La présence d’arbres en milieu urbain, où vit plus de la moitié de la population mondiale, participe à l’amélioration de la qualité́ de vie des citadins par les services écosystémiques qu’ils nous rendent. Cependant, de nombreuses études ont mis en évidence l’importante mortalité́ et la faible espérance de vie des arbres en ville du fait des stress hydriques. Nos résultats dendroclimatiques ont pu montrer qu’en comparaison avec les arbres de parc urbain ou d’arboretum, les arbres de rue ont généralement une croissance plus faible. Les précipitations en automne et au printemps semblent jouer un rôle prépondérant pour la croissance annuelle des tilleuls argentés urbains. Nos résultats sur le niveau des réserves (lipides et glucides) montrent que les arbres en condition de stress hydrique pourraient activement réguler leurs réserves de C selon une stratégie de survie à long terme. Les jeunes tilleuls argentés, quant à eux, semblent privilégier l’allocation du C dans la croissance radiale. Nos résultats sur la signature isotopique en 18O et en 2H des sources d’eau en ville, indiquent enfin que les arbres en rue semblent dépendre principalement de l'eau du sol très superficiel (couche 0-20 cm). Cette eau est un mélange d'eau de pluie et d'eau non potable plus ou moins évaporées, bien que ces arbres ne soient soumis à aucune stratégie d'irrigation particulière à Paris. Les arbres les plus matures en rue semblent disposer d’une plus faible disponibilité́ en eau due à la plus forte évaporation des sols en surface. En conclusion, cette étude appelle à (i) la protection des sols nus d’une évaporation excessive, et (ii) une irrigation en harmonie avec la phénologie. / The presence of trees in urban areas, where more than half of the world's population lives, contributes to improving the quality of city through ecosystem services they provide. However, many studies have shown that urban trees face high mortality rates and low life expectancy due to water stress. Dendroclimatic results have showed that, in comparison with the urban park or arboretum trees, street trees generally have lower annual growth rate. Precipitation in autumn and spring seem to play the main role in the annual growth of urban silver lindens. Reserve measurements (lipids and carbohydrates) show that trees under water stress could priorize C reserves as a long-term survival strategy. On the contrary, younger silver lindens seem to favor the allocation of C in the radial growth. Our results on the isotope signature in 18O and 2H of water sources in the city, indicated that street trees seem to depend mainly on soil water in upper layers (0-20 cm layer). This water is a mixture, more or less evaporated, from precipitation and non potable water, although street trees are not subject to any particular irrigation strategy in Paris. Larger street trees seem to have lower water availability due to increase of surface soils evaporation. To conclude, This study would rethink current irrigation strategies in the city, focusing on (i) the protection of bare soil from excessive evaporation, and (ii) an irrigation in harmony with the phenology of species.

Desde a revolução industrial, o consumo de combustíveis fósseis pelo homem vem crescendo em ritmo acelerado. Com isso, aumentam também as concentrações dos chamados gases-estufa (CO2, CH4 e NxO). Isso gera alterações no clima, causando mudanças em fatores bióticos e abióticos, tanto em ambientes naturais quanto em ambientes urbanos. Algumas dessas mudanças são típicas de ambientes urbanos, como as Ilhas de Calor Urbanas e a Inversão Térmica, e devido ao fato de grande parte da população atual viver neste tipo de ambiente, acabam causando diversos problemas de saúde. É importante, portanto, conhecer como o clima destes ambientes tem se comportado nos últimos anos, e isso é possível através da análise dos anéis de crescimento de árvores urbanas. Além disso, os dados de crescimento podem ser utilizados para calibrar modelos de dinâmica florestal. Sendo assim, o presente trabalho pretende construir cronologias de anéis de crescimento de cedro (Cedrela fissilis L.) da cidade de São Paulo, e utilizá-las para reconstruir o clima do último século para essa cidade, além de usar estes dados de crescimento para a parametrização de novos elementos em um modelo de dinâmica florestal já existente. Para isso, utilzou-se 43 indivíduos coletados em 4 localidades da cidade de São Paulo, que foram colados em suporte, polidos, datados, fotografados e tiveram a largura dos anéis de crescimento medidas. Além disso, também tomou-se medidas de áreas de vaso para alguns anéis pré-determinados. As larguras dos anéis foram utilizadas para a construção de cronologias, que posteriormente foram usadas para a criação de modelos de reconstrução climática. Foi possível encontrar relações entre precipitação e temperatura e o crescimento das árvores para dois dos locais de coleta, sendo que para um deles foi possível reconstruir estas variáveis climáticas para determinados meses do ano. Com os dados de crescimento, foi possível parametrizar uma nova equação inserida no modelo de Falster et al., 2011, que insere o efeito de temperatura na parte do modelo relacionada à fotossíntese da espécie simulada. Após a inserção da nova equação, foi possível observar mudanças na periodicidade dos ciclos de recrutamento da floresta. / Since the Industrial Revolution, fossil fuel consumption by man has been rising steeply. This way the concentration of greenhouse-gases (CO2, CH4 and NxO) rise too. That causes the climate to change, generating alterations in biotic and abiotic factors both in natural and urban environments. Some of these changes are typical from urban environments such as Urban Heat Islands and Thermal Inversion, and since great part of human population live in this type of environment, health problems are common. Thus it is important to know how the climate have behaved in this environments in the past years, and this is possible by analyzing the tree rings from urban trees. Furthermore, growth data can be used to calibrate forest dynamic models. Therefore the present work aims to build tree-ring chronologies of cedro (Cedrela fissilis L.) from the city of São Paulo, and to use them to reconstruct climate for the last century in this city, in addition to use these growth data to parameterize new elements in an existent forest dynamic model. For this, 43 individuals were sampled in 4 different sites in São Paulo, which were glued in wood support, sanded, dated, photographed and had their growth rings measured. Furthermore vessel area was measured for some predetermined rings. The growth rings widths were used to build chronologies, that were later used to generate climate reconstruction models. It was possible to fin relations between temperature and precipitation and the tree growth in 2 of the sampling sites, and in one it was possible to build reconstruction models for some months. With growth data, it was possible to parameterize a new equation inserted in Falster et al. Model, which inputs temperature effect in the photosynthesis-related part of the model. After inputting the new equation it was possible to observe changes in the periodicity of the recruitment cycles in this forest

The aim of this study was to contribute to the comprehension of the connection of element uptake in trees at the Laacher See in Germany and climatic parameters on different time scales. Understanding the relationship of certain elements in trees and temperature might enable the assignment of extraordinary high peaks in the elemental concentration, which cannot be explained by temperature, to another process as CO2 degassing of the mofettes, which are relics of the volcanic past of the lake. Beech and oak trees at the Laacher See are not growing close to their climatic distribution limit. The relationship between tree-ring width and temperature might be not distinct enough and therefore insufficient to reconstruct climate back in time based on typical dendrochronological methods. Increasing temperatures affect the production of biomass and the release of elements in the soil. These elements are taken up by roots of trees and are implemented in yearly forming tree-rings. Using elements in tree-rings is discussed to be an alternative method for the reconstruction of climate back in time. However, there is an ongoing debate about dendrochemical methods as it is still not clear how much the resolution of the results is affected by translocation of elements between tree-rings. In this study, tree-cores of living beech and oak trees, sampled 2020, have been measured using an energy dispersive x-ray fluorescence technique (ED-XRF), which is a non-destructive method for multi-element analysis. Eleven elements (Ca, Co, Cu, Cr, Ge, Fe,K, Mn, Ni, Sc, Zn) and three elemental ratios (K/Ca, Ca/Mn, Fe/Mn) have been found to show significant positive or negative correlations in the time period from 1901 to 2018 between their concentration in tree-rings and temperature. Since Cu, Ge and K also show significant correlations with temperature in 10-year periods, higher mobility between tree-rings is assumed for those elements. Low mobility is suggested for the elements Ca and Mn as their concentration in the bark and in the wood shows little correlation. Low mobility indicated by significant correlations between elements and yearly temperature or a lack ofcorrelation between the concentration in the bark and in the wood, makes elements more suitable as indicators for temperature. However, the explanation of element concentration in tree-rings is complex, as elements are influencing each other. Antagonistic behaviour has especially been observed for the elements Ca, Co, Ge, Fe, K, Mn, Ni and Sc. These elements are showing significant correlations with temperature as well, which reveals the dependency of elemental concentrations on more than one variable. Furthermore, acidic soil at the study site might be caused by elevated CO2 concentrations, which originate from mofettes. Increasing concentrations of Fe and Ca in tree-rings give indication for decreasing soil pH. Acidification is a contrary process to temperature increase, as it generally reduces the microbial activity and therefore the availability of nutrients.

We examined the radial growth - climate association of a disjunct population of white spruce (Picea glauca (Moench) Voss) at its southern limit of distribution. Forty-four white spruce tree islands were sampled over four mixed-grass prairie preserves in the Spruce Woods Provincial Park located in the forestprairie boundary of southwestern Manitoba. Reduced radial growth occurred during the 1910s, 1930s, early 1960s, and the late 1970s to the early 1980s and corresponded to periods of drought on the Canadian prairies, and the Great Plains of the United States. Correlation and response function coefficients indicated that conditions in the summer and fall of the previous year (t-1), and the summer of the current year (t) strongly influenced white spruce growth. Growth was positively correlated with August-September (t-1) and May-June-July (t) precipitation and moisture index (precipitation minus potential evapotranspiration). Radial growth was positively associated with June-July-August (t) river discharge. Growth was most correlated with maximum and mean temperature compared with minimum temperature. Precipitation and maximum temperature accounted for the greatest variation in radial growth (61%). The results suggest that white spruce growth is sensitive to climatic fluctuations because growth is restricted by moisture deficiency exacerbated by temperature-induced drought stress.

O presente estudo tem por objetivo avaliar o crescimento e a qualidade do lenho das árvores de Cariniana legalis submetidas a diferentes espaçamentos (3x1,5; 3x2; 3x2,5 m). O experimento localiza-se na Estação Experimental de Luiz Antônio-SP, do Instituto Florestal do Estado de São Paulo. Foram selecionadas 30 árvores de jequitibá rosa (10 árvores/tratamento) e seccionados discos na base, DAP e a cada 5m do tronco até a altura comercial das árvores. Foram realizadas as análises (i) anatômicas, com a descrição macro e microscópica do lenho com ênfase aos anéis de crescimento e (ii) dendrocronológicas, para a comprovação da anuidade da formação dos anéis de crescimento; (iii) densitometria de raios X, para obtenção do perfil longitudinal - radial de densidade aparente do lenho e imagem digital do lenho; (iv) dendroclimatologia, para verificar a influência dos fatores climáticos, como a precipitação e temperatura na formação dos anéis de crescimento e da (v) influência do espaçamento no crescimento radial acumulado/médio anual do tronco e no volume das árvores/ha. Os resultados indicaram que as árvores de C. legalis apresentam anéis de crescimento distintos, com a dendrocronologia confirmando a idade das árvores (38 anos) e a anuidade da formação dos anéis de crescimento. A densidade aparente do lenho decresce da base até a região intermediária, tendendo a aumentar próximo ao topo do tronco das árvores, com o maior valor no maior e menor espaçamento. As imagens digitais do lenho indicaram um decréscimo da densidade aparente do lenho no sentido medula - casca. Nos três espaçamentos, a análise dendroclimatológica indicou uma influência significativa das variáveis climáticas no crescimento radial do tronco das árvores de Cariniana legalis. Os meses do ano que influenciaram o crescimento radial do tronco das árvores foram distintos entre os tratamentos sendo que, entretanto, verifica-se um padrão de crescimento do tronco semelhante e relacionado com a precipitação mensal acumulada. O espaçamento entre árvores influenciou diretamente no ritmo de crescimento do tronco das árvores, sendo que as do maior espaçamento apresentaram a maior produção volumétrica do lenho, e as do menor espaçamento, o maior volume de madeira/ha. Conclui-se que a área do espaço vital (espaçamento) influencia significativamente o desenvolvimento das árvores de Cariniana legalis. / The present study aims to assess growth and wood quality of Cariniana legalis trees in forest plantations under different espacements (1.5x3, 3x2, 3x2.5 m). The experiment is located in Luiz Antônio, São Paulo, at the Experimental Station belonging to the Forest Institute of São Paulo. It was selected 30 trees of \"jequitibá rosa\" (10 per treatment) and sectioned discs were removed at the base, DBH and every 5m to commercial height. With these samples 5 different analyzis were performed: (i) anatomical, by means of wood macroscopic and microscopic description with a view to growth rings, (ii) dendrochronological, to prove growth rings annuality; (iii) X-ray densitometry and digital X-rays to obtain the radial density profile in the longitudinal and radial direction; (iv) dendroclimatological, for checking the influence of climatic factors (monthly precipitation and average annual temperature) in growth rings formation and (v) verification of espacement influence on cumulative and annual radial growth, volume per tree and per hectare. Wood description indicates C. legalis trees have distinct growth rings. Dendrochronology confirmed annuity formation of growth rings as the number of rings found matches with the age of plantation, 38 years old. Apparent density decreases from the base to the middle region of the stem and tends to increase near the top, with higher average values in both widest and closest espacements. The analysis of digital images indicated a decrease in apparent density in pith-bark direction. Dendroclimatology indicated there was significant influence of climatic variables on radial growth of Cariniana legalis trees. The months influencing radial growth were different between treatments, however there is a similar pattern of growth related to monthly precipitation. The espacements used influenced directly the growth rate of the trees. The ones inserted in widest espacements had the highest volumetric production, on the other hand the largest volume per hectare occurred in the closest espacements. The conclusion was that size of living space influences significantly the development of C. legalis trees.

Cette thèse a pour objectif de déterminer le devenir des populations marginales d’arbres boréo-montagnards dans le contexte des changements climatiques. La réponse dendroclimatique et la structure génétique des espèces sont analysées conjointement sur des gradients incluant les zones de distributions continues et marginales. Les deux modèles biologiques choisis sont le thuya occidental en limite nordique (forêt boréale canadienne) et le pin cembro en limite occidentale (Alpes). Les hypothèses suivantes ont été testées : le réchauffement climatique au cours du XXe siècle a entrainé une augmentation de croissance ; la variabilité de croissance est reliée à la structure génétique aux niveaux intra- et inter-populationnels. Une baisse de croissance du thuya a été observée après 1980 en zone marginale, qui serait liée à une limitation par la sécheresse. Pour les deux espèces, les relations climat-croissance étaient essentiellement modulées par le volume des précipitations, mais également par des variables édaphiques et par la taille des arbres. L’existence d’un lien significatif entre la structure génétique et certaines variables climatiques laisse néanmoins espérer un potentiel d'adaptation génétique, dont l’ampleur dépendra de la diversité génétique disponible pour la sélection naturelle. Par ailleurs, le synchronisme de croissance entre les arbres était à la fois influencé par la diversité génétique intra-populationnelle et par le volume des précipitations. En conclusion, il apparaît très difficile de distinguer les effets du climat et de la génétique sur la croissance des arbres étudiés. / This thesis aims to assess the fate of marginal populations, in the context of climate change, for boreo-mountain tree species. The dendroclimatic response and the genetic structure of the species are jointly analyzed on gradients including both the continuous and the marginal distribution zones. Two biological models have been chosen for this research, white cedar at its northern limit (boreal forest) and stone pine at its western limit (temperate mountain forest). The following hypotheses were tested: global warming during the twentieth century has led to increased growth; growth variability is related to the genetic structure at the intra- and inter-population levels. A decline in cedar growth was observed after 1980 in marginal zone, which could be linked to drought constraints on growth. For both species, climate-growth relationships were essentially modulated by the amount of precipitation, but also by soil and tree-size variables. The existence of a significant link between genetic structure and some climatic variables still leaves some hope for a genetic adaptation potential, which magnitude will depend on the genetic diversity available for natural selection. The growth synchronicity between the trees was both influenced by the intra-population genetic diversity and the amount of precipitation. In conclusion, it is very difficult to disentangle the effects of climate and genetics on the growth of the studied trees.

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.

The tropical warm pool waters surrounding Indonesia are one of the equatorial heat and moisture sources that are considered as a driving force of the global climate system. The climate in Indonesia is dominated by the equatorial monsoon system, and has been linked to El Niño-Southern Oscillation (ENSO) events, which often result in severe droughts or floods over Indonesia with profound societal and economic impacts on the populations living in the world's fourth most populated country. The latest IPCC report states that ENSO will remain the dominant mode in the tropical Pacific with global effects in the 21st century and ENSO-related precipitation extremes will intensify. However, no common agreement exists among climate simulation models for projected change in ENSO and the Australian-Indonesian Monsoon. Exploring high-resolution palaeoclimate archives, like tree rings or varved lake sediments, provide insights into the natural climate variability of the past, and thus helps improving and validating simulations of future climate changes. Centennial tree-ring stable isotope records | Within this doctoral thesis the main goal was to explore the potential of tropical tree rings to record climate signals and to use them as palaeoclimate proxies. In detail, stable carbon (δ13C) and oxygen (δ18O) isotopes were extracted from teak trees in order to establish the first well-replicated centennial (AD 1900-2007) stable isotope records for Java, Indonesia. Furthermore, different climatic variables were tested whether they show significant correlation with tree-ring proxies (ring-width, δ13C, δ18O). Moreover, highly resolved intra-annual oxygen isotope data were established to assess the transfer of the seasonal precipitation signal into the tree rings. Finally, the established oxygen isotope record was used to reveal possible correlations with ENSO events. Methodological achievements | A second goal of this thesis was to assess the applicability of novel techniques which facilitate and optimize high-resolution and high-throughput stable isotope analysis of tree rings. Two different UV-laser-based microscopic dissection systems were evaluated as a novel sampling tool for high-resolution stable isotope analysis. Furthermore, an improved procedure of tree-ring dissection from thin cellulose laths for stable isotope analysis was designed. The most important findings of this thesis are: I) The herein presented novel sampling techniques improve stable isotope analyses for tree-ring studies in terms of precision, efficiency and quality. The UV-laser-based microdissection serve as a valuable tool for sampling plant tissue at ultrahigh-resolution and for unprecedented precision. II) A guideline for a modified method of cellulose extraction from wholewood cross-sections and subsequent tree-ring dissection was established. The novel technique optimizes the stable isotope analysis process in two ways: faster and high-throughput cellulose extraction and precise tree-ring separation at annual to high-resolution scale. III) The centennial tree-ring stable isotope records reveal significant correlation with regional precipitation. High-resolution stable oxygen values, furthermore, allow distinguishing between dry and rainy season rainfall. IV) The δ18O record reveals significant correlation with different ENSO flavors and demonstrates the importance of considering ENSO flavors when interpreting palaeoclimatic data in the tropics. The findings of my dissertation show that seasonally resolved δ18O records from Indonesian teak trees are a valuable proxy for multi-centennial reconstructions of regional precipitation variability (monsoon signals) and large-scale ocean-atmosphere phenomena (ENSO) for the Indo-Pacific region. Furthermore, the novel methodological achievements offer many unexplored avenues for multidisciplinary research in high-resolution palaeoclimatology. / Die tropischen Gewässer um Indonesien sind eine der äquatorialen Wärme- und Feuchtigkeitsquellen, die als treibende Kraft des globalen Klimasystems betrachtet werden können. Das Klima in Indonesien ist geprägt durch das Australisch-Indonesische Monsunsystem. Weiterhin besteht eine Verknüpfung mit El Niño-Southern Oszillation (ENSO) Ereignissen, die oft zu schweren Dürren oder Überschwemmungen in der Region mit tiefgreifenden gesellschaftlichen und wirtschaftlichen Folgen führen. Der neueste IPCC-Bericht legt dar, dass ENSO auch in den nächsten 100 Jahren das vorherrschende Klimaphänomen im tropischen Pazifik bleiben wird. Ferner wird davon ausgegangen, dass sich die ENSO-bezogenen Niederschlagsextrema intensivieren werden. Wenig Übereinstimmung herrscht jedoch bislang zwischen den Klimasimulationsmodellen in Bezug auf die voraussichtlichen Veränderungen von ENSO und dem Australisch-Indonesischen Monsunsystem. Hochaufgelöste Paläoklima-Archive, wie z.B. Jahrringe oder warvierte Seesedimente, geben Auskunft über die natürliche Klimavariabilität der Vergangenheit und können somit dazu beitragen, die Computersimulationen der künftigen Klimaentwicklung zu verbessern und zu validieren. Hundertjährige stabile Jahrring-Isotopenchronologien | Das Hauptziel dieser Doktorarbeit war es, dass Potenzial von tropischen Jahrringen zur Aufzeichnung von Klimasignalen herauszustellen und deren Evaluierung als Paläoklimaproxys. Im Detail wurden stabile Kohlenstoff- (δ13C) und Sauerstoff- (δ18O) Isotopenverhältnisse in Teakbäumen analysiert, und die ersten gut replizierten hundertjährigen (AD 1900-2007) stabilen Isotopenchronologien aus Java (Indonesien) erstellt. Dabei wurden verschiedene klimatische Einflussgrößen getestet, ob diese signifikante Korrelationen mit den Jahrringparametern aufzeigen. Weiterhin wurden hochaufgelöste intra-annuelle Sauerstoffisotopenzeitreihen erstellt, um den Transfer des saisonalen Niederschlagssignals in den jeweiligen Jahrring zu bemessen. Die ermittelte Sauerstoff-Isotopenchronologie wurde anschließend auf mögliche ENSO Signale hin untersucht. Methodische Errungenschaften | Ein zweites Ziel dieser Arbeit war es neue Verfahren zur Analyse stabiler Isotope in Baumjahrringen zu entwickeln und zu optimieren. Zwei verschiedene UV-Lasermikrodissektions-Systeme wurden getestet als neues präzises Präparationswerkzeug für stabile Isotopenstudien. Darüber hinaus wurde eine verbesserte Methode für die Probenaufbereitung stabiler Isotopenmessungen anhand von Zellulose-Dünnschnitten entwickelt. Die wichtigsten Ergebnisse dieser Doktorarbeit sind: I) Die hier vorgestellten neuartigen Techniken zu Probenvorbereitung verbessern die Analyse stabiler Isotope für Jahrringstudien in Hinsicht auf Präzision, Effizienz und Qualität. Es wurde gezeigt, dass die UV-Lasermikrodissektion eine wertvolle Technik ist, um die Beprobung von Pflanzengewebe in höchster Auflösung und beispielloser Präzision durchzuführen. II) Es ist gelungen, einen Leitfaden für ein modifiziertes Verfahren der Zelluloseextraktion an Gesamtholz-Dünnschnitten und der anschließenden Jahrringaufbereitung zu erstellen. Diese neuartige Methode optimiert die Analyse stabiler Isotopenzeitreihen in zweierlei Hinsicht: schnellere und effiziente Zelluloseextraktion und präzise Trennung der Jahrringsequenzen in inter-annueller bis intra-annuelle Auflösung. III) Die hundertjährigen stabilen Jahrring-Isotopenchronologien weisen signifikante Korrelationen mit dem regionalen Niederschlag auf. In den hochaufgelösten stabilen Sauerstoffisotopenwerten spiegelt sich deutlich das Niederschlagssignal der Trocken- und der Regenzeit wieder. IV) Die stabile Sauerstoffisotopenzeitreihe zeigt signifikante Korrelationen mit verschiedenen ENSO Phasen. Dies betont, dass die verschiedenen ENSO Phasen bei der Interpretation von tropischen Paläodaten zu berücksichtigen sind. Die Ergebnisse der Dissertation zeigen, dass saisonal aufgelöste stabile Sauerstoffisotopenchronologien von indonesischen Teakbäumen ein geeigneter Proxy für mehrhundertjährige Rekonstruktionen der regionalen Niederschlagsvariabilität (Monsun-Signale) und großräumiger Ozean-Atmosphären-Systeme (ENSO) für den Indopazifik ist. Darüber hinaus bieten die neuartigen methodischen Errungenschaften viele neue Ansätze für multidisziplinäre hochaufgelöste Studien in der paläoklimatologischen Forschung.

A 616-year Douglas-fir (Pseudotsuga menziesii) chronology was developed to examine the history of drought and moisture variability in the Sooke Watershed, near Victoria, British Columbia. Ring-width chronologies were compared to historical precipitation, air temperature and drought variables (Palmer Drought Severity Index (PDSI) and Standardized Precipitation Index (SPI)) to determine the climate/radial-growth response to moisture stress on the sampled stands. Correlations between the ring-width chronologies and climate variables revealed that May to July precipitation, May-June SPI and July PDSI were significant limiting factors to radial-width growth. A transfer function was established for each of these variables to create a proxy climate reconstruction of drought in the watershed. The summer precipitation model provided the most accurate representation of past moisture variability (R2 = 0.20) and reveals substantial variation in precipitation over the past six centuries. Evidence from the periodicity of the tree-ring record to suggest that some modes of atmospheric circulation are influencing precipitation supply to the watershed.

A 616-year Douglas-fir (Pseudotsuga menziesii) chronology was developed to examine the history of drought and moisture variability in the Sooke Watershed, near Victoria, British Columbia. Ring-width chronologies were compared to historical precipitation, air temperature and drought variables (Palmer Drought Severity Index (PDSI) and Standardized Precipitation Index (SPI)) to determine the climate/radial-growth response to moisture stress on the sampled stands. Correlations between the ring-width chronologies and climate variables revealed that May to July precipitation, May-June SPI and July PDSI were significant limiting factors to radial-width growth. A transfer function was established for each of these variables to create a proxy climate reconstruction of drought in the watershed. The summer precipitation model provided the most accurate representation of past moisture variability (R2 = 0.20) and reveals substantial variation in precipitation over the past six centuries. Evidence from the periodicity of the tree-ring record to suggest that some modes of atmospheric circulation are influencing precipitation supply to the watershed.