GÖTTINGER ZENTRUM FÜR BIODIVERSITÄTSFORSCHUNG UND ÖKOLOGIE - GÖTTINGEN CENTRE FOR BIODIVERSITY AND ECOLOGY - Interacting effects of forest edge, tree diversity and forest stratum on the diversity of plants and arthropods in Germany’s largest deciduous forest Dissertation zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultäten der Georg-August-Universität Göttingen vorgelegt von M.Sc. Claudia Normann aus Düsseldorf Göttingen, März 2015 1. Referent: Prof. Dr. Teja Tscharntke 2. Korreferent: Prof. Dr. Stefan Vidal Tag der mündlichen Prüfung: 27.04.2015 TABLE OF CONTENTS TABLE OF CONTENTS CHAPTER 1 GENERAL INTRODUCTION ................................................................................. - 7 - Introduction ....................................................................................................................... - 8 - Study region ..................................................................................................................... - 10 - Chapter outline ................................................................................................................ - 15 - References ....................................................................................................................... - 18 - CHAPTER 2 HOW FOREST EDGE–CENTER TRANSITIONS IN THE HERB LAYER INTERACT WITH BEECH DOMINANCE VERSUS TREE DIVERSITY ....................................................... - 23 - Abstract ............................................................................................................................ - 24 - Keywords ......................................................................................................................... - 24 - Introduction ..................................................................................................................... - 25 - Material and Methods ...................................................................................................... - 27 - Results ............................................................................................................................. - 31 - Discussion ........................................................................................................................ - 37 - Conclusions ..................................................................................................................... - 39 - Acknowledgements ......................................................................................................... - 40 - References ....................................................................................................................... - 41 - Appendix ......................................................................................................................... - 46 - CHAPTER 3 TREE DIVERSITY AND SPECIES’ TRAITS MODERATE FOREST EDGE RESPONSES OF GROUND-DWELLING BEETLES AND SPIDERS ........................................................................ - 65 - Abstract ............................................................................................................................ - 66 - Keywords ......................................................................................................................... - 66 - Introduction ..................................................................................................................... - 67 - Material and Methods ...................................................................................................... - 69 - Results ............................................................................................................................. - 74 - Discussion ........................................................................................................................ - 79 - Conclusions ..................................................................................................................... - 83 - Acknowledgements ......................................................................................................... - 84 - References ....................................................................................................................... - 85 - Appendix ......................................................................................................................... - 92 - CHAPTER 4 INTERACTING EFFECTS OF FOREST STRATUM, EDGE AND TREE DIVERSITY ON BEETLES ............................................................................................................................. - 101 - Abstract .......................................................................................................................... - 102 - Keywords ....................................................................................................................... - 102 - Introduction ................................................................................................................... - 103 - Methods ......................................................................................................................... - 105 - Results ........................................................................................................................... - 110 - Discussion ...................................................................................................................... - 116 - Conclusions ................................................................................................................... - 120 - Acknowledgements ....................................................................................................... - 120 - References ..................................................................................................................... - 122 - Appendix ....................................................................................................................... - 130 - I TABLE OF CONTENTS SUMMARY........................................................................................................................... - 147 - ZUSAMMENFASSUNG .......................................................................................................... - 153 - ACKNOWLEDGEMENTS/DANKSAGUNG ............................................................................. - 157 - PUBLICATIONS ................................................................................................................... - 159 - CURRICULUM VITAE .......................................................................................................... - 161 - THESIS DECLARATION ....................................................................................................... - 163 - II CHAPTER 1 GENERAL INTRODUCTION - 7 - CHAPTER 1 Introduction Worldwide, forests are under pressure through global change. Since the climate of the Northern Hemisphere is predicted to become drier and warmer in the future (IPCC, 2007), current forest management schemes aim at converting mono-specific forest stands into structurally more diverse forests with a higher abundance and diversity of native deciduous tree species (Brang et al., 2008; Kolström et al., 2011; Pretzsch et al., 2013; Schmitz et al., 2014). The goal of this is not only to reduce the susceptibility of forests to climate change and pests („Insurance-Hypothesis“ (Yachi & Loreau, 1999)) but also to preserve overall biodiversity (Fritz, 2006). This last goal is embedded in the convention on biological diversity (Rio, 1992) (BMU, 2010). Yet, evidence for overall positive effects of increased tree diversity on biodiversity in temperate forests is scarce. Studies on tree diversity effects so far provide opposing results across study regions and taxa (Vehviläinen et al., 2007; Sobek et al., 2009a, 2009c; Schuldt et al., 2010; Scherber et al., 2014). Another aspect of global change and a major threat to biodiversity is the increasing fragmentation of habitats (Fahrig, 2003). Once covering the major part of the land surface (Ellenberg & Leuschner, 2010), today forests constitute only one third of the total area of Germany (Schmitz et al., 2014) and primeval forests completely vanished. As a result, in Central Europe and globally forests are highly fragmented (Harper et al., 2005). Forest fragmentation is accompanied by an increase in forest edge zones. Edge effects can strongly alter environmental conditions and resource distribution in forest remnants and affect species invasion from the matrix (surrounding habitat), community composition and biotic interactions (Murcia, 1995; Ries et al., 2004). Thus, small fragments are exposed to the risk of not holding an “interior zone/habitat” anymore - to the detriment of species relying on inner forest conditions (Laurance & Yensen, 1991; Bender et al., 1998; Tscharntke et al., 2012). Therefore, from a conservation perspective it is important to assess not only depth and strength that edge effects penetrate into forests, but also where they occur, where they do not occur and which species are affected (Ries & Sisk, 2010 and references therein). Edge effects are commonly believed to extend only a few meters into forests, generally not exceeding a depth of 50 m (Murcia, 1995). Hence, the majority of studies only assessed edge effects or edge vs. interior differences on small spatial scales (Duelli et al., 2002; Pohl et al., 2007; Wermelinger et al., 2007; Noreika & Kotze, 2012; Vodka & Cizek, 2013). However, evidence is increasing that edge effects can occur