The late Miocene Xiaolongtan megaflora from Kaiyuan in southeast Yunnan (23°48′45″N, 103°11′52″E, 1050 m a.s.l.) was chosen for palaeoclimatic reconstruction using three quantitative techniques, i.e. the Coexistence Approach (CA), Leaf Margin Analysis (LMA), and the Climate-Leaf Analysis Multivariate Program (CLAMP). The reconstructed climatic parameters are also compared with those of the two adjacent Miocene floras currently available in Yunnan, i.e. the early to middle Miocene carpological Mangdan flora (24°24′N, 97°49′E, 1620 m a.s.l.) and the late Miocene Lühe palynoflora (25°10′N, 101°22′E, 1930 m a.s.l.). Quantitative analyses of the Xiaolongtan flora supports the previous qualitative results of a southern, humid subtropical climate, being more humid and having a slightly higher mean annual temperature (MAT) than today. The MATs calculated by CA, LMA, and CLAMP overlap (16.7-19.2 °C, 22.3 ± 2.05 °C, 18.1 ± 1.2 °C, respectively) and are close to the present day value (19.7 °C). The overlapping of temperatures derived using the three techniques is unusual and probably related to the low latitude of the Xiaolongtan area and the southern subtropical nature of its vegetation. Both the mean temperatures of the warmest month (WMT) and of the coldest month (CMT) reconstructed by CA (WMT = 25.4-26.0 °C, CMT = 7.7-8.7 °C) and CLAMP (WMT = 25.9 ± 1.6 °C, CMT = 10.8 ± 1.9 °C) are similar to those of today (WMT = 24.3 °C, CMT = 12.8 °C), but great changes appear in the mean annual precipitation (MAP). The CLAMP results suggest a higher precipitation (1964 ± 335.9 mm) than CA (1215-1639 mm), but they are much higher than the present MAP (820.5 mm). This is consistent with results from the Lühe palynoflora, which also developed under a warmer subtropical climate with higher precipitation (803.6-1254.7 mm) than that of today (815.9 mm). In contrast, the Mangdan flora, situated in a more complicated topographic region to the west of Xiaolongtan and near the Sino-Myanmar border, implies a slightly lower precipitation (1170-1300 mm) than that of today (1300-1400 mm). Overall, the wetter climate during the late Miocene around the Xiaolongtan area suggests that the Himalayas had not yet uplifted to its present altitudes at that time.

Climate is changing and it is certain that this change is due to human activities. Atmospheric greenhouse gases have been rising in an unprecedented way during the last two centuries, although the land biosphere has dampened their increase by absorbing CO2 emitted by anthropogenic activities. However, it is unclear if this will continue in the future. This uncertainty makes it difficult to predict future climate changes and to determine how much greenhouse gas emissions must be reduced to protect climate. To understand the future role of plants in limiting the atmospheric CO2 level, the effect of increasing CO2 on plant photosynthesis and productivity has been studied. However, studies on trees showed contradictory results, which depended on the duration of the experiment. This revealed that an initial strong CO2 fertilization may be a transient response that disappears after a few years. Because climate changes over centuries, we must explore the response of vegetation to increasing CO2 on this time scale. Studying tree rings is a good alternative to impractical decade-long experiments, because trees have experienced the CO2 increase during the last 200 years and may already have responded to it. This thesis shows that the intramolecular distribution of the stable hydrogen isotope deuterium (deuterium isotopomer distribution, DID) of tree rings is a reliable tool to study long-term plant-climate adaptations. The premise for this is that the deuterium abundance in tree rings depends on environmental as well as physiological factors. Using newly developed methodology for DID measurements, the influences of both factors can be separated. Applied to tree rings, separating both factors opens a strategy for simultaneous reconstruction of climate and of physiological responses. The results presented show that DIDs are influenced by kinetic isotope effects of enzymes, allowing studies of metabolic regulation. We show that the abundances of specific D isotopomers in tree-ring cellulose indeed allow identifying environmental and physiological factors. For example, the D2 isotopomer is mostly influenced by environment, its abundance should allow better reconstruction of past temperature. On the other hand, the abundance ratio of two isotopomers (D6R and D6S) depends on atmospheric CO2, and might serve as a measure of the efficiency of photosynthesis (ratio of photorespiration to assimilation). The presence of this dependence in all species tested and in tree-ring cellulose allows studying adaptations of plants to increasing CO2 on long time scales, using tree-ring series or other remnant plant material. / Klimatet förändras och det är numera allmänt vedertaget att detta beror på människans aktiviteter. Halten av växthusgaser har stigit onormalt mycket under de senaste två århundradena och detta beror i största del på människans användning av fossila bränslen. Landbiosfären har hittills haft en buffrande effekt på klimatförändringen eftersom den tar upp och lagrar mycket av växthusgasen CO2. Det är dock osäkert om, och i så fall hur länge, denna effekt kvarstår. Detta gör det mycket svårt att förutsäga framtida klimatförändringar, och därmed hur mycket utsläppen av växthusgaser måste reduceras för att skydda klimatet. För att förstå växternas framtida förmåga att begränsa halten atmosfäriskt CO2 har man studerat effekten av förhöjda halter av CO2 på växters fotosyntes och produktivitet. Resultaten av dessa försök varierar i stor omfattning. Studier på träd odlade under höga halter CO2 indikerar att den initiala ökningen av en trädets produktivitet kan vara en temporär effekt som försvinner redan efter några år. Eftersom klimatförändringen sker under århundraden, måste även växternas anpassningar på förhöjd CO2 halt utforskas på denna tidsskala, men experiment som skulle ta tiotals år är opraktiska att utföra. Trädringar är ett bra sätt att studera sådana anpassningar, eftersom träd redan har upplevt de senaste två hundra årens ökning av koldioxid och dess trädringar därför kan innehålla information om en respons som redan skett. Denna avhandling visar att den intramolekylära fördelningen av den stabila väteisotopen deuterium i trädringar är en tillförlitlig metod för att studera växters anpassningsförmåga till långsiktiga klimatförändringar. Antagandet bakom denna strategi är att isotopfördelningen i trädringar beror på faktorer både från miljön och växtens fysiologi. Om båda faktorerna skulle kunna utvinnas från trädringar, skulle detta öppna en helt ny väg för parallell rekonstruktion av klimatet och växters anpassning till det. Avhandlingen presenterar den första tekniken för att mäta isotopfördelningen av deuterium i växtglukos. Resultaten visar att deuteriumfördelningen hos växtglukos påverkas av enzymers isotopeffekter, vilket möjliggör att regleringen av växternas metabolism kan kartläggas. I avhandlingen bevisas att halten deuterium i skilda intramolekylära positioner (isotopomerer) av glukos från trädringcellulosa bestäms av miljöfaktorer respektive trädets fysiologi. T.ex. påverkas deuteriumhalten i position 2 (D2 isotopomer) av glukosmolekylen huvudsakligen av miljön, vilket kan användas för att förbättra temperaturrekonstruktioner från trädringar. Å andra sidan är kvoten deuterium mellan två andra positioner (D6R och D6S) relaterat till halten atmosfäriskt koldioxid, och kvoten skulle kunna användas som mått för fotosyntesens effektivitet, dvs. förhållandet mellan fotorespiration och fotosyntes. Närvaron av denna relation i trädringar och annat växtmaterial i alla de växter vi hittills studerat, öppnar en helt ny möjlighet att studera växters anpassning till den ökande mängden CO2 i atmosfären under århundraden.

This thesis describes the development and the use of quantitative deuterium Nuclear Magnetic Resonance spectroscopy (NMR) as a tool in two areas of environmental research: the study of long term climate-plant interactions and the source tracking of persistent organic pollutant. Long-term interactions between plants and climate will influence climate change during this century and beyond, but cannot be studied in manipulative experiments. We propose that long tree rings series can serve as records for tracking such interactions during past centuries. The abundance of the stable hydrogen isotope deuterium (D) is influenced by physical and biochemical isotope fractionations. Because the overlapping effects of these fractionations are not understood, studies of the D abundance of tree rings led to conflicting results. We hypothesized that both types of fractionations can be separated if the D abundance of individual C-H groups of metabolites can be measured, that is if individual D isotopomers are quantified. The first paper describes a technique for quantification of D isotopomers in tree-ring cellulose by NMR. The technique showed that the D isotopomers distribution (DID) was non-random. Therefore, the abundance of each isotopomer potentially contains individual information which suggests an explanation for the conflicting results obtained by measuring the overall D abundance (dD). In the second paper, this technique was used to study hydrogen isotope exchange during cellulose synthesis in tree rings. This revealed that some C-H positions exchange strongly with xylem water, while others do not. This means that the exchanging C-H positions should acquire the D abundance of source water, which is determined by physical fractionations, while non-exchanging C-H positions of tree-ring cellulose should retain biochemical fractionations from the leaf level. Therefore, the abundance of the corresponding D isotopomers should contain information about climate and physiology. When analysing tree-ring series, the DIDs should reflect information about temperature, transpiration and regulation of photosynthesis. In the third paper, we showed that CO2 concentration during photosynthesis determines a specific abundance ratio of D isotopomers. This dependence was found in metabolites of annual plants, and in tree-ring cellulose. This result shows that D isotopomers of tree-ring series may be used to detect long-term CO2 fertilisation effects. This information is essential to forecast adaptations of plants to increasing CO2 concentrations on time scales of centuries. In the fourth paper, the source of persistent organic pollutants in the environment was tracked using DID measurements. The dD values of two compounds of related structures were not enough to show indisputably that they did not originate from the same source. However, the DIDs of the common part between the two compounds proved that they did not originate from the same source. These results underline the superior discriminatory power of DIDs, compared to dD measurements. The versatility of DID measurements makes them a precious tool in addressing questions that can not be answered by dD measurements. / Betson, Tatiana R

The potential increase in frequency and magnitude of extreme floods is currently discussed in terms of global warming and the intensification of the hydrological cycle. The profound knowledge of past natural variability of floods is of utmost importance in order to assess flood risk for the future. Since instrumental flood series cover only the last ~150 years, other approaches to reconstruct historical and pre-historical flood events are needed. Annually laminated (varved) lake sediments are meaningful natural geoarchives because they provide continuous records of environmental changes > 10000 years down to a seasonal resolution. Since lake basins additionally act as natural sediment traps, the riverine sediment supply, which is preserved as detrital event layers in the lake sediments, can be used as a proxy for extreme discharge events. Within my thesis I examined a ~ 8.50 m long sedimentary record from the pre-Alpine Lake Mondsee (Northeast European Alps), which covered the last 7000 years. This sediment record consists of calcite varves and intercalated detrital layers, which range in thickness from 0.05 to 32 mm. Detrital layer deposition was analysed by a combined method of microfacies analysis via thin sections, Scanning Electron Microscopy (SEM), μX-ray fluorescence (μXRF) scanning and magnetic susceptibility. This approach allows characterizing individual detrital event layers and assigning a corresponding input mechanism and catchment. Based on varve counting and controlled by 14C age dates, the main goals of this thesis are (i) to identify seasonal runoff processes, which lead to significant sediment supply from the catchment into the lake basin and (ii) to investigate flood frequency under changing climate boundary conditions. This thesis follows a line of different time slices, presenting an integrative approach linking instrumental and historical flood data from Lake Mondsee in order to evaluate the flood record inferred from Lake Mondsee sediments. The investigation of eleven short cores covering the last 100 years reveals the abundance of 12 detrital layers. Therein, two types of detrital layers are distinguished by grain size, geochemical composition and distribution pattern within the lake basin. Detrital layers, which are enriched in siliciclastic and dolomitic material, reveal sediment supply from the Flysch sediments and Northern Calcareous Alps into the lake basin. These layers are thicker in the northern lake basin (0.1-3.9 mm) and thinner in the southern lake basin (0.05-1.6 mm). Detrital layers, which are enriched in dolomitic components forming graded detrital layers (turbidites), indicate the provenance from the Northern Calcareous Alps. These layers are generally thicker (0.65-32 mm) and are solely recorded within the southern lake basin. In comparison with instrumental data, thicker graded layers result from local debris flow events in summer, whereas thin layers are deposited during regional flood events in spring/summer. Extreme summer floods as reported from flood layer deposition are principally caused by cyclonic activity from the Mediterranean Sea, e.g. July 1954, July 1997 and August 2002. During the last two millennia, Lake Mondsee sediments reveal two significant flood intervals with decadal-scale flood episodes, during the Dark Ages Cold Period (DACP) and the transition from the Medieval Climate Anomaly (MCA) into the Little Ice Age (LIA) suggesting a linkage of transition to climate cooling and summer flood recurrences in the Northeastern Alps. In contrast, intermediate or decreased flood episodes appeared during the MWP and the LIA. This indicates a non-straightforward relationship between temperature and flood recurrence, suggesting higher cyclonic activity during climate transition in the Northeast Alps. The 7000-year flood chronology reveals 47 debris flows and 269 floods, with increased flood activity shifting around 3500 and 1500 varve yr BP (varve yr BP = varve years before present, before present = AD 1950). This significant increase in flood activity shows a coincidence with millennial-scale climate cooling that is reported from main Alpine glacier advances and lower tree lines in the European Alps since about 3300 cal. yr BP (calibrated years before present). Despite relatively low flood occurrence prior to 1500 varve yr BP, floods at Lake Mondsee could have also influenced human life in early Neolithic lake dwellings (5750-4750 cal. yr BP). While the first lake dwellings were constructed on wetlands, the later lake dwellings were built on piles in the water suggesting an early flood risk adaptation of humans and/or a general change of the Late Neolithic Culture of lake-dwellers because of socio-economic reasons. However, a direct relationship between the final abandonment of the lake dwellings and higher flood frequencies is not evidenced. / Ein verstärktes Auftreten von Hochwassern, sowohl in ihrer Häufigkeit als auch in ihrer Frequenz, wird im Zuge der Klimaerwärmung und einer möglichen Intensivierung des hydrologischen Kreislaufs diskutiert. Die Kenntnis über die natürliche Variabilität von Hochwasserereignissen ist dabei eine grundlegende Voraussetzung, um die Hochwassergefahr für die Zukunft abschätzen zu können. Da instrumentelle Hochwasserzeitreihen meist nur die letzten 150 Jahre abbilden sind andere Methoden erforderlich, um das Auftreten von historischen und prä-historischen Hochwassern festzustellen. Jährlich laminierte (warvierte) Seesedimente sind bedeutende natürliche Archive, denn sie liefern kontinuierliche Zeitreihen > 10000 Jahre mit einer bis zur saisonalen Auflösung. Seebecken stellen natürliche Sedimentfallen dar, wobei eingetragenes Flusssediment in den Seesedimenten als eine distinkte detritische Lage aufgezeichnet wird, und daher zur Rekonstruktion von extremen Abflussereignissen genutzt werden. Im Rahmen meiner Doktorarbeit habe ich einen 8.50 m langen Sedimentkern aus dem Mondsee (Nordostalpen) untersucht, welcher die letzten 7000 Jahre abdeckt. Dieser Sedimentkern besteht aus Kalzitwarven und eingeschalteten detritischen Lagen mit einer Mächtigkeit von 0.05-32 mm. Detritische Lagen wurden mit Hilfe einer kombinierten Methode untersucht: Mikrofaziesanalyse, Rasterelektronenmikroskopie, Röntgenfluoreszenzanalyse (µXRF) und magnetische Suszeptibilität. Dieser Ansatz ermöglicht die Charakterisierung der einzelnen detritischen Lagen bezüglich der Eintragsprozesse und die Lokalisierung des Einzugsgebietes. Auf Grundlage der Warvenzählung und 14C Datierungen sind die wichtigsten Ziele dieser Arbeit: (i) die Identifizierung der Eintragsprozesse, welche zu einem Sedimenteintrag vom Einzugsgebiet bis in den See führen und (ii) die Rekonstruktion der Hochwasserfrequenz unter veränderten Klimabedingungen. Diese Arbeit zeigt eine Untersuchung auf verschiedenen Zeitscheiben, wobei instrumentelle und historische Daten genutzt werden, um die Aufzeichnung von pre-historischen Hochwasser in den Mondseesedimenten besser zu verstehen. Innerhalb der letzten 100 Jahre wurden zwölf Abflussereignisse aufgezeichnet. Zwei Typen von detritschen Lagen können anhand von Korngröße, geochemischer Zusammensetzung und des Verteilungsmusters unterschieden werden. Detritische Lagen, welche aus siliziklastischen und dolomitischen Material bestehen, zeigen eine Sedimentherkunft vom Teileinzugsgebiet des Flysch (nördliches Einzugsgebiet) und der Nördlichen Kalkalpen (südliches Teileinzugsgebiet) auf. Diese Lagen sind im Nördlichen Becken mächtiger (0.1-3.9 mm) als im südlichen Seebecken (0.05-1.6 mm). Detritische Lagen, welche nur aus dolomitischem Material bestehen und Turbititlagen aufzeigen (0.65-32 mm), weisen auf eine Herkunft aus den Nördlichen Kalkalpen hin. Im Vergleich mit instrumentellen Zeitreihen, stammen die mächtigeren Lagen von lokalen Murereignissen im Sommer und feinere Eintragslagen von regionalen Frühjahrs- und Sommerhochwassern. Extreme Sommerhochwasser am Mondsee werden hauptsächlich durch Zyklonen vom Mittelmeer ausgelöst, z.B. Juli 1954, Juli 1997 und August 2002. Die Untersuchung des langen Sedimentkerns vom Mondsee zeigt während der letzten 2000 Jahre signifikante Hochwasserintervalle mit dekadischen Hochwasserepisoden während der Völkerwanderungszeit und im Übergang vom Mittelalter in die Kleine Eiszeit. Dies weist auf eine Verknüpfung von Abkühlungsphasen und Sommerhochwassern im Nordostalpenraum hin. Während der Mittelalterlichen Wärmephase und in der Kleinen Eiszeit kam es jedoch zu einer geringeren Hochwasseraktivität. Dies zeigt einen komplexen Zusammenhang von Temperaturentwicklung und Hochwasseraktivität in den Nordostalpen, mit einer erhöhten Zyklonenaktivät in den Übergängen von wärmeren zu kälteren Phasen. Während der letzten 7000 Jahre wurden 47 Muren und 269 Hochwasser aufgezeichnet, wobei es eine signifikante Änderung mit erhöhter Häufigkeit um 3500 und 1500 Warvenjahre v. h. gab (v.h. = vor heute = AD 1950). Diese signifikante Änderung stimmt mit einem langfristigem Abkühlungstrend überein, welcher durch alpine Gletschervorstöße und das Absinken von Baumgrenzen seit etwa 3300 Warvenjahre v.h. berichtet wird. Trotz relativ geringer Hochwasseraktivität um 1500 Warvenjahre v.h., könnte das Auftreten von Hochwasser auch das Leben Menschen in Neolithischen Pfahlbausiedlungen (5750-4750 cal. yr BP) beeinflusst haben. Während die ersten Pfahlbauten noch als Feuchtbodensiedlungen am Land entstanden, wurden spätere Siedlungen eventuell als Anpassung an stark schwankenden Seewasserspiegeln auf Pfählen im Wasser gebaut und/oder zeigen eine allgemeine Veränderung der Siedlungsaktivitäten der Neolithischen Pfahlbaukultur an, aufgrund sozio-ökonomischer Veränderungen. Ein direkter Zusammenhang zwischen dem Verlassen der Pfahlbausiedlungen und einer erhöhten Hochwasseraktivität konnte jedoch nicht festgestellt werden.

High resolution dating of loess on the Chinese Loess Plateau (CLP) using Optically Stimulated Luminescence (OSL) has increased the understanding of past monsoon climate but also raised questions regarding dust mass accumulation rate (MAR), the presence of disturbances or gaps in the sediment record, a possible teleconnection between North Atlantic and East Asian monsoon climate, and whether these events are due to climate variability, local settings, or age model uncertainties. This study undertakes a detailed (<20cm sampling resolution) -OSL investigation of the Lingtai section to create an independent age model using linear regression, to reconstruct monsoon climate changes using magnetic susceptibility(MS) and grain size (GS) proxies, as well as to calculate MAR for the site. The data shows that between 44-15 ka climate changes from a period of strong summer monsoon to a strong winter monsoon. GS data show variable trends attributed to changes in dust storm activity and local environmental conditions. MAR data does not correlate with grain size and is different from other loess records on the CLP. Such differences are either due to local variations or age model uncertainties. No clear correlation with Heinrich events or teleconnection with North Atlantic climate is visible in the records over the Last Glacial period, and hiatuses or gaps are not obviously present at this site. It is suggested that using linear regression for continuous age model construction from the luminescence ages comes with uncertainties due to subjective bias when fitting the lines and determining shifts in the data, especially during MAR calculations. Further studies are needed to ascertain optimal methods for creating age models, and to constrain the reasons behind the variability between different sites and loess records on the CLP. / Högupplöst OSL-datering av loessjordar från CLP har ökat förståelsen av dåtida monsunklimat, men har även lyft frågan gällande MAR, närvaron av avbrott eller småskaliga event i jordsektionerna, möjligheten av en relation mellan de Nordatlantiska och Ostasiatiska monsunklimaten, och om dessa förändringar sker till följd av faktisk klimatvariation, lokala förutsättningar, eller osäkerheter i åldersmodellen. Studien genomförde en detaljerad (<20cm) OSL-undersökning av Lingtai-sektionen för att skapa en oberoende åldersmodell, återge monsunklimatförändringarna genom tillämpning av MS och GS proxies, samt beräkna MAR från platsen. Resultaten påvisar att mellan 44-15 ka förändrades klimatet från en period av stark sommar- till en stark vinter-monsun. Kornstorleks-resultaten påvisar stora variationer vilka kan kopplas till en förändring i sandstormsaktivitet samt de lokala förutsättningarna för deposition av sediment. MAR-resultaten överensstämmer inte med kornstorleksdatan och skiljer sig från den övriga empirin, detta kan bero på lokala variationer i regionen eller osäkerheter i åldermodellen. Det finns ingen klar korrelation mellan "Heinrich events" eller en "teleconnection" i sektionen, och avbrott samt störningar i sektionen är inte förekommande. Avsaknaden av korrelation antyder att användningen av regressionslinjer för att skapa kontinuerliga åldermodeller kommer innebära fortsatta osäkerheter i empirin, speciellt gällande beräking av MAR. Ytterligare studier krävs för att bestämma optimala metoder för att framställa åldersmodeller, samt att utröna orsaken till skillnaden mellan resultat från olika platser på plat

No / The potential of Mg in Arctica islandica as a climate proxy is explored through analysis of live-collected shells from Irvine Bay, NW Scotland. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis of the right hand valve from two specimens indicates that seasonal Mg/Ca variations do not correlate with seawater temperature. The highest Mg/Ca typically occurs at the annual growth checks in ~ November¿February. Mg/Ca variations between growth checks are significant in one specimen but usually not significant in the other. Mg/Ca measurements taken laterally across the band (i.e. perpendicular to direction of the growth) to determine heterogeneity of the aragonite deposited at the same time indicates that Mg/Ca concentration decreases with increasing distance from the periostracum in both shells. X-ray Absorption Near Edge Spectroscopy (XANES) indicates that Mg is not substituted into aragonite but is hosted by a disordered phase e.g. organic components or nanoparticles of an inorganic phase. Shell Mg/Ca variations may reflect changes in the concentration or composition of the disorded phase, as well as changes in the composition of the extrapallial fluid used for calcification. Such changes could reflect the relative transportation rates of Mg and Ca to the calcification site.

This thesis demonstrates some of the potential of Libocedrus bidwillii Hook. f. (Kaikawaka) for dendroclimatological research by developing tree-ring chronologies and then using these chronologies to reconstruct palaeoclimates. In order to assist with the modelling of tree-growth and climate relationships (response function analysis), the annual nature of Libocedrus bidwillii growth was investigated. Results showed that seedlings of Libocedrus bidwillii were sensitive to temperature and soil moisture. Greatest growth was at high soil moisture and under a variable temperature regime. It was also found that there was an obvious seasonal variation in the growth of the seedlings. Such information allowed some confidence in the use of the species as a proxy-climatic indicator. Twenty-three tree-ring chronologies were developed from different areas of New Zealand. These included 12 new sites, 5 sites collected by other people but then updated and 6 sites that were not updated. Standardisation of the tree-ring series from each site used double detrending methods - ERH+SP67% (linear-Exponential or linear Regression or a Horizontal detrending plus SPline detrending fitted to 2/3 the length of the tree-ring series). This meant some long-term trends in the data were retained (i. e. greater than 120 year cycles) although this led to some reduction of the strength of the common signal in the chronology as measured by EPS (Expressed Population Signal) and SNR (Signal of Noise Ratio). The retention of long-term trends in the chronologies was thought to be important because some low frequency signals, which are longer than 120 years, are present in the climate data. Autocorrelation in the chronologies was removed by the ARSTAN program using the Aikaike Information Criterion (AIC) to determine the filter model. No significant autocorrelations were left in the residual chronologies produced by this method. Inter-comparison of the chronologies showed a highly consistent and significant pattern between most of the sites. There was little reduction in inter-chronology correlation with separation distance. However, there was a difference, or an effect, due to altitude. In general the response functions for the relationship between climate variables and ring-width in any given growing season showed a negative relationship between temperature for the prior growth months February, March and current December, while there was a positive response to temperature in September and February. There were three significant negative coefficients (previous March, April and August) and one positive (current February) for precipitation. The results of using principal component analysis (PCA) showed that all the 27 significant response function analyses could be divided into four groups. The response pattern in the four groups was similar for temperature but the rainfall response was more variable. The climate reconstructions were based on two groups of chronologies: eleven chronologies from all over New Zealand and a subset of only the three longest chronologies. Comparison of the climate data of different seasons with the two groups of chronologies was carried out using the "bootstrap" transfer function. The average February-March temperature and total March-April precipitation were finally selected as the reconstructed variables. Both of the groups reconstructed the hot years better than the cold years. The reconstructed temperature series were similar to all the earlier New Zealand dendroclimatic reconstructions. The warming and cooling periods, extremely warm and extremely cold years were identified and compared with some other sources of evidence and found to be highly consistent. This led to the conclusion that Libocedrus bidwillii is very useful as a high resolution palaeotemperature indicator. In the precipitation reconstruction, all the periodicities (both high and low) in the observed data were reconstructed. The dry and wet periods, severe drought and very wet years were identified in both precipitation reconstructions and also compared with other more limited sources of evidence.

La variabilité du système climatique influence la productivité et la distribution des espèces marines sur toutes les échelles de temps, de la variabilité saisonnière et inter-annuelle aux cycles glaciaires-interglaciaires. Mais ces liens entre climat et écosystèmes marins sont encore largement méconnus, de telle sorte que les prévisions des changements à venir sont difficiles. De plus, parce que les indicateurs paléoclimatiques issus des archives marines sont souvent liés au fonctionnement de l’écosystème, cette méconnaissance limite la fiabilité de la reconstruction de la variabilité climatique passée.Ce travail de thèse vise à améliorer notre connaissance de ces liens entre climat et écosystèmes marins : nous nous sommes intéressés aux changements de productivité marine au cours du dernier cycle glaciaire-interglaciaire, et nous nous sommes aussi penchés sur la réponse de l’écosystème, incluant l'ensemble des niveaux de la chaine trophique, à la variabilité inter-annuelle à décennale en climat pré-industriel. Ce travail est basé sur l’utilisation d’un modèle climatique (IPSL-CM), d’un modèle de biogéochimie marine (PISCES) et d’un modèle de niveaux trophiques supérieurs (APECOSM).Dans un premier temps, nous montrons que le lien entre l’intensité de la mousson indienne et la productivité primaire marine, en été boréal dans la mer d’Arabie, n’est pas direct. En effet, il apparait indispensable pour comprendre les changements de productivité de considérer, en plus de l'intensité de la mousson, la structure de la mousson. En particulier, la position du Jet de Findlater par rapport à la côte de la péninsule arabique est un paramètre important puisqu'elle conditionne la dynamique d'Ekman dans la région.Dans un second temps, nous avons étudié les variations de la productivité marine au large de l'embouchure du fleuve Congo et leurs liens avec le fleuve et les changements de dynamique atmosphérique africaine. Ce travail a mis en évidence que la relation entre l'intensité de la mousson et l'intensité des alizés, souvent utilisée dans les reconstructions climatiques, n'est pas toujours vérifiée. Selon le climat étudié, l'importance des effets thermiques ou dynamiques sur les changements de précipitations et de vents simulés est différente.Dans un troisième temps, nous avons étudié l'effet de la variabilité inter-annuelle sur les changements de productivité passés et sur le signal climatique potentiellement enregistré par des indicateurs climatiques biologiques.Enfin, la dernière partie de cette thèse se focalise sur la réponse des organismes marins des haut-niveaux trophiques à la variabilité climatique à différentes fréquences. Ce travail a révélé que les organismes marins répondent de façons différentes aux variations environnementales en fonction de leur taille et de leur habitat. / Climate variability influences marine primary productivity and marine species distribution over all timescales, from seasonal to interannual variability and glacial-interglacial cycles. The links between climate and marine ecosystems are still sparsely known so that the predictions of futur changes are difficult. Moreover, because paleoclimate recorders extracted from marine archives are often linked to the functionning of the ecosystem, this lack of knowledge limits our ability to reconstruct past climate variability.This thesis work aims at improving our knowledge of these links between climate and marine ecosystems : we have looked into marine productivity changes during the last glacial-interglacial cycle, but we also examined the "end-to-end" ecosystem response to inter-annual to decadal variability in a pre-industrial climate. This work uses a climate model (IPSL-CM), a bio-geochemical model (PISCES) and a model of high trophic levels (APECOSM).First, we show that the link between Indian summer monsoon intensity and marine primary productivity in the Arabian Sea is indirect. Indeed, it appears necessary to consider the monsoon pattern, such as the Findlater Jet position, which drives the Ekman dynamics in the region, as well as its intensity to understand the productivity changes.Second, we study the marine productivity changes off the Congo river mouth and their links with the river runoff and the African atmospheric dynamics. This work shows that the relationship between monsoon intensity and trade winds intensity, often used to reconstruct past changes, is not always verified. Depending on the climate, thermal or dynamical effects are more or less prominent drivers of the simulated changes in precipitation and winds. Productivity off the Congo river mouth, which is mainly located in the subsurface, seems more affected by the ocean and atmosphere dynamics than by the river supply in nutrients.Third, we study the inter-annual variability effects over past productivity changes and over the climatic signal potentially recorded in the biological climate proxies.Finally, the last part of the thesis focuses on high trophic levels marine organisms response to climate variability at different frequencies. This study shows that marine organisms response to environmental changes varies with the organism' size and habitat.

Aeolian dust that gets deposited builds up loess sequences that cover 10% of the Earth's continents. Such sequences can be several metres thick with material deposited over thousands of years, and therefore act like archives of past climates. The glacial and interglacial cycles during the late Quaternary affects the loess deposition and the dust in the atmosphere, which has an impact on the global climate. Loess material is deposited during colder and drier periods. Paleosols have often been developed in the loess sequences, reflecting a warmer and wetter climate with decreased dust deposition. By sampling loess from different depths of the sequence and analysing different properties of the material, a reconstruction of past environment and climate can be done. Two commonly used methods are magnetic susceptibility analysis and grain size analysis and differences in the result can show differences in the climate and environment at the time the material was deposited. The late Quaternary climate was influenced by changes in the North Atlantic, and loess in the area is important to study to get a better understanding of the climate at the time it was deposited. In this project, loess material from a 10 metres thick sequence at the Romont site, Belgium has been analysed with grain size and magnetic susceptibility measurements to reconstruct past climate. The results show differences in the magnetic enhancement and the grain size as a gradual decrease in the magnetic enhancement, indicating a colder climate as confirmed by an increase in the U-ratio. This is followed by the abrupt onset of the warm Holocene period, matching the marine isotope record at the approximate same time period. The magnetic susceptibility data identifies the Rocourt tephra layer and also shows evidence of erosion of material between the Kincamp soil and the Nagelbeek Tongue Horizon. / Fint sandmaterial som transporteras med vinden kallas för stoft, när det sedan avsätts på marken bygger det upp så kallade för löss-sekvenser. En löss-sekvens kan vara flera meter tjock och uppbyggd under tusentals år, vilket innebär att materialet på olika djup reflekterar hur klimatet var då det avsattes. Klimatet under senkvartär tid reflekterar istider och mellanistider, vilket påverkar mängden stoft i atmosfären och avsättningen av materialet. Materialet har främst avsatts under kalla och torra perioder. Avsättningen minskade under varma och blöta perioder, vilket var optimalt för så kallade  paleosoler att bildas genom vittring. Genom att ta prover från olika djup i en löss-sekvens och analysera dem är det möjligt att tolka tidigare förändringar i klimatet. Två vanliga analysmetoder är att mäta materialets magnetiska mottaglighet och kornstorleken på materialet. Klimatet under senkvartär tid (130 - 12 tusen år sedan) påverkades av norra Atlanten. Det är därför av stor vikt att analysera prover från platser i närheten, för att bättre förstå hur klimatet varierat då materialet avsattes. I det här projektet har material från en 10 meter tjock löss-sekvens i Romont, Belgien analyserats. Resultatet visar variationer i kornstorlek och magnetisk mottaglighet. Ett vulkaniskt lager som kallas Rocourt identifierades, följt av en gradvis minskning av den magnetiska mottagligheten som visar på ett gradvis kallare klimat fram till början på den varma Holocen-perioden som vi befinner oss i nu. Resultatet visar också bevis för erosion mellan två enheter i sekvensen.

The Earth's climate system has recently experienced substantial warming which likely impacts temperature-limited communities close to their distribution margins. The alpine treeline ecotone represents upper distributional limit of montane/subalpine forests. This biogeographic boundary relies mainly on decreasing temperature with increasing elevation. Surprisingly the response of treeline ecotone to ongoing warming has varied a lot and the reasons of this variability are poorly understood. The aim of this dissertation thesis is the assessment of growth trends and tree ring response of Norway spruce (Picea abies[L.] Karst.) to climatic oscillations at treelines and montane forests of East-Central Europe. This dissertation deals with both inter-regional and intra-regional (aspect, elevation) variability of tree growth. The presented results are based on an extensive data set of growth curves for almost 1400 trees. All study sites revealed close relationship between tree ring widths and growing season temperatures as well as the temperatures of October preceding to ring formation season. The main site-dependent differences in growth trends and temperature responses were attributed to elevation, the effect of aspect was relatively less significant. At treelines between the Krkonoše Mts. and Nízké Tatry...