京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第18523号 / 農博第2080号 / 新制||農||1026(附属図書館) / 学位論文||H26||N4867(農学部図書室) / 31409 / 京都大学大学院農学研究科農学専攻 / (主査)教授 白岩 立彦, 教授 奥本 裕, 教授 稲村 達也 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

<p>This thesis focuses on responses in raised bogs to changes in the effective humidity during the Holocene. Raised bogs are terrestrial deposits that can provide contiguous records of past climate changes. Information on and knowledge about past changes in climate is crucial for our understanding of natural climate variability. Analyses on different spatial and temporal scales have been conducted on a number of raised bogs in south-central Sweden in order to gain more knowledge about Holocene climate variability.</p><p>Peatlands are useful as palaeoenvironmental archives because they develop over the course of millennia and provide a multi-faceted contiguous outlook on the past. Peat humification, a proxy for bog surface wetness, has been used to reconstruct palaeoclimate. In addition measurements of carbon and nitrogen on sub-recent peat from two bogs have been performed. The chronologies have been constrained by AMS radiocarbon dates and tephrochronology and by SCPs for the sub-recent peat.</p><p>A comparison between a peat humification record from Värmland, south-central Sweden, and a dendrochronological record from Jämtland, north-central Sweden, indicates several synchronous changes between drier and wetter climate. This implies that changes in hydrology operate on a regional scale.</p><p>In a high resolution study of two bogs in Uppland, south-central Sweden, C, N and peat humification have been compared to bog water tables inferred from testate amoebae and with meteorological data covering the last 150 years. The results indicate that peat can be subjected to secondary decomposition, resulting in an apparent lead in peat humification and C/N compared to biological proxies and meteorological data.</p><p>Several periods of wetter conditions are indicated from the analysis of five peat sequences from three bogs in Värmland. Wetter conditions around especially c. 4500, 3500, 2800 and 1700-1000 cal yr BP can be correlated to several other climate records across the North Atlantic region and Scandinavia, indicating wetter and/or cooler climatic conditions at these times. Frequency analyses of two bogs indicate periodicities between 200 and 400 years that may be caused by cycles in solar activity.</p>

This thesis focuses on responses in raised bogs to changes in the effective humidity during the Holocene. Raised bogs are terrestrial deposits that can provide contiguous records of past climate changes. Information on and knowledge about past changes in climate is crucial for our understanding of natural climate variability. Analyses on different spatial and temporal scales have been conducted on a number of raised bogs in south-central Sweden in order to gain more knowledge about Holocene climate variability. Peatlands are useful as palaeoenvironmental archives because they develop over the course of millennia and provide a multi-faceted contiguous outlook on the past. Peat humification, a proxy for bog surface wetness, has been used to reconstruct palaeoclimate. In addition measurements of carbon and nitrogen on sub-recent peat from two bogs have been performed. The chronologies have been constrained by AMS radiocarbon dates and tephrochronology and by SCPs for the sub-recent peat. A comparison between a peat humification record from Värmland, south-central Sweden, and a dendrochronological record from Jämtland, north-central Sweden, indicates several synchronous changes between drier and wetter climate. This implies that changes in hydrology operate on a regional scale. In a high resolution study of two bogs in Uppland, south-central Sweden, C, N and peat humification have been compared to bog water tables inferred from testate amoebae and with meteorological data covering the last 150 years. The results indicate that peat can be subjected to secondary decomposition, resulting in an apparent lead in peat humification and C/N compared to biological proxies and meteorological data. Several periods of wetter conditions are indicated from the analysis of five peat sequences from three bogs in Värmland. Wetter conditions around especially c. 4500, 3500, 2800 and 1700-1000 cal yr BP can be correlated to several other climate records across the North Atlantic region and Scandinavia, indicating wetter and/or cooler climatic conditions at these times. Frequency analyses of two bogs indicate periodicities between 200 and 400 years that may be caused by cycles in solar activity.

Diatoms are microscopic algae found in almost all aquatic environments. They are habitat specific and have silica frustules which preserve well in sediments. They have been used extensively to provide a multitude of palaeoecological data relating to pH, nutrient loads and water levels. Here, the diatoms in a lake sediment core from Hluhluwe-Imfolozi, South Africa, are analysed to show fluctuations in littoral to benthic taxa, and brackish to freshwater taxa as indicators of lake level changes over time. Changes in lake level act as a proxy for warm/dry or cold/wet periods over time. During the last 240 years lake levels have remained consistently low but nevertheless indicate four alternating periods of cold/wet and warm/dry climate. From c. A.D. 1770 (the last few decades of the Little Ice Age) to the c. A.D. 1840 the climate was cool and wet, but nonetheless gradually warmed up and became drier. From c. A.D. 1840 through to c. A.D. 1920 a there was a gradual increase in temperature and corresponding decrease in rainfall. Then, from c. A.D. 1920 till c. A.D. 1980 there was another colder, wetter period. Finally, very recently, from around c. A.D. 1980 till the present day, Hluhluwe-Imfolozi has experienced warmer, drier conditions once. Pollution-tolerant diatoms increase during the last 100 years and indicate eutrophication of the lake, a consequence of anthropogenic activity in the region. The diatom sequence from Phindiswene provides a high resolution climatic proxy for the critical period covering the latter stages of the Little Ice Age (LIA), post LIA warming, and recent increasing anthropogenic impacts.

En Afrique subsaharienne, une large partie de la population pratique l’agriculture pluviale. Cette agriculture est particulièrement sensible à la variabilité climatique. Le mil (Pennisetum glaucum L Br) est une des céréales pluviales qui jouent un rôle majeur dans la sécurité alimentaire en Afrique subsaharienne. L’apparenté sauvage du mil cultivé pousse dans des environnements encore plus extrêmes que la forme cultivée. L’objectif de la thèse est l’étude de l’adaptation du mil à la variation environnementale. En utilisant des approches d’association génotype /phénotype, nous avons démontré que le gène de la myosine 11 est associé à la variation du nombre de fleurs chez le mil sauvage observée le long d’un gradient environnemental. En plus, ce gène a également été identifié dans les candidats pour les gènes sélectionnés durant la domestication. En utilisant des données génomiques, nous avons aussi démontré que le gène du Photochrome C déjà connu pour son rôle dans le contrôle de la variation du temps de floraison chez le mil cultivé, est aussi associé à la variation du temps de floraison chez le mil sauvage. Nous avons aussi démontré l'existence d'un polymorphisme fonctionnel cryptique (caché) qui n’apparaît que dans certaines conditions particulières associées au temps de floraison. Ce polymorphisme cryptique peut être mobilisé dans des conditions climatiques ou environnementales particulières. Chez le mil cultivé, nous avons aussi pu mettre en évidence la sélection in situ sur deux gènes de floraison. Nos résultats suggèrent que de nombreux polymorphismes associés à l’adaptation sont présents dans les populations et peuvent être partagés entre forme sauvage et cultivée. En réponse aux changements environnementaux, ces polymorphismes pourraient être mobilisés pour proposer des variétés mieux adaptées. / In sub-Saharan Africa, a large fraction of the population practice rainfed agriculture. Rainfed agriculture is particularly sensitive to climate variability. Pearl millet (Pennisetum glaucum L R) is one of the main cereals that play an important role in food security in sub-Saharan Africa. Wild pearl millet populations grow also in more extreme climate conditions up to the limit of the desert. The aim of this PhD was to study pearl millet adaptation to climate variation. Using an association genotype / phenotype approach, we demonstrated that the myosin 11 gene is associated with flower number variation in wild millet along an environmental gradient. Interestingly, this gene was also a candidate gene target of selection during domestication. The Myosin XI gene is thus a good candidate for fitness related adaptation in wild populations. We also demonstrated that Photochrome C gene, already known for its role in cultivated pearl millet, is also related to flowering time variation in wild pearl millet. We have demonstrated the existence of cryptic functional polymorphisms associated with flowering time. Such cryptic functional polymorphism might contribute to adaptation in specific new environment. In cultivated pearl millet, we also show in situ selection on two flowering genes. Our results suggest that the functional polymorphisms are observed in these populations, some genes are also associated with both adaptations in wild and cultivated populations. In response to environmental changes, such polymorphism could be used to propose better adapted cultivated varieties.

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No. of bitstreams: 1 Amanda Veit Braune Alvarez.pdf: 3256884 bytes, checksum: 8bc5e93bc57f146f1519c7695a8d09ca (MD5) Previous issue date: 2018-02-28 / Esse estudo tem como objetivo analisar como os membros da cadeia de suprimentos de cacau no Brasil percebem a influência da variação climática nos riscos existentes nesta cadeia. Essa cadeia foi escolhida devido a sua grande importância na economia brasileira. Para que essa análise fosse possível, foram identificados os principais riscos desta cadeia, bem como eventos climáticos recentes, suas possíveis influências e as ações mitigadoras adotadas pelos membros da cadeia. Foram feitas 17 entrevistas semiestruturadas com respondentes de todos os elos da cadeia: produtores, atravessadores, moageiras e indústrias de chocolates. Alguns dos resultados da pesquisa apontam que essa cadeia é afetada por riscos relacionados à carência de informação entre os elos, baixa manutenção dos equipamentos e pouca tecnologia na produção, baixa precisão de previsão de safra e, inclusive, problemas na qualidade e produtividade na produção. Mudanças de temperaturas, ventos e umidade também foram considerados como riscos nesta cadeia. Essas alterações climáticas aumentam a incidência dos outros riscos, por exemplo: pragas na produção, necessidade de importação, riscos financeiros e dificuldade logística. A seca de 2016 afetou diretamente a exposição e vulnerabilidade dessa cadeia aos riscos, tendo como consequências diretas a redução da produtividade e da qualidade das amêndoas. Além disso, este evento causou rupturas na cadeia, ocasionando a saída de alguns produtores e indústrias do mercado. Ações mitigadoras têm sido implementadas por associações que auxiliam produtores de cacau, indústrias moageiras e de chocolates e, por grandes produtores. Grande parte dessas ações são referentes a como os produtores podem lidar com as influências das variações climáticas em suas produções. Um dos objetivos dessas ações é que as fazendas possam aumentar a produtividade e qualidade de suas amêndoas, com inclusão de tecnologias para o manejo do cacau e de outras culturas na produção. Como consequência, moageiras e industrias de chocolate também poderão reduzir seus riscos, minimizando a necessidade de importar amêndoas e aumentando a qualidade de seus produtos. / The aim of this study is to analyze how members of the Brazilian cocoa supply chain perceive the influence of climate variations on other supply chain risks. This chain was chosen due to its importance in the Brazilian economy. Conducting this analysis entailed identifying not only the main risks to the Brazilian cocoa supply chain but also recent climatic events and their likely influence; the mitigating strategies adopted by supply chain members were also analyzed. A total of 17 semi-structured interviews were conducted with respondents belonging to all nodes of the chain: producers, middlemen, and the grinding and chocolate industries. Some of the research results indicate that the Brazilian cocoa supply chain is affected by risks related to a lack of information among its members, low equipment maintenance and poor production technology, low precision of crop forecasting, quality problems, and low productivity at production. Temperature variations, winds and humidity were also considered as chain risks. Climate variations increase the incidence of other risks, such as pests in production, import necessity, financial risks and logistical bottlenecks. The 2016 drought directly affected the exposure and vulnerability of this chain to risks, resulting in reduced productivity and quality of cocoa beans. In addition, the drought caused supply chain disruptions, which caused some producers and industries to leave the market. Mitigating actions have been implemented by associations that provide help to cocoa producers, grinding and chocolate factories, and large scale producers. Many of these actions are related to how producers can deal with the influence of climate variations on their crops. One of the goals of these actions targets the fact that farms can increase their cocoa bean productivity and quality by learning about additional technologies for handling cocoa and about new crops that could be incorporated into production. By adopting these strategies, the grinding and chocolate industries could also reduce their risks, minimizing the need to import cocoa beans while increasing the quality of their products.