Submitted by (lucia.rodrigues@ufrpe.br) on 2017-03-14T16:00:03Z No. of bitstreams: 1 Kesia Ferreira Alves.pdf: 466143 bytes, checksum: 66630edcc98b43dfb320ee8189581aa0 (MD5) / Made available in DSpace on 2017-03-14T16:00:03Z (GMT). No. of bitstreams: 1 Kesia Ferreira Alves.pdf: 466143 bytes, checksum: 66630edcc98b43dfb320ee8189581aa0 (MD5) Previous issue date: 2008-02-28 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Anthracnose is considered an important disease of bell pepper (Capsicum annuum L.) in the state of Pernambuco and in various parts of the world, causing significant losses for fruit commercialization. Actions directed to preventive measures such as alternative control, are of great importance through the exploration of secondary compounds present in medicinal plants with antimicrobial activity. This study aimed to, assess the efficiency of crude extracts in the control of anthracnose in bell pepper, and analyze the control stability of promising treatments in relation to different extract, inoculum, temperature and pathogen isolates concentrations. In preliminary selection, 16 plant species were used in order to obtain aqueous and hidroalcoólico extracts. The aqueous extracts of garlic (Allium sativum L.), Mallow (Malva sp.), and ginger (Zingiber officinale Roscoe.) showed greater than 97% reductions in disease severity levels. The greatest value of CL75 was found for the garlic extract (3.5%), while the lowest value of CL75 was verified with the application of the ginger extract (2.1%). The lowest rate of efficiency reduction of the anthracnose control (TRE) with the pathogen inoculum increase occurred with garlic extract. With regard to different C. gloeosporioides isolates, significant interaction was found between the different extracts and isolates of the pathogen. The plant extracts were effective in controlling the disease in temperatures of 20, 25 and 30 ° C, while temperatures in the 10, 15and 35 ° C there was no disease. There were no differences in the efficiencies of garlic and ginger extracts, while the extract of hollyhock had the lower efficiency at 20 ° C, differing from the other temperatures, and other extracts at this temperature. The results obtained in this study indicate the great potential for use of the garlic extract (6%) in anthracnose control of bell pepper, considering its stability in different situations. / A antracnose é considerada uma importante doença do pimentão (Capsicum annuum L.) no Estado de Pernambuco e em várias partes do mundo, causando perdas significativas à produção de frutos para comercialização. Ações voltadas para medidas preventivas como o controle alternativo, são de grande relevância por meio da exploração de compostos secundários presentes em plantas medicinais com atividade antimicrobiana. O presente trabalho teve por objetivo, avaliar a eficiência de extratos vegetais brutos no controle da antracnose em pimentão, bem como analisar a estabilidade do controle dos tratamentos promissores em relação a.diferentes concentrações dos extratos, concentrações do inoculo e isolados do patógeno e, temperaturas. Na seleção preliminar foram utilizadas 16 espécies vegetais para obtenção de extratos aquosos e etanólicos. Os extratos aquosos de alho (Allium sativum L.), malva (Malva sp.) e gengibre (Zingiber officinale Roscoe.) propiciaram reduções superiores a 97% nos níveis de severidade. O maior valor de CL75 foi constatado para o extrato de alho (3,5%), enquanto o menor valor de CL75 foi verificado com a aplicação de extrato de gengibre (2,1%). A menor taxa de redução da eficiência do controle (TRE) da antracnose com o incremento do inóculo do patógeno ocorreu no extrato de alho. Com relação a diferentes isolados de C. gloeosporioides, foi constatada interação significativa entre os tipos de extratos e os isolados do patógeno. Os extratos vegetais foram eficientes no controle da doença nas temperaturas de 20, 25 e 30 oC, enquanto nas temperaturas 10, 15 e 35 °C não houve doença. Não houve diferenças nas eficiências dos extratos de alho e gengibre, enquanto o extrato de malva apresentou a menor eficiência a 20 oC, diferindo das outras temperaturas, bem como dos demais extratos nessa temperatura. Os resultados obtidos nesse estudo indicam o grande potencial de utilização do extrato de alho a 6% no controle da antracnose em pimentão, considerando sua estabilidade em diferentes situações.

Made available in DSpace on 2016-06-02T20:34:26Z (GMT). No. of bitstreams: 1 3716.pdf: 15456968 bytes, checksum: 4a39e68e7b10a9e50bb83087365cf289 (MD5) Previous issue date: 2011-09-26 / Financiadora de Estudos e Projetos / Ten herbs used in traditional medicine supported by literature for its effectiveness to osteoarticular diseases were selected to conduct a screening of inhibition activity against the cathepsin K, an important enzyme responsible for cleavage of collagen, the main constituent of extracellular matrix of cartilage and bone. Out of the ten herbs selected (ginger, saffron, camellia, cat s claw, mentrasto , moringa , babaçu , devil s claw, urtica e pequi ), one, gengibre (Z. officinale), should be highlighted by a high inhibitory activity of its extracts and fractions against cathepsin K and due to its ancient use as a therapeutic agent. From the dichloromethane fraction obtained of the crude extract of the rhizome of Z. officinale were isolated and identified 18 compounds (4-gingerol, 6-gingerol, 8-gingerol, 6-shogaol, 8-shogaol, 10-shogaol, 6- paradol, 6-gingerdiol, methyl 6-gingerol, methyl 6-shogaol, diacetoxy-6-gingerdiol, methyl diacetoxy-6-gingerdiol, zingerone, gingerenone A, galanolactone, 3-acetoxy- 5-hydroxy-1,7-bis(4 -hydroxy-3 -methoxyphenyl)-heptane and hexahydrocurcumin). From the hexane fraction and essential oil were identified two monoterpenes and four sesquiterpenes. The most active compounds against cathepsin K were gingerols and shogaols with longer alkyl chain. Optimization of the separation of major compounds (6, 8 and 10-gingerol) and an overload study of C18 column was performed using HPLC, obtained as result dozens to hundreds of milligrams of each gingerol with high purity. Structural modifications of 6-gingerol were carried out and of the seven derivatives obtained 4 presented significant increase in inhibition of cathepsin K. Of all the compounds, three, SSi6, 10-gingerol, 6-shogaol, were selected for later tests: determinating of the mode the inhibition against cathepsin K, inhibition against cathepsin K and inhibition of nitric oxide (NO) production, in cellular culture. The inhibitions determined were: partially noncompetitive, partially uncompetitive and complete uncompetitive for the SSi6, 10-gingerol and 6-shogaol, respectively. Excellent inhibition activity against the cathepsin K, in cellular culture, can be observed for SSi6 and 6-shogaol. In the inhibition assay of NO production, the 6- shogaol was the only compound that appeared as effective. / Dez plantas utilizadas pela medicina tradicional com indicativos na literatura de suas eficácias frente a doenças osteoarticulares foram selecionadas para a realização de uma triagem de atividade inibitória frente à catepsina K, uma importante enzima responsável pela clivagem do colágeno, principal constituinte da matriz extracelular da cartilagem e ossos. Das dez plantas selecionadas (gengibre, açafrão, camélia, unha-de-gato, mentrasto, moringa, babaçu, garra-do-diabo, urtigão e pequi), uma, gengibre (Zingiber officinale), merece destaque pela alta inibição de seu extrato e frações frente à catepsina K e por seu uso milenar como agente terapêutico. Da fração de diclorometano obtida do extrato bruto dos rizomas de Z. officinale isolou-se e identificou-se 18 substâncias (4-gingerol, 6-gingerol, 8-gingerol, 6-shogaol, 8- shogaol, 10-shogaol, 6-paradol, 6-gingerdiol, metil-6-gingerol, metil-6-shogaol, diacetato de 6-gingerdioila, diacetato de metil-6-gingerdioila, zingerona, gingerenona A, galanolactona, 3-acetato de 5-hidroxi-1,7-bis(4 -hidroxi-3 -metoxifenil)-heptila e hexaidrocurcumina). Da fração de n-hexano e do óleo essencial, foram identificados 2 monoterpenos e 4 sesquiterpenos. As substâncias mais ativas frente à catepsina K foram os gingerois e shogaois de maior cadeia alquílica. Otimização da separação das substâncias majoritárias (6, 8 e 10-gingerol) e um estudo de sobrecarga de uma coluna C18 por CLAE, foram realizados, obtendo-se como resultado o isolamento de dezenas a centenas de miligramas de cada gingerol com considerável grau de pureza. Modificações estruturais do 6-gingerol foram realizadas e, das sete substâncias obtidas, 4 tiveram um aumento considerável do poder inibitório. Das substâncias obtidas, três, SSi6, 10-gingerol, 6-shogaol, foram selecionadas para ensaios posteriores: determinação do tipo de inibição frente à catepsina K, inibição da catepsina K e inibição da produção de óxido nítrico (NO), em meio celular. As inibições determinadas foram não-competitiva parcial, acompetitiva parcial e acompetitiva completa, para o SSi6, 10-gingerol e 6-shogaol, respectivamente. Excelentes atividades de inibição frente à catepsina K, em meio celular, puderam ser observadas para o SSi6 e 6-shogaol. No ensaio de inibição da produção de NO, o 6- shogaol foi a única substância que se apresentou como efetivo.

Made available in DSpace on 2014-06-11T19:24:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-06Bitstream added on 2014-06-13T19:31:19Z : No. of bitstreams: 1 chung_a_me_sjc.pdf: 3221604 bytes, checksum: 5b16f37a62e8b9804f944b0be536c388 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A proposta deste trabalho foi detectar microrganismos e avaliar in vivo a ação do extrato glicólico de gengibre 20% (GENG), do hipoclorito de sódio 1% (NaOCl), da clorexidina gel 2% (CLX) como soluções irrigadoras e da medicação intracanal (MIC) de hidróxido de cálcio sobre microrganismos e endotoxinas em dentes com necrose pulpar e lesão periapical. Para isso 36 pacientes portadores de dente com necrose pulpar e lesão periapical visível radiograficamente foram submetidos ao tratamento endodôntico e divididos em 3 grupos (n=12), de acordo com a substância química auxiliar utilizada durante o preparo biomecânico: GENG; NaOCl ou CLX intercalado com solução salina fisiológica. Foram realizadas coletas do conteúdo do canal radicular com cones de papel absorvente após a abertura do dente, após a instrumentação e, após 14 dias da ação da MIC. Para todas as coletas foram realizados os seguintes testes: a) avaliação da atividade antimicrobiana pela contagem de UFC/mL e método molecular – PCR e; b) análise da quantidade de endotoxina verificada pelo lisado de amebócitos de Limulus. Os resultados foram submetidos à análise descritiva e estatística de Kruskal-Wallis e teste de Dunn. Os resultados mostraram presença de DNA bacteriano em todas as coletas, sendo que Parvimonas micra foi a espécie mais frequente. A instrumentação com as substâncias testadas reduziram significativamente microrganismos e endotoxinas dos canais radiculares. A utilização da MIC não foi capaz de potencializar os efeitos antimicrobianos nem sobre endotoxinas. Pôde-se concluir que o preparo biomecânico com GENG foi eficiente tanto em reduzir microrganismos quanto endotoxinas dos canais radiculares. A MIC de Ca(OH)2 não foi capaz de potencializar a neutralização de endotoxinas após PBM / The purpose of this study was to detect microorganisms and to evaluate in vivo the action of 20% ginger glycolic extract (GENG), 1% sodium hypochlorite (NaOCl) and 2% chlorhexidine gel (CLX) as irrigating solutions and intracanal medication (ICM) of calcium hydroxide on microorganisms and endotoxins in teeth with necrotic pulp and periapical lesions. Thirty six patients with tooth with pulp necrosis and radiographically visible periapical lesion were submitted to endodontic treatment and divided into 3 groups (n = 12), according to the auxiliary chemical substance used during the biomechanical preparation: GENG, NaOCl or CHX interspersed with saline solution. Samples of the root canal were taken with paper cones immediately after exposure of the canal, immediately after instrumentation and 14 days after MIC. For all samples were performed the following tests: a) evaluation of antimicrobial activity by counting the CFU / mL and molecular method - PCR and b) quantification of endotoxins verified by the Limulus amoebocyte lysate. The results showed the presence of bacterial DNA in all samples, and Parvimonas micra was the most frequent species. The instrumentation with all substances tested reduced significantly microorganisms and endotoxins from root canals. The use of ICM was not able to potentiate the antimicrobial effects either on endotoxins. It was concluded that biomechanical preparation with glycolic extract of ginger was effective in reducing microorganisms and endotoxins from root canals with no significant differences from NaOCl or chlorhexidine. The Ca(OH)2 ICM could not enhance the neutralization of endotoxins after biomechanical preparation

No description available.

<p>U okviru ove doktorske disertacije ispitane su i<br />poređene različite ekstrakcione tehnike korena<br />gaveza, lista crnog duda i peteljki tre&scaron;nje. Poređene<br />su konvencionalne i savremene ekstrakcione<br />tehnike i izvedena je optimizacija ekstrakcionih<br />postupaka s ciljem dobijanja ekstrakata ispitivanih<br />biljnih vrsta sa najvećom bioaktivno&scaron;ću. Za svaku<br />ekstrakcionu tehniku ispitan je uticaj najznačajnijih<br />parametara: maceracija (rastvarač i vreme<br />ekstrakcije), ubrzana ekstrakcija (temperatura i<br />rastvarač), supekritična ekstrakcija (pritisak i<br />koncentracija ko-rastvarača) i ekstrakcija<br />subkritičnom vodom (temperatura, pritisak, vreme<br />ekstrakcije i brzina me&scaron;anja). Ekstrakcija polifenola<br />korena gaveza, lista crnog duda i peteljki tre&scaron;nje je<br />bila najefikasnija ekstrakcijom subkritičnom<br />vodom. Primenjene su tehnika visokopritisne tečne<br />hromatografije spregnute sa masenom<br />spektrometrijom uz primenu različitih masenih<br />analizatora, masenog analizatora na bazi vremena<br />preleta jona i tandema kvadrupolnog i analizatora<br />na bazi vremena preleta jona. Za karakterizaciju<br />dobijenih ekstrakata instrumentalnom analizom su<br />određene kvalitativne i kvantitativne karakteristike dobijenih ekstrakata korena gaveza, lista crnog duda i peteljki tre&scaron;nje. HPLC-ESI-QTOF-MS/MS analizom ekstrakata identifikovano je vi&scaron;e od 27 novih jedinjenja različitih hemijskih klasa u svakom od ispitivanih biljnih matriksa.</p> / <p>Within the scope of this doctoral dissertation,<br />different extraction techniques of comfrey root,<br />black mulberry leaves and sweet cherry stems were<br />applied and compared. Conventional and novel<br />extraction techniques were optimized and<br />compared in order to obtain plant extracts with the<br />highest content of bioactive compounds. The<br />influence of the most important parameters was<br />investigated for each extraction technique:<br />maceration (solvent and extraction time),<br />accelerated solvent extraction (temperature and<br />solvent), supercritical fluid extraction (co-solvent<br />percentage and pressure) and subcritical water<br />extraction (temperature, pressure, extraction time<br />and agitation rate). Extraction of polyphenolic<br />compounds from comfrey root, black mulberry<br />leaves and sweet cherry stems was the most<br />effective using subcritical water. High-pressure<br />liquid chromatography coupled to mass<br />spectrometry techniques using time-of-flight and<br />quadrupole-time-of-flight mass analyzers have<br />been used to characterize bioactive compounds.<br />Qualitative and quantitative characteristics of the<br />obtained comfrey root, black mulberry leaves and sweet cherry stem extracts were determined. HPLC-ESI-QTOF-MS/MS revealed the presence of more than 27 compounds of different chemical classes that have been identified for the first time in&nbsp; the plant matrix.</p>

No description available.

Comprendre le fonctionnement des écosystèmes est un enjeu crucial, en particulier dans un contexte de changements globaux. Afin de mieux prédire les processus écosystémiques, j’ai testé la précision et les limites des hypothèses du biomass-ratio de Grime (HBMR) et de l’annulation idiosyncratique (HAI), cette dernière étant une hypothèse originale de cette thèse. Pour cela, j’ai appliqué le principe du biomass-ratio aux traits fonctionnels, en employant la méthode des traits agrégés en communauté, pour estimer la réponse globale des espèces en mélange. La décomposition des litières plurispécifiques constitue un bon modèle biologique, pour lequel je me suis posé les questions suivantes : (1) est-ce que l’HBMR prédit bien les taux de décomposition en mélanges plurispécifiques ? ; (2) est-ce que le degré de variabilité de ces taux diminue pour des raisons biologiques avec l’augmentation de la richesse spécifique (RS) des mélanges (HAI) ? ; (3) est-ce que la variabilité des taux entre mélanges diminue quand les conditions abiotiques du site deviennent plus limitantes ? ; (4)considérant que les mélanges plus contrastés fonctionnellement sont susceptibles de développer plus d’interactions, est-ce que la déviation à la prédiction augmente avec la dispersion fonctionnelle des mélanges(« FDis », La liberté & Legendre 2010) ? Cette thèse inclut deux expériences de décomposition en sachets à litières : (1) à Sherbrooke (QC, Canada) avec des microcosmes, impliquant des litières de six espèces d’arbres, décomposant seules et en mélanges et (2) sur trois sites au climat contrasté dans la région de Clermont-Ferrand (France) avec des litières de quatre espèces d’herbacées, décomposant seules et en mélanges. Les résultats montrent des déviations positives et négatives par rapport aux taux prédits, mais l’HBMR décrit bien la réponse moyenne des litières plurispécifiques. Bien que l’HAI ait été rejetée, les résultats montrent une convergence des taux observés vers les taux prédits quand (1) la RS des mélanges augmente, (2)l’échelle spatiale augmente et (3) le climat est plus limitant pour la décomposition. Enfin, malgré des corrélations entre FDis et interactions entre espèces dans les litières, cette relation n’est pas généralisable et l’hypothèse de corrélation positive entre FDis et déviation à l’HBMR a été rejetée. / Understanding ecosystem functioning is a key goal in ecology, especially in the context of global changes. To better predict ecosystem processes, I tested the accuracy and the limits of Grime’s biomass-ratio (BMRH) hypothesis and a novel idiosyncratic annulment (IAH) hypothesis. I applied the biomass-ratio to functional traits, using the community-weighted means (CWM) to estimate the global response of species in mixtures. I studied the decomposition of litter species mixtures as a biological model and asked the following questions : (1) does the BMRH predict well the decomposition rates of mixed species litters ? ; (2) does the degree of variability of these rates decrease with increasing species richness (SR) beyond that expected from purely mathematical causes (IAH) ? ; (3) does the variability of rates between mixtures decrease with less favourable abiotic conditions for decomposition ? ; (4) as more functionally contrasted mixtures are expected to develop more interactions, does the deviation from prediction increase with increasing functional dispersion in mixtures (« FDis », Laliberté & Legendre 2010) ? This study involves two decomposition experiments using litterbags : (1) at Sherbrooke (QC, Canada), in microcosms, involving litters from six tree species, decomposed alone and in mixtures and (2) in three climatically contrasted sites in the region of Clermont-Ferrand (France) with litters from four herbaceous species, decomposed alone and in mixtures. Despite both positive and negative deviations from expectation occurring at all levels of SR, the BMRH well described the average response of mixed species litters. Although I rejected the IAH, the results showed a convergence to the predicted values based on CWM with (1) increasing the SR in mixtures, (2) increasing the spatial scale of the study and (3) a less favourable climate to decomposition. Finally, although there was a correlation between litter interactions and functional divergence, this relationship was not generalizable and I rejected the hypothesis of a positive correlation between FDis and the deviations from BMRH.

Sommaire : Comprendre le fonctionnement des écosystèmes est un enjeu crucial, en particulier dans un contexte de changements globaux. Afin de mieux prédire les processus écosystémiques, j’ai testé la précision et les limites des hypothèses du biomass-ratio de Grime (HBMR) et de l’annulation idiosyncratique (HAI), cette dernière étant une hypothèse originale de cette thèse. Pour cela, j’ai appliqué le principe du biomass-ratio aux traits fonctionnels, en employant la méthode des traits agrégés en communauté, pour estimer la réponse globale des espèces en mélange. La décomposition des litières plurispécifiques constitue un bon modèle biologique, pour lequel je me suis posé les questions suivantes : (1) est-ce que l’HBMR prédit bien les taux de décomposition en mélanges plurispécifiques ? ; (2) est-ce que le degré de variabilité de ces taux diminue pour des raisons biologiques avec l’augmentation de la richesse spécifique (RS) des mélanges (HAI) ? ; (3) est-ce que la variabilité des taux entre mélanges diminue quand les conditions abiotiques du site deviennent plus limitantes ? ; (4) considérant que les mélanges plus contrastés fonctionnellement sont susceptibles de développer plus d’interactions, est-ce que la déviation à la prédiction augmente avec la dispersion fonctionnelle des mélanges (« FDis », Laliberté & Legendre 2010) ? Cette thèse inclut deux expériences de décomposition en sachets à litières : (1) à Sherbrooke (QC, Canada) avec des microcosmes, impliquant des litières de six espèces d’arbres, décomposant seules et en mélanges et (2) sur trois sites au climat contrasté dans la région de Clermont-Ferrand (France) avec des litières de quatre espèces d’herbacées, décomposant seules et en mélanges. Les résultats montrent des déviations positives et négatives par rapport aux taux prédits, mais l’HBMR décrit bien la réponse moyenne des litières plurispécifiques. Bien que l’HAI ait été rejetée, les résultats montrent une convergence des taux observés vers les taux prédits quand (1) la RS des mélanges augmente, (2) l’échelle spatiale augmente et (3) le climat est plus limitant pour la décomposition. Enfin, malgré des corrélations entre FDis et interactions entre espèces dans les litières, cette relation n’est pas généralisable et l’hypothèse de corrélation positive entre FDis et déviation à l’HBMR a été rejetée. // Abstract : Understanding ecosystem functioning is a key goal in ecology, especially in the context of global changes. To better predict ecosystem processes, I tested the accuracy and the limits of Grime’s biomass-ratio (BMRH) hypothesis and a novel idiosyncratic annulment (IAH) hypothesis. I applied the biomass-ratio to functional traits, using the community-weighted means (CWM) to estimate the global response of species in mixtures. I studied the decomposition of litter species mixtures as a biological model and asked the following questions : (1) does the BMRH predict well the decomposition rates of mixed species litters? ; (2) does the degree of variability of these rates decrease with increasing species richness (SR) beyond that expected from purely mathematical causes (IAH)? ; (3) does the variability of rates between mixtures decrease with less favourable abiotic conditions for decomposition? ; (4) as more functionally contrasted mixtures are expected to develop more interactions, does the deviation from prediction increase with increasing functional dispersion in mixtures (« FDis », Laliberté & Legendre 2010)? This study involves two decomposition experiments using litterbags: (1) at Sherbrooke (QC, Canada), in microcosms, involving litters from six tree species, decomposed alone and in mixtures and (2) in three climatically contrasted sites in the region of Clermont-Ferrand (France) with litters from four herbaceous species, decomposed alone and in mixtures. Despite both positive and negative deviations from expectation occurring at all levels of SR, the BMRH well described the average response of mixed species litters. Although I rejected the IAH, the results showed a convergence to the predicted values based on CWM with (1) increasing the SR in mixtures, (2) increasing the spatial scale of the study and (3) a less favourable climate to decomposition. Finally, although there was a correlation between litter interactions and functional divergence, this relationship was not generalizable and I rejected the hypothesis of a positive correlation between FDis and the deviations from BMRH.

Sommaire : Comprendre le fonctionnement des e??cosyste??mes est un enjeu crucial, en particulier dans un contexte de changements globaux. Afin de mieux pre??dire les processus e??cosyste??miques, j???ai teste?? la pre??cision et les limites des hypothe??ses du biomass-ratio de Grime (HBMR) et de l???annulation idiosyncratique (HAI), cette dernie??re e??tant une hypothe??se originale de cette the??se. Pour cela, j???ai applique?? le principe du biomass-ratio aux traits fonctionnels, en employant la me??thode des traits agre??ge??s en communaute??, pour estimer la re??ponse globale des espe??ces en me??lange. La de??composition des litie??res plurispe??cifiques constitue un bon mode??le biologique, pour lequel je me suis pose?? les questions suivantes : (1) est-ce que l???HBMR pre??dit bien les taux de de??composition en me??langes plurispe??cifiques ? ; (2) est-ce que le degre?? de variabilite?? de ces taux diminue pour des raisons biologiques avec l???augmentation de la richesse spe??cifique (RS) des me??langes (HAI) ? ; (3) est-ce que la variabilite?? des taux entre me??langes diminue quand les conditions abiotiques du site deviennent plus limitantes ? ; (4) conside??rant que les me??langes plus contraste??s fonctionnellement sont susceptibles de de??velopper plus d???interactions, est-ce que la de??viation a?? la pre??diction augmente avec la dispersion fonctionnelle des me??langes (?? FDis ??, Laliberte?? & Legendre 2010) ? Cette the??se inclut deux expe??riences de de??composition en sachets a?? litie??res : (1) a?? Sherbrooke (QC, Canada) avec des microcosmes, impliquant des litie??res de six espe??ces d???arbres, de??composant seules et en me??langes et (2) sur trois sites au climat contraste?? dans la re??gion de Clermont-Ferrand (France) avec des litie??res de quatre espe??ces d???herbace??es, de??composant seules et en me??langes. Les re??sultats montrent des de??viations positives et ne??gatives par rapport aux taux pre??dits, mais l???HBMR de??crit bien la re??ponse moyenne des litie??res plurispe??cifiques. Bien que l???HAI ait e??te?? rejete??e, les re??sultats montrent une convergence des taux observe??s vers les taux pre??dits quand (1) la RS des me??langes augmente, (2) l???e??chelle spatiale augmente et (3) le climat est plus limitant pour la de??composition. Enfin, malgre?? des corre??lations entre FDis et interactions entre espe??ces dans les litie??res, cette relation n???est pas ge??ne??ralisable et l???hypothe??se de corre??lation positive entre FDis et de??viation a?? l???HBMR a e??te?? rejete??e. // Abstract : Understanding ecosystem functioning is a key goal in ecology, especially in the context of global changes. To better predict ecosystem processes, I tested the accuracy and the limits of Grime???s biomass-ratio (BMRH) hypothesis and a novel idiosyncratic annulment (IAH) hypothesis. I applied the biomass-ratio to functional traits, using the community-weighted means (CWM) to estimate the global response of species in mixtures. I studied the decomposition of litter species mixtures as a biological model and asked the following questions : (1) does the BMRH predict well the decomposition rates of mixed species litters? ; (2) does the degree of variability of these rates decrease with increasing species richness (SR) beyond that expected from purely mathematical causes (IAH)? ; (3) does the variability of rates between mixtures decrease with less favourable abiotic conditions for decomposition? ; (4) as more functionally contrasted mixtures are expected to develop more interactions, does the deviation from prediction increase with increasing functional dispersion in mixtures (?? FDis ??, Lalibert?? & Legendre 2010)? This study involves two decomposition experiments using litterbags: (1) at Sherbrooke (QC, Canada), in microcosms, involving litters from six tree species, decomposed alone and in mixtures and (2) in three climatically contrasted sites in the region of Clermont-Ferrand (France) with litters from four herbaceous species, decomposed alone and in mixtures. Despite both positive and negative deviations from expectation occurring at all levels of SR, the BMRH well described the average response of mixed species litters. Although I rejected the IAH, the results showed a convergence to the predicted values based on CWM with (1) increasing the SR in mixtures, (2) increasing the spatial scale of the study and (3) a less favourable climate to decomposition. Finally, although there was a correlation between litter interactions and functional divergence, this relationship was not generalizable and I rejected the hypothesis of a positive correlation between FDis and the deviations from BMRH.

Comprendre le fonctionnement des écosystèmes est un enjeu crucial, en particulier dans un contexte de changements globaux. Afin de mieux prédire les processus écosystémiques, j'ai testé la précision et les limites des hypothèses du biomass-ratio de Grime (HBMR) et de l'annulation idiosyncratique (HAI), cette dernière étant une hypothèse originale de cette thèse. Pour cela, j'ai appliqué le principe du biomass-ratio aux traits fonctionnels, en employant la méthode des traits agrégés en communauté, pour estimer la réponse globale des espèces en mélange. La décomposition des litières plurispécifiques constitue un bon modèle biologique, pour lequel je me suis posé les questions suivantes : (1) est-ce que l'HBMR prédit bien les taux de décomposition en mélanges plurispécifiques ? ; (2) est-ce que le degré de variabilité de ces taux diminue pour des raisons biologiques avec l'augmentation de la richesse spécifique (RS) des mélanges (HAI) ? ; (3) est-ce que la variabilité des taux entre mélanges diminue quand les conditions abiotiques du site deviennent plus limitantes ? ; (4)considérant que les mélanges plus contrastés fonctionnellement sont susceptibles de développer plus d'interactions, est-ce que la déviation à la prédiction augmente avec la dispersion fonctionnelle des mélanges(" FDis ", La liberté & Legendre 2010) ? Cette thèse inclut deux expériences de décomposition en sachets à litières : (1) à Sherbrooke (QC, Canada) avec des microcosmes, impliquant des litières de six espèces d'arbres, décomposant seules et en mélanges et (2) sur trois sites au climat contrasté dans la région de Clermont-Ferrand (France) avec des litières de quatre espèces d'herbacées, décomposant seules et en mélanges. Les résultats montrent des déviations positives et négatives par rapport aux taux prédits, mais l'HBMR décrit bien la réponse moyenne des litières plurispécifiques. Bien que l'HAI ait été rejetée, les résultats montrent une convergence des taux observés vers les taux prédits quand (1) la RS des mélanges augmente, (2)l'échelle spatiale augmente et (3) le climat est plus limitant pour la décomposition. Enfin, malgré des corrélations entre FDis et interactions entre espèces dans les litières, cette relation n'est pas généralisable et l'hypothèse de corrélation positive entre FDis et déviation à l'HBMR a été rejetée.