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  • 1
    Call number: AWI G5-20-93989
    Type of Medium: Dissertations
    Pages: viii, 139 Seiten , Illustrationen, Diagramme
    Language: English
    Note: Dissertation, Universität Potsdam, 2018 , Table of Content I. Abstract II. Deutsche Zusammenfassung 0 Preface 1 Scientific Background 1.1 Paleoenvironmental changes since the gLGM in arid Central Asia and north-western High Asia 1.1.1 Paleoclimatic changes 1.1.2 Lake level fluctuations following climatic changes 1.1.3 Inferred terrestrial vegetation responses to environmental changes and possible human impact 1.2 The role of proxy records in tracing environmental changes 1.2.1 Archives and Proxies investigated in environmental studies in Central Asia 1.2.2 Limnological systems as environmental archives 1.2.3 The multiproxy approach as a tool to decipher environmental change 1.3 Study area 1.4 Material and Method Overview 1.4.1 Field based sampling 1.4.2 Outline of material and methods 1.5 Aim and objectives ofthis thesis 1.6 Thesis outline 1.7 Contribution of the authors 1.7.1 Manuscript I - published 1.7.2 Manuscript II - published 1.7.3 Manuscript III - published 1.7.4 Manuscript IV - in preparation 2 Manuscript I Climatic and limnological changes at Lake Karakul (Tajikistan) during the last ~29 cal ka 2.1 Abstract 2.2 Introduction 2.3 Study Area 2.4 Material and methods 2.4.1 Fieldwork 2.4.2 Laboratory analysis 2.5 Results 2.5.1 Age-depth relationship in core KK12-1 2.5.2 TIC, TOC, TOC/TN, δ18Ocarb and δ13CCarb 2.5.3 Grain-size distribution and results ofend-member modelling 2.5.4 XRF data 2.5.5 Ordination results of sediment parameters 2.6 Discussion 2.6.1 Paleoenvironmental indicators from sediment variables 2.6.2 Implications ofthe Lake Karakul sediment record 2.6.3 Linking lake internal development to climate change 2.7 Conclusions 2.8 Acknowledgements 2.9 Data availability 3 Manuscript II Aquatic macrophyte dynamics in Lake Karakul (Eastern Pamir) over the last 29 cal ka revealed by sedimentary ancient DNA and geochemical analyses of macrofossil remains 3.1 Abstract 3.2 Introduction 3.3 Material and Methods 3.3.1 Sample acquisition and treatment 3.3.2 Genetic approach 3.3.3 Elemental isotopic analyses ofaquatic macrophyte remains 3.4 Results 3.4.1 Macrophyte records along lake depth transects in Lake Karakul 3.4.2 Submerged plant content 3.4.3 Ancient DNA analyses 3.4.4 C, N, δ13C and δ15N of Stuckenia cf. pamirica remains 3.5 Discussion 3.5.1 Assessment of aDNA and chemical aquatic macrophyte data as proxies for the macrophyte composition and the paleo-productivity 3.5.2 Changes of past submerged plant composition and productivity and potential drivers 3.6 Conclusions 3.7 Acknowledgements 3.8 Data Availability 4 Manuscript III Radiocarbon and optical stimulated luminescence dating of sediments from Lake Karakul, Tajikistan 4.1 Abstract 4.2 Introduction 4.3 Regional setting 4.4 Methods 4.4.1 Collection and correlation of cores 4.4.2 Radiocarbon dating 4.4.3 Optically stimulated luminescence (OSL) dating 4.4.4 Establishment ofage-depth model 4.4.5 Investigation of exposed lake sediments 4.5 Results 4.6 Discussion 4.6.1 Recovered sediments and correlation ofcores from Lake Karakul 4.6.2 Age-depth model, and assessment of radiocarbon and OSL age data 4.6.3 Significance ofexposed sediments at section KK13-S1 4.6.4 Implications ofthe chronological data 4.7 Conclusion 4.8 Acknowledgements 5 Manuscript IV Vegetation change in the Eastern Pamir Mountains inferred from Lake Karakul pollen spectra of the last 28 ka 5.1 Abstract 5.2 Introduction 5.3 Study site 5.4 Material and Methods 5.4.1 Sediment cores and chronology 5.4.2 Pollen sample preparation and pollen analyses 5.4.3 Pollen data treatment 5.5 Results 5.5.1 Composite core (KK12-1/2; 27.6 cal ka BP to present) 5.5.2 Short core TAJ-Kar-08-lB 5.6 Discussion 5.6.1 Interpretation of pollen data 5.6.2 Terrestrial vegetation change in the Eastern Pamir Mountains in response to past climate change 5.7 Conclusions 5.8 Acknowledgements 5.9 Data Availability 6 Synthesis 6.1 Proxy evaluation 6.1.1 Age-depth relationship 6.1.2 Limnological proxies 6.1.3 Terrestrial proxies 6.2 The potential of Lake Karakul as archive for long term environmental change in the Eastern Pamir 6.3 Climate and moisture availability changes over time - inferred from sedimentary proxies 6.4 Assessment ofthe aquatic macrophyte composition and paleoproductivity within Lake Karakul 6.5 Inferred terrestrial vegetation changes as responds to climatic changes over the last 28 cal ka 6.6 Comparison inferred regional vegetation, lake internal and lake external variations and changes in climate reconstructed in other studies 6.6.1 Pre- gLGM and global Last Glacial Maximum (27.6 to 19 cal ka BP) 6.6.2 Late glacial 6.6.3 Early to middle Holocene 6.6.4 Middle to late Holocene 6.7 Outlook 7 Appendix 7.1 Supplementary information for Manuscript I 7.2 Supplementary information for Manuscript II 7.3 Supplementary information for Manuscript III 8 References Danksagung Eldesstattliche Erklärung
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  • 2
    Call number: AWI Bio-20-93988
    Type of Medium: Dissertations
    Pages: x, 181 Seiten , Illustrationen, Diagramme
    Language: English
    Note: Dissertation, Universität Potsdam, 2017 , Contents Abstract Kurzfassung Contents 1. List of figures 2. List of tables Chapter 1. General introduction 1. Motivation 2. Scientific background 3. Objectives of the thesis 4. Thesis outline Chapter 2. Manuscript 1: Treeline dynamics in Siberia under changing climates as inferred from an individual-based model for Larix 1. Abstract 2. Introduction 3. Material and Methods 4. Results 5. Discussion 6. Acknowledgements Chapter 3. Manuscript 2: Field and simulation data reveal dissimilar responses of Larix gmelinii stands to increasing temperature across the Siberian treeline ecotone 1. Abstract 2. Introduction 3. Methods 4. Results 5. Discussion 6. Acknowledgements Chapter 4. Manuscript 3: High gene flow and complex treeline dynamics on the Taymyr Peninsula (north-central Siberia), revealed by nuclear microsatellites of Larix 1. Abstract 2. Introduction 3. Materials and methods 4. Results 5. Discussion 6. Acknowledgements Chapter 5. Manuscript 4: Dispersal distances at treeline in Siberia - genetic guided model improvement 1. Abstract 2. Introduction 3. Methods 4. Results 5. Discussion 6. Acknowledgements Chapter 6. Synopsis 1. Towards a better understanding of Siberian treeline dynamics 2. Methodological challenges to reconstruct and predict the treeline advance 3. Conclusions 4. Outlook Appendix 1. Supplementary information for manuscript 1 (Chapter 2) 2. Supplementary information for manuscript 2 (Chapter 3) 3. Supplementary information for manuscript 3 (Chapter 4) 4. Supplementary information for manuscript 4 (Chapter 5) Bibliography Acknowledgements - Danksagung Declaration
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  • 3
    Call number: AWI Bio-20-93992
    Type of Medium: Dissertations
    Pages: XIII, 137 Seiten , Illustrationen, Diagramme , 1 CD-ROM
    Language: English
    Note: Dissertation, Universität Potsdam, 2017 , Content List of Abbreviations List of Figures List of Tables Summary Zusammenfassung Motivation Chapter 1 1. Scientific background 1.1 Late Quaternary climate changes and treeline transition in northern Siberia 1.2 Natural archives and proxies to assess vegetation history 1.3 Study area 1.3 Objectives of the thesis 1.4 Thesis outline 1.4.1 Chapters and manuscripts 1.4.2 Author's contribution 1.4.2.1 Manuscript I - published 1.4.2.2 Manuscript II - submitted 1.4.2.3 Manuscript III - prepared for submission Chapter 2 2. Manuscript I: Sedimentary ancient DNA and pollen reveal the composition of plant organic matter in Late Quaternary permafrost sediments of the Buor Khaya Peninsula (north-eastern Siberia) 2.1 Abstract 2.2 Introduction 2.3 Geographical settings 2.4 Material and methods 2.4.1 Core material 2.4.2 Subsampling of the permafrost core 2.4.3 Molecular genetic laboratory work 2.4.4 Analysis of sequence data and taxonomic assignments 2.4.5 Pollen sample treatment and analysis 2.4.6 Statistical analyses and visualization 2.5 Results 2.5.1 SedaDNA 2.5.1.1 SedaDNA of terrestrial plants 2.5.1.2 SedaDNA of swamp and aquatic plants 2.5.1.3 SedaDNA of bryophytes and algae 2.5.2 Pollen 2.5.2.1 Pollen of terrestrial plants 2.5.2.2 Pollen and spores of swamp and aquatic plants 2.5.2.3 Spores and algae 2.5.3 Ratios of terrestrial to swamp and aquatic taxa and Poaceae to Cyperaceae 2.6 Discussion 2.6.1 Quality and proxy value of sedaDNA and pollen data 2.6.2 Environmental conditions during the pre-LGM (54-51 kyr BP, 18.9-8.35 m) and composition of deposited organic matter 2.6.3 Environmental conditions during the post-LGM (11.4-9.7 kyr BP (13.4-11.1 cal kyr BP)) and composition of deposited organic matter 2.7 Conclusions 2.8 Acknowledgements Chapter 3 3. Manuscript II: Genetic variation of larches at the Siberian tundra-taiga ecotone inferred from the assembly of chloroplast genomes and mitochondrial sequences 3.1. Abstract 3.2. Introduction 3.3. Material and methods 3.3.1 Plant material 3.3.2 DNA isolation and sequencing 3.3.3 Sequence processing and de novo assembly 3.3.4 Chloroplast genome assembly, annotation and variant detection 3.3.5 Mitochondrial sequences 3.3.6 Analyses of genetic variation 3.4 Results 3.4.1 Chloroplast genome structure and genetic variation 3.4.2 Mitochondrial sequences and genetic variation 3.5 Discussion 3.5.1 De novo assembly and genetic variation of chloroplast genomes and mitochondrial sequences 3.5.2 The distribution of genetic variation at the tundra-taiga ecotone 3.6 Conclusions 3.7 Acknowledgements Chapter 4 4. Manuscript III: The history of tree and shrub taxa and past genetic variation of larches on Bol'shoy Lyakhovsky Island (New Siberian Archipelago) since the last interglacial uncovered by sedimentary ancient DNA 4.1 Abstract 4.2 Introduction 4.3 Materials and methods 4.3.1 Geographic setting 4.3.2 Core material 4.3.2.1 Core L14-02: Yedoma Ice Complex 4.3.2.2 Core L14-03: Thermo terrace 4.3.2.3 Core L14-04 and hand-pieces L14-04B and L14-04C: Thermo terrace including Eemian deposits 4.3.2.4 Core L14-05: Alas 4.3.3 Core sub-sampling 4.3.4 Molecular genetic laboratory work 4.3.4.1 Sedimentary ancient DNA metabarcoding approach 4.3.4.2 Specific amplification of Larix from sedimentary ancient DNA 4.3.5 Filtering of Illumina sequencing data and taxonomic assignments 4.3.6 Statistical analyses and visualization 4.3.7 Geochronology 4.4. Results 4.4.1 Overall composition of the DNA metabarcoding data 4.4.2 Terrestrial vegetation composition 4.4.2.1 Core L14-02: Late Pleistocene Yedoma Ice Complex 4.4.2.2 L14-03: Deeper late Pleistocene deposits 4.4.2.3 L14-04 Thermo terrace including Eemian deposits 4.4.2.4 Core L14-05: Alas with Holocene lake deposits and taberits of the Yedoma Ice Complex 4.4.2.5 The multivariate structure of the terrestrial vegetation among samples and cores 4.4.3 Genetic variation ofsediment-derived Larix sequences 4.5 Discussion 4.5.1 Tree taxa in the sedaDNA record - where do they come from? 4.5.2 Terrestrial plant community changes of warm phases since the last interglacial 4.5.3 Past genetic diversity of larch populations on Bol'shoy Lyakhovsky Island 4.6 Conclusion 4.7 Acknowledgements Chapter 5 5. Synopsis 5.1 The proxy potential of sedaDNA in paleobotanical reconstructions from sedimentary deposits 5.1.1 Combining sedaDNA and pollen to assess plant diversity and vegetation composition 5.1.2 Current limits and opportunities of sedaDNA approaches 5.2 Using genomic data to trace modern and past treeline dynamics 5.2.1 Modern genomic variation at the Siberian treeline 5.2.2 PCR-based markers for paleoenvironmental genetics 5.3 Terrestrial plant community changes and treeline dynamics in north-eastern Siberia since the last interglacial 5.3.1 Vegetation changes in north-eastern Siberia since the last interglacial 5.3.2 Implications for treeline dynamics 5.4 Conclusion 5.5 Outlook Appendix 1. Supplementary material for Manuscript I (Chapter 2) 2. Supplementary material for Manuscript II (Chapter 3) 3. Supplementary material for Manuscript III (Chapter 4) References Acknowledgements Erklärung
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  • 4
    Call number: AWI Bio-20-93993
    Type of Medium: Dissertations
    Pages: III, 127 Seiten , Illustrationen
    Language: English
    Note: Dissertation, Universität Potsdam, 2014 , Table of contents I - Abstract II - Zusammenfassung Chapter 1 - Introduction 1.1. Introduction 1.1.1 Motivation 1.1.2 Organisation of thesis 1.1 Scientific background 1.2.1 Arctic and wetland bryophytes 1.2.2 Bryophyte remains as palaeo-environmental indicators 1.2.3 Regional setting 1.3 Objectives ofthe thesis 1.4 Overview of the manuscripts 1.5 Contribution of the authors Chapter 2 - Manuscript #1 Abstract 2.1 Introduction 2.2 Geographic setting 2.3 Materials and methods 2.3.1 Fieldwork 2.3.2 Radiocarbon dating 2.3.3 Geochemical, stable carbon isotope, and granulometric analyses 2.3.4 Analyses of moss remains and vascular plant macrofossils 2.3.5 Pollen analysis 2.3.6 Diatom analysis 2.3.7 Statistical analysis 2.4 Results 2.4.1 High-resolution spatial characteristics oft the investigated polygon and vegetation pattern 2.4.2 Geochronology and age-depth relationships 2.4.3 General properties of the sedimentary fill 2.4.4 Bioindicators 2.4.5 Characterization oftwo different types of polygon pond sediment 2.5. Discussion 2.5.1 Small-scale spatial structure of polygons 2.5.2 Age-depth relationships 2.5.3 Proxy value of the analysed parameters 2.5.4 The general polygon development 2.5.5 Polygon development as a function of external controls and internal adjustment mechanisms 2.6 Conclusions Chapter 3 - Manuscript #11 Abstract 3.1 Introduction 3.2 Material und methods 3.2.1 Regional setting 3.2.3 Field methods and environmental data collection 3.2.4 Data analysis 3.3 Results 3.3.1 Major characteristics of the investigated polygons 3.3.2 Vegetation cover and its relationships with micro-relief and vegetation type 3.3.3 Vegetation alpha-diversity and its relationship with micro-relief and vegetation type 3.3.4 Vegetation composition and its relationship with micro-relief and vegetation type 3.4 Discussion 3.4.1 Patterns of cover, alpha-diversity and compositional turnover of vascular plants and bryophytes along the rim-pond transect (local-scale) 3.4.2 Patterns of cover, alpha-diversity and compositional turnover of vascular plants and bryophytes along the regional-scale forest-tundra transect 3.4.3 Indicator potential ofvascular plant and bryophyte remains from polygonal peats for the reconstruction of local hydrological and regional vegetation changes 3.4.4. Implications of the performed vegetation transect studies for future Arctic warming 3.5 Acknowledgements 2.4.4 Bioindicators 2.4.5 Characterization of two different types of polygon pond sediment 2.5. Discussion 2.5.1 Small-scale spatial structure of polygons 2.5.2 Age-depth relationships 2.5.3 Proxy value of the analysed parameters 2.5.4 The general polygon development 2.5.5 Polygon development as a function of external controls and internal adjustment mechanisms 2.6 Conclusions Chapter 3 - Manuscript #II Abstract 3.1 Introduction 3.2 Material und methods 3.2.1 Regional setting 3.2.3 Field methods and environmental data collection 3.2.4 Data analysis 3.3 Results 3.3.1 Major characteristics of the investigated polygons 3.3.2 Vegetation cover and its relationships with micro-relief and vegetation type 3.3.3 Vegetation alpha-diversity and its relationship with micro-relief and vegetation type 3.3.4 Vegetation composition and its relationship with micro-relief and vegetation type 3.4 Discussion 3.4.1 Patterns of cover, alpha-diversity and compositional turnover of vascular plants and bryophytes along the rim-pond transect (local-scale) 3.4.2 Patterns of cover, alpha-diversity and compositional turnover of vascular plants and bryophytes along the regional-scale forest-tundra transect 3.4.3 Indicator potential of vascular plant and bryophyte remains from polygonal peats for the reconstruction of local hydrological and regional vegetation changes 3.4.4. Implications of the performed vegetation transect studies for future Arctic warming 3.5 Acknowledgements Chapter 4 - Manuscript #3 Abstract 4.1 Introduction 4.2 Material and methods 4.2.1 Sites 4.2.2 Sampling 4.2.3 Investigated moss species 4.2.4 Measurements 4.2.5 Statistical Tests 4.3 Results 4.4 Discussion Chapter 5 - Discussion 5.1 Bryophytes of polygonal landscapes in Siberia 5.1.1 Modern bryophytes in the Siberian Arctic 5.1.2 Biochemical and isotopic characteristics of mosses 5.1.3 Reliability and potential of fossil bryophyte remains as palaeoproxies 5.2 Dynamics of low-centred polygons during the late Holocene 5.3 Outlook Appendix I - Preliminary Report Motivation Material and methods Results and first interpretation Appendix II Additional tables and figures of manuscript #1 Appendix III Additional figures of manuscript #2 Appendix IV - Quantitative approach of Standard Moss Stem (SMS3) Bibliography Acknowledgements Eidesstattliche Erklärung
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  • 5
    Call number: AWI Bio-20-93994
    Type of Medium: Dissertations
    Pages: viii, 140 Seiten , Illustrationen, Diagramme
    Language: English
    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
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  • 6
    Call number: ZSP-168-600
    In: Berichte zur Polar- und Meeresforschung
    Description / Table of Contents: This report summarizes activities and field work results of the joint Russian-German expedition "Lena 2009". The 11th expedition to the Lena River Delta is part of the Russian-German science cooperation "System Laptev Sea" and continues the long-term investigations of permafrost and periglacial environmentsi n Arctic Siberia. [...] The expedition took place during the period June 24 to August 26, 2009 in different regions. The study areas comprise (i) the central Lena River Delta, with the Russian German station on Samoylov as base camp (ii) a north-south transect extending from the western part of the lower Lena River into the Lena Delta (realized by helicopter) and (iii) the eastern part of the delta (realized by riverboat).
    Pages: Online-Ressource
    ISSN: 1866-3192
    Series Statement: Berichte zur Polar- und Meeresforschung 600
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  • 7
    Publication Date: 2015-03-25
    Description: The reconstruction of past temperatures with ground ice, especially with ice wedges is possible, but reduced by the missing correlation of ice veins to the exact year of their formation. Therefore, we performed recent cryogenesis tracer experiments on Samoylov Island, Northern Siberia, to calibrate a stable isotope thermometer for ice wedges. In 2002, a low centre polygon (20 m in diameter) was selected showing clearly visible (several mm wide) frost cracks and a well-developed relief between polygon wall and centre. Here, coloured Lycopodium spores, (each year a different colour) have been applied in autumn to a polygon with recent ice-wedge growth (between 2002 and 2009) to trace ground ice formed in the considered years. The spores should to be transported with snow/snowmelt into the open frost crack in spring. In 2010, 13 permafrost cores were taken from the ice-wedge polygon. In the cold laboratory, these ground-ice cores have been processed and individual ice veins have been sampled for spore identification and stable isotope analyses. Single ice veins were melted and examined under the light microscope for spores. All spores colours could be recovered, with red spores (2002) being most abundant followed by green (2003) and violet (2004). An overall decrease in spore abundance is probably related to changing hydrological conditions and polygon degradation. Additionally, frost cracking experiments (breaking cables) were installed to the polygon, intended to break when a sudden rupture (i.e. a frost cracking event) takes place. Data loggers detected the precise moments of cracking on Samoylov Island generally occurring between November, 8 and February, 10 (N=12). The stable isotope composition of every single melted ice vein has been analysed with a Picarro L2120i water isotope analyser and, if spores were present, attributed to the respective year of formation. However, attribution to the year of formation is complicated by eventual occurrence of more than one colour in a sample, which has been assessed by statistical methods. The isotope composition of single ice veins could be measured for the first time in high resolution with a Picarro laser-optical spectrometer and showed no significant isotope fractionation during freezing. The combination with meteorological data allows correlating the local temperature with the δ18O of ice-wedge ice formed in a discrete year. The δ18O and δD values of recent ice veins correspond roughly to the LMWL in Tiksi (δD=7.57 δ18O–6.8), indicative for meteoric precipitation stored in ice wedges. However, the broad scatter of the data shows large inter-annual and seasonal variability of the frost cracking process. A first comparison with meteorological data indicates that December temperatures may best explain the variability in recent ice wedge isotope composition.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 8
    Publication Date: 2015-02-26
    Description: Thermal permafrost degradation and coastal erosion in the Arctic remobilize substantial amounts of organic carbon (OC) and nutrients which have been accumulated in late Pleistocene and Holocene unconsolidated deposits. Their vulnerability to thaw subsidence, collapsing coastlines and irreversible landscape change is largely due to the presence of large amounts of massive ground ice such as ice wedges. However, ground ice has not, until now, been considered to be a source of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and other elements, which are important for ecosystems and carbon cycling. Here we show, using geochemical data from a large number of different ice bodies throughout the Arctic, that ice wedges have the greatest potential for DOC storage with a maximum of 28.6 mg L−1 (mean: 9.6 mg L−1). Variation in DOC concentration is positively correlated with and explained by the concentrations and relative amounts of typically terrestrial cations such as Mg2+ and K+. DOC sequestration into ground ice was more effective during the late Pleistocene than during the Holocene, which can be explained by rapid sediment and OC accumulation, the prevalence of more easily degradable vegetation and immediate incorporation into permafrost. We assume that pristine snowmelt is able to leach considerable amounts of well-preserved and highly bioavailable DOC as well as other elements from surface sediments, which are rapidly stored in ground ice, especially in ice wedges, even before further degradation. In the Yedoma region ice wedges represent a significant DOC (45.2 Tg) and DIC (33.6 Tg) pool in permafrost areas and a fresh-water reservoir of 4172 km³. This study underlines the need to discriminate between particulate OC and DOC to assess the availability and vulnerability of the permafrost carbon pool for ecosystems and climate feedback upon mobilization.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 9
    Publication Date: 2015-04-16
    Description: The organic-carbon (OC) pool accumulated in Arctic permafrost (perennially frozen ground) equals the carbon stored in the modern atmosphere. To give an idea of how Yedoma region permafrost could respond under future climatic warming, we conducted a study to quantify the organic-matter quality (here defined as the intrinsic potential to be further transformed, decomposed, and mineralized) of late Pleistocene (Yedoma) and Holocene (thermokarst) deposits on the Buor-Khaya Peninsula, northeast Siberia. The objective of this study was to develop a stratigraphic classified organic-matter quality characterization. For this purpose the degree of organic-matter decomposition was estimated by using a multiproxy approach. We applied sedimentological (grain-size analyses, bulk density, ice content) and geochemical parameters (total OC, stable carbon isotopes (δ13C), total organic carbon : nitrogen (C / N) ratios) as well as lipid biomarkers (n-alkanes, n-fatty acids, hopanes, triterpenoids, and biomarker indices, i.e., average chain length, carbon preference index (CPI), and higher-plant fatty-acid index (HPFA)). Our results show that the Yedoma and thermokarst organic-matter qualities for further decomposition exhibit no obvious degradation–depth trend. Relatively, the C / N and δ13C values and the HPFA index show a significantly better preservation of the organic matter stored in thermokarst deposits compared to Yedoma deposits. The CPI data suggest less degradation of the organic matter from both deposits, with a higher value for Yedoma organic matter. As the interquartile ranges of the proxies mostly overlap, we interpret this as indicating comparable quality for further decomposition for both kinds of deposits with likely better thermokarst organic-matter quality. Supported by principal component analyses, the sediment parameters and quality proxies of Yedoma and thermokarst deposits could not be unambiguously separated from each other. This revealed that the organic-matter vulnerability is heterogeneous and depends on different decomposition trajectories and the previous decomposition and preservation history. Elucidating this was one of the major new contributions of our multiproxy study. With the addition of biomarker data, it was possible to show that permafrost organic-matter degradation likely occurs via a combination of (uncompleted) degradation cycles or a cascade of degradation steps rather than as a linear function of age or sediment facies. We conclude that the amount of organic matter in the studied sediments is high for mineral soils and of good quality and therefore susceptible to future decomposition. The lack of depth trends shows that permafrost acts like a giant freezer, preserving the constant quality of ancient organic matter. When undecomposed Yedoma organic matter is mobilized via thermokarst processes, the fate of this carbon depends largely on the environmental conditions; the carbon could be preserved in an undecomposed state till refreezing occurs. If modern input has occurred, thermokarst organic matter could be of a better quality for future microbial decomposition than that found in Yedoma deposits.
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    Type: Article , NonPeerReviewed , info:eu-repo/semantics/article
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  • 10
    Publication Date: 2015-05-05
    Description: Thermal permafrost degradation and coastal erosion in the Arctic remobilize substantial amounts of organic carbon (OC) and nutrients which have accumulated in late Pleistocene and Holocene unconsolidated deposits. Permafrost vulnerability to thaw subsidence, collapsing coastlines and irreversible landscape change are largely due to the presence of large amounts of massive ground ice such as ice wedges. However, ground ice has not, until now, been considered to be a source of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and other elements which are important for ecosystems and carbon cycling. Here we show, using biogeochemical data from a large number of different ice bodies throughout the Arctic, that ice wedges have the greatest potential for DOC storage, with a maximum of 28.6 mg L−1 (mean: 9.6 mg L−1). Variation in DOC concentration is positively correlated with and explained by the concentrations and relative amounts of typically terrestrial cations such as Mg2+ and K+. DOC sequestration into ground ice was more effective during the late Pleistocene than during the Holocene, which can be explained by rapid sediment and OC accumulation, the prevalence of more easily degradable vegetation and immediate incorporation into permafrost. We assume that pristine snowmelt is able to leach considerable amounts of well-preserved and highly bioavailable DOC as well as other elements from surface sediments, which are rapidly frozen and stored in ground ice, especially in ice wedges, even before further degradation. We found that ice wedges in the Yedoma region represent a significant DOC (45.2 Tg) and DIC (33.6 Tg) pool in permafrost areas and a freshwater reservoir of 4200 km³. This study underlines the need to discriminate between particulate OC and DOC to assess the availability and vulnerability of the permafrost carbon pool for ecosystems and climate feedback upon mobilization.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
    Format: application/pdf
    Format: application/pdf
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