New genome-editing approaches, such as the CRISPR/Cas system, have opened up great opportunities to insert or delete genes at targeted loci and have revolutionized genetics in model organisms like the zebrafish. The Cre-loxp recombination system is widely used to activate or inactivate genes with high spatial and temporal specificity. Using a CRISPR/Cas9-mediated knock-in strategy, we inserted a zebrafish codon-optimized CreERT2 transgene at the otx2 gene locus to generate a conditional Cre-driver line.We chose otx2 as it is a patterning gene of the anterior neural plate that is expressed during early development. By knocking in CreERT2 upstream of the endogenous ATG of otx2, we utilized this gene’s native promoter and enhancer elements to perfectly match CreERT2 and endogenous otx2 expression patterns. Next, by combining this novel driver line with a Cre-dependent reporter line, we show that only in the presence of tamoxifen can efficient Cre-loxp-mediated recombination be achieved in the anterior neural plate-derived tissues like the telencephalon, the eye and the optic tectum. Our results imply that the otx2:CreERT2 transgenic fish will be a valuable tool for lineage tracing and conditional mutant studies in larval and adult zebrafish.

Auf Versuchsflächen des Friedhofes in Pirna (Sachsen) wurden unter alten und jungen Birken verschiedene Stauden und Gräser getestet. Untersucht wurde, wie sich die Konkurrenz um Wasser, Nährstoffe und der Einfluss von Schatten und Laubfall der Gehölze auf das Anwuchsverhalten, die Entwicklung, den Pflege- und Materialaufwand der getesteten Pflanzen auswirkt. Besonders geeignet als Unterpflanzen sind im Ergebnis der fünfjährigen Versuche die Gänsekresse (Arabis), das Stachelnüsschen (Acaena) und der Schlangenbart (Ophiopogon). Der Bericht enthält Informationen zum Anwuchsverhalten der Arten in den ersten zwei Jahren und ihrer weiteren Entwicklung. Empfehlenswert sind eine optimale Pflanzvorbereitung mit mindestens 10 cm Bodenaustausch, die Pflanzdichte von 18 Pfl./m² und vier Pflegedurchgänge im Jahr. Ein Ereigniskalender zeigt die Monate der Blüten- und Fruchtschmuckbildung und der Laubfärbung der Versuchspflanzen.

No description available.

No description available.

Der Replikation des NV-Genoms geht die kotranslationale Spaltung des vom ORF1 kodierten Polyproteins durch die viruseigene Protease, voraus. Erst in cis und in trans Prozessierungen an definierten Spaltmotiven innerhalb des Polyproteins ermöglichten die Freisetzung der strukturellen und nicht-strukturellen Proteine, die für den Aufbau des Replikationskomplexes und für die Initiation der Replikation essentiell sind. Die Regulation der Polyproteinprozessierung war allerdings bislang unbekannt. In der Charakterisierung der sequentiellen und differentiellen Prozessierung des Polyproteins bestand demnach die Hauptaufgabe dieser Arbeit. Dafür wurde zunächst ein NV-Volle-Länge-cDNA-Klon aus sechs sich überlappenden cDNA-Einzelfragmenten, unter Verwendung der overlap-extension PCR, hergestellt. Dieser Volle-Länge cDNA-Klon diente als Template für die Generierung von Vorläuferkonstrukten, die für die Charakterisierung der in cis und in trans Prozessierung des Polyproteins verwendet wurden. Die cis-Spaltung des Polyproteins konnte sowohl in E.coli als auch in humanen 293-T Zellen anhand eines Vorläuferproteins, das die komplette Sequenz der 3CLpro enthält, die 5`-seitig von der Spaltstelle zum VPg Protein und 3`-seitig vom N-Termins der 3DLpol flankiert ist, verifiziert werden. Infolge der kotranslationalen cis-Spaltung dieses Vorläuferproteins kam es zur Freisetzung der 3CLpro, die anschließend aufgereinigt wurde. Zusätzlich wurde das Fusionsprotein 3CLproµE1189A3DLpol aufgereinigt, bei dem das Spaltmotiv E/G zwischen der 3CLpro und der 3DLpol so mutiert wurde, dass die kotranslationale Spaltung des Fusionsproteins verhindert wurde. Anhand der 3CLpro sowie dessen Vorläufers 3CLproµE1189A3DLpol sollte die differentielle und sequentielle Spaltung des Polyproteins in trans charakterisiert werden. Dafür wurden synthetisch hergestellte Peptide, die die authentischen Spaltmotive innerhalb des Polyproteins aufwiesen, sowohl mit der 3CLpro als auch mit der 3CLproµE1189A3DLpol in einem trans-Spaltungsassay inkubiert und anschließend die Spaltung mit Hilfe der reversed-phase Chromatographie analysiert. Im Rahmen dieser Versuche konnte gezeigt werden, dass nur die Spaltmotive zwischen dem N-terminalem Protein p37 und der 2CNTPase sowie zwischen der 2CNTPase und dem Protein p20 in trans von der 3CLpro gespalten wurden. Massenspektrometrische Analysen wiesen nach, dass die Spaltungen jeweils zwischen den Aminosäureresten Q/G stattgefunden hatte. Zusätzlich zu den Peptiden p37/2CNTPase und 2CNTPase/p20 konnte das Peptid VPg/3CLpro durch das Fusionsprotein 3CLproµE1189A3DLpol an der Schnittstelle E/G prozessiert werden. Anhand von Berechnungen zur relativen Spalteffizienz von 3CLpro und 3CLproµE1189A3DLpol wurde nachgewiesen, dass 3CLpro eine signifikant höhere Spezifität zu den Spaltmotiven der Peptide p37/2CNTPase und 2CNTPase/p20 aufwies als das Fusionsprotein 3CLproµE1189A3DLpol. Die Spaltspezifität der 3CLpro war dabei an dem Spaltmotiv zwischen der 2CNTPase und dem Protein p20 signifikant höher als an dem Spaltmotiv zwischen dem N-terminalem Protein p37 und der 2CNTPase. In vitro Translationsstudien des NV-ORF1 im zellfreien System bestätigten, dass die kotranslationale in trans-Spaltung des Polyproteins nur zwischen dem Protein p37 und der 2CNTPase und der 2CNTPase und dem Protein p20 stattfand. Darüber hinaus konnte anhand dieses Versuches gezeigt werden, dass die initiale Prozessierung des Polyproteins auf der trans-Aktivität der 3CLpro beruht, was in der Freisetzung der Proteine p37, 2CNTPase und des Fusionsproteins VPg3CLpro[delta]3DLpol resultiert. Eine weitere Spaltung von VPg3CLpro[delta]3DLpol konnte im Rahmen dieses Versuches nicht gezeigt werden. Mit Hilfe des humanen Zellkultursystems sollte anschließend untersucht werden, ob zelluläre Faktoren in die Prozessierung des p20VPg Vorläuferproteins involviert sind. Dafür wurden Koexpressionsstudien des Vorläuferproteins p20VPg mit dem 3CLpro Vorläuferprotein [delta]VPg3CLpro[delta]3DLpol durchgeführt. Doch auch in dieser Expressionsstudie konnte eine Spaltung des Vorläuferproteins nicht beobachtet werden. Interessanterweise wurde allerdings die cis-Spaltung des Vorläuferproteins [delta]VPg3CLpro[delta]3DLpol durch die Koexpression mit [delta]VPg3CLpro[delta]3DLpol verhindert. Unter Verwendung des trans-Spaltungsassays konnte daraufhin in vitro verifiziert werden, dass p20VPg die Aktivität der 3CLpro am Peptid p37/2CNTPase signifikant reduzierte. Der initiale Schritt der NV-Replikation basiert auf der Aktivität der 3CLpro. Eine Inaktivierung dieses Enzyms würde demnach den Replikationszyklus verhindern. Somit stellt dieses Enzym ein geeignetes Target für anti-NV Medikamente dar. Aus diesem Grund wurden in dieser Arbeit mögliche 3CLpro Inhibitoren getestet. Anhand dieser Testreihen konnte gezeigt werden, dass die Substanz CMK eine mögliche Grundlage, für die Entwicklung von NV-3CLpro spezifischen Chlormethylketon-Peptidanaloga als Inhibitoren, darstellen könnte.

Lipid homeostasis is an essential factor for proper function both at the level of a cell and of an organism. Dysregulation of this process is responsible for some of the major health concerns of our societies such as obesity and atherosclerosis. Considering the wide variety of lipids and the high dynamic of the system, it is clear that regulation is required to keep the appropriate balance between the different lipids. Although a few regulation pathways are already characterized, some others still wait to be discovered. In order to unravel new players involved in lipid regulation, a screening procedure was developed combining RNA interference in Hela cells and thin layer chromatography. Thereby, it is possible to monitor modifications of lipid composition resulting from siRNA knock-down. Furthermore, the potential of mass spectrometry as a lipid analysis tool in large-scale studies was evaluated. This method was then applied to an essential family of regulatory proteins, the kinases. Lipid composition of 600 kinases knock-downs was analyzed. Mostly, variations in triglyceride and cholesterol levels were observed, suggesting that these lipids are more subject to variation in the cells. Unfortunately, it appears that the screen suffered from a high-rate of off-targets effects, implying that most of the phenotypes observed can’t reliably be linked to the corresponding kinase knock-downs. However, several interesting conclusions can still be derived from this screen. First, it was observed that several siRNA induce a decrease in cholesterol, which is coupled to accumulation of a new lipid. Several lines of evidence suggest that this new lipid is in fact a methylated sterol precursor such as lanosterol or demethyllanosterol. Previously, HMG-CoA reductase was considered as the rate-limiting enzyme of cholesterol biosynthesis and the major regulated step of this process. These data show that another major regulation step occurs more downstream in the pathway at the level of methylated cholesterol precursors. Furthermore, MAPK9 was identified as a new regulator of triglyceride homeostasis at the cellular level. Upon MAPK9 knock-down, an increase in triglyceride content was observed both by thin layer chromatography and mass spectrometry. Accordingly, these cells present an increase in lipid droplets, the cellular organelles responsible for triglyceride storage. Sty1 was also identified as the functional homolog of MAPK9 in S. pombe for this process, as similar increase in triglyceride and lipid droplets is observed in a deletion strain for this gene. Although more detailed studies will be necessary to unravel the molecular mechanism of this process, these data suggest the evolutionary conserved implication of the MAP kinase pathway in the regulation of lipid storage both in humans and in yeasts.

Sterol is an abundant component of eukaryotic cell membranes and is thought to influence membrane properties such as permeability, fluidity and microdomain formation. Drosophila is an excellent model system in which to study functional requirements for membrane sterol because, although it does not synthesize sterol, it nevertheless requires sterols to complete development. Moreover, Drosophila normally incorporates sterols into cell membranes. Thus, dietary sterol depletion can be used to specifically reduce membrane sterol levels. In contrast, vertebrates do synthesize cholesterol. In this way, sterol depletion in vertebrates demand the use of approaches such as chemical extractions, drug treatments or genetic manipulation which are prone to have side effects. We have controlled the level and type of dietary sterol available to developing Drosophila larvae in order to investigate the requirement for sterol in cell membranes, and to distinguish it from the function of sterol as a precursor for signaling molecules. Strikingly, we show that membrane sterol levels can be reduced 6-fold in most tissues without affecting cell or larval viability. Larvae respond to sterol depletion by arresting their growth and development, and by increasing the level of specific sphingolipid variants that promote survival when sterol is scarce. Thus, non-sterol lipids are able to substitute for sterols in the maintenance of basic membrane biophysical properties required for life. Despite this, Drosophila larvae regulate their growth to maintain membrane sterol levels within tight limits. The existence of this novel membrane sterol-dependent growth control mechanism indicates an important role for bulk membrane sterol in the tissue specific functions of differentiated cells.

During the last 50 years, plastic industry has grown exponentially with an estimated 8300 million metric tonnes of plastic produced to date. Regardless of the large variety of polymers available, 99% are entirely fossil-fuel based which compromises its degradability after use. Major synthetic polymers in use today are polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyurethane (PU) and polyethylene terephthalate (PET). The current methods for disposing of plastic waste mainly include landfilling, incineration, mechanical and chemical recycling. Despite of the significant improvement of these technologies, it is still necessary to overcome several limitations and deficiencies. Polyurethane (PU) is a synthetic polymer used as raw material in several industries. In 2015, PU global production reached 27 million metric tons, making the sixth most-used plastic worldwide. The main constituents of polyurethane are isocyanates, polyols and chain extenders. Unfortunately, the mismanaged plastic has spread out in different habitats across our planet including cold marine areas and uninhabited places, threatening wildlife and ecosystems. In order to avoid further contamination, it is necessary to transform plastic waste by restoring functional properties, providing added value and exploring new application areas that could provide economic benefits in a long- term perspective. In the last 10 years, a transition from a linear economy to a sustainable, bio-based circular economy has become fundamental to cope the fossil fuel-driven climate change and global plastic pollution. This transformation involves industrial and basic research strongly focused on biotechnology and bioprocesses. Within this transition, microorganisms are key players due to the wide diversity of enzymes and metabolic pathways that could be used for the development of sustainable processes and biomaterials. Recently, microorganisms with plastic-degrading potential have been regularly identified in different environments such as waste disposal, landfills, plastic refineries, open dumps, etc. Selective pressure and evolution of genetically flexible mechanisms have contribute to metabolize anthropogenic compounds, which it has been noted in several enzymatic reactions designed for the efficient degradation of a wide variety of recalcitrant substrates, leading to novel metabolic pathways. Even though several bacterial genera have been reported in the degradation of environmental pollutants, Pseudomonas species are amongst the most cited degraders of aromatic hydrocarbons and plastic polymers. The genus Pseudomonas incorporates one of the most complex, diverse, and ecologically significant group of bacteria on the planet. Members of this genus are found in large numbers in all the major natural environments (terrestrial, freshwater, and marine) and form intimate associations with plants and animals. This universal distribution suggests a remarkable degree of physiological and genetic adaptability. In fact, Pseudomonas have been most frequently linked with PU degradation. Chemically, polyester-based PUs are semi-crystalline structures containing hydrolysable ester and urethane bonds that are fragmented by extracellular enzymes (hydrolases), releasing oligomeric and monomeric building blocks. For instance, amines, alcohols, acids, aromatics, and other residues, such as EG (ethylene glycol), 1,4-butanediol (BDO), adipic acid (AA) ,4′-methylenedianiline (MDA) and 2,4- toluene diamine (2,4-TDA) are constantly present during PU degradation. However, MDA and 2,4-TDA are considered environmental pollutants, which represent a major risk for species in the aquatic and terrestrial areas. This fragmentation of the polymer is known as depolymerization and it is essential for strengthening recycling processes that use plastic waste as feedstock. The broad spectrum of building blocks might be used as carbon and energy source for microorganisms that degrade these compounds and/or use them for the production of higher-value elements. This latter is considered a promising upcycling strategy to reduce fossil-fuel plastic waste and promote new waste management strategies. Previous studies have revealed that extracellular enzymes are essential for biofilm formation on the polymer surface, reducing the resistance and durability of plastic materials. This first step promotes microbial attachment and further degradation. Enzymes with hydrolytic and proteolytic activity have been detected in spherical structures called outer membrane vesicles (OMVs) in several Pseudomonas species. Generally, OMVs play a key role in establishing inter- and intra-species communication, acquisition of nutrients, stress response, delivery of toxins, adhesion and virulence factors, biofilm formation, etc. Even though numerous bacterial strains and enzymes are involved in degradation processes, the complete catabolic mechanism is not totally understood yet. This thesis also centers on the characterization of outer membrane vesicles for extracellular degradation of a polyurethane oligomer and elucidation of the degradation pathway for the polyurethane monomer 2,4-diaminotoluene (2,4-TDA) by Pseudomonas capeferrum TDA1. In the first chapter, bacterial isolation from soil samples and the subsequent protocols to quantify biodegradation of polyurethane building blocks were fully described. The isolated strain was able to use a PU oligomer and 2,4-TDA as sole source of carbon. The latter compound also served as nitrogen source. These results provided a key insight into the catabolic mechanism of the soil bacterium as a potential PU monomer and oligomer-degrader. The second chapter described the identification of the isolated strain as Pseudomonas sp. by partial 16S rRNA gene sequencing, membrane fatty acid profile and structural gene for the cis/trans isomerase (cti). In addition, genomic DNA was isolated from bacterial cells grown on succinate and utilized for whole genome sequencing in order to detect catabolic genes related to aromatic compounds degradation. Preliminary, enzymes involved in the metabolic pathway were identified, which eventually led to a suggested degradation pathway for Pseudomonas sp. grown on 2,4-TDA. The strain was identified as Pseudomonas capeferrum (type strain WCS358) using the full 16S rRNA gene sequence. The third chapter reported a new method of RNA extraction from Pseudomonas capeferrum TDA1 growing on 2,4-TDA. Phenols and catechols are central intermediates of the aromatics biodegradation that can be easily oxidized to yield the corresponding quinones, which interfere with nucleic acids and tend to co- precipitate or degrade RNA. The chemical process is regulated by the activity of polyphenol oxidases enzymes, which have been identified in several Pseudomonas species previously. This optimized protocol incorporated several modifications including the use of a carrier, pooled samples and a final cleaning up step that could improve it significantly, yielded a high-quality RNA measured by A260/A280, A260/230 ratios (2.02 ± 0.16, 1.95 ± 0.01, respectively) from cells grown on 2,4-TDA compared to standard assays. Moreover, RIN (RNA integrity number) values were analyzed and samples with a RIN higher than 7.0 were selected for downstream applications, confirming the RNA quality. Finally, the fourth chapter evaluated the transcriptional changes in Pseudomonas capeferrum TDA1 grown on 2,4-TDA using RNA-seq. From all the expressed genes, one third were overexpressed in comparison to the control (succinate). These alterations in the gene expression demonstrates that aromatic compounds trigger adaptive responses that modify the transcriptional regulation mechanism including important changes not only in the catabolic system, but also in other patterns related to bacterial cell physiology and biofilm formation. In order to evaluate extracellular degradation, OMVs isolated from P. capeferrum TDA1 grown on a PU oligomer were tested for hydrolytic activity. Purified OMVs showed higher esterase activity compared to cell pellets. Relative OMV yields in TDA1 raised significantly in PU oligomer (0.28 ± 0.05%) compared to succinate (0.09 ± 0.01%). This three-fold increased activity could demonstrate that the release of OMV is part of the adaptive mechanisms of bacteria to stressful environmental conditions. The macromolecular degradation may occur through the action of both periplasmic and membrane-bound hydrolases harbored inside of OMVs and can be considered as a supporting mechanism for biodegradation. The results of this thesis present a further understanding of the transcriptome response in P. capeferrum TDA1 exposed to a PU monomer, suggest a model for extracellular degradation involving OMVs and propose a complete catabolic mechanism for the biodegradation of polyester-based PU containing intra and extracellular enzymes. Moreover, further studies on biological degradation of PU will contribute to redesign plastic polymers considering biodegradable building blocks and improving biocatalytic degradation, which could provide a sustainable use of PU plastic waste in the future.

When it comes to perception, one of the most remarkable characteristics of the brain is its omnipresent variability: Even to identical sensory stimuli, no neural response is the same. It has been hypothesized that this response variability is induced by fluctuations of the brain’s instantaneous state, yet the underlying dynamics that link such neural states with stimulus-related processes remain poorly understood. Specifically, fluctuations of excitability in sensory regions of the cortex may shape the brain’s response to external stimuli and hence the perception thereof. The current work aimed at characterizing the modulatory role and spatiotemporal organization of cortical excitability in a series of three somatosensory stimulation paradigms in humans, employing electroencephalography (EEG) to examine the interplay between pre-stimulus oscillatory state and short-latency somatosensory evoked potentials, as well as their association with the consciously accessible stimulus percept. Excitability dynamics of the primary somatosensory cortex were found to be (i) temporally structured in a special way (long-range temporal dependencies in line with the concept of criticality), (ii) linked to the behaviorally perceived stimulus intensity already through initial cortical responses, and (iii) organized with spatially confined, somatotopic patterns. Taken together, these findings suggest that fluctuations of cortical excitability reflect the maintenance of a sensitive tradeoff between robustness and flexibility of neural responses to sensory stimuli, enabling the brain to adaptively change the neural encoding of even low-level stimulus features, such as the stimulus’ intensity. Importantly, however, moment-to-moment neural response variability appears not to occur “at random”, that is, in a stochastically independent manner, but to be organized according to specific principles – both in the temporal and spatial domain.

Northern peatlands store large amounts of soil organic carbon that are extremely vulnerable to climate change. Direct environmental changes as temperature increase and water table drawdown might not only release more C as CO2 into the atmosphere, but will likely result in increasing vascular plants at the expense of Sphagnum mosses as well. Therefore, the question arises how different plant functional types (shrubs and sedges) with distinctly different functional strategies compared to Sphagnum mosses control C allocation in peatlands and what this means for peat decomposition. Therefore, the key objective of this thesis was to study the patterns of belowground C input by shrubs and sedges and how their above- to belowground C allocation might impact the decomposition of the present moss-dominated peat at different temperatures. To this aim, we applied a plant removal experiment on hummocks with mixed sedge-shrub vegetation in two moss-dominated peatlands located in the Italian Alps at different altitude, i.e. different temperatures. Subsequent measurements of soil respiration, dissolved organic carbon concentration and stable isotope composition (δ13C) of dissolved organic carbon in pore water were used as proxies to estimate the root derived C input by different plant functional type. With in situ 13C pulse-labelling, we assessed the above-to belowground C allocation by quantifying 13C in plant leaves and soil respiration and by measuring δ13C in dissolved organic carbon and in different depths of the peat. In additional peat cores taken under adjacent shrub and sedge plants, we used elemental analysis of carbon, nitrogen, their stable isotopes and analytical pyrolysis gas chromatography mass spectrometry to assess effects of vascular plants (sedge, shrub) on chemical properties and decomposition of the moss-dominated peat. The results provide a mechanistic evidence that plant functional types differ profoundly in their above- to belowground C allocation in peatlands. With shrubs, recently assimilated photosynthates are more likely to be allocated aboveground and turned over belowground than with sedges. Moreover, shrubs showed a fast and tightly coupled processes chain of C assimilation, subsequent C translocation to roots and finally C turnover to CO2, possibly supported by their mutualistic association to mycorrhizal fungi. Though sedges had a higher root-derived C input per unit of biomass than shrubs, the belowground C turnover of recently assimilated C was lower. At the same time, sedges allocated more C belowground to roots than shrubs. For sedges, belowground C turnover processes occurred decoupled from aboveground biomass. The temperature difference between sites did neither increase aboveground C allocation significantly nor belowground C allocation and turnover. However, a higher vascular plant biomass increased the root-derived C input, particularly with shrubs at higher temperatures. Multiple parameters also revealed a higher degree of decomposition of moss-dominated peat collected under sedges than under shrubs, particularly at the high temperature site. Temperature effects on peat decomposition were less pronounced than those of sedges. Eventually, it was not the higher belowground C turnover triggered by shrubs that accelerated decomposition of the present moss-dominated peat but likely the belowground C allocation to the roots by sedges. It can be concluded that the contribution of root exudates to belowground C allocation plays no decisive role in peat decomposition. Yet, the contribution of belowground biomass, particularly of sedges, but also litter of shrubs may impact decomposition processes in a changing climate. Hence, it can be expected that in northern peatlands with increasing shrub biomass, ancient C stores will not be mobilized, while with increasing sedge biomass, C stores are likely at risk.:Thesis at a glance 2 1 Introduction 5 1.1 Northern peatlands and climate change . . . . . . . . . . . . . . . . . . . . . 5 1.2 Vegetation and its impact on carbon cycling in northern peatlands in a warmer climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.3 In situ approaches to study plant functional type effects on peat decomposition in response to climate change . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.4 Objectives, hypotheses and experimental approach . . . . . . . . . . . . . . . 14 2 Study I 21 2.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.2 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.4 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.5 Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.6 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 2.7 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 2.8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 2.9 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 3 Study II 47 3.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.2 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.4 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.6 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 3.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 3.8 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4 Study III 75 4.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 4.3 Material and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 4.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 4.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 4.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 4.7 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 5 Synthesis 97 5.1 Regulations of root-derived carbon input and above- to belowground carbon allocation by vascular plants in peatlands . . . . . . . . . . . . . . . . . . . . 97 5.2 The effect of different above- to belowground carbon allocation patterns of vascular plants on Sphagnum-derived peat decomposition at different temperatures103 6 Conclusions 105 6.1 Implications of belowground carbon allocation by vascular plants for peat decomposition in a warmer climate . . . . . . . . . . . . . . . . . . . . . . . . . 105 6.2 Towards a dynamic understanding of the impact of roots on peatland carbon cycling in a warmer climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 7 Acknowledgements 109 References 111 List of publications and license agreements 139 Curriculum Vitae 149 / Moore der nördlichen Hemisphäre speichern große Mengen an organischem Kohlenstoff im Boden, der durch den Klimawandel extrem gefährdet ist. Direkte Umweltveränderungen wie ein Temperaturanstieg und die Absenkung des Grundwasserspiegels könnten nicht nur mehr Kohlenstoff als CO2 in die Atmosphäre freisetzen, sondern werden wahrscheinlich auch zu einer Zunahme von Gefäßpflanzen auf Kosten von Torfmoosen führen. Daher stellt sich die Frage, wie verschiedene funktionellen Pflanzengruppen (Sträucher und Seggen) mit deutlich unterschiedlichen funktionellen Strategien im Vergleich zu Torfmoosen die Kohlenstoff-Allokation in Mooren steuern und was dies für den Torfabbau bedeutet. Daher war das Hauptziel dieser Arbeit, die Muster des unterirdischen Kohlenstoff-Eintrags durch Sträucher und Seggen zu untersuchen und festzustellen, wie sich ihre ober- und unterirdische Kohlenstoff-Allokation auf die Zersetzung des moosdominierten Torfs bei unterschiedlichen Temperaturen auswirken könnte. Zu diesem Zweck haben wir ein Pflanzenentfernungs-Experiment auf Bulken mit gemischter Seggen- und Strauchvegetation in zwei moosdominierten Hochmooren in den italienischen Alpen auf unterschiedlichen Höhenlagen, d. h. bei unterschiedlichen Temperaturen, durchgeführt. Anschließende Messungen der Bodenatmung, der Konzentration des gelösten organischen Kohlenstoffs und der stabilen Isotopenzusammensetzung (δ13C) des gelösten organischen Kohlenstoffs im Porenwasser dienten als Indikatoren für den von den Wurzeln stammenden Kohlenstoff-Eintrag der verschiedenen funktionellen Pflanzengruppen. Mit Hilfe der In-situ-13C-Pulsmarkierung wurde die ober- und unterirdische Kohlenstoff-Allokation durch die Quantifizierung von 13C in den Pflanzenblättern und in der Bodenatmung sowie durch die Messung von δ13C im gelösten organischen Kohlenstoff und im Torf aus verschiedenen Tiefen festgestellt. In zusätzlichen Torfkernen, die unter benachbarten Strauch- und Seggenpflanzen entnommen wurden, haben wir Elementaranalyse von Kohlenstoff, Stickstoff und deren stabile Isotope sowie die analytische Pyrolyse-Gaschromatographie-Massenspektrometrie verwendet, um die Auswirkungen von Gefäßpflanzen (Seggen, Sträucher) auf die chemischen Eigenschaften und den Abbau des moosdominierten Torfs zu bewerten. Die Ergebnisse liefern einen mechanistischen Beweis dafür, dass sich funktionelle Pflanzengruppen in ihrer ober- und unterirdischen Kohlenstoff-Allokation in Mooren stark unterscheiden. Bei Sträuchern wird kürzlich assimilierter Kohlenstoff eher oberirdisch allokiert und unterirdisch umgesetzt als bei Seggen. Darüber hinaus wiesen Sträucher eine schnelle und eng gekoppelte Prozesskette aus Kohlenstoff-Assimilation, anschließender Kohlenstoff-Translokation in die Wurzeln und schließlich Kohlenstoff-Umsatz zu CO2 auf, was möglicherweise durch ihre mutualistische Beziehung zu Mykorrhiza Pilzen unterstützt wird. Obwohl Seggen gegenüber Sträuchern einen höheren Kohlenstoff-Eintrag aus den Wurzeln pro Biomasseeinheit hatten, war der unterirdische Kohlenstoff-Umsatz von kürzlich assimiliertem C geringer. Gleichzeitig bauten Seggen unterirdisch mehr Kohlenstoff in die Wurzeln ein als Sträucher. Bei Seggen fand der unterirdische Kohlenstoff-Umsatz entkoppelt von der oberirdischen Biomasse statt. Der Temperaturunterschied hatte weder Einfluss auf die oberirdische Kohlenstoff-Allokation noch auf die unterirdische Kohlenstoff-Verlagerung und -Umsatz. Ein höherer Anteil an Gefäßpflanzen, insbesondere an Sträuchern, erhöhte jedoch den aus den Wurzeln stammenden Kohlenstoffeintrag, insbesondere bei höheren Temperaturen. Mehrere Parameter zeigten einen höheren Abbaugrad des moosdominierten Torfs unter Seggen gegenüber Sträuchern an, insbesondere am Standort mit hohen Temperaturen. Die Auswirkungen des Temperaturanstiegs auf den Torfabbau waren weniger ausgeprägt als die Auswirkungen durch Seggen. Schlussendlich war es nicht der durch Sträucher ausgelöste höhere unterirdische Kohlenstoff-Umsatz, der die Zersetzung des vorhandenen moosdominierten Torfs beschleunigte, sondern wahrscheinlich die unterirdische Kohlenstoff-Allokation zu den Wurzeln der Seggen. Daraus lässt sich schließen, dass der Beitrag der Wurzelexsudate zur unterirdischen Kohlenstoff-Allokation bei der Torfzersetzung keine entscheidende Rolle spielt. Der Eintrag der unterirdischen Biomasse, insbesondere der Seggen, aber auch der Streu von Sträuchern, kann jedoch die Abbauprozesse in einem sich ändernden Klima beeinflussen. Daher ist zu erwarten, dass in Moore der nördlichen Hemisphäre mit zunehmender Strauchbiomasse alte Kohlenstoff-Speicher nicht mobilisiert werden, während mit zunehmender Seggenbiomasse die Kohlenstoff-Speicher wahrscheinlich gefährdet sind.:Thesis at a glance 2 1 Introduction 5 1.1 Northern peatlands and climate change . . . . . . . . . . . . . . . . . . . . . 5 1.2 Vegetation and its impact on carbon cycling in northern peatlands in a warmer climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.3 In situ approaches to study plant functional type effects on peat decomposition in response to climate change . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.4 Objectives, hypotheses and experimental approach . . . . . . . . . . . . . . . 14 2 Study I 21 2.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.2 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.4 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.5 Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.6 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 2.7 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 2.8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 2.9 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 3 Study II 47 3.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.2 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.4 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.6 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 3.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 3.8 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4 Study III 75 4.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 4.3 Material and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 4.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 4.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 4.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 4.7 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 5 Synthesis 97 5.1 Regulations of root-derived carbon input and above- to belowground carbon allocation by vascular plants in peatlands . . . . . . . . . . . . . . . . . . . . 97 5.2 The effect of different above- to belowground carbon allocation patterns of vascular plants on Sphagnum-derived peat decomposition at different temperatures103 6 Conclusions 105 6.1 Implications of belowground carbon allocation by vascular plants for peat decomposition in a warmer climate . . . . . . . . . . . . . . . . . . . . . . . . . 105 6.2 Towards a dynamic understanding of the impact of roots on peatland carbon cycling in a warmer climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 7 Acknowledgements 109 References 111 List of publications and license agreements 139 Curriculum Vitae 149