Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-07-27T12:14:16Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tese Doutorado Hiram Falcão.pdf: 1589850 bytes, checksum: c86ffb35f5d0263dbd80e96c156b8065 (MD5) / Made available in DSpace on 2017-07-27T12:14:16Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tese Doutorado Hiram Falcão.pdf: 1589850 bytes, checksum: c86ffb35f5d0263dbd80e96c156b8065 (MD5) Previous issue date: 2016-02-24 / CAPES / Para o estabelecimento de populações vegetais em ambientes que são heterogêneos no tempo e no espaço, como florestas que passam por processo de regeneração natural, é fundamental a capacidade de apresentar respostas plásticas em atributos funcionais foliares em resposta às variações ambientais. Plantas pioneiras apresentam estratégias ecofisiológicas distintas de plantas de estádios sucessionais tardios, ocupando posições opostas no espectro de economia foliar. No entanto algumas plantas conseguem se estabelecer, ao mesmo tempo, em áreas em diferentes momentos do processo sucessional. Dessa forma, o presente trabalho teve como objetivo avaliar a variação nos atributos funcionais de três espécies de diferentes hábitos, numa cronosequência (inicial (22 anos), intermediária (44 anos), e tardia (+ 60 anos)) de floresta tropical sazonalmente seca em três estações chuvosas consecutivas. As espécies selecionadas foram: Poincianella pyramidalis (Tul.) L.P. Queiroz (Fabaceae), arbórea; Hyptis suaveolens (L.) Poit. (Lamiaceae), herbácea; e Sida galheirensis Ulbr. (Malvaceae), subarbustiva. As duas primeiras são encontradas nos três estádios sucessionais, e a última apenas nos estádios inicial e tardio. Todas as coletas foram realizadas no período chuvoso, no mês de abril, entre os anos de 2012 e 2015. Foram mensuradas as trocas gasosas, o potencial hídrico foliar, o conteúdo e a eficiência no uso dos nutrientes, a área foliar específica, o conteúdo de compostos fenólicos, o custo de construção foliar e o tempo de compensação. As respostas ecofisiológicas das plantas foram influenciadas tanto pelo estádio sucessional quanto pela precipitação entre os anos. De um modo geral, as plantas do estádio tardio apresentaram maiores taxas de trocas gasosas, potencial hídrico, eficiência no uso dos nutrientes e investimento em defesa, especialmente em 2014, o ano mais chuvoso. Além disso, um maior custo de construção foliar e um menor tempo de compensação foram observados nas plantas da área tardia, evidenciando que em áreas preservadas as plantas são mais eficientes no uso da energia. No entanto a variação nos atributos foliares foi mais intensa entre os anos de coleta. Dentre os atributos funcionais, o potencial hídrico apresentou a maior capacidade de aclimatação à variação ambiental, seguido da eficiência no uso dos nutrientes e da área foliar específica. O atributo com a menor capacidade de resposta plástica foi o custo de construção foliar. No entanto esse atributo foi mostrou-se como um dos mais importantes na classificação das plantas de acordo com o estádio sucessional. Os resultados mostram que a água é o principal filtro ambiental que coordena as respostas ecofisiológicas na floresta tropical sazonalmente seca brasileira. No entanto as diferentes espécies captam e utilizam a água disponível de forma distinta, evidenciando uma diferenciação de nicho com relação ao uso da água. A variação nos atributos funcionais em função do estádio sucessional sugere que as espécies analisadas têm a capacidade de ajustar o seu espectro de economia foliar, utilizando-se de estratégia de captação ou de conservação de recursos de acordo com as exigências do ambiente. / For establishing plant populations in environments that are heterogeneous in time and space, as forests that pass through natural regeneration process, it is essential the ability to present plastic responses in leaf functional traits in response to environmental variations. Pioneer plants have different ecophysiological strategies in comparison plants of late successional stages, occupying opposite positions in the leaf economics spectrum. However some plants can be established, at the same time, in areas at different stages in succession process. Thus, this study aimed to evaluate the changes in the functional attributes of three species of different habits, in a chronosequence (early (22 years), intermediate (44 years) and late ( + 60 years)) of a seasonally tropical dry forest in three consecutive rainy seasons. The species selected were: Poincianella pyramidalis (Tul.) L.P. Queiroz (Fabaceae), a tree; Hyptis Suaveolens (L.) Poit. (Lamiaceae), a herb; and Sida galheirensis Ulbr. (Malvaceae), a subshrub. The first two are found in the three successional stages, and the last one only in the early and late stages. All samples were collected in the rainy season, in April, between the years 2012 and 2015. The gas exchange, leaf water potential, the content and the nutrient use efficiencies, specific leaf area, the content of phenolics, the leaf construction cost and payback time, were measured. Ecophysiological responses of plants were influenced both by the successional stage as the rainfall between years. In general, plants from late stage had higher rates of gas exchange, leaf water potential, nutrients use efficiency and investment in defense, especially in 2014, the wettest year. Furthermore, a higher leaf construction cost and a shorter payback time were observed in late area, showing that, in preserved areas, plants are more efficient in energy use. However the variation in leaf traits was more intense between the years of collection. Among the functional traits, the water potential presented the highest acclimatization capacity to environmental variation, followed by the nutrient use efficiencies and specific leaf area. The leaf trait with the lowest plastic response was the leaf construction cost. However, this trait was one of the most important in classifying the plants according to successional stage. The results showed that water is the main environmental filter that coordinates the ecophysiological responses in the Brazilian seasonally tropical dry forest. However the different species capture and utilize the available water separately, showing a niche differentiation related to water use. The variation in functional traits as a function of the succession stages, suggests that the species in this study have the ability to adjust its leaf economics spectrum economy, by using a resource capture or a conservative strategy according to the requirements of the environment.

Anticiper les impacts des changements climatiques sur les écosystèmes terrestres, notamment sur le cycle du carbone, nécessite la compréhension et la quantification du fonctionnement photosynthétique des végétaux et leurs réponses aux contraintes abiotiques. Suivre l’évolution des propriétés spectrales des couverts végétaux par la télédétection permet d’avoir accès à leur fonctionnement à des échelles spatiales et temporelles variées. Plusieurs indicateurs optiques ont été développés afin d’accéder à la structure, la biochimie et le fonctionnement écophysiologique des végétaux. Le PRI (photochemical reflectance index), déterminé à partir de la réflectance mesurée dans des bandes étroites à 531 nm et 570 nm, est un proxy de l’efficacité de la plante à utiliser la lumière (LUE, light use efficiency) et plus particulièrement du cycle des xanthophylles, utilisé par la plante pour dissiper l’énergie lumineuse excédentaire sous forme de chaleur. Cependant son usage à l’échelle du couvert végétal, ou à plus larges échelles temporelles et spatiales, entraine l’implication de nombreuses sources de variabilités qui masquent la sensibilité du PRI au fonctionnement photosynthétique, particulièrement les variations biochimiques et phénologiques. L’objectif de ce travail est de mieux comprendre les facteurs qui jouent sur la variabilité du PRI à l’échelle de la feuille et du couvert, afin de caractériser ses réponses aux variations abiotiques de l’environnement et de démêler la composante phénologique de la composante physiologique du PRI. Des études ont été menées en conditions contrôlées, semi-naturelles et naturelles, sur des jeunes arbres et en forêt adulte, soumis à différentes contraintes abiotiques. L’analyse des courbes de réponse du PRI aux variations de lumière incidente utilisée pour la photosynthèse (PAR, photosynthetically active radiation) permet d’isoler 3 paramètres. Le PARsat, la valeur de PAR pour laquelle le PRI sature, le PRI₀, la valeur du PRI à une intensité lumineuse faible (mesurée) ou nulle (estimée) et le ∆PRI, l’amplitude de variation entre le PRI₀ et la valeur de PRI maximum. En période de végétation, la variabilité du PARsat est principalement contrôlée par la disponibilité en eau pour la plante. La variabilité du PARsat est aussi impactée par la concentration d’ozone atmosphérique. En période de débourrement et de sénescence, la variabilité du contenu en chlorophylle régit la valeur du PARsat. Ce paramètre explique la variabilité physiologique du PRI et varie en fonction du facteur limitant la photosynthèse. La variabilité du PRI₀ a été expliquée par la variabilité du contenu biochimique des feuilles en réponse au cycle saisonnier de la chlorophylle et à sa variabilité en conditions de stress. A l’échelle de la canopée, la variabilité de la structure du couvert s’ajoute à la variabilité biochimique du PRI₀. Le PRI₀, en temps que composante phénologique de la variabilité du PRI, peut être utilisé pour corriger le PRI afin de lui soustraire la variabilité structurale et obtenir un PRIc fortement corrélé à la LUE. A l’échelle de la canopée, il a été montré que le PRI est principalement représentatif de la strate supérieure du couvert. Le ∆PRI n’a montré aucune variation intra et inter-journalière, suggérant que le PRI répond non pas au contenu en xanthophylle des plantes, mais à un ratio maintenu constant. Ces résultats mettent en évidence l’importance d’isoler les différentes sources de variabilité du PRI avant de l’utiliser comme proxy du fonctionnement photosynthétique des écosystèmes terrestres. / Anticipating impacts of climate change on terrestrial ecosystems, particularly on the carbon cycle, requires the understanding and the quantification of the plant photosynthetic functioning and of their responses to abiotic factors. Tracking variations of spectral properties of plants using remote sensing allows the access of plant functioning at various spatial and temporal scales. Several optical indices have been developed to assess plant canopy structure, biochemistry and ecophysiological functioning. The PRI (photochemical reflectance index), determined from reflectances measured in narrow bands at 531 nm and 570 nm, may be used as a proxy of light use efficiency (LUE) at leaf and canopy scales, and more particularly of the xanthophyll cycle used by plants to dissipate the excess light energy as heat. However the use of PRI at the canopy scale and at large temporal and spatial scales faces several difficulties related to the involvement of different sources of variability that blur PRI sensitivity to photosynthetic functioning. These sources of PRI variability are particularly linked to spatial and temporal variations of biochemical and phenological canopy properties. The aim of these studies is to better understand the factors affecting PRI variability at leaf and canopy scales, to assess the strength of the relationships between PRI and vegetation responses to environmental abiotic constraints and disentangling the phenological component from the physiological component of PRI. Studies were conducted under controlled, semi-natural and natural conditions, on young trees and a mature deciduous forest subjected to various abiotic constraints. The analysis of PRI responses to the variations of photosynthetically active radiation (PAR) allowed isolating three parameters. The PARsat, the PAR value at the PRI saturation; the PRI₀, the value of PRI at dim light (measured) or in darkness (estimated) and the ΔPRI, the range of PRI variations between the PRI₀ and the maximum value of PRI. During the leaf growing season, PARsat variability is mainly controlled by the availability of water content for the plant. The PARsat variability is also impacted by the atmospheric ozone concentration. During the phenological phases of budburst and the senescence, the variability of the leaf chlorophyll content governs PARsat values. This parameter describes the physiological variability of PRI and varies depending on the limiting factor for photosynthesis. The PRI₀ variability has been explained by the dynamic of the biochemical content of the leaves linked to the seasonal variations of chlorophyll content and to abiotic stress conditions. At canopy scale, the structural variability is added to the biochemical variability of PRI₀. The PRI₀, as the phenological component of PRI variability, can be used to correct PRI, removing its structural variability to obtain a PRIc strongly correlated to LUE. At canopy scale, it was shown that the PRI is mostly representative of the upper layer of the canopy. The ΔPRI showed no variation within and between days, suggesting that the PRI does not respond to the plant xanthophyll content but rather to a ratio maintained constant. These results highlight the importance of isolating the different sources of PRI variability before its use as a proxy of the photosynthetic functioning of terrestrial ecosystems.

Dans le contexte actuel de changement climatique, anticiper la réponse des écosystèmes forestiers face à un risque de sécheresse accrue constitue un enjeu socio-économique, écologique et scientifique majeur. Les îles antillaises au-delà de leur statut de « hot spot de biodiversité », se situent dans un « hot-spot climatique », particulièrement à même d’être affecté par la réduction des précipitations. L’archipel Guadeloupéen constitue un modèle de choix dans l’étude des réponses végétales aux conditions environnementales. Il abrite l’ensemble de la diversité des écosystèmes caribéens, distribués le long d’un gradient altitudinal et de pluviométrie. Aux deux extrémités de ce gradient se situent des formations forestières expérimentant des conditions environnementales très contrastées : la forêt sèche et la forêt de nuage. Le premier objectif de cette étude était de caractériser les stratégies de croissance et la réponse physiologique à la contrainte hydrique de 8 espèces d’arbres structurants la forêt sèche et la forêt de nuage de Guadeloupe. Dans un premier temps, nous avons quantifié in situ, à différentes saisons, un large panel de traits fonctionnels intervenant à différentes échelles (cellule, feuille, individu) reflétant les principales fonctions végétatives des arbres (croissance, photosynthèse, transport hydraulique). Cette approche a permis de dresser un portrait fin du fonctionnement hydrique et carboné des espèces. L’approfondissement de la caractérisation de l’architecture hydraulique des espèces a été réalisée ex situ à travers une analyse structurelle (anatomique, morphologique) et fonctionnelle (résistance du xylème à la cavitation et des feuilles au flétrissement) afin de préciser leur potentiel de résistance à la sécheresse. Cette approche des différentes composantes du fonctionnement hydrique, rarement mise en œuvre, a permis de cerner les réponses des arbres de façon intégrée. Une importante diversité fonctionnelle a été mise en évidence au sein de chaque écosystème. Les espèces de forêt sèche, subissant une contrainte hydrique saisonnière marquée, montrent une capacité de résistance à la contrainte hydrique supérieure à celle des espèces de forêt de nuage. Cependant, la coexistence de différentes stratégies phénologiques dans cet écosystème aboutit à une importante diversité de stratégies hydriques et de croissance. En forêt de nuage, la contrainte hydrique édaphique est rare mais les espèces sont à même de subir une contrainte hydrique liée aux conditions atmosphériques. Dans cet écosystème, une diversité de comportement dépendant de la capacité des espèces à maintenir leur fonctionnement en cas de contrainte atmosphérique a aussi été mise en évidence. Nous avons identifié des corrélations intervenant entre la croissance cambiale, la résistance à la cavitation, la résistance au flétrissement foliaire et ses mécanismes d’ajustements sous-jacents ainsi que la sensibilité stomatique. Ces relations ont matérialisé un continuum cohérent et robuste de réponses fonctionnelles. La forte diversité relevée au sein des deux écosystèmes a induit une mixité de répartition des espèces le long de ce continuum. Afin de simplifier et résumer cette diversité mise en évidence nous avons cherché à former des groupes d’espèces déterminés par un jeu de traits morphologiques faciles à acquérir pour 14 espèces de forêt sèche et de forêt de nuage. / In the current context of climate change, anticipate the response of forest ecosystems facing an increased risk of drought is a socio- economic, ecological and scientific major issue. The Caribbean islands, beyond their status as «biodiversity hot spot», are in a "climate hot-spot ", particularly likely to be affected by reduced rainfall. The Guadeloupe archipelago is a model of choice in the study of plant responses to environmental conditions. It harbors all the diversity of Caribbean ecosystems, distributed along an altitudinal gradient and rainfall. At both ends of this gradient fall forest formations with contrasting environmental conditions: dry forest and montane cloud forest. The first aim of this study was to characterize growth strategies and the physiological response to water stress of 8 species of trees structuring the dry forest and cloud forest of Guadeloupe. First, we quantified in situ, in different seasons, a wide range of functional traits occurring at different scales (cell, leaf, individual) reflecting the main vegetative functions of trees (growth, photosynthesis, water transport). The deepening of the characterization of the hydraulic architecture of the species was carried out ex situ through a structural (anatomical, morphological) and functional (xylem resistance to cavitation and leaves wilt) analysis to clarify their potential resistance drought. This approach has enabled the identification of fine portrait of the water and carbon-functioning in the species. An important functional diversity has been demonstrated within each ecosystem. Dry forest species experience a marked seasonal water stress, show a higher resistance to water stress than that of cloud forest species. However, the coexistence of different phenological strategies in this ecosystem leads to a wide diversity of water and growth strategies. In cloud forest, edaphic water stress is rare but the species are likely to suffer water stress due to atmospheric conditions. In this ecosystem, a behavioral diversity dependent of the species' ability to maintain their functioning during atmospheric strain was also highlighted. We identified correlations between cambial growth, cavitation resistance, leaf wilt resistance and stomatal sensitivity. These relationships have materialized a coherent and robust continuum of functional responses. The high diversity recorded in the two ecosystems induced a mix of species distribution along this continuum.To simplify and summarize this diversity we sought to form groups of species determined by a set of morphological traits easy to acquire for 14 species of dry forest and cloud forest. This method produced groups reflecting different strategies for carbon management, influenced by the phenology of species. In contrast, groups obtained did not reflect drought response of species.Finally, because the seedling stage is a primary stage in terms of natural regeneration potential of forests, we evaluated ex situ the resistance to drought of dry forest seedlings. Like the adults, the dry forest seedlings showed a variety of strategies to cope drought.

Drosophila suzukii est une drosophile invasive en Europe, Amérique du Nord et Amérique du Sud. Contrairement aux autres espèces de drosophiles, les femelles parasitent les fruits mûrs que les larves consomment, engendrant d’importants dégâts sur les cultures fruitières. Les stratégies mises en place par cette espèce pour tolérer les températures hivernales sous nos latitudes sont encore peu comprises. Par conséquent, l’objectif de ma thèse était d’acquérir des connaissances fondamentales sur la thermotolérance de cette espèce, en m’intéressant notamment à la plasticité de la tolérance au froid et aux mécanismes physiologiques sous-jacents à l’acclimatation. J’ai évalué la thermotolérance basale de D. suzukii en soumettant des adultes et des pupes à un large panel de températures (froides et chaudes). Ces expérimentations ont permis de confirmer que cette espèce était intolérante au froid et que des températures supérieures à 32°C impactaient grandement sa survie. Par la suite, j’ai évalué la plasticité de sa tolérance au froid. Mes travaux ont permis de confirmer que sa thermotolérance était effectivement plastique, puisque l’utilisation de températures fluctuantes ou l’acclimatation permettaient de réduire sa mortalité lors d’expositions aux basses températures. L’acclimatation chez D. suzukii était corrélée à de nombreuses modifications physiologiques, telles que l’accumulation de cryoprotecteurs, un réajustement de la composition des phospholipides membranaires et des réserves lipidiques, une régulation des gènes liés à l’activité des transporteurs ioniques ainsi qu’un maintien de l’homéostasie métabolique. Ces modifications, également observées chez d’autres espèces d’insectes, pourraient être liées à l’augmentation de la tolérance au froid de D. suzukii, jouant probablement un rôle important dans sa survie hivernale et donc dans le succès de son invasion. Ces connaissances acquises sur sa thermobiologie contribueront sans doute à mieux cerner les limites physiologiques de cette espèce et prédire l’évolution de son invasion, ainsi que sa phénologie et les variations de populations au cours des saisons dans les zones déjà envahies. Mes résultats ouvrent également des perspectives intéressantes pour la mise en place de techniques de lutte intégrée contre D. suzukii. / Drosophila suzukii is an invasive pest in Europe, North and South America. Unlike other drosophilids, females oviposit in ripe fruits that larvae consume, provoking important damages on fruit productions. The overwintering strategies of this fly are yet poorly understood. Therefore, the aim of my thesis was to acquire new fundamental knowledge about the thermal biology of this fly, and more specifically the plasticity of its thermal tolerance and the physiological mechanisms underpinning cold acclimation. In order to define its basal thermal tolerance, adults and pupae were subjected to a large set of high and low temperatures. My data confirmed that this pest was chill susceptible, and showed that survival was greatly compromised during exposures above 32°C. Next, I evaluated its thermal tolerance plasticity. My data confirmed the high plasticity of its cold tolerance, as fluctuating thermal regimes and acclimation were able to decrease the mortality due to cold exposures. Acclimation in this species was correlate with several physiological adjustments, such as: cryoprotectant accumulation, remodeling of membrane phospholipids and lipidic reserves, upregulation of genes linked with activity of ionic transporters and maintenance of metabolic homeostasis. Those modifications (which are shared among temperate insect species) are likely linked with cold tolerance increase provoked by acclimation. Therefore, these physiological adjustments could play an important role in its overwintering success in Europe and Canada, which can facilitate its invasion in these regions. These new data will participate to a better understanding of its physiological limits, and are thus of importance for predicting the evolution of its invasion front and its phenology and demographic variations in invaded areas. My results are also of interest regarding the set-up of integrated pest management strategies against this fly.

My master's work was done within the context of the PhytoVaLix project, a research project that brings together researchers from the Université de Montréal and private companies. The goal of this project is to develop a technology for the phytotreatment of leachate from engineered landfill sites using willows to replace conventional techniques. A filtering plantation of miyabeana willow (Salix miyabeana) is currently in place on the experimental site. The willows are watered with leachate so that they use ammoniacal nitrogen, the main pollutant, for their growth. In my study, I focused on the morphological and physiological responses developed by four willow species when subjected to various treatments combining flooding and nitrogen overfertilization. The study aimed to compare the potential of these species for nitrogenous water phytoremediation as well as two leachate application methods. Responses to flooding and overfertilization with nitrogen varied and reveal much about the strategies adopted by each species. The biomass of S. miyabeana, S. amygdaloides and S. nigra was not impacted by the leachate treatments, while S. bebbiana suffered greatly from the flooding periods. The native species S. nigra and S. amygdaloides positively stood out in their ability to remove nitrogen from leachate (>75 kg/ha). It would be relevant to continue research on these two with the aim of using them in projects where leachate phytotreatment and biodiversity go hand in hand. / Mon travail de maitrise a été réalisé dans le cadre du projet PhytoVaLix, un projet de recherche qui réunit des chercheurs de l'Université de Montréal et des entreprises privées. Le but de ce projet est de développer une technologie de phytotraitement de lixiviat provenant de lieux d’enfouissement technique à l’aide de saules pour remplacer les techniques conventionnelles. Une plantation filtrante de saule miyabeana (Salix miyabeana) est présentement en place sur le site expérimental. Les saules y sont arrosés avec du lixiviat afin qu’ils utilisent l’azote ammoniacal, le polluant principal, pour leur croissance. Dans mon étude, je me suis intéressée aux réponses morphologiques et physiologiques développées par quatre espèces de saule lorsqu’elles sont soumises à divers traitements combinant l’inondation et la surfertilisation à l’azote. L’étude avait comme objectif de comparer le potentiel de ces espèces pour la phytoremédiation d’eau azotée et de deux méthodes d’application du lixiviat. Les réponses à l’inondation et à la surfertilisation à l’azote furent variées et en révèlent beaucoup sur les stratégies adoptées par chacune des espèces. La biomasse de S. miyabeana, S. amygdaloides et S. nigra ne fut pas impactée par les traitements de lixiviat, alors que S. bebbiana a grandement souffert des périodes d’inondation. Les espèces indigènes S. nigra et S. amygdaloides se sont positivement démarqués quant à leur capacité à retirer l’azote du lixiviat (>75 kg/ha). Il serait pertinent de continuer à faire des recherches sur celles-ci dans le but de les utiliser dans des projets où le phytotraitement du lixiviat et la biodiversité vont de pair.

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Most climate change predictions focus on the response of individual species to changing local conditions and ignore species interactions, largely due to the lack of a sound theoretical foundation for how interactions are expected to change with climate and how to incorporate them into climate change models. Much of the variability in species interaction strengths may be governed by fundamental constraints on physiological rates, possibly providing a framework for including species interactions into climate change models. Metabolic rates, ingestion rates and many other physiological rates are relatively predictable from body size and body temperature due to constraints imposed by the physical and chemical laws that govern fluid dynamics and the kinetics of biochemical reaction times. My dissertation assesses the usefulness of this framework by exploring the community-level consequences of physiological constraints. In Chapter 2, I incorporated temperature and body size scaling into the biological rate parameters of a series of realistically structured trophic network models. The relative magnitude of the temperature scaling parameters affecting consumer energetic costs (metabolic rates) and energetic gains (ingestion rates) determined how consumer energetic efficiency changed with temperature. I systematically changed consumer energetic efficiency and examined the sensitivity of network stability and species persistence to various temperatures. I found that a species' probability of extinction depended primarily on the effects of organismal physiology (body size and energetic efficiency with respect to temperature) and secondarily on the effects of local food web structure (trophic level and consumer generality). This suggests that physiology is highly influential on the structure and dynamics of ecological communities. If consumer energetic efficiency declined as temperature increased, that is, species did best at lower temperatures, then the simulated networks had greater stability at lower temperatures. The opposite scenario resulted in greater stability at higher temperatures. Thus, much of the community-level response depends on what species energetic efficiencies at the organismal-level really are, which formed the research question for Chapter 3: How does consumer energetic efficiency change with temperature? Existing evidence is scarce but suggestive of decreasing consumer energetic efficiency with increasing temperature. I tested this hypothesis on seven rocky intertidal invertebrate species by measuring the relative temperature scaling of their metabolic and ingestion rates as well as consumer interaction strength under lab conditions. Energetic efficiencies of these rocky intertidal invertebrates declined and species interaction strengths tended to increase with temperature. Thus, in the rocky intertidal, the mechanistic effect of temperature would be to lower community stability at higher temperatures. Chapter 4 tests if the mechanistic effects of temperature on ingestion rates and species interaction strengths seen in the lab are apparent under field conditions. Bruce Menge and I related bio-mimetic estimates of body temperatures to estimates of per capita mussel ingestion rates and species interaction strengths by the ochre sea star Pisaster ochraceus, a keystone predator of the rocky intertidal. We found a strong, positive effect of body temperature on both per capita ingestion rates and interaction strengths. However, the effects of season and the unique way in which P. ochraceus regulates body temperatures were also apparent, leaving room for adaptation and acclimation to partially compensate for the mechanistic constraint of body temperature. Community structure of the rocky intertidal is associated with environmental forcing due to upwelling, which delivers cold, nutrient rich water to the nearshore environment. As upwelling is driven by large-scale atmospheric pressure gradients, climate change has the potential to affect a wide range of significant ecological processes through changes in water temperature. In Chapter 5, my coauthors and I identified long-term trends in the phenology of upwelling events that are consistent with climate change predictions: upwelling events are becoming stronger and longer. As expected, longer upwelling events were related to lower average water temperatures in the rocky intertidal. Furthermore, recruitment rates of barnacles and mussels were associated with the phenology of upwelling events. Thus climate change is altering the mode and the tempo of environmental forcing in nearshore ecosystems, with ramifications for community structure and function. Ongoing, long-term changes in environmental forcing in rocky intertidal ecosystems provide an opportunity to understand how temperature shapes community structure and the ramifications of climate change. My dissertation research demonstrates that the effect of temperature on organismal performance is an important force structuring ecological communities and has potential as a tractable framework for predicting the community level effects of climate change. / Graduation date: 2013 / Access restricted to the OSU Community, at author's request, from Nov. 20, 2012 - Nov. 20, 2014

Les aires de répartition des arbres pourraient être grandement affectées par le changement climatique. Les résultats d’analyses paléogéographiques ont montré que ces dernières se sont déjà déplacées avec les variations passées du climat. Ces études ont permis de déterminer la direction et la vitesse de migration des espèces, données utilisées actuellement pour générer des prédictions sur l’évolution de l’aire de répartition des espèces forestières en réponse au réchauffement du climat. Cependant, le contexte écologique dans lequel les arbres font face à ces changements est très différent par rapport aux changements climatiques passés : l'augmentation actuelle des températures est plus rapide, les surfaces susceptibles d’être colonisées sont occupées par des écosystèmes très différents et variés (forêts, surfaces agricoles, zones urbaines). Par conséquent, les arbres pourront-ils faire face à la rapidité des changements globaux actuels ? Auront-ils la capacité de migrer pour trouver des conditions plus favorables ou pourront-ils s’adapter et survivre à de nouvelles conditions environnementales ? Dans un premier temps, l’analyse de données historiques (plans d’aménagements de l’Office Nationale des Forêts et Inventaires Forestiers Espagnols) a permis de mettre en évidence des évènements de colonisation et d’extirpation et de quantifier la vitesse de migration de populations situées au cœur ou aux marges de leur aire de répartition. Une colonisation massive de Quercus ilex dans les dunes boisées atlantiques (limite Nord d’aire de répartition) a été mise en évidence au cours des 130 dernières années, confirmant les tendances prédites par les modèles. Cependant, les vitesses de colonisation de cette espèce restent bien inférieures aux déplacements de son bioclimat estimés à partir de modèles de niche. Les espèces localisées en limite Sud d’aire de répartition présentent des remontées altitudinales plus importantes que pour celles situées au cœur de leur aire. En conclusion, nos résultats montrent que les changements globaux ont déjà impactés la répartition des arbres malgré l’existence d’un décalage temporel entre les réponses migratoires des espèces forestières et le déplacement de leur bioclimat. Le stress hydrique est le facteur prépondérant pouvant expliquer le dépérissement des arbres dans un milieu dont la disponibilité en eau est limitée, notamment en marge chaude d’aire de répartition. Nous avons, par conséquent, étudié la résistance à la sécheresse et ses mécanismes chez les plusieurs espèces d’Angiospermes. Nos résultats montrent qu’un seuil de 90% d’embolie mène à des dommages physiologiques irréversibles de la plante et à la mort par déshydratation. Ce seuil est considérablement plus élevé que celui précédemment observé chez les conifères. L’étude du fonctionnement hydraulique d’espèces de chênes co-occurrentes nous a permis de montrer que la survie de Q. robur pourrait être menacée dans les forêts atlantiques dans un contexte de sécheresses de plus en plus intenses car il y subit des taux d’embolie native élevés. Au contraire, Q. ilex présente des taux d’embolie négligeables sur ce même site d’étude.Les vitesses réelles de migrations constituent des données empiriques essentielles qui nous renseignent sur les capacités migratoires effectives des arbres. Elles pourront être intégrées dans les modèles de répartition, tout comme les seuils d’embolie induisant la mort des arbres. / Tree distribution could be highly affected by climate change. Results of paleogeographic studies showed that tree distribution ranges have already shifted with past climate changes. These data are currently used to model the evolution of species distribution in response to global warming. However, the ecological context in which species have to cope with climate change is very different than the past one: the current increase of temperature occurs faster than the past global warming, the areas being likely colonized are covered by various ecosystems (forests, agricultural surfaces, urban areas). So will tree species be able to cope with the current global change? Will they be able to migrate to find more favourable conditions or to survive to drier environmental conditions? Firstly, the analysis of historical data (French National Forest Office and Spanish National Forest Inventories) allowed determining colonization and extirpation events, and quantifying migration rates of tree species populations situated at the edges or the core of their distribution range. We evidenced that Q. ilex has substantially colonized new areas at its northern margin during the last 130 years, confirming the model trends. However, the colonization rates of Q. ilex are much lower than the shift of its bioclimate predicted by bioclimatic models. Species located at their rear edge showed higher upward shifts than other species located at the core of their range. To conclude, our results showed that global change have already impacted tree distribution although a time-lag between forest species migration responses and their bioclimate shift. Water stress is the main factor explaining tree dieback when water is limited and so particularly at the warm limit of tree species distribution range. Therefore, we studied drought resistance and its mechanisms in angiosperm tree species. Our results showed that embolism threshold of 90% leads to irreversible damages and tree death by dehydration. This threshold is considerably higher than the observed in Conifers. The study of hydraulic functioning of co-occurring oaks showed that the survival of Q. robur could be threatened in the context of increasing drought in the Atlantic forests because of its functioning at high levels of embolism. On the contrary, Q. ilex presented negligible levels of embolism in the same study area. The migration rates form primordial empirical data that give us information about tree effective migration abilities. They could be integrated within vegetation distribution models as well as embolism thresholds leading to tree mortality.

Synura petersenii represents a complex of pseudo-cryptic species. These are planktonic colonial organisms belonging to the class Chrysophyceae. The species are abundant in spring and autumn, when they produce golden-brown blooms in oligo-mesotrophic waters. In this thesis, I focused on investigating the effect of temperature to growth parameters of four selected species: S. petersenii, S. americana, S. glabra and S. conopea. Several temperature experiments were performed and statistically analyzed. According to growth curves the temperature 25 žC was mostly stressful for these organisms. Only S. petersenii sensu stricto was sometimes able to growth at this temperature. In general, the significant differences in growth rates were detected between S. petersenii and S. americana. In all experiments, S. petersenii had the lowest growth rate. This ubiquitous species probably acts as a K-strategist. S. americana grew generally very quickly, especially at temperature 13 žC that is obviously optimal for it. Further, I observed a significant strain specificity, which is largely a well-known phenomenon in the ecophysiology. Significant differences in growth rates were noted between temperatures 13 žC and 16 žC, where all tested species grew best, as well. This is in accordance with a general recognition of...