Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-07-20T11:44:47Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tese Catarina Maria Aragao de Mello.pdf: 5575765 bytes, checksum: b3c4ea02e6cc1d75d2d5ecf461a8b707 (MD5) / Made available in DSpace on 2017-07-20T11:44:47Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tese Catarina Maria Aragao de Mello.pdf: 5575765 bytes, checksum: b3c4ea02e6cc1d75d2d5ecf461a8b707 (MD5) Previous issue date: 2015-05-29 / FACEPE / O conhecimento da diversidade de fungos micorrízicos arbusculares em raízes de plantas cultivadas é um pré-requisito para o manejo efetivo e a sustentabilidade de sistemas agrícolas. O objetivo deste trabalho foi determinar qualitativa e quantitativamente as comunidades de FMA em agrossistemas plantados com milho, em Pernambuco. Na primeira etapa do trabalho foram realizadas coletas em três estações experimentais do Instituto Agronômico de Pernambuco: uma localizada em área úmida (Zona da Mata - Itambé) e duas no semiárido (Agreste – Caruaru; Sertão - Serra Talhada) em 2010 e 2011. A análise morfológica dos esporos permitiu a diferenciação de 57 espécies de FMA, das quais duas novas para a ciência. Maior densidade de esporos ocorreu na área do agreste, que apresentou menor riqueza de espécies de FMA. Na área mais úmida foi registrada maior riqueza. A estrutura das comunidades de FMA diferiu entre os locais, segundo o teste de procedimento de permutação multi-resposta (MRPP), em função de diferenças nos atributos químicos e granulométricos dos solos. Duas novas espécies foram descritas: Fuscutata aurea, registrada em Itambé e Paraglomus pernambucanum, encontrada em amostras coletadas em Caruaru e Serra Talhada. Foi proposta uma nova combinação para Paraglomus (P. bolivianum) e revisada a ocorrência mundial dos representantes de Paraglomus e Pacispora. Na segunda etapa do estudo (2012) foram realizadas coletas em três propriedades privadas irrigadas, localizadas também nas Zonas da Mata, Agreste e Sertão, respectivamente nos municípios de Igarassu, Passira e Serra Talhada, em dois períodos de desenvolvimento do milho (60 – floração e 90 dias – colheita). A análise morfológica dos esporos revelou a presença de 43 espécies de FMA. Também foram realizadas análises moleculares da raiz, sendo sequenciados 433 clones do SSU rDNA, dos quais 93 pertencentes a indivíduos das ordens Diversisporales, Gigasporales, Glomerales e Paraglomerales. Dentre os 259 clones do LSU rDNA, 153 corresponderam a gêneros incluídos em Diversisporales, Gigasporales e Glomerales. Os demais clones foram relacionados a outros grupos de eucariotas. Em todas as áreas predominaram representantes de Acaulospora e Glomus. Houve diferença significativa entre as áreas para a maioria dos atributos químicos e composição granulométrica dos solos. A estrutura das comunidades de FMA foi significativamente diferente entre as áreas, de acordo com a ordenação (NMS) e o método estatístico (PERMANOVA). A maior porcentagem de raiz colonizada ocorreu em plantas coletadas em Igarassu (Mata), enquanto a maior riqueza de espécies foi encontrada em solos de Passira (Agreste). A diversidade de FMA no solo difere daquela encontrada no sistema radicular de plantas colonizadas. Representantes dos gêneros Claroideoglomus, Diversispora, Dominikia, Intraornatospora, Redeckera e Rhizoglomus não foram identificados no solo rizosférico, enquanto Ambispora e Paradentiscutata foram observados apenas a partir da análise morfológica dos esporos presentes no solo, não sendo obtidas sequências desses gêneros. A rizosfera de plantios de milho, mesmo em áreas com diferentes características edafoclimáticas, abriga diversificada comunidade de FMA, com dominância dos gêneros Glomus e Acaulospora. O estádio fenológico do milho pode influenciar a diversidade, e a composição das comunidades de FMA pode ser melhor determinada com o uso conjunto de ferramentas moleculares e morfológicas para identificação dos fungos. / The effective management and sustainability of agricultural systems depends on the knowledge of the diversity of AMF in roots of cultivated plant. The aim of this study was to determine qualitatively and quantitatively the AMF communities in corn agrosystems, in Pernambuco, Northeast Brazil. In the first stage of this work collections were carried out in three experimental stations of the Agronomic Institute of Pernambuco: one located in an Atlantic rain forest area (Forest Zone - Itambé) and two in semiarid areas ("Agreste" - Caruaru and "Sertão" - Serra Talhada), in 2010 and 2011. Fifty seven taxa were found, two of which are new species. In the “agreste” area we found higher number of spores and lower richness of AMF species. The highest species richness was registered in the most humid area. The structure of the AMF communities differed among the sites, according to the multi-response permutation procedure test (MRPP), due to differences in chemical and physical soil attributes. The new species described are: Fuscutata aurea, registered in Itambé (humid area) and Paraglomus pernambucanum found in samples from the semiarid areas. A new combination for Paraglomus (P. bolivianum) was proposed, and a survey of the global occurrence of Paraglomus and Pacispora was performed. In the second stage of this study (2012), samples were taken in three private properties, with irrigated fields of corn also located in the three areas: rain Forest (Igarassu), "Agreste" (Passira) and "Sertão" (Serra Talhada). The collections were performed in two periods of corn development (60 days – flowering, and 90 days - harvest). The morphological analysis revealed the presence of 43 AMF taxa. Molecular root analyses were performed, and 433 clones sequenced (SSU rDNA), of which 93 belonged to individuals of the orders Diversisporales, Gigasporales, Glomerales and Paraglomerales. Among the 259 clones of the LSU rDNA, 153 corresponded to genera included in Diversisporales, Gigasporales and Glomerales. The remaining clones were related to other eukaryotic groups. Species of Acaulospora and Glomus predominated in the areas. Significant differences among the areas for most chemical and physical soil attributes were found. The structure of the AMF communities was significantly different among the areas, according to the ordination (NMS) and the statistical method (PERMANOVA). The highest percentage of root colonization occurred in plants collected in Igarassu (Forest), while the highest species richness was found in Passira soils (Agreste). The diversity of AMF in the soil differs from that found in the root system of colonized plants. The genera Claroideoglomus, Diversispora, Dominikia, Intraornatospora, Redeckera and Rhizoglomus were only detected through molecular analysis, while Ambispora and Paradentiscutata were observed just from morphological analysis. The rhizosphere of corn crops in areas with different soil and climatic characteristics has a diverse community of AMF, with dominance of Glomus and Acaulospora species. The growth stage of corn plants can influence the diversity of AMF fungi, which decreased in the rhizosphere of older plants. The simultaneous use of morphological and molecular approaches can improve the knowledge about the composition of AMF communities.

Les plantes et les insectes forment l’un des principaux niveaux trophiques des écosystèmes au cours des 325 derniers millions d’années. Aujourd’hui, l’augmentation rapide et continuelle de la température principalement causée par l’activité humaine depuis les derniers siècles, perturbe la balance des écosystèmes sur Terre. En conséquence, comprendre le rôle des interactions entre les plantes et les insectes, à travers le temps mais aussi les réseaux trophiques, est essentiel. Le registre fossile est une opportunité exceptionnelle d’examiner les réponses aux interactions plante-insecte lors de longues variations climatiques et à travers des traces de réaction de la plante sachant que la Terre a déjà été soumise à de nombreux changements climatiques. Durant les derniers 3 millions d’années, des oscillations entre de longues périodes froides et de courtes périodes chaudes ont eu lieu. Les écosystèmes Européens ont particulièrement été impactés par ces oscillations. Le Langerstätte de Willershausen (Allemagne) a été particulièrement étudié. C’est un gisement contenant plus de 8000 feuilles fossiles. Ces feuilles relatent d’une paléoforêt ayant existé il y a 3- 2,6 Ma dans un climat plus chaud qu’aujourd’hui (ca.+5°C). Dans ces conditions climatiques, de nombreuses espèces d’écosystèmes Méditerranéens étaient présentes, telles que l’Érable de Montpellier ou l’Olivier. En comparaison, d’autres paléoforêts ont été prise en compte : Berga (du même âge et proche de Willershausen) et Bernasso (plus jeune que Willershausen (2,16 — 1,96 Ma) localisée dans le sud de la France près de la Méditerranée. Ces forêts sont comparables notamment du fait des nombreux taxons communs qu’elles partagent. En outre, certaines de ces espèces sont aujourd’hui endémiques de la région du Caucase, telles que le Parrotie de Perse ou encore l’orme du Caucase. Le but de cette étude a été de déterminer en quoi les différences climatiques peuvent être impliquées dans les changements des interactions plante-insecte au sein des paléoforêts Européennes de la fin du Pliocène - début du Pléistocène. Les résultats obtenus ont permis de mettre en évidence les impacts de la saisonnalité des températures et précipitations facteurs impactants les interactions plante-insecte des paléoforêts Européennes. Il est apparu que les écosystèmes sujets à d’intenses saisonnalités hydriques ont pu engendrer une plus grande spécialisation des interactions plante-insecte déduite d’un fort taux d’interactions spécialistes observées. En parallèle, les températures les plus froides durant l’année semble être un facteur important dans la faible diversité de dégâts, probablement dû à un faible métabolisme de la majorité des insectes. L’absence de corrélation convergente entre la richesse des plantes et la richesse des interactions pourrait suggérer que l’influence des facteurs climatiques surpasse l’impact potentiel des interactions biotiques locales. Pour l’ensemble de ces paramètres qui ont pu avoir un impact sur les interactions plante-insecte, nos connaissances actuelles sont encore insuffisantes. Il serait intéressant de focaliser davantage d’études sur les forêts modernes avec les méthodes appliquées dans le fossile. C’est dans cette intention qu’une partie de cette étude a étudié une espèce de plante (Parrotia persica) actuellement endémique de la forêt Hyrcanienne (Iran). Cette forêt est supposée être une forêt analogue des paléoforêts Européennes étudiées dans cette thèse. Pour le moment, les observations qui ont été faites en Iran semblent corroborer notre interprétation. Au final, les études sur les interactions plante-insecte des forêts anciennes et actuelles, combinés avec les études de changements climatiques, pourraient nous permettre de mieux caractériser les relations entre les insectes et les plantes au sein d’une forêt. / Insects are the most diverse animals on Earth, and neatly associated with plants they represent two of the major groups of organisms both in species diversity and biomass quantity. The majority of their interactions involves insect feeding and insect parasitism mostly on leaves. Plant and insect compose one of the main trophic levels in ecosystems over the 325 million years. Today, the continuous and fast rising of temperature mostly due to human activities since the last century is disturbing the balance of ecosystems on Earth. Consequently, to understand the role of plant and insect interactions, through time but also trophic networks, becomes crucial. The fossil record is an exceptional opportunity to survey responses of plant-insect interaction to climate variations over long time interval through traces of plants reactions caused by interaction with insects, as Earth has already experienced many climate changes. For the last 3 million years, oscillations between long cold periods and short warm periods have occurred. Europe ecosystems has been particularly impacted. The Lagerstätte of Willershausen (Germany) was specifically study. It is an exceptional fossil outcrop that contains ca. 8000 collected fossil leaves. These leaves testify a paleoforest developed there around 3—2.6 Ma ago in a climate warmer than today (ca. +5°C). Under these conditions, many plant species typical of the Mediterranean ecosystems were settled there, such as Montpellier maple or Olive tree. For comparison, other paleoforests were studied: Berga (similar in age and geographically close to Willershausen) and Bernasso (younger than Willershausen (2.16—1.96 Ma) and located in southern France close to Mediterranean. These forests were compared as many common plant taxa were similar between each other. Furthermore, some species today endemic to the Caucasian region, such as Persian ironwood or Caucasian elm, were also present in these outcrops. The aim of this study is to determine how far the climate differences could be involved in the changes of plant-insect interactions in European paleoforests of the late Pliocene – early Pleistocene. Results highlighted the impacts of both hydric and temperature seasonality, hitherto underestimated in the fossil record, on the patterns of plant-insect interaction in the European paleoforests. It appeared that ecosystems subject to intense hydric seasonality could led to higher specialization of plant-insect interaction inferred by higher rate of observed damages due to ‘specialists insects’. In parallel, the coolest temperature during the year seems to be a major factor in the low diversity of damage in paleoforest, presumably due to lower insect metabolism. Absence of convergent correlations between plant richness and damage richness could suggested that influence of climatic factors override impact of these local biotic factors. In order to understand the whole parameters that could have an impact on plant-insect interactions, our current knowledges are still insufficient. It would be wise to make more investigations on modern forests with the methods as applied in fossil record community structure studies. These investigations could help to understand the factors potentially involved in the establishment of a pattern of plant-insect interactions. It is in this perspective that a part of this study was precisely focused on one plant species (Parrotia persica) currently endemic to the Hyrcanian forest (Iran). This forest is supposed to be an analogue forest of the European paleoforests as those studied in this thesis. For now, observations made in Iran tend to corroborate our interpretation. Finally, the studies on plant-insect interactions in past and extant ecosystems, combined with the study of climatic changes, should permit us to better characterize the relations between plants and insects in forests through time.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The variation on the richness species in regional scales has been debated a lot. Three of the hypotheses mot frequently discussed as determinants of regional variability in richness species are energy, contemporary climatic conditions and habitat heterogeneity. Studies at mesoscale are very important to discover different patterns that underlying the variability in richness species. As the bats are so common in whole world and ecologically diverse, these organisms are excellent environmental characterized. On this basis, the goals of this study were to link the bat species composition with the vegetation in forest-grassland transition area in the Southeastern of South America and to assess the space influence on the bat species richness by environmental variables. The study area includes the southeastern of South America. Species distribution data were obtained by museums, review and database on line .The distribution s estimate for each species was done on a map with 139 cells 1º latitude by 1º longitude. It was collected distribution data to 79 bat species. Rain Forest and Seasonal Forest had the largest species richness. The cluster analysis based on the cells revealed three major clusters: the Forest cluster (at north), the Araucaria cluster (at middle), and the Grassland cluster (at south). The Araucaria cluster was associated to the Grassland cluster. The cluster analysis based in the phytogeographic zones revealed four clusters, where the Araucaria Forest was associated with the forested regions. The contemporary climatic conditions hypothesis was the best explained the variability on the richness data, where the mean annual temperature the main predictor variable, followed by extent of relief and AET, respectively. With the whole variables, the OLS regression also indicated the mean annual temperature as the main predictor variable, followed by AET. These same variables also explained the variability in the species richness in Phyllostomidae, Molossidae and Vespertilionidae. The Araucaria Forest is a filter area to the dispersal of tropical species into subtropical and temperate areas of South America, because the hard winters in that area, what may be explained likely for the intolerance of some species in colder climates. / A variação da riqueza de espécies em escala regional tem sido intensivamente discutida. Três das principais hipóteses que buscam explicar esse padrão de variação são as hipóteses energética, climática e de heterogeneidade do habitat. Estudos em meso-escala são importantes para descobrir padrões diferentes que influenciam a variação na riqueza de espécies. Como os morcegos são muito abundantes globalmente e bem diversificados ecologicamente, esses organismos são ótimos caracterizadores ambientais. Com base nisso, os objetivos deste estudo foram relacionar a composição das espécies de morcegos com a vegetação em área de transição floresta-campo no sudeste da América do Sul e avaliar a influência do espaço sobre a riqueza de morcegos através de variáveis ambientais. A área de estudo compreende a porção sudeste da América do Sul. Os dados de distribuição das espécies foram coletados através de visita a museus, revisão bibliográfica e consulta a bancos de dados on line. Foi feita a estimativa de distribuição para cada espécie sobre um mapa contendo 139 quadrículas de 1º de latitude por 1º de longitude. Foram obtidos dados de distribuição para 79 espécies de morcegos. Áreas de Floresta Ombrófila Densa e de Floresta Estacional possuíram a maior riqueza de espécies. A análise de agrupamento com base nas quadrículas formou três grupos nítidos: grupo Florestal (ao norte), Araucária (intermediário) e Campestre (ao sul). O grupo Araucária ficou associado ao grupo Campestre. A análise de agrupamento com base nas regiões fitogeográficas formou quatro grupos nítidos, sendo que a Floresta de Araucária ficou associada às formações florestais. A hipótese climática foi a que melhor explicou a variação dos dados de riqueza, sendo a temperatura média anual a principal variável preditora, seguida pela amplitude da altitude e pela AET, respectivamente. Considerando todas as variáveis, a regressão OLS também apontou a temperatura média anual como a principal variável preditora, seguida pela AET. Essas variáveis também explicaram a variação na riqueza de espécies das famílias Phyllostomidae, Molossidae e Vespertilionidae. A Floresta de Araucária é uma área filtro para a dispersão de espécies tropicais para as regiões subtropicais e temperadas da América do Sul, devido aos invernos rigorosos presentes nessa área, o que pode ser explicado principalmente pela intolerância de algumas espécies a climas mais frios.

Climate change is a well-studied subject but large uncertainties still exist in future projections. These uncertainties are even larger on future runoff projections at catchment scales due to the differences in local landscape factors. Continuous assessments are therefore needed to improve our understanding and increase our preparedness for the future. One way forward is to assess the impact of climate change on runoff with the new hydrological model PERSiST. PERSiST was calibrated to four study catchments that spread out along a south-north climate gradient of Sweden. The model well simulated the stream discharges with Nash-Sutcliffe values ranging from 0.55 to 0.76. The model was then driven by downscaled and bias-corrected weather data (2061–2090) from an ensemble of 15 Regional Climate Models. The runoff projections showed that the impact of climate change on runoff would differ across the catchments. All catchments would see an increase in annual runoff with the greatest increase in the northernmost catchment. The northernmost catchment would also see a likely decline in spring flood, a shift in timing of the spring flood from May to April and an increase in winter runoff. As a result of an increase in winter runoff, there could be a loss of seasonality. In the more southern catchments the present-day runoff was more evenly distributed during the year and the projected loss of seasonality was not as pronounced. The conclusion was that the impact of climate change on runoff would increase northward, due to the higher response to climate change in the northernmost catchments. / Klimatförändringar är ett välstuderat ämne men stora osäkerheter kvarstår vad gäller framtida projektioner. Dessa osäkerheter är ännu större när det kommer till framtida projektioner av avrinning på grund av stora olikheter i lokala faktorer. Därför är fortsatta utvärderingar av nytta för att öka förståelsen och förbättra förberedelsen för framtiden. Ett steg i rätt riktning är att utvärdera klimatförändringars effekt på avrinning med hjälp av den nya hydrologiska modellen PERSiST. PERSiST kalibrerades för fyra olika avrinningsområden som var utspridda längs en syd-nord-gradient av Sverige. Den kalibrerade modellen simulerade det observerade flödet med Nash-Sutcliffe värden från 0,55 till 0,76. Modellen kördes sedan med nerskalad och bias-korrigerad väderdata (2061–2090) från en ensemble av 15 regionala klimatmodeller. Resultatet visade att klimatförändringars effekt på avrinning varierade mellan avrinningsområdena. Alla avrinningsområden påvisade en ökning i total årlig avrinning. Den största ökningen stod att finna i det nordligaste avrinningsområdet. Det nordligaste avrinningsområdet påvisade även en trolig minskning i vårflodsvolym, en skiftning av vårfloden från maj till april samt högre flöden vintertid. Som ett resultat av högre flöden vintertid uppstod en minskning av säsongsvariation. I de sydligare avrinningsområdena var dagens flöden jämnare fördelade över året, vilket gjorde att minskningen av säsongsvariation inte var lika stor. Slutsatsen var att klimatförändringarnas effekt på avrinning ökar norrut.

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. / 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.