Response of European beech to decreasing summer precipitation under global climate change Dissertation zur Erlangung des mathematisch-naturwissenschaftlichen Doktorgrades „Doctor rerum naturalium“ der Georg-August University School of Science (GAUSS) Promotionsstudiengang Biodiversität und Ökologie vorgelegt von Florian Knutzen aus Hamburg Göttingen, Juli 2016 Betreuungsausschuss und Mitglieder der Prüfungskommission Prof. Dr. Christoph Leuschner (Referent), Abteilung Pflanzenökologie und Ökosystemforschung, Georg-August-Universität Göttingen Prof. Dr. Markus Hauck (Korreferent), Abteilung Pflanzenökologie und Ökosystemforschung, Georg-August-Universität Göttingen Dr. Ina Christin Meier, Abteilung Pflanzenökologie und Ökosystemforschung, Georg-August-Universität Göttingen Weitere Mitglieder der Prüfungskommission Prof. Dr. Christian Ammer, Waldbau und Waldökologie der gemäßigten Zonen, Georg-August-Universität Göttingen Prof. Dr. Erwin Bergmeier, Abteilung Vegetationsanalyse und Phytodiversität, Georg-August-Universität Göttingen Prof. Dr. Dirk Hölscher, Abteilung Waldbau und Waldökologie der Tropen, Georg-August-Universität Göttingen Prof. Dr. Hermann Behling, Palynologie und Klimadynamik, Georg-August-Universität Göttingen Tag der mündlichen Prüfung: 16. September 2015 Table of contents Summary ................................................................................................................................ 2 1. General introduction ........................................................................................................ 3 Global warming and regional consequences .......................................................................... 4 Plant responses to changing climate ....................................................................................... 7 Forest trees under global warming ......................................................................................... 8 European beech .................................................................................................................... 11 European beech under global warming ................................................................................ 12 Main study objectives ........................................................................................................... 15 Methodological approach ..................................................................................................... 16 Study sites ............................................................................................................................ 17 Edaphic gradient ................................................................................................................... 19 References ............................................................................................................................ 22 2. Drought adaptations in young beech provenances ...................................................... 39 Abstract ................................................................................................................................ 42 Introduction .......................................................................................................................... 43 Material and methods ........................................................................................................... 47 Results .................................................................................................................................. 53 Discussion ............................................................................................................................ 62 Conclusions .......................................................................................................................... 67 Acknowledgments ................................................................................................................ 68 Conflict of interest ................................................................................................................ 68 References ............................................................................................................................ 69 Appendix .............................................................................................................................. 78 3. Climate change effects on mature Beech ...................................................................... 87 Abstract ................................................................................................................................ 88 Introduction .......................................................................................................................... 89 Material and methods ........................................................................................................... 92 Results .................................................................................................................................. 98 Discussion .......................................................................................................................... 108 Conclusions ........................................................................................................................ 112 Acknowledgements ............................................................................................................ 113 TABLE OF CONTENTS Conflict of interest .............................................................................................................. 113 References .......................................................................................................................... 114 Appendix ............................................................................................................................ 122 4. Adaptability of the hydraulic system of beech ........................................................... 127 Abstract .............................................................................................................................. 128 Introduction ........................................................................................................................ 129 Material and methods ......................................................................................................... 132 Results ................................................................................................................................ 139 Discussion .......................................................................................................................... 150 Conclusion .......................................................................................................................... 154 Acknowledgements ............................................................................................................ 155 Conflict of interest .............................................................................................................. 155 References .......................................................................................................................... 156 Appendix ............................................................................................................................ 165 5. Synopsis ......................................................................................................................... 171 Drought response of young beech trees ............................................................................. 172 Global warming-related effects on mature beech forests ................................................... 174 Hydraulic adaption potential of European beech to global warming ................................. 175 Main conclusion ................................................................................................................. 177 Future threats by global warming on European beech ....................................................... 178 Further research recommendations .................................................................................... 181 References .......................................................................................................................... 182 6. General Appendix ............................................................................................................. I Index of Figures .................................................................................................................... II Index of Tables ..................................................................................................................... VI Curriculum Vitae ............................................................................................................... VIII Danksagung .......................................................................................................................... IX Declaration of originality and certificate of ownership........................................................ XI Summary Global warming-related summer precipitation reduction represents a major threat on tree vitality and persistence and hence on forest productivity over large parts of the temperate zone. European beech (Fagus sylvatica L.) is the most important broadleaf tree species of Central Europe’s natural forest vegetation and one of the economically most important trees in Germany. Although this forest tree shows a wide tolerance toward a wide range of climatic and edaphic growing