Dans les pays du Sud ruraux et à faibles revenus, la vulnérabilité des zones agricoles pluviales, face à la variabilité pluviométrique, nécessite de trouver des solutions efficaces pour limiter les effets des aléas climatiques sur les récoltes. La prévision des caractéristiques des saisons des pluies quelque temps avant leur démarrage devrait aider à l’établissement de stratégies agricoles d’adaptation aux aléas pluviométriques. C’est à cet objectif que s’attache ce travail, appliqué à l’Afrique de l’Est (Kenya et nord de la Tanzanie), et articulé en 3 parties :- Définir et comprendre le comportement des descripteurs intra saisonniers (DIS) qui feront l’objet de l’étude de prévisibilité. Un travail spécifique a permis le développement d’une nouvelle approche méthodologique dans la manière de définir les démarrages (DSP) et fins (FSP) de saisons des pluies à l’échelle régionale. Cette approche basée sur une analyse multivariée, permet de s’affranchir des choix subjectifs de seuils pluviométriques imposés par les définitions communément utilisée en agro-climatologie. Une analyse de cohérence spatiale à l’échelle inter annuelle montre que, pour les deux saisons des pluies (long rains et short rains), le cumul saisonnier et le nombre de jours de pluie présentent une forte cohérence spatiale, tandis qu’elle est plus modérée pour le démarrage et fin des saisons et faible pour l’intensité quotidienne moyenne.- Analyser la prévisibilité des DIS aux 2 échelles spatiales régionale et locale en s’appuyant sur les simulations numériques du modèle climatique global ECHAM 4.5. Les précipitations quotidiennes simulées par le modèle, même après correction des biais, ne permettent pas d’appréhender correctement la variabilité interannuelle des DIS. Une spécification de la variabilité des DSP et FSP menée par le biais de modèles statistiques construits à partir d’indices climatiques observés, présuppose une prévisibilité modérée des deux descripteurs à l’échelle locale (régionale), et cela quelle que soit la saison. Le développement de modèles statistico-dynamiques à partir des champs de vents simulés par ECHAM 4.5, en mode forcé par les températures marines observées d’une part et prévues d’autre part, montre également des performances faibles localement et régionalement. - Explorer la manière dont la variabilité spatio-temporelle des paramètres climatiques et environnementaux module la variabilité des rendements de sorgho. Ces rendements sont simulés par le modèle agronomique SARRA-H à partir de données climatiques observées (1973-2001) dans 3 stations localisées à différentes altitudes le long des pentes orientales du Mt Kenya. Le cumul précipité et la durée de la saison expliquent une part importante de la variabilité des rendements. D’autres variables apparaissent comme jouant un rôle non négligeable ; le nombre de jours de pluies, l’intensité quotidienne moyenne ou encore certains DIS relatifs à l’organisation temporelle des pluies au sein d’une saison en font partie. L’influence des autres variables météorologiques est seulement visible pour les ‘long rains’ avec une covariation négative entre les rendements et les températures maximales ou, le rayonnement global. La date de semis semble jouer un rôle dans la modulation des rendements pour les stations de haute et moyenne altitudes, mais avec des différences notables entre les deux saisons des pluies. / In Southern countries with rural low income populations, the vulnerability of rainfed agriculture to rainfall variability requires effective solutions to mitigate the effects of climatic hazards on crops. Predicting the characteristics of rainy seasons some time before they start should help the establishment of agricultural adaptation strategies to rainfall hazards. This is the objective of the present study, focused on East Africa (Kenya and northern Tanzania), and divided in three parts:- Define and document intra-seasonal descriptors (ISD) that will be considered in the predictability study. A new methodological approach has been developed in order to define the onset date (ORS) and the cessation date (CRS) of the rainy seasons at the regional level. Based on a multivariate analysis, it eliminates the subjective choice of rainfall thresholds imposed by the definitions commonly used in agroclimatology. An analysis of spatial coherence at interannual time-scale shows that for the two rainy seasons ("long rains" and "short rains"), the seasonal amount and the number of rainy days have a high spatial coherence, while it is medium for the onset and cessation dates and low for the average daily rainfall intensity.- Analyze the predictability of the ISD at both regional and local scales based on numerical simulations from the global climate model ECHAM 4.5. Daily precipitation simulated by the model, even after bias correction, do not correctly capture the IDS interannual variability. A specification of the ORS and CRS variability using statistical models applied to observed climate indices, suggests quite a low predictability of the descriptors at the local (regional) scale, regardless of the season. The development of statistical-dynamical models from wind fields simulated by ECHAM 4.5, in experiments forced by either observed or predicted sea temperatures, also shows quite poor skills locally and regionally.- Explore how the space-time variability of climatic and environmental factors modulate the variations of sorghum yields. Crop yields are simulated by the agronomic model SARRA-H using observed climate data (1973-2001) at three stations located at different elevations along the eastern slopes of Mt Kenya. The seasonal rainfall accumulation and the duration of the season account for a large part of the yields variability. Other rainfall variables also play a significant role, among which the number of rainy days, the average daily intensity and some ISD related to the temporal organization of rainfall within the season. The influence of other meteorological variables is only found during the long rains, in the form of a negative correlation between yields and both maximum temperature and global radiation. Sowing dates seem to play a role in modulating yields for high and medium altitude stations, but with notable differences between the two rainy seasons.

A consequence of climate change may be higher frequencies and higher intensities of extreme climate events all over the world. This paper takes a closer look at the Northern Vietnam climate conditions. The area of interest are the geographical regions North East, North West, Red River Delta and North Central Coast. For research of extreme climate, the data from 72 meteorological stations for the time period from 1975 to 2006 were used and tested for the rainy season with the method of indices for climate change research created by Expert Team on Climate Change Detection (ETCCDI). Apparently, there is a linkage between the indices and topics of social and economic impacts, but this is not a clear fact. The climate change and extreme precipitation indices of the annual total precipitation above the 95th percentile (R95p), the annual total precipitation above the 99th percentile (R99p), the simple precipitation intensity amount (SDII), the annual total precipitation on wet days (PRCPTOT) and a modified annual total precipitation above 50 mm (R50mm) are used in this study. The question, whether there are statistically significant trends is answered using the Mann-Kendall Trend test. The results show that the indices are strongly influenced by the variations of the Vietnamese climate. Hence many stations have no significant trends. For the investigated time period, most of significance trends were decreasing. But there is a positive correlation between the total precipitation in the rainy season (PRCPTOT) and the frequencies of extreme climate events above the indices thresholds from R95p and R99p. Concluding, climate models show that higher total precipitations are likely for the area of interest. Therefore, it can be expected that, in a changing climate, more extreme climate events with higher intensities will occur. / Biến đổi khí hậu có thể dẫn đến sự gia tăng về tần số và cường độ của các hiện tượng thời tiết cực đoan trên toàn thế giới. Nghiên cứu này sẽ xem xét kỹ hơn về các điều kiện khí hậu ở miền Bắc Việt Nam. Địa điểm nghiên cứu bao gồm các khu vực địa lý Đông Bắc, Tây Bắc, Đồng bằng sông Hồng và Bắc Trung Bộ. Để nghiên cứu về khí hậu cực đoan, các dữ liệu trong khoảng thời gian từ 1975 đến 2006 đã được thu thập từ 72 trạm khí tượng. Những dữ liệu này được dùng để kiểm chứng đối với mùa mưa theo phương pháp chỉ số nghiên cứu biến đổi khí hậu của Nhóm chuyên gia về phát hiện biến đổi khí hậu (ETCCCDI). Hiển nhiên có một mối liên hệ giữa các chỉ số với các chủ đề về tác động kinh tế và xã hội, tuy nhiên thực tế này vẫn chưa rõ ràng. Các chỉ số biến đổi khí hậu và mưa cực đoan của tổng mưa hằng năm trên 95 phần trăm (R95p), tổng mưa hằng năm trên 99 phần trăm (R99p), chỉ số cường độ mưa trên ngày (SDII), tổng mưa hằng năm vào những ngày ẩm ướt – mùa mưa (PRCPTOT) và tổng mưa hằng năm biến đổi trên 50mm (R50mm) được sử dụng trong nghiên cứu này. Câu hỏi về sự tồn tại của các xu hướng quan trọng về mặt thống kê được trả lời bằng phương pháp Mann-Kendall Trend. Các kết quả chỉ ra rằng các chỉ số chịu ảnh hưởng lớn từ sự biến đổi của khí hậu Việt Nam. Do vậy, ở một số trạm khí tượng không có các xu hướng có ý nghĩa. Trong khoảng thời gian nghiên cứu, các xu hướng quan trọng đều giảm. Tuy nhiên, có một mối tương quan thuận giữa tổng lượng mưa trong mùa mưa (PRCPTOT) và cường độ của các hiện tượng thời tiết cực đoan trên các cực của chỉ số từ R95P và R99p. Kết luận, các mô hình thời tiết cho thấy tổng lượng mưa lớn hơn có khả năng sẽ xảy ra trên địa bàn nghiên cứu. Vì vậy, có thể phỏng đoán rằng khi thay đổi khí hậu, sẽ diễn ra nhiều hiện tượng thời tiết cực đoan với cường độ cao.

Euclea undulata Thunb. var myrtina is a widely distributed shrub in South Africa. The roots are used by traditional healers for the treatment of diabetes. Research indicates that roots contain epicatechin, lupeol as well α-amyrin-3O-β-(5-hydroxy) ferulic acid. It was found that α-amyrin-3O-β-(5-hydroxy) ferulic acid inhibits α-glucosidase while epicatechin lowers glucose levels in the blood. Existing literature also indicates the presence of the naphthoquinone 7-methyl-juglone in the roots, although it was not detected in all cases. Due to its cytotoxic nature, 7-methyl-juglone poses a potential threat when E. undulata is used as medicinal treatment. In order to assist the effective and safe use of this plant as a treatment for diabetes, this project aims to determine whether the presence of these metabolites is seasonal. It further aims to contribute to more sustainable harvesting methods by investigating stems and leaves in addition to the roots for the presence of these metabolites. / Environmental Sciences / M. Sc. (Environmental Science)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Animal performance was evaluated in bovine cattle livestock systems using tropical pasture based diets through a meta-analysis process, which included a database of scientific articles, dissertations and theses. Data was tabulated and categorized identifying the scientific work, the experiment, animals, animal performance, pasture, supplements and grazing. The conversion efficiency of supplement use was evaluated in the studies containing control (no supplementation), and calculated as the change in average daily gain of individual weight (CoEfADGan) or area (ha, CoEfADGha) per kg of supplement offered. Data distribution from a general database was assessed. To analyze the factors affecting animal performance variables the general database was sub-divided into two sub-bases, rainy and dry season. To evaluate the factors affecting animal performance variables data was weighted by n treatments and analysis of variance and covariance was used. The average daily gain of body weight per animal (ADGan, 0.870 vs. 0.611 kg / animal / day) and per hectare (ADGha vs. 5.76. 4.59 kg / ha / day), as well as daily animal load per hectare (DALha, 1483 vs. 1211 kg / ha / day) were higher (P <0.05) during the rainy season than during the dry season. During the rainy season, ADGan was lower in the genus Brachiaria and superior in the Panicum (P <0.05), but the DALha and ADGha were higher (P <0.05) in Cynodon. In dry season, ADGan was lower (P <0.05) in the Brachiaria than in Cynodon and Panicum, and ADGha was higher (P <0.05) in Panicum. In both dry and rainy seasons, ADGan, ADGha and DALha increased linearly (P <0.01) with increasing levels of supplementation, which ranged from zero to 1.6% of live weight (LW). The ADGan increased linearly (P <0.05) and DALha decreased linearly (P <0.05), while ADGha was quadratically (P <0.05) related to the increased availability of herbage. Animal performance was linear and positively correlated with leaf: stem proportion from pastures (P <0.05), both in the rainy and dry seasons. During the rainy season the best responses in ADGan and ADGha were obtained from the use of protein supplement compared with supplemental energy or proteinated salt (P <0.05), while the use of energy supplement enabled a higher DALha (P <0,05). During the dry season, ADGha was not affected by supplement type, but the best responses were obtained for ADGan with energy supplement (P <0.05) while protein supplementation, either through proteinated salt or protein supplement, was associated with a higher DALha (P <0.05). During the rainy season animal performance was quadratically (P <0.05) related to live weight (LW) of animals, and ADGan maximized in animals weighing about 380 kg and ADGha maximized in animals weighting about 400 kg. In the dry season, ADGan and ADGha were linearly and positively related animal LW (P <0.05). Pasture neutral detergent fiber (NDF) content ranged from 46 to 82% in dry matter (DM) and was quadratically related to ADGan (P <0.05) being that maximum gain was obtained with NDF content around 66%. Crude protein (CP) of pasture ranged from 1.9 to 21.6% in DM and was linear and positively correlated with ADGan (P <0.05). The ADGan was linear and negatively associated with the value obtained by the ratio between the content (% DM) of total digestible nutrients (TDN) and CP of pasture (P <0.05). Nitrogen fertilizer was linearly (P <0.05) associated with increased DALha, both in the rainy and dry seasons. The CoEfADGan and the CoEfADGha decreased lineally (P <0.05) with increasing animal LW during the rainy season, becoming negative from around 360 kg. In the rainy season as well as in the dry season, both efficiencies were also negatively (P <0.05) related to the CP content of pasture, being also negative from 10% CP, and positive and quadratically (P <0.05) related to the leaf: stem ratio of the pastures. Highest efficiencies were observed with leaf: stem ratio 3.7:1. During the dry season EfCoGMD and EfCoGAD decreased (P < 0.05) with the increasing the value obtained by the TDN: CP supplement ratio, becoming negative from 4,3:1. In conclusion, the meta-analysis enabled the identification of beef cattle performance in tropical pastures showing that it is influenced in an integrated manner by factors associated with several features such as climate, pasture, animal, handling and supplementation. However, the degree to which each factor influences animal performance could be more accuratelly assessed if publications were standardized and contained essential information regarding more detailed methodological descriptions and basic statistical information. / Foi avaliado o desempenho animal em sistemas pecuários bovinos utilizando dietas à base de pastagens tropicais através de processo meta-analítico, que incluiu na base de dados artigos científicos, dissertações e teses. Foram tabulados e categorizados dados de identificação do trabalho científico, do experimento, dos animais, do desempenho animal, da pastagem, dos suplementos e do método de pastejo. A eficiência de conversão do uso do suplemento foi avaliada nos estudos contendo tratamento testemunha (sem suplementação), e calculada como a variação do ganho médio diário de peso individual (EfCoGMD) ou por área (EfCoGAD) por kg de suplemento ofertado. Foi avaliada a distribuição dos dados da base geral e, para analisar os fatores que afetam as variáveis de desempenho animal, a base geral foi subdividida nas sub-bases águas e secas. Para avaliação dos fatores que afetam as variáveis de desempenho animal os dados foram ponderados pelo n dos tratamentos e utilizado análise de variância e covariância. O ganho médio de peso individual (GMD, 0,870 vs. 0,611 kg/animal/dia) e o ganho por área (GAD, 5,76 vs. 4,59 kg/ha/dia), assim como a carga animal (CAD, 1483 vs. 1211 kg/ha/dia) foram maiores (P<0,05) no período das águas que no período das secas. No período das águas o GMD foi menor na Brachiaria e superior no gênero Panicum (P<0,05), mas a CAD e GAD foram superiores (P<0,05) no Cynodon. Nas secas, o GMD foi menor (P<0,05) na Brachiaria que no Cynodon ou Panicum, e o GAD foi maior (P<0,05) no Panicum. Independentemente do período do ano, o GMD, o GAD e a CAD aumentaram linearmente (P<0,01) com o aumento do nível de suplementação, o qual variou de zero a 1,6% do peso vivo (PV). O GMD aumentou linearmente (P<0,05) e a CAD diminuiu linearmente (P<0,05), enquanto o GAD foi quadraticamente (P<0,05) relacionado com o aumento da oferta de forragem total. O desempenho animal foi linear e positivamente relacionado com proporção folha:colmo das pastagens (P<0,05), tanto no período das águas quanto no período das secas. No período das águas as melhores respostas em GMD e GAD foram obtidas com o uso de suplemento protéico quando comparado com suplemento energético ou sal proteinado (P<0,05), enquanto o uso de suplemento energético possibilitou maior CAD (P<0,05). No período das secas o GAD não foi afetado pelo tipo de suplemento, mas as melhores respostas para GMD foram obtidas com suplemento energético (P<0,05) enquanto que a suplementação proteica, seja através de sal proteinado ou suplemento proteico, foi relacionada com maior CAD (P<0,05). No período das águas o desempenho animal foi quadraticamente (P<0,05) relacionado com o peso vivo (PV) dos animais, sendo o GMD maximizado com animais pesando em torno de 380 kg e o GAD maximizado com animais de 400 kg. Nas secas o GMD e o GAD foram linear e positivamente relacionados com o PV dos animais (P<0,05). O teor de fibra em detergente neutro (FDN) da pastagem variou de 46 a 82 % na matéria seca (MS) e foi quadraticamente relacionado com o GMD (P<0,05) sendo que o máximo GMD foi obtido com teor de FDN em torno de 66%. O teor de proteína bruta (PB) da pastagem variou de 1,9 a 21,6 % na MS e foi linear e positivamente relacionado com GMD (P<0,05). O GMD foi linear e negativamente associado com o valor obtido pela razão (relação) entre o teor (% na MS) de nutrientes digestíveis totais (NDT) e PB da pastagem (P<0,05). A adubação nitrogenada foi linearmente (P<0,05) relacionada com aumento da CAD tanto no período das águas como no período das secas. A EfCoGMD e a EfCoGAD diminuíram linearmente (P<0,05) com o aumento do PV dos animais no período das águas, passando a serem negativas a partir de em torno de 360 kg. Tanto nas águas como nas secas, ambas as eficiências também foram negativamente (P<0,05) relacionadas com o teor de PB da pastagem, passando a serem negativas a partir de 10% de PB, e positiva e quadraticamente (P<0,05) relacionadas com a relação folha:colmo das pastagens. Máximas eficiências foram observadas com relação folha:colmo em torno de 3,7:1. No período das secas a EfCoGMD e a EfCoGAD diminuíram linearmente (P<0,05) com o aumento do valor observado na relação NDT:PB do suplemento, passando a serem negativas a partir de 4,3:1. Em conclusão, a meta-análise possibilitou identificar que o desempenho de bovinos de corte em pastagens tropicais é influenciado de forma integrada por fatores associados às características do clima, das pastagens, dos animais, do manejo e da suplementação. Contudo, o grau de influência de cada fator seria melhor definido se as publicações nessa área de conhecimento fossem padronizadas e contivessem informações mínimas tanto em relação à descrição da metodologia como em relação à presença de informações estatísticas básicas.