ALBERT

Note: Dissertation, Universität Potsdam, 2017 , Table of Contents I. Abstract II. Deutsche Zusammenfassung 0 Challenge 1 Introduction 1.1 The treeline ecotone 1.2 Stand structure drivers in the treeline ecotone 1.3 Climate change and recent treeline changes 1.4 Methods for treeline studies 1.4.1 Overview 1.4.2 Field-based treeline studies 1.4.3 Modelling treeline dynamics 1.5 Study Area 1.6 The Siberian treeline ecotone 1.7 Larix as study Species 1.8 Objectives of this thesis 1.9 Thesis outline 1.10 Contribution of the authors 1.10.1 Manuscript!- published 1.10.2 Manuscript II - submitted 1.10.3 Manuscript III-in preparation 1.10.4 Manuscript IV-submitted 2 Manuscript I Treeline dynamics in Siberia under changing climates as inferred from an individual-based model for Larix 2.1 Abstract 2.2 Introduction 2.3 Materials and Methods 2.3.1 Reference sites 2.3.2 Description of the model LAVESI 2.3.3 The ODD-Protocol for LAVESI 2.3.4 Parameterization 2.3.5 Khatanga climate time-series 2.3.6 Sensitivity analysis 2.3.7 Model experiments 2.4 Results 2.4.1 Sensitivity analysis 2.4.2 Taymyr treeline application 2.4.3 Temperature experiments 2.5 Discussion 2.5.1 Assessment of LAVESI sensitivity 2.5.2 Larix stand simulation under the Taymyr Peninsula weather 2.5.3 Transient Larix response to hypothetical future temperature changes 2.5.4 Conclusions 2.6 Acknowledgements 3 Manuscript II Dissimilar responses of larch stands in northern Siberia to increasing temperatures - a field and simulation based study 3.1 Abstract 3.2 Introduction 3.3 Methods 3.3.1 Study area 3.3.2 Field-based approach 3.3.3 Age analyses 3.3.4 Stand structure analyses 3.3.5 Seed analyses 3.3.6 Establishment history 3.3.7 Modelling approach 3.4 Results 3.4.1 Field data 3.4.2 Simulation study 3.5 Discussion 3.5.1 Data acquisition 3.5.2 Larch-stand patterns across the Siberian treeline ecotone 3.5.3 Warming causes densification in the forest-tundra 3.5.4 Intra-specific competition inhibits densification in the closed forest 3.5.5 Recruitment limitation decelerates densification and northward expansion ofthe single-tree tundra 3.6 Conclusions 3.7 Acknowledgements 4 Manuscript III Spatial patterns and growth sensitivity of larch stands in the Taimyr Depression 4.1 Abstract 4.2 Introduction 4.3 Methods 4.3.1 Study Area 4.3.2 Field data collection 4.3.3 Spatial point patterns 4.3.4 Dendrological approach 4.4 Results 4.4.1 Spatial patterns 4.4.2 Tree growth 4.5 Discussion 4.5.1 Spatial patterns 4.5.2 Tree chronology characteristics 4.6 Conclusion 5 Manuscript IV Patterns of larch stands under different disturbance regimes in the lower Kolyma River area (Russian Far East) 5.1 Abstract 5.2 Introduction 5.3 Methods 5.3.1 Study area and field data collection 5.3.2 Site description 5.3.3 Dendrochronological approach 5.3.4 Statistical analyses 5.4 Results 5.4.1 General stand characteristics and age structure 5.4.2 Spatial patterns 5.5 Discussion 5.5.1 Fire related disturbances 5.5.2 Water-related disturbances: lake drainage, flooding, polygon development 5.5.3 Implications and conclusion 6 Synthesis and Discussion 6.1 Assessment of applied methods 6.1.1 Field-based observations: 6.1.2 Modelling 6.2 Overview of larch stand structures and spatial pattern on different spatial scales 6.2.1 Recent stand structures 6.2.2 Spatial Patterns 6.3 Stand structure drivers and treeline changes 6.3.1 Climate change 6.3.2 Disturbances 6.3.3 Autecology 6.4 Conclusion 6.5 Outlook 7 Appendix 7.1 Supplementary information for Manuscript I 7.2 Supplementary information for Manuscript II 7.2.1 Manuscript II: Appendix 1. Climatic information for the study region 7.2.2 Manuscript II: Appendix 2. Plot-specific values and krummholz appearance 7.2.3 Manuscript II: Appendix 3. Regression analysis for age data 7.2.4 Manuscript II: Appendix 4. Model description 7.3 Supplementary information for Manuscript III 7.4 Supplementary information for Manuscript IV 7.5 Supplementary information 8 References Danksagung Eidesstattliche Erklärung