Kooperativer Bibliotheksverbund

UID:

Format: XIV, 173 S.

Edition: 1. publ.

ISBN: 1852930489

Note: Zugl.: Oslo, Univ., Diss., 1986

Language: English

Subjects: Economics

Keywords: Nordsee ; Internationaler Umweltschutz ; Nordsee ; Umweltpolitik ; Nordseeraum ; Umweltschutz ; Hochschulschrift ; Hochschulschrift

UID:

Format: XII, 264 S. , graph. Darst., Kt.

Edition: 1. publ.

ISBN: 9781844078264

Content: Introduction -- Criteria-based definitions of scientific terms -- Comparisons between generations -- Objections to theories of generational justice -- What to sustain? : capital or well being as an axiological goal -- How much to sustain? : the demands of justice in the intergenerational context -- Conclusion

Note: Includes bibliographical references and index , Teilw. zugl.: Düsseldorf, Univ., Diss.

Additional Edition: Online-Ausg. Tremmel, Jörg, 1970 - A theory of intergenerational justice London [u.a.] : Earthscan, 2009 ISBN 9781844078264

Language: English

Keywords: Generationengerechtigkeit ; Hochschulschrift

URL: http://www.gbv.de/dms/zbw/773904042.pdf

Author information: Tremmel, Jörg 1970-

UID:

Format: xvii, 103 Seiten , Illustrationen

Content: In ice-rich permafrost regions, changes in the permafrost thermal regime cause surface disturbances. These changes are amplified by the increase in air temperatures recorded in the Arctic in the past decades. Thermokarst is a process that leads to surface subsidence and formation of characteristic landforms following thawing of ice-rich permafrost or melting of massive ice. Thermokarst is widespread on hillslopes and the number of associated landforms is increasing in the Arctic. Through this process large amounts of material are eroded and transported to the sea or accumulate along hillslopes. While hillslope thermokarst modifies terrestrial and aquatic ecosystems, there is limited understanding of its environmental impact at a regional scale. In this thesis we quantify the environmental impacts of hillslope thermokarst on the valley and nearshore ecosystems along the Yukon Coast, Canada. Using supervised machine learning, we identified geomorphic factors that favour the development of coastal retrogressive thaw slump (RTS), one of the most dynamic hillslope thermokarst landform. Coastal geomorphology and ground ice type and content play a major role in RTS occurrence. Using aerial photographs and satellite imagery, we traced the evolution of RTSs between 1952 and 2011. During this time, the number and areal coverage of RTSs increased by 73%. RTSs eroded and partly released to the nearshore zone organic carbon contained in millions of cubic meters of material. Our results show that 56% of the RTSs identified along the coast in 2011 have eroded 16.6 × 10^6 m3 of material; a large part (45%) was transported alongshore due to coastal processes. Moreover, we show that RTSs are a major contributor to the carbon budget in the nearshore ecosystem: 17% of the coastal RTSs identified in 2011 contributed annually up to 0.6% of the organic carbon released by coastal retreat along the Yukon Coast. To assess the impact of hillslope thermokarst on the terrestrial ecosystem, we measured the spatial distribution of soil organic carbon (SOC) and total nitrogen (TN) along hillslopes in three Arctic valleys. We highlight the high spatial variability in the distribution of SOC and TN in the valleys. This distribution is caused by complex soil processes occurring along the hillslopes. Hillslope thermokarst impacts the degradation of organic matter and affects the storage of SOC and TN.

Note: Dissertation, Universität Potsdam, 2018 , Contents Acknowledgements Abstract (English/Deutsch/Français) List of figures List of tables 1 Introduction 1.1 Scientic background 1.1.1 The Arctic coast, permafrost and climate change 1.1.2 Organic carbon in permafrost soils 1.1.3 Hillslope thermokarst processes 1.2 Aims 1.3 Study region 1.4 Methods 1.4.1 Mapping 1.4.2 Spline interpolation and volumes estimations 1.4.3 Fieldwork 1.4.4 Geochemical analyses 1.4.5 Statistical analyses 1.5 Thesis outline 1.6 Authors’ contributions 2 Synthesis 2.1 Retrogressive thaw slumps are widely spread in ice-rich permafrost areas 2.2 Retrogressive thaw slumps contribute signicantly to the nearshore or-ganic carbon 2.3 Thermokarst impacts the distribution of soil organic carbon along hill-slopes 2.4 Outlook . 3 Terrain Controls on the Occurrence of Coastal RTSs 3.1 Abstract 3.2 Introduction 3.3 Study area 3.4 Methods 3.4.1 Mapping of retrogressive thaw slumps and landform classication 3.4.2 Environmental variables 3.4.3 Univariate regression trees 3.5 Results 3.5.1 Characteristics of retrogressive thaw slumps 3.5.2 Density and areal coverage of retrogressive thaw slumps 3.6 Discussion 3.6.1 Characteristics and distribution of retrogressive thaw slumps 3.6.2 Terrain factors explaining retrogressive thaw slump occurrence 3.6.3 Coastal Processes 3.7 Conclusion 4 RTSs release sediments and organic carbon into the Arctic Ocean 4.1 Abstract 4.2 Introduction 4.3 Study Area 4.4 Methods 4.4.1 Evolution of retrogressive thaw slumps 4.4.2 Volume Estimations 4.4.3 Estimates of soil and dissolved organic carbon values 4.5 Results 4.5.1 Evolution of retrogressive thaw slumps between 1952 and 2011 4.5.2 Eroded material and estimated amount of mobilized SOC and DOC 4.6 Discussion 4.6.1 Increase in slump activity 4.6.2 Eroded material from retrogressive thaw slumps and organic car-bon uxes 4.6.3 Impact of retrogressive thaw slumps on the coastal ecosystem 4.7 Conclusion 5 Snapshot of carbon and nitrogen distribution in Arctic valleys 5.1 Abstract 5.2 Introduction 5.3 Study Area 5.4 Methods 5.4.1 Spatial analyses 5.4.2 Sampling Scheme 5.4.3 Geochemical analyses 5.4.4 Environmental variables and statistical analyses 5.5 Results 5.5.1 Geomorphology of the valleys 5.5.2 Spatial distribution of carbon and nitrogen 5.5.3 Correlations between soil characteristics and geochemical variables 5.6 Discussion 5.6.1 Variability in soil and geochemical properties in Arctic valleys 5.6.2 Hillslope Processes 5.7 Conclusion 6 Eidessttatliche Erklärung A Appendix A.1 Chapter 3 A.2 Chapter 4 A.3 Chapter 5 Bibliography

Language: English

Keywords: Hochschulschrift

URL: https://doi.org/10.25932/publishup-42186

UID:

Format: 1 Band (verschiedene Seitenzählungen) , Illustrationen

ISSN: 1400-3813

Series Statement: Earth Sciences Centre, Göteborg University : A 77

Note: Enthält 5 Zeitschriftenaufsätze , Dissertation, Göteborgs Universitet, 2002 , Table of Contents: Introduction Methods Summary of Papers Paper I Paper II Paper III Paper IV Paper V Conclusions and discussion Acknowledgements References Appendices Paper I: Late Quaternary stratigraphy of western Yamal Peninsula, Russia : new constraints on the configuration of the Eurasian ice sheet / Forman, S. L., Ingólfson, Ó., Gataullin, V., Manley, W. F., Lokrantz, H. Paper II: Late Quaternary stratigraphy, glacial limits and paleoenvironments of the Maresale area, western Yamal Peninsula, Russia / Forman, S. L., Ingólfson, Ó., Gataullin, V., Manley, W. F., Lokrantz, H. Paper III: Late Quaternary stratigraphy, Radiocarbon Chronology, and Glacial History at Cape Shpindler, Southern Kara Sea, Arctic Russia / Manley, W. F., Lokrantz, H., Gataullin, V., Ingólfson, Ó., Andersson, T. Paper IV: Glaciotectonised Quaternary sediments at Cape Shpindler, Yugorski Peninsula, Arctic Russia : implications of glacial history, ice movements and Kara Sea Ice Sheet configuration / Lokrantz, H., Ingólfson, Ó. and Forman, S. L. Paper V: Origin of a massive ground ice body on Yugorski Peninsula, Arctic Russia : buried glacier ice or intrasedimental segregation ice? / Lokrantz, H. and Ingólfson, Ó.

Language: English

Keywords: Hochschulschrift

UID:

Format: 155 Seiten , Illustrationen, Diagramme

ISBN: 978-3-7696-5279-6 , 9783769652796

ISSN: 0174-1454

Series Statement: Wissenschaftliche Arbeiten der Fachrichtung Geodäsie und Geoinformatik der Leibniz Universität Hannover Nr. 369

Note: Auch veröffentlicht in: Deutsche Geodätische Kommission bei der Bayerischen Akademie der Wissenschaften, Reihe C, Nr. 867, München 2021, ISBN 978-3-7696-5279-6 , Dissertation, Gottfried Wilhelm Leibniz Universität Hannover, 2021 , Contents 1. Introduction 1.1. Motivation 1.2. Main Contributions 1.3. Thesis Outline 2. Basics 2.1. Feature based Image Matching 2.1.1. Overview: What is Feature based Image Matching? 2.1.2. Desired Properties for Detected Features and Descriptors 2.1.3. Scale-Invariant Feature Detection 2.1.4. Feature Affine Shape Estimation 2.1.5. Feature Orientation Assignment 2.1.6. Feature Description 2.1.7. Descriptor Matching 2.2. Convolutional Neural Network (CNN) 2.2.1. Architecture of CNN 2.2.2. Training of CNN 2.3. Siamese Convolutional Neural Network 3. Related Work 3.1. Local Feature Detection 3.1.1. Translation and Rotation Invariant Features 3.1.2. Scale Invariant Features 3.1.3. Detectors based on a Comparison of Grey Values or Saliency 3.1.4. Detectors based on Machine Learning 3.2. Feature Orientation and Affine Shape Estimation 3.2.1. Orientation Assignment 3.2.2. Affine Shape Estimation 3.3. Local Feature Description 3.3.1. Hand Crafted Descriptors 3.3.2. Machine Learning based Descriptors 3.4. An Application: Orientation of Oblique Aerial Images 3.5. Discussion 3.5.1. Orientation Assignment and Affine Shape Estimation 3.5.2. Descriptor Learning 3.5.3. An Aerial Photogrammetric Benchmark 3.5.4. Ability to Transfer Learned Modules 4. Deep Learning Feature Representation 4.1. Overview of the Methodology 4.2. Descriptor Learning using Active Weak Match Finder - WeMNet 4.2.1. Descriptor Learning Architecture 4.2.2. Generation of Training Pairs 4.2.3. Loss Function 4.2.4. Weak Match Branch 4.3. Self Supervised Feature Affine Shape Learning - MoNet 4.3.1. Affine Transformation Decomposition 4.3.2. Self Supervised Affine Shape Estimation Module 4.4. Self Supervised Orientation Assignment Module - MGNet 4.5. Full Affine Estimation Network - Full-AfFNet 4.5.1. Full Affine Network 4.5.2. Training Loss 4.5.3. Data Augmentation 4.6. Inference based on the Trained Networks 4.7. Discussion 4.7.1. Descriptor Learning 4.7.2. Affine Shape Estimation 4.7.3. Orientation Assignment Learning 4.7.4. The Inference Pipeline 5. Experiments and Results 5.1. Datasets 5.1.1. Datasets for Training 5.1.2. Datasets for Testing 5.2. Evaluation and Analysis Criteria 5.2.1. Task A: Patch based Image Matching 5.2.2. Task B: Descriptor Distance Analysis 5.2.3. Task C: Feature based Image Matching 5.2.4. Task D: Image Orientation 5.2.5. Summary of Tasks and Involved Datasets 5.3. Descriptor Learning and Patch Based Image Matching 5.3.1. Parameter Study for WeMNet 5.3.2. Comparison to Related Work 5.4. Descriptor Distance Analysis 5.4.1. Translation 5.4.2. Rotation 5.4.3. Affine Shape Transformation 5.5. Image Matching Analysis 5.5.1. Parameter Study for Affine Shape Learning 5.5.2. Image Matching for Rotation Dataset 5.5.3. Image Matching for Hpatches Affine Dataset 5.6. Image Orientation 5.6.1. Determination of Image Orientation 5.6.2. Experiment Setup Details 5.6.3. Orientation Result of Different Blocks 5.6.4. Matching Quality Analysis 6. Discussion 6.1. Descriptor Learning and Patch Based Image Matching 6.1.1. Parameter Study 6.1.2. Comparison to Related Works 6.2. Descriptor Distance Analysis 6.2.1. Translation 6.2.2. Rotation 6.2.3. Affine Shape Transformation 6.3. Feature based Image Matching 6.3.1. Parameter Study 6.3.2. Rotation Set 6.3.3. Affine Set 6.4. Image Orientation 7. Conclusion and Outlook Bibliography A. Affine Shape Adaptation Theory A.l. transformation of affine Gaussian scale-space A.2. Local affine distortion measurement A.3. More affine transformation

In: Wissenschaftliche Arbeiten der Fachrichtung Geodäsie und Geoinformatik der Leibniz Universität Hannover

Language: English

Keywords: Hochschulschrift

Author information: Chen, Lin 1987-

UID:

Format: xxi, 197 Seiten , Illustrationen, Diagramme

Content: Earth's climate varies continuously across space and time, but humankind has witnessed only a small snapshot of its entire history, and instrumentally documented it for a mere 200 years. Our knowledge of past climate changes is therefore almost exclusively based on indirect proxy data, i.e. on indicators which are sensitive to changes in climatic variables and stored in environmental archives. Extracting the data from these archives allows retrieval of the information from earlier times. Obtaining accurate proxy information is a key means to test model predictions of the past climate, and only after such validation can the models be used to reliably forecast future changes in our warming world. The polar ice sheets of Greenland and Antarctica are one major climate archive, which record information about local air temperatures by means of the isotopic composition of the water molecules embedded in the ice. However, this temperature proxy is, as any indirect climate data, not a perfect recorder of past climatic variations. Apart from local air temperatures, a multitude of other processes affect the mean and variability of the isotopic data, which hinders their direct interpretation in terms of climate variations. This applies especially to regions with little annual accumulation of snow, such as the Antarctic Plateau. While these areas in principle allow for the extraction of isotope records reaching far back in time, a strong corruption of the temperature signal originally encoded in the isotopic data of the snow is expected. This dissertation uses observational isotope data from Antarctica, focussing especially on the East Antarctic low-accumulation area around the Kohnen Station ice-core drilling site, together with statistical and physical methods, to improve our understanding of the spatial and temporal isotope variability across different scales, and thus to enhance the applicability of the proxy for estimating past temperature variability. The presented results lead to a quantitative explanation of the local-scale (1–500 m) spatial variability in the form of a statistical noise model, and reveal the main source of the temporal variability to be the mixture of a climatic seasonal cycle in temperature and the effect of diffusional smoothing acting on temporally uncorrelated noise. These findings put significant limits on the representativity of single isotope records in terms of local air temperature, and impact the interpretation of apparent cyclicalities in the records. Furthermore, to extend the analyses to larger scales, the timescale-dependency of observed Holocene isotope variability is studied. This offers a deeper understanding of the nature of the variations, and is crucial for unravelling the embedded true temperature variability over a wide range of timescales.

Note: Kumulative Dissertation , Dissertation Universität Potsdam 2018 , Contents: 1 General introduction. - 1.1 Challenges of isotope-based temperature reconstructions. - 1.2 Thesis overview. - 1.3 Author contributions. - 2 Theoretical background. - 2.1 The isotopic composition of firn and ice. - 2.1.1 Fractionation of water isotopologues. - 2.1.2 Relationship with temperature. - 2.1.3 Measuring of the isotopic composition. - 2.2 Processes within the firn column. - 2.2.1 The firn column of polar ice sheets. - 2.2.2 The density of firn. - 2.2.3 The temperature profile of firn. - 2.2.4 Vapour diffusion in firn. - 2.3 Internal climate variability. - 3 Regional climate signal vs.local noise: a two-dimensional view of water isotopes. - 3.1 Introduction. - 3.2 Data and methods. - 3.3 Results. - 3.3.1 Trench isotope records. - 3.3.2 Single-profile representativity. - 3.3.3 Mean trench profiles. - 3.3.4 Spatial correlation structure. - 3.3.5 Statistical noise model. - 3.4 Discussion. - 3.4.1 Local noise vs. regional climate signal. - 3.4.2 Representativity of isotope signals. - 3.4.3 Implications. - 3.5 Conclusions. - 3.6 Appendix A: Derivation of noise model. - 3.6.1 Definitions. - 3.6.2 Derivation of model correlations. - 3.6.3 Estimation of parameters. - 3.7 Appendix B: Noise level after diffusion. - 4 Constraints on post-depositional isotope modifications in east antarctic firn. - 4.1 Introduction. - 4.2 Data and methods. - 4.2.1 Sampling and measurements. - 4.2.2 Trench depth scale. - 4.2.3 Spatial variability of trench profiles. - 4.2.4 Quantification of downward advection, densification and diffusion. - 4.2.5 Statistical tests. - 4.3 Results. - 4.3.1 Comparison of T15 and T13 isotope data. - 4.3.2 Expected isotope profile changes. - 4.3.3 Temporal vs. spatial variability. - 4.4 Discussion. - 4.4.1 Densification, diffusion and stratigraphic noise. - 4.4.2 Additional post-depositional modifications. - 4.5 Conclusions. - 5 On the similarity and apparent cycles of isotope variations. - 5.1 Introduction. - 5.2 Data and Methods. - 5.2.1 Data. - 5.2.2 Spectral analysis. - 5.2.3 Rice’s formula. - 5.2.4 Cycle length and amplitude estimation. - 5.2.5 Model for vertical isotope profiles. - 5.3 Results. - 5.3.1 Spectral analysis of isotope profiles. - 5.3.2 Theoretical and observed cycle length. - 5.3.3 Illustrative examples. - 5.3.4 Depth dependency of cycle length. - 5.3.5 Simulated vs. observed isotope variations. - 5.4 Discussion and summary. - 5.5 Conclusions. - 5.6 Appendix A: Input sensitivity. - 5.7 Appendix B: Additional results. - 5.8 Appendix C: Spectral significance testing. - 6 Timescale-dependency of antarctic isotope variations. - 6.1 Introduction. - 6.2 Data and methods. - 6.2.1 DML and WAIS isotope records. - 6.2.2 Spectral model. - 6.2.3 Timescale-dependent signal-to-noise ratio. - 6.2.4 Effects of diffusion and time uncertainty. - 6.2.5 Present-day temperature decorrelation. - 6.3 Results. - 6.3.1 Illustration of model approach. - 6.3.2 DML and WAIS isotope variability. - 6.4 Discussion. - 6.4.1 Interpretation of noise spectra. - 6.4.2 Interpretation of signal spectra. - 6.4.3 Signal-to-noise ratios. - 6.4.4 Differences between DML and WAIS. - 6.5 Conclusions. - 7 Declining temperature variability from LGM to holocene. - 8 General discussion and conclusions. - 8.1 Short-scale spatial and temporal isotope variability. - 8.1.1 Local spatial variability. - 8.1.2 Seasonal to interannual variability. - 8.1.3 Spatial vs. temporal variability. - 8.2 Extension to longer scales. - 8.2.1 Spatial vs. temporal variability on interannual timescales. - 8.2.2 Holocene and longer timescales. - 8.3 Concluding remarks and outlook. - Bibliography. - A Methods to: declining temperature variability from lgm to holocene. - A.1 Temperature proxy data. - A.2 Model-based temperature and variability change. - A.3 Temperature recalibration of proxy records. - A.3.1 Recalibration of ice-core records. - A.3.2 Recalibration of marine records. - A.4 Variance and variance ratio estimation. - A.5 Noise correction. - A.5.1 Testing effect of noise correction. - A.6 Effect of ecological adaption and bioturbation. - A.7 Effect of proxy sampling locations. - B Layering of surface snow and firn: noise or seasonal signal?. - B.1 Introduction. - B.2 Materials and methods. - B.2.1 Firn-core density profiles. - B.2.2 Trench density profiles. - B.2.3 Dielectric profiling and density estimates. - B.2.4 Comparison of DEP and CT density. - B.2.5 Ion measurements. - B.3 Results. - B.3.1 2-D trench density data. - B.3.2 Spatial correlation structure. - B.3.3 Comparison of mean density, isotope and impurity profiles. - B.3.4 Spectral analysis of vertical density data. - B.4 Discussion. - B.4.1 Spatial variability. - B.4.2 Representativeness of single profiles. - B.4.3 Seasonal cycle in snow density. - B.4.4 Density layering in firn and impurities. - B.5 Conclusions. - Acknowledgements - Danksagung.

Language: English

Keywords: Hochschulschrift

URL: https://nbn-resolving.org/urn:nbn:de:kobv:517-opus4-414963

Author information: Laepple, Thomas

UID:

Format: xix, 223 Seiten , Illustrationen, Diagramme

Content: The concept of hydrologic connectivity summarizes all flow processes that link separate regions of a landscape. As such, it is a central theme in the field of catchment hydrology, with influence on neighboring disciplines such as ecology and geomorphology. It is widely acknowledged to be an important key in understanding the response behavior of a catchment and has at the same time inspired research on internal processes over a broad range of scales. From this process-hydrological point of view, hydrological connectivity is the conceptual framework to link local observations across space and scales. This is the context in which the four studies this thesis comprises of were conducted. The focus was on structures and their spatial organization as important control on preferential subsurface flow. Each experiment covered a part of the conceptualized flow path from hillslopes to the stream: soil profile, hillslope, riparian zone, and stream. For each study site, the most characteristic structures of the investigated domain and scale, such as slope deposits and peat layers were identified based on preliminary or previous investigations or literature reviews. Additionally, further structural data was collected and topographical analyses were carried out. [...]

Note: Kumulative Dissertation , Dissertation Universität Potsdam 2018

Additional Edition: Erscheint auch als

Language: English

Keywords: Hochschulschrift

DOI: 10.25932/publishup-42454

URN: urn:nbn:de:kobv:517-opus4-424542

URL: http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-424542

Author information: Blume, Theresa

Author information: Merz, Bruno

UID:

Format: x, 121 Seiten , Illustrationen

Content: The deciduous needle tree larch (Larix Mill.) covers more than 80% of the Asian boreal forests. Only a few Larix species constitute the vast forests and these species differ markedly in their ecological traits, most importantly in their ability to grow on and stabilize underlying permafrost. The pronounced dominance of the summergreen larches makes the Asian boreal forests unique, as the rest of the northern hemisphere boreal forests is almost exclusively dominated by evergreen needle-leaf forests. Global warming is impacting the whole world but is especially pronounced in the arctic and boreal regions. Although adapted to extreme climatic conditions, larch forests are sensitive to varying climatic conditions. By their sheer size, changes in Asian larch forests as range shifts or changes in species composition and the resulting vegetation-climate feedbacks are of global relevance. It is however still uncertain if larch forests will persist under the ongoing warming climate or if they will be replaced by evergreen forests. It is therefore of great importance to understand how these ecosystems will react to future climate warmings and if they will maintain their dominance. One step in the better understanding of larch dynamics is to study how the vast dominant forests developed and why they only established in northern Asia. A second step is to study how the species reacted to past changes in the climate. The first objective of this thesis was to review and identify factors promoting Asian larch dominance. I achieved this by synthesizing and comparing reported larch occurrences and influencing components on the northern hemisphere continents in the present and in the past. The second objective was to find a possibility to directly study past Larix populations in Siberia and specifically their genetic variation, enabling the study of geographic movements. For this, I established chloroplast enrichment by hybridization capture from sedimentary ancient DNA (sedaDNA) isolated from lake sediment records. The third objective was to use the established method to track past larch populations, their glacial refugia during the Last Glacial Maximum (LGM) around 21,000 years before present (ka BP), and their post-glacial migration patterns. To study larch promoting factors, I compared the present state of larch species ranges, areas of dominance, their bioclimatic niches, and the distribution on different extents and thaw depths of permafrost. The species comparison showed that the bioclimatic niches greatly overlap between the American and Asian species and that it is only in the extremely continental climates in which only the Asian larch species can persist. I revealed that the area of dominance is strongly connected to permafrost extent but less linked to permafrost seasonal thaw depths. Comparisons of the paleorecord of larch between the continents suggest differences in the recolonization history. Outside of northern Asia and Alaska, glacial refugial populations of larch were confined to the southern regions and thus recolonization could only occur as migration from south to north. Alaskan larch populations could not establish wide-range dominant forest which could be related to their own genetically depletion as separated refugial population. In Asia, it is still unclear whether or not the northern refugial populations contributed and enhanced the postglacial colonization or whether they were replaced by populations invading from the south in the course of climate warming. Asian larch dominance is thus promoted partly by adaptions to extremely continental climates and by adaptations to grow on continuous permafrost but could be also connected to differences in glacial survival and recolonization history of Larix species. Except for extremely rare macrofossil findings of fossilized cones, traditional methods to study past vegetation are not able to distinguish between larch species or populations. Within the scope of this thesis, I therefore established a method to retrieve genetic information of past larch populations to distinguish between species. Using the Larix chloroplast genome as target, I successfully applied the method of DNA target enrichment by hybridization capture on sedaDNA samples from lake records and showed that it is able to distinguish between larch species. I then used the method on samples from lake records from across Siberia dating back up to 50 ka BP. The results allowed me to address the question of glacial survival and post-glacial recolonization mode in Siberian larch species. The analyzed pattern showed that LGM refugia were almost exclusively constituted by L. gmelinii, even in sites of current L. sibirica distribution. For included study sites, L. sibirica migrated into its extant northern distribution area only in the Holocene. Consequently, the post-glacial recolonization of L. sibirica was not enhanced by northern glacial refugia. In case of sites in extant distribution area of L. gmelinii, the absence of a genetic turn-over point to a continuous population rather than an invasion of southern refugia. The results suggest that climate has a strong influence on the distribution of Larix species and that species may also respond differently to future climate warming. Because species differ in their ecological characteristics, species distribution is also relevant with respect to further feedbacks between vegetation and climate. With this thesis, I give an overview of present and past larch occurrences and evaluate which factors promote their dominance. Furthermore, I provide the tools to study past Larix species and give first important insights into the glacial history of Larix populations.

Note: Dissertation, Universität Potsdam, 2022 , Table of Contents Summary Deutsche Zusammenfassung Table of Contents 1 Introduction 1.1 Larix forests in a changing climate 1.2 The genus Larix 1.3 Larix distribution in the world and their dominance in northern Asia 1.4 Methods to study past species dynamics 1.4.1 Modern genetic marker studies 1.4.2 Lake sediments as archives of the past 1.4.3 Pollen and macrofossils 1.4.4 Metabarcoding of sedimentary ancient DNA 1.4.5 Metagenomic shotgun sequencing 1.4.6 Target enrichment by hybridization capture 1.5 Thesis Objectives 1.6 Thesis outline & author contributions 2 Manuscript I 2.1 Abstract 2.2 Introduction 2.3 Material and methods 2.3.1 Bioclimatic limits 2.3.2 Pollen, macrofossil, and DNA datasets 2.3.3 Ice sheets 2.4 Results 2.4.1 Bioclimatic limits of Larix and its distribution on permafrost 2.4.2 Glacial occurrence patterns of Larix 2.5 Discussion 2.5.1 Are differences in species bioclimatic limits responsible for disparity in Larix distribution across continents? 2.5.2 Do high latitude glacial refugia guarantee larch dominance? 2.5.3 What role does postglacial migration play in larch dominance? 2.5.4 Fire as an additional factor 2.5.5 Outlook 2.6 Conclusion 2.7 Acknowledgements 2.8 Author contributions 2.9 References 3 Manuscript II 3.1 Abstract 3.2 Introduction 3.3 Methods 3.3.1 Sample material 3.3.2 Laboratory work 3.3.3 Data analysis 3.4 Results 3.4.1 Overview of the shotgun and hybridization capture data sets 3.4.2 Ancient DNA authenticity 3.4.3 Retrieval of the Larix chloroplast genome 3.5 Discussion 3.5.1 Taxonomic classification—conservative approach results in low numbers of assignment 3.5.2 Target enrichment success—Larix reads increased by orders of magnitude along with other taxonomic groups 3.5.3 Complete retrieval of ancient Larix chloroplast genomes 3.5.4 Larix sibirica variants present over time 3.5.5 Larch forest decline over the last 7000 years 3.6 Conclusion 3.7 Acknowledgments 3.8 Author contributions 3.9 References 4 Manuscript III 4.1 Abstract 4.2 Introduction 4.3 Results & Discussion 4.3.1 Chloroplast and repetitive DNA enrichment in the sedaDNA samples 4.3.2 A wider pre-glacial distribution of L. sibirica 4.3.3 Larix gmelinii formed northern LGM refugia across Siberia 4.3.4 Postglacial colonization history - differences among larch species 4.3.5 Environment likely plays a more important role than biogeography 4.4 Conclusion 4.5 Material & methods 4.5.1 Sample material 4.5.2 Sequence data analysis 4.6 Data availability 4.7 Acknowledgments 4.8 Author contributions 4.9 References 5 Discussion and synthesis 5.1 Hybridization capture is a well-suited method to study ancient species dynamics 5.1.1 Advantages and limitations of shotgun sequencing 5.1.2 Successful hybridization capture enrichment using chloroplast DNA 5.1.3 Challenges in single-copy target enrichment 5.1.4 Limitations and potentials to improve sedaDNA capture studies 5.2 Factors promoting Asian larch dominance 5.3 Drivers of Larix species distribution 5.3.1 Implications for larch forests under climate warming 5.4 Conclusion 5.5 Outlook 6 References 7 Appendix 7.1 Appendix to manuscript I 7.2 Appendix to manuscript II 7.3 Appendix to manuscript III 7.3.1 Material and Methods 7.3.2 Additional Results & Discussions 7.3.3 References Acknowledgements Eidesstattliche Erklärung

Language: English

Keywords: Hochschulschrift

DOI: 10.25932/publishup-55878

URN: urn:nbn:de:kobv:517-opus4-558782

URL: https://doi.org/10.25932/publishup-55878

UID:

Format: VI, 108 Blätter , Illustrationen

Content: Assumed comparable environmental conditions of early Mars and early Earth in 3.7 Ga ago – at a time when first fossil records of life on Earth could be found – suggest the possibility of life emerging on both planets in parallel. As conditions changed, the hypothetical life on Mars either became extinct or was able to adapt and might still exist in biological niches. The controversial discussed detection of methane on Mars led to the assumption, that it must have a recent origin – either abiotic through active volcanism or chemical processes, or through biogenic production. Spatial and seasonal variations in the detected methane concentrations and correlations between the presence of water vapor and geological features such as subsurface hydrogen, which are occurring together with locally increased detected concentrations of methane, gave fuel to the hypothesis of a possible biological source of the methane on Mars. Therefore the phylogenetically old methanogenic archaea, which have evolved under early Earth conditions, are often used as model-organisms in astrobiological studies to investigate the potential of life to exist in possible extraterrestrial habitats on our neighboring planet. In this thesis methanogenic archaea originating from two extreme environments on Earth were investigated to test their ability to be active under simulated Mars analog conditions. These extreme environments – the Siberian permafrost-affected soil and the chemoautotrophically based terrestrial ecosystem of Movile cave, Romania – are regarded as analogs for possible Martian (subsurface) habitats. Two novel species of methanogenic archaea isolated from these environments were described within the frame of this thesis. It could be shown that concentrations up to 1 wt% of Mars regolith analogs added to the growth media had a positive influence on the methane production rates of the tested methanogenic archaea, whereas higher concentrations resulted in decreasing rates. Nevertheless it was possible for the organisms to metabolize when incubated on water-saturated soil matrixes made of Mars regolith analogs without any additional nutrients. Long-term desiccation resistance of more than 400 days was proven with reincubation and indirect counting of viable cells through a combined treatment with propidium monoazide (to inactivate DNA of destroyed cells) and quantitative PCR. Phyllosilicate rich regolith analogs seem to be the best soil mixtures for the tested methanogenic archaea to be active under Mars analog conditions. Furthermore, in a simulation chamber experiment the activity of the permafrost methanogen strain Methanosarcina soligelidi SMA-21 under Mars subsurface analog conditions could be proven. Through real-time wavelength modulation spectroscopy measurements the increase in the methane concentration at temperatures down to -5 °C could be detected. The results presented in this thesis contribute to the understanding of the activity potential of methanogenic archaea under Mars analog conditions and therefore provide insights to the possible habitability of present-day Mars (near) subsurface environments. Thus, it contributes also to the data interpretation of future life detection missions on that planet. For example the ExoMars mission of the European Space Agency (ESA) and Roscosmos which is planned to be launched in 2018 and is aiming to drill in the Martian subsurface

Note: kumulative Dissertation , Dissertation, Universität Potsdam, 2015 , Table of contents Preface Table of contents Summary Zusammenfassung 1. Introduction 1.1. Environmental conditions on past and present Mars 1.2. Detection of methane on Mars 1.3. Methanogenic archaea 1.4. Description of study sites 1.5. Aims and approaches 1.6. Overview of the publications 2. Publication I: Methanosarcina soligelidi sp. nov., a desiccationandfreeze-thaw-resistant methanogenic archaeon from a Siberianpermafrost-affected soil 3. Publication II: Methanobacterium movilense sp. nov.,ahydrogenotrophic, secondary-alcohol-utilizing methanogen fromthe anoxic sediment of a subsurface lake 4. Publication III: Influence of Martian Regolith Analogs on the activityand growth of methanogenic archaea,with special regard to long-term desiccation 5. Publication IV: Laser spectroscopic real time measurements ofmethanogenic activity under simulated Martian subsurface conditions 6. Synthesis and Conclusion 6.1. Synthesis 6.2. Conclusion and future perspectives 7. References 8. Acknowledgments

Language: English

Keywords: Hochschulschrift

URN: urn:nbn:de:kobv:517-opus4-73010

URL: http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-73010

UID:

Format: Getrennte Zählung , Illustrationen

ISBN: 91-86746-48-0

ISSN: 0281-3033

Series Statement: Lundqua thesis 48

Content: The North Taymyr ice-marginal zone (NTZ) on the Taymyr Peninsula, Arctic Siberia and the Ugleelv Valley on Jameson Land, East Greenland, have been investigated with the aim of reconstructing the glacial history, including depositional processes and environments. Geomorphological, sedimentological, stratigraphical and remote sensing methods have been combined to give a comprehensive view of developments in the two areas. Optically stimulated luminescence (OSL) and radiocarbon (14 C) dates provide the chronological control. The Kara Sea shelf was glaciated three times during the Weichselian, each time with a smaller ice cover than before. The ice sheets caused a reversal of the fluvial drainage towards the south on the Taymyr Peninsula and, during the Early-Middle Weichselian, also the damming of proglacial lakes. The youngest ice-advance, but probably also the older ones, was warm-based and ‘surge-like’. After it had reached its maximum position, the margin froze to its base and compressional flow took place there. The North Taymyr ice-marginal zone (NTZ) was initiated during an Early Weichselian retreat stage (c. 80 ka BP) and added to during the Middle (c. 65 ka BP) and Late Weichselian (〈20 ka BP) ice advances, thus revealing a complex history. It comprises ice-marginal and supraglacial landsystems dominated by 2-3 km wide thrust-block moraines. Large areas are still underlain by remnant glacier ice and a supraglacial landscape with numerous ice-walled lakes and kames is forming even today. The proglacial landsystem is characterised by subaqueous or terrestrial environments, depending on altitude and time of formation. The sedimentary succession in the Ugleelv area comprises three tills, glaciolacustrine, glaciofluvial and aeolian sediments. The depositional history started in the early Saalian with a prograding delta in a lake dammed by an outlet glacier in Scoresby Sund. Soon thereafter, and also once during the Weichselian, Jameson Land was inundated by glaciers emanating from Liverpool Land in the east. These glaciers were warm-based and deposited glaciofluvial sediments, local tills and small end moraines. Conditions were less dynamic later in the glacial cycles. During most of the Weichselian the Ugleelv area was ice free and aeolian activity took place, but in the late Saalian the Greenland ice sheet expanded eastwards over the area. This ice was mainly cold- based but in places temporarily warm-based, where a lodgement till was deposited. During deglaciation there was substantial glaciofluvial erosion. The Kara Sea ice sheet and the Greenland ice sheet behave differently through a glacial cycle. The shelf-centred Kara Sea ice experiences large shifts in areal extent and disappears completely during interglacials. ‘Individual’ ice advances seem to be gover- ned by internal ice dynamics rather than by climatic changes. Contrary to this, the Greenland ice sheet is relatively stable and the climatically driven expansion or retreat of its outlet glaciers through the fjords represents the major changes.

Note: Zugleich: Dissertation, Lund, Lund University, 2002 , Contents Introduction Study areas Methods Results - summaries of papers Fieldwork and authorship contributions Paper I Paper II Paper III Paper IV Discussion Glaciations and landsystems Ice-sheet limits The nature of glacial cycles Conclusions Implications and ideas for the future Acknowledgements Svensk sammanfattning References Appendices I: Alexanderson, J.H. 2000: Landsat mapping of ice-marginal features on the Taymyr Peninsula, Siberia – image interpretation versus geological reality. Geological Quarterly 44(1) , 15-25. II: Alexanderson, H. , Hjort, C., Möller, P., Antonov, O. & Pavlov, M. 2001: The North Taymyr ice-marginal zone, Arctic Siberia – a preliminary overview and dating. Global and Planetary Change 31(1-4), 427-445. III: Alexanderson, H. , Adrielsson, L., Hjort, C., Möller, P., Antonov, O., Eriksson, S. & Pavlov, M. 2002: Depositional history of the North Taymyr ice-marginal zone, Siberia – a landsystem approach. Journal of Quaternary Science 17(4) , 361-382. IV: Adrielsson, L. & Alexanderson, H.: Two cycles of ice-sheet and coastal mountain glaciation in central East Greenland. Manuscript submitted to Boreas.

Language: English

Keywords: Hochschulschrift

URL: https://lucris.lub.lu.se/ws/portalfiles/portal/4769236/3159911.PDF