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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

Anmerkung: Table of contents Abstract Zusammenfassung Abbreviations and Nomenclature 1. Introduction 1.1 Scientific Background 1.1.1 Climate and Permafrost 1.1.2 Remote Sensing 1.1.3 Research Questions 1.2 General Approach 1.3 Thesis Structure 1.4 Author’ s contributions 1.4.1 Chapter 2 1.4.2 Chapter 3 1.4.3 Chapter 4 1.4.4 Chapter 5 1.4.5 Appendix Paper 1 2. Detection of landscape dynamics in the Arctic Lena Delta withtemporally dense Landsat time-series Stacks 2.1 Abstract 2.2 Introduction 2.3 Study Area and Data 2.3.1 Study Area 2.3.2 Data 2.3.3 Methods/processing 2.4 Results 2.4.1 Regional Scale changes 2.4.2 Local scale changes 2.5 Discussion 2.5.1 Regional scale changes 2.5.2 Local scale changes 2.5.3 Data quality 2.5.4 Data usage and outlook 2.6 Conclusion 2.7 Data Archive 2.8 Acknowledgements 2.9 Appendix A. Supplementary Data 3. Landsat-Based Trend Analysis of Lake Dynamics across NorthernPermafrost Regions 3.1 Abstract 3.2 Introduction 3.3 Study Sites 3.3.1 Alaska North Slope (NSL) 3.3.2 Alaska Kobuk-Selawik Lowlands (AKS) 3.3.3 Central Yakutia (CYA) 3.3.4 Kolyma Lowland (KOL) 3.4 Data and Methods 3.4.1 Data and Trend Analysis 3.4.2 Pixel-Based Machine-Leaming Classification 3.4.3 Object-Based Image Analysis 3.4.4 Data Quality and Post-Processing 3.4.5 Calculation of Lake Change Statistics 3.5 Results 3.5.1 NSL (Alaska North Slope) 3.5.2 AKS (Alaska Kobuk-Selawik Lowlands) 3.5.3 CYA (Central Yakutia) 3.5.4 KOL (Kolyma Lowland) 3.6 Discussion 3.6.1 Data Analysis 3.6.2 Comparison of Sites and Prior Studies 3.7 Conclusions 3.8 Supplementary Materials 3.9 Acknowledgements 3.10 Appendix A 4. Remotely sensing recent permafrost region disturbances across Arcticto Subarctic transects 4.1 Abstract 4.2 Introduction 4.3 Results 4.3.1 Lakes 4.3.2 Retrogressive Thaw Slumps 4.3.3 Wildfire 4.4 Discussion 4.5 Methods 4.5.1 Remote Sensing Data Processing 4.5.2 Auxiliary Data Sources 5. Tundra landform and Vegetation productivity trend maps for theArctic Coastal Plain of northern Alaska 5.1 Abstract 5.2 Background & Summary 5.3 Methods 5.3.1 Polygonal tundra geomorphology mapping 5.3.2 Image processing 5.3.3 Image Classification 5.3.4 Decadal scale NDVI trend analysis 5.4 Data Records 5.5 Technical Validation 5.5.1 Tundra Geomorphology Map 5.5.2 NDVI Trend Map 5.6 Data Citation 6. Discussion/Synthesis 6.1 Landsat-based trend analysis 6.1.1 Spatial Scale 6.1.2 Time series analysis 6.1.3 Model complexity 6.2 Mapping of permafrost landscape dynamics 6.2.1 Lake dynamics 6.2.2 Wildfire 6.2.3 Retrogressive Thaw Slumps 6.3 Pan-arctic scale distribution and consequences of changes inpermafrost 6.4 Outlook Bibliography A-1. Appendix: Reduced arctic tundra productivity linked with landform and climate change interactions A-1.1 Abstract A-1.2 Introduction A-1.3 Methods A-1.4 Results A-1.5 Discussion Danksagung/Acknowledgements Eidesstattliche Erklärung

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: Table of contents Abstract Zusammenfassung 1 Motivation 2 Introduction 2.1 Arctic climate changes and their impacts on Coastal processes 2.2 Shoreline retreat along Arctic coasts 2.3 Impacts of Coastal erosion 2.3.1 Material fluxes 2.3.2 Retrogressive thaw slumps 2.3.3 Socio-economic impacts 2.4 Objectives 2.5 Study area 2.6 Thesis structure 2.7 Authors’ contributions 3 Variability in rates of Coastal change along the Yukon coast, 1951 to 2015 3.1 Introduction 3.2 Study Area 3.3 Data and Methods 3.3.1 Remote sensing data 3.3.2 Field survey data 3.3.3 Classification of shoreline 3.3.4 Transect-wise analyses of shoreline movements through time 3.4 Results 3.4.1 Temporal variations in shoreline change rates 3.4.2 Alongshore rates of change 3.4.3 Shoreline dynamics along field sites 3.4.4 Dynamics of lagoons, barrier Islands and spits (gravel features) 3.4.5 Yukon Territory land loss 3.5 Discussion 3.5.1 Temporal variations in shoreline change rates 3.5.2 Alongshore rates of change 3.5.3 Dynamics of lagoons, barrier Islands, and spits (gravel features) 3.5.4 Expected shoreline changes as a consequence of future climate warming 3.6 Conclusions Context 4 Coastal erosion of permafrost Solls along the Yukon Coastal Plain and Kuxes oforganic carbon to the Canadian Beaufort Sea 4.1 Introduction 4.2 Study Area 4.3 Methods 4.3.1 Sample collection and laboratory analyses 4.3.2 Soll organic carbon determinations 4.3.3 Flux of organic soil carbon and Sediments 4.3.4 Fate of the eroded soil organic carbon 4.4 Results 4.4.1 Ground lce 4.4.2 Organic carbon contents 4.4.3 Material fluxes 4.5 Discussion 4.5.1 Ground lce 4.5.2 Organic carbon contents 4.5.3 Material fluxes 4.5.4 Organic carbon in nearshore Sediments 4.6 Conclusion Context 5 Terrain Controls on the occurrence of Coastal retrogressive thaw slumpsalong the Yukon Coast, Canada 5.1 Introduction 5.2 Study Area 5.3 Methods 5.3.1 Mapping of RTSs and landform Classification 5.3.2 Environmental variables 5.3.3 Univariate regression trees 5.4 Results 5.4.1 Characteristics of RTS along the coast 5.4.2 Density and areal coverage od RTSs along the Yukon Coast 5.5 Discussion 5.5.1 Characteristics and distribution of RTSs along the Yukon Coast 5.5.2 Terrain factors explaining RTS occurrence 5.5.3 Coastal processes 5.6 Conclusions Context 6 Impacts of past and fiiture Coastal changes on the Yukon coast - threats forcultural sites, infrastructure and travel routes 6.1 Introduction 6.2 Study Area 6.3 Methods 6.3.1 Data for shoreline projections 6.3.2 Shoreline projection for the conservative scenario (S1) 6.3.3 Shoreline Projection for the dynamic scenario (S2) 6.3.4 Positioning and characterizing of cultural sites 6.3.5 Calculation of losses under the S1 and S2 scenarios 6.3.6 Estimation of future dynamics in very dynamic areas 6.4 Results and discussion 6.4.1 Past and future shoreline change rates 6.4.2 Cultural sites 6.4.3 Infrastructure and travel routes 6.5 Conclusions 7 Discussion 7.1 The importance of understanding climatic drivers of Coastal changes 7.2 The influence of shoreline change rates on retrogressive thaw slump activity 7.3 On the calculation of carbon fluxes from Coastal erosion along the Yukon coast 7.4 Impacts of present and future Coastal erosion on the natural and human environment 7.5 Synthesis 8 Summary and Conclusions Bibliography Supporting Material Data Set ds01 Table S1 Table S3 Abbreviations and Nomendature Acknowledgements