ALBERT

Anmerkung: Table of contents Abstract Zusammenfassung Abbreviations and nomenclatureI 1. Introduction 1.1 Scientific background 1.1.1 Permafrost and ground ice 1.1.2 Organic carbon pools and fluxes into the Arctic Ocean 1.1.3 Climate warming and permafrost thaw 1.1.4 Permafrost degradation and coastal erosion 1.1.5 Study area Yukon coast and Qikiqtaruk 1.2 Knowledge gaps 1.3 Aims and objectives 1.4 Thesis structure and author's contribution 2. Eroding permafrost coasts release low amounts of dissolved organic carbon (DOC) from ground ice into the nearshore zone of the Arctic Ocean 2.1 Abstract 2.2 Introduction 2.3 Study area 2.4 Methods 2.4.1 Field work 2.4.2 DOC concentration 2.4.3 DOC flux estimation 2.5 Results 2.5.1 Segmentation of the coast - literature synthesis 2.5.2 DOC concentration 2.5.3 DOC stocks and fluxes 2.6 Discussion 2.6.1 DOC concentrations in ground ice 2.6.2 DOC fluxes from the YC 2.6.3 DOC fluxes and the Arctic carbon budget 2.7 Conclusion and Outlook 2.8 Acknowledgements 3.Transformation of terrestrial organic matter along thermokarst-affected permafrost coasts in the Arctic 3.1 Abstract 3.2 Introduction 3.3 Study area 3.3 Methods 3.3.1 Field work 3.3.2 Sedimentology, stratigraphy, and vegetation 3.3.3 Organic matter 3.3.4 Statistics 3.3.5 Transformation of organic matter 3.3.6 Fate of organic matter in the nearshore zone 3.4 Results 3.4.1 Sedimentology, stratigraphy, and vegetation 3.4.2 Organic matter 3.4.3 C/N-ratios and δ13C 3.4.4 Biomarkers 3.5 Discussion 3.5.1 Transformation of organic matter in the disturbed zone 3.5.2 Fate of organic matter in the nearshore zone 3.5.3 Environmental impact of the RTS 3.6 Conclusion 3.7 Acknowledgements 4. Rapid greenhouse gas release from eroding permafrost coasts 4.1 Summary 4.2 Background 4.3 Study site 4.4 Sampling and incubation setup 4.5 Findings and discussion 4.6 Conclusion 4.7 Methods 4.7.1 Incubation conditions 4.7.2 Gas measurements 4.7.3 Geo- and hydrochemical analysis 4.8 Acknowledgements 5. Synthesis 5.1 Mobilization of permafrost OC pools by coastal erosion 5.2 Transformation of permafrost OM on transit from land to sea 5.3 Fate and pathways of permafrost OC in the nearshore zone 5.4 Conclusion and outlook References Appendix I: Dissolved organic carbon (DOC) in Arctic ground ice I-1 Abstract I-2 Introduction I-3 Study area and study sites I-4 Material and methods I-4-1 Laboratory analyses I-4-2 Statistical methods I-5 Results I-5-1 DOC and DIC concentrations I-5-2 Correlation matrix I-5-3 Principal components I-5-4 Univariate Tree Model (UTM) I-6 Discussion I-6-1 DOC stocks in ground ice and relevance to carbon cycling I-6-2 Carbon sequestration and origin in relation to inorganic geochemistry I-6-3 DOC mobility and quality upon permafrost degradation I-7 Conclusions and outlook I-8 Acknowledgements Appendix II: Supplementary material for Chapter 2 II-1 Supplementary table - Ground ice and geochemical data II-2 Supplementary table - Coastal segments and DOC flux Appendix III: Supplementary material for Chapter 3 III-1 Normalized Differenced Vegetation Index map III-2 Photograph of a massive ice bed in a RTS III-3 Calculation of biomarker proxies III-4 Supplementary table - Summary of geochemical data III-5 Supplementary table - Summary of statistical analysis AppendixI V: Supplementary material for Chapter 4 IV-1 Design of the incubation experiment IV-2 Photograph of a standard incubation setup IV-3 Conversion of gas amounts into mass IV-4 Total and daily aerobic CH4 production IV-5 Histogram summarizing OC losses and CO2 emissions IV-6 Supplementary table - Summary of TOC, DOC, and pH data IV-7 Supplementary table - Summary of TN, TOC/TN, and δ13C-TOC data IV-8 Supplementary table - Summary of total CO2 and CH4 production data IV-9 Supplementary table - Comparison of incubation setups IV-10 Supplementary table - Summary of daily CO2 production data IV-11 Supplementary table - Summary of daily CH4 production data Acknowledgements-Danksagung

Anmerkung: Contents Summary 1. Introduction 1.1 Background 1.1.1 Precipitation changes 1.1.2 Large-scale atmospheric patterns 1.2 Objectives and research questions 1.3 Thesis outline and author contribution High spatial and temporal organization of changes inprecipitation over Germany for 1951–2006 2.1 Introduction 2.2 Data 2.3 Methods 2.3.1 Threshold between wet and dry days 2.3.2 Derivation of time series of precipitation characteristics 2.3.3 Trend analyses under consideration of temporal and spatial correlation 2.3.4 Visualization of results 2.4 Results and discussion 2.4.1 Changes in total precipitation 2.4.2 Changes in mean, variability, and heavy precipitation indicators 2.4.3 Transition probabilities 2.4.4 Seven-day precipitation amount with return period 100 years 2.5 Conclusions Can local climate variability be explained by weatherpatterns? A multi-station evaluation for the Rhine basin 3.1 Introduction 3.2 Data 3.3 Methods 3.3.1 Weather pattern classification 3.3.2 Finding optimal classification parameters 3.3.3 Evaluation of classifications 3.4 Results 3.4.1 Stratification of local climate variables 3.4.2 Performance of GCMs 3.5 Discussion 3.5.1 On the optimal classification 3.5.2 On the skill of GCMs 3.6 Conclusions 3.7 Data availability 3.A Appendix Do changing weather types explain observed climatictrends in the Rhine basin? An analysis of within andbetween-type changes 4.1 Introduction 4.2 Data and weather pattern classification 4.3 Methods 4.3.1 Relationship of WPs and large-scale circulation modes 4.3.2 Trend detection methods 4.3.3 Relative share of between- and within-type changes 4.4 Results 4.4.1 Attribution of WPs to large-scale circulation modes 4.4. 2Between-Type Changes 4.4.3 Within-Type Changes 4.4.4 Relative share of between- and within-type changes 4.5 Discussion and conclusions 4.A Appendix 4.S Supplementary Discussion and conclusions 5.1 Main results 5.2 Discussion and directions for further research 5.2.1 Weather pattern classification for downscaling 5.2.2 Limitations for downscaling 5.3 Concluding remarks Bibliography

Anmerkung: 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