terms used in database. 32 3.1 Native and established insect pests of oak trees in the UK. 50 3.2 Non-native insects posing a potential future risk to oak health in the UK. 55 4.1 Diagnosis of oak damage: Biotic causes – Disease: number of reports from 81 1972 – 2017 to Forest Research Tree Health Advisory Service. 4.2 Priority diseases currently causing significant or regular damage to oak and 82 potential future threats to oak trees in the UK. 5.1 Impacts on biodiversity under five alternative oak futures produced under 106 current drivers of change for high forest oak ecosystems. 5.2 Impacts on biodiversity under five alternative oak futures produced under 108 current drivers of change for open oak ecosystems. 6.1 The main oak provenance trial series located in Britain and elsewhere along 133 with details of the total number of provenances, number of British provenances, number of sites, site locations, traits assessed and main findings. 6.2 List of oak plus trees and their origin according to country and seed zone. 134 6.3 List of trial sites along with the number of half-sib families, number of plants 135 per family, total number of plants planted and number of plants remaining in 2007. 7.1 Summary of available survey information. 152 7.2 Summary of priority research areas currently being investigated for Action 153 Oak. 9.1 Summary of selected studies on subject of pesticides. 181 9.2 Assessment of weight of evidence for main conclusions in the review. 182 vi Action Oak - Knowledge Review 1. Oak Health Knowledge Review – Introduction and Synthesis Christopher Quine, Nick Atkinson, Sandra Denman, Marie-Laure Desprez- Loustau, Robert Jackson, Keith Kirby Introduction and scope of the Knowledge Review Context Oak (Quercus robur and Q. petraea) has a special place in the public consciousness, in British culture, and contributes to environmental stability, the woodland economy and biodiversity. It is the most common broadleaf tree species in Britain, supports more species and stores more carbon than any other native tree. In general oaks are regarded as robust and well adapted to a range of environmental conditions, but both these species are subject to a range of pests and diseases and are now facing many other pressures, such as increased air and soil pollutants, environmental pressures, and changing climate patterns with extreme weather events. Concern about the health of oaks has been heightened by people’s memories of Dutch elm disease, and by the recent arrival of ash dieback emphasising the risks of new introductions. This report confirms that the concern about oak health is justified and proposes what could be done to obtain the knowledge necessary to address these issues. The Action Oak public/private partnership is a new initiative to protect and improve the UK’s oak trees – acknowledging their iconic and important role and responding to concerns over multiple threats to their health. The knowledge review was commissioned by Defra on behalf of the partnership to establish a baseline against which new knowledge is gained and proposals for new research are assessed.