O conhecimento das associações entre os microrganismos componentes da microbiota dos solos é de grande interesse no meio científico, principalmente relacionado aos microrganismos que se associam de forma benéfica com as plantas. Neste contexto, destaca-se a micorriza arbuscular, que é a associação entre os fungos micorrízicos arbusculares (FMAs) e uma amplitude de espécies vegetais. Além desta íntima interação entre estes organismos, torna-se necessário conhecer a importância dos demais componentes do sistema solo, como a microbiota formada por fungos e bactérias dos solos, para o estabelecimento desta interação. Os objetivos dos estudos componentes desta tese se concentraram na avaliação de FMAs (D. heterogama, R. clarus e Gi. rosea) inoculados em sistemas alterados quanto à composição das comunidades microbianas dos solos, promovidas pela metodologia de \'diluição para extinção\'. No primeiro estudo foram encontradas respostas diferenciais na capacidade de colonização micorrízica (%CM) de plantas de cana-de-açúcar pelos FMAs inoculados nos diferentes sistemas, além do efeito diferencial dos FMAs quanto às alterações nas comunidades de fungos e bactérias do solo. Num estudo mais detalhado, desenvolvido apenas com R. clarus em plantas de milho, foi verificado que a maiores diversidades microbianas do solo resultaram em maior colonização do hospedeiro, principalmente no período inicial de desenvolvimento das plantas. Neste experimento foi descrita a correlação direta da capacidade de colonização do FMA com a riqueza e a diversidade filogenética da microbiota dos solos. A descrição dos perfis metabólicos dos solos contendo diferentes comunidades microbianas revelou a capacidade diferencial destes solos em utilizar diferentes fontes de carbono, além de demonstrar um aumento no metabolismo (evidenciado pelo consumo total de fontes de carbono) devido à inoculação do FMA. Em conjunto, os dados obtidos nos dois estudos indicam que a micorrização das plantas depende da ação de outros microrganismos do sistema solo, que atuam como um terceiro fator nesta simbiose e que a microbiota do solo responde a inoculação de um organismo exógeno, primordialmente aumentando seu metabolismo. Deve-se, portanto, considerar que a degradação biológica dos solos, com perda de sua biodiversidade, pode ter papel determinante no funcionamento de interações específicas e benéficas às plantas. / Knowledge about the associations between microbial components of soil microbiota is of great interest in the scientific community, primarily related to microorganisms that are associated beneficially with plants. In this context, there is the arbuscular mycorrhiza, which is made of the association between mycorrhizal fungi (AMF) and a range of plant species. In this close interaction between these organisms, it is necessary to describe the importance of other components of the soil system, such as the microbiota formed by fungi and bacteria from the soil, to establish this interaction. The objectives of the studied that compose this thesis focused on the evaluation of AMF (D. heterogama, R. clarus and Gi. rosea) fitness, when inoculated in modified systems on the composition of the microbial communities in the soil, with alterations promoted by the \'dilution to extinction\' methodology. In the first study, differential responses were found in root colonization capacity (% CM) of sugarcane by AMF inoculated in different systems, and the differential effect of AMFs, changing the communities of fungi and bacteria of soil. In a more detailed study, designed only to R. clarus in corn plants, it was found that higher microbial diversity of soil resulted in higher colonization of the host, especially in the initial period of plant development. In this experiment it was described the direct correlation of AMF colonization capacity with richness and phylogenetic diversity of soil microbiota. The description of the metabolic profiles of soil containing various microbial communities revealed the differential ability of these soils utilize different carbon sources, in addition to demonstrating an increase in metabolism (as evidenced by the total consumption of carbon sources) due to inoculation of the AMF. Together, the data from the two studies indicate that colonization of plants by AMF depends on the action of other microorganisms soil system, which act as a third factor in this symbiosis, and that the soil microbes respond to inoculation of an exogenous organism, primarily increasing its metabolism. One should therefore consider that the biological degradation of the soil, with loss of biodiversity, may have crucial role in the functioning of specific and beneficial interactions to plants.

O conhecimento das associações entre os microrganismos componentes da microbiota dos solos é de grande interesse no meio científico, principalmente relacionado aos microrganismos que se associam de forma benéfica com as plantas. Neste contexto, destaca-se a micorriza arbuscular, que é a associação entre os fungos micorrízicos arbusculares (FMAs) e uma amplitude de espécies vegetais. Além desta íntima interação entre estes organismos, torna-se necessário conhecer a importância dos demais componentes do sistema solo, como a microbiota formada por fungos e bactérias dos solos, para o estabelecimento desta interação. Os objetivos dos estudos componentes desta tese se concentraram na avaliação de FMAs (D. heterogama, R. clarus e Gi. rosea) inoculados em sistemas alterados quanto à composição das comunidades microbianas dos solos, promovidas pela metodologia de \'diluição para extinção\'. No primeiro estudo foram encontradas respostas diferenciais na capacidade de colonização micorrízica (%CM) de plantas de cana-de-açúcar pelos FMAs inoculados nos diferentes sistemas, além do efeito diferencial dos FMAs quanto às alterações nas comunidades de fungos e bactérias do solo. Num estudo mais detalhado, desenvolvido apenas com R. clarus em plantas de milho, foi verificado que a maiores diversidades microbianas do solo resultaram em maior colonização do hospedeiro, principalmente no período inicial de desenvolvimento das plantas. Neste experimento foi descrita a correlação direta da capacidade de colonização do FMA com a riqueza e a diversidade filogenética da microbiota dos solos. A descrição dos perfis metabólicos dos solos contendo diferentes comunidades microbianas revelou a capacidade diferencial destes solos em utilizar diferentes fontes de carbono, além de demonstrar um aumento no metabolismo (evidenciado pelo consumo total de fontes de carbono) devido à inoculação do FMA. Em conjunto, os dados obtidos nos dois estudos indicam que a micorrização das plantas depende da ação de outros microrganismos do sistema solo, que atuam como um terceiro fator nesta simbiose e que a microbiota do solo responde a inoculação de um organismo exógeno, primordialmente aumentando seu metabolismo. Deve-se, portanto, considerar que a degradação biológica dos solos, com perda de sua biodiversidade, pode ter papel determinante no funcionamento de interações específicas e benéficas às plantas. / Knowledge about the associations between microbial components of soil microbiota is of great interest in the scientific community, primarily related to microorganisms that are associated beneficially with plants. In this context, there is the arbuscular mycorrhiza, which is made of the association between mycorrhizal fungi (AMF) and a range of plant species. In this close interaction between these organisms, it is necessary to describe the importance of other components of the soil system, such as the microbiota formed by fungi and bacteria from the soil, to establish this interaction. The objectives of the studied that compose this thesis focused on the evaluation of AMF (D. heterogama, R. clarus and Gi. rosea) fitness, when inoculated in modified systems on the composition of the microbial communities in the soil, with alterations promoted by the \'dilution to extinction\' methodology. In the first study, differential responses were found in root colonization capacity (% CM) of sugarcane by AMF inoculated in different systems, and the differential effect of AMFs, changing the communities of fungi and bacteria of soil. In a more detailed study, designed only to R. clarus in corn plants, it was found that higher microbial diversity of soil resulted in higher colonization of the host, especially in the initial period of plant development. In this experiment it was described the direct correlation of AMF colonization capacity with richness and phylogenetic diversity of soil microbiota. The description of the metabolic profiles of soil containing various microbial communities revealed the differential ability of these soils utilize different carbon sources, in addition to demonstrating an increase in metabolism (as evidenced by the total consumption of carbon sources) due to inoculation of the AMF. Together, the data from the two studies indicate that colonization of plants by AMF depends on the action of other microorganisms soil system, which act as a third factor in this symbiosis, and that the soil microbes respond to inoculation of an exogenous organism, primarily increasing its metabolism. One should therefore consider that the biological degradation of the soil, with loss of biodiversity, may have crucial role in the functioning of specific and beneficial interactions to plants.

Les Technosols ont des propriétés et une pédogenèse influencées par des matériaux technogéniques qui les constituent. Le modèle expérimental de Technosol construit a été choisi et résulte de l’utilisation délibérée de matériaux technogéniques au sein d’un profil. L’objectif scientifique est d’évaluer la contribution de la faune du sol aux processus impliqués dans le fonctionnement et l’évolution des Technosols. Des expérimentations en laboratoire (cosmes) et en conditions climatiques réelles (lysimètres, parcelles) ont été menées de l’échelle ultrastructurale à celle du pédon. Les résultats indiquent que (i) le Technosol construit est un support de vie de la faune, (ii) le modèle d’ingénieur de l’écosystème : Lumbricus terrestris, par la création de macroporosité et par ses structures biogéniques contribue à sa structuration, son agrégation et à la décomposition de sa matière organique, (iii) lorsque plusieurs groupes d’organismes assurant des fonctions différentes sont associés, des effets sont mesurés majoritairement sur la décomposition de la matière organique. La forte disponibilité des ressources du Technosol autorise la présence de la faune mais masquent en partie ses effets et inhibent les interactions faunistiques qui auront un effet sur les fonctions des sols. Un modèle d’évaluation de l’effet de Lumbricus terrestris sur la macroporosité est proposé. En termes de génie pédologique, un projet de modèle d’aide à la décision résulte des acquis scientifiques. L’inoculation de la faune contribuerait ainsi à initier des mécanismes d’évolution des sols et à les accélérer / Technosols are soils whose properties and pedogenesis are influenced by technical materials which take part in their constitution. The experimental model used here is a constructed Technosol which is deliberately composed of technical materials in a soil profile. The scientific objective is to evaluate the contribution of soil fauna to processes implied in soil functioning and evolution. Experiments in laboratory (cosms) and in climatic conditions (lysimeters, field) are conducted from ultrastructural scale to soil profile scale. Results indicate that (i) constructed Technosol can support soil fauna, (ii) the model of ecosystem engineer: Lumbricus terrestris, by macroporosity and by stables biogenic structures, contribute to the structuration, the aggregation and the decomposition of organic matter of the Technosol, (iii) when several groups of organisms implied in differents soil functions are used, effects are observed on organic matter decomposition. The huge availability of resources in the Technosol allow the presence of soil fauna but its effects and reduce soil fauna interactions which can have effects on soil functioning. A model whose objective is to evaluate effect of Lumbricus terrestris on macroporosity is proposed. In terms of soil engineering, a project of decision support model results of scientific experiences. Soil fauna inoculation in soil engineering could contribute to initiate and accelerate mechanisms of Technosol evolution

Il est de plus en plus admis que pour comprendre le fonctionnement des écosystèmes, une approche aérienne associée à une approche souterraine est nécessaire en raison des rétroactions entre plantes et sol. La structure des communautés végétales peut affecter le fonctionnement du sol en altérant la quantité et la qualité des ressources intégrant le sol. Les contrôles abiotiques des processus microbiens du sol sont largement documentés, mais les potentiels effets de la composition de la communauté végétale et des traits racinaires sont peu connus. L'étude a été menée sur des prairies méditerranéennes du sud de la France. Nous avons sélectionné 12 communautés contrastées le long d'un gradient de disponibilité des ressources du sol principalement lié à la texture du sol. Les objectifs de cette thèse sont d'évaluer i) la réponse de la composition floristique et des traits foliaires et racinaires mesurés au niveau de la communauté le long gradient édaphique et à travers les saisons, et ii) leurs effets sur trois processus microbiens du sol impliqués dans les cycles du carbone (C) et de l'azote (N) : la respiration potentielle (SIR), la nitrification (NEA) et la dénitrification (DEA). Dans les sols sableux (parcelles peu productives), la communauté végétale possède une stratégie de conservation au niveau des feuilles et une stratégie d'acquisition des ressources au niveau des racines suggérant une forte plasticité des traits racinaires en réponse à la limitation des ressources ; les taux de SIR et NEA sont élevés. Un patron opposé est observé dans les sols argileux des milieux productifs. La DEA ne varie pas le long du gradient. Aucun effet de la richesse spécifique, de l'équitabilité ou de la biomasse végétale sur la SIR ou la NEA n'a été trouvé. Cependant, nous avons démontré qu'il y a une forte influence de la composition fonctionnelle des communautés végétales (abondance des graminoïdes), et surtout des traits racinaires. Nos résultats les plus novateurs montrent que la NEA et dans une moindre mesure la SIR sont positivement corrélés à la concentration en N des racines de la communauté et négativement corrélés à leur ratio C/N, tandis que les traits foliaires analogues ont seulement un effet mineur sur les activités microbiennes. Ces résultats suggèrent que la qualité chimique des racines est le principal pilote des activités du sol et que cela est maintenu à travers les saisons. D'importantes variations saisonnières de la composition floristique des communautés, de leurs traits racinaires et des activités microbiennes, excepté la DEA, ont été mises en avant. Les variations saisonnières des traits racinaires sont interprétées comme un changement relatif de la proportion de racines jeunes/vieilles et suggèrent une asynchronie entre la croissance aérienne et souterraine. Pour la première fois, nous montrons qu'en conditions naturelles, les changements saisonniers des traits fonctionnels racinaires peuvent être impliqués dans le pilotage de la NEA et de la SIR. Ce résultat démontre la nécessité d'études plus approfondies pour comprendre le rôle des traits racinaires comme pilote du fonctionnement du sol. / It is increasingly recognized that the understanding of ecosystem functioning requires a combined above- and belowground approach, because of the importance of feedbacks between plants and soil. Plant community structure may affect soil functioning by altering the quantity and the quality of resources entering the soil. Abiotic controls on soil microbial processes are well documented, but potential effects of plant composition and root traits are poorly understood. The study was conducted in Mediterranean grasslands located in southern France. We selected 12 contrasting communities along a gradient of soil resource availability, which is mainly driven by soil texture. The aims of the thesis were to evaluate: i) the response of plant composition and leaf and root traits measured at the community level along the soil gradient and across seasons, ii) their effect on three soil microbial processes involved in carbon (C) and nitrogen (N) cycling, i.e. substrate-induced respiration (SIR), nitrifying (NEA) and denitrifying enzyme activities (DEA). In sandy soils (unproductive plots) plant communities had a conservation strategy at the leaf level and an acquisitive strategy at the root level suggesting a strong plasticity of root traits in response to resource limitation; rates of SIR and NEA were higher. Opposite pattern was observed in clay productive soils. DEA did not vary along the gradient. We did not find evidence of a species richness, evenness, or plant biomass effect on SIR and NEA. However, we demonstrated that they were strongly influenced by plant functional composition (abundance of graminoids), and particularly by root traits. Our most innovative finding evidences that NEA, and to a lesser extent SIR, were positively correlated with root nitrogen (N) concentration and negatively correlated with C/Ncom, whereas analogous leaf traits have only minor effect on microbial activities. Our results suggested that the chemical quality of roots is the main driver of soil activities and this was confirmed across the seasons. We highlight strong seasonal variations in plant community composition, root traits and soil microbial activity, except DEA. Seasonal variations in root traits were interpreted as a relative change in the proportion of young versus old roots and suggested an asynchrony between above– and belowground growth. We showed for the first time evidences that in natural conditions, seasonal changes in root functional traits could be implicated in driving NEA and SIR. This result demonstrates the need to further develop studies allowing a better understanding of the role of root traits as soil functioning drivers.

L’objectif de cette thèse est d’établir et comprendre le cycle biogéochimique du bore et de ses isotopes au sein d’un écosystème forestier. Dans ce contexte, beaucoup de questions subsistent à propos du cycle biogéochimique du bore dans les écosystèmes terrestres, à savoir : • Quelles sont les sources majeures de bore dans les écosystèmes forestiers ? • Quelles sont les types de transfert entre les différents compartiments de l’environnement ? • Quels mécanismes contrôlent ces échanges ? Pour établir ce cycle, nous allons quantifier les différents stocks (végétation, sol) et flux (apports atmosphériques dissous et particulaires, pluviolessivats, ruissellements de tronc, litières, profils de sol et drainage) de bore dans le site atelier de l’OPE situé dans la forêt domaniale de Montiers-Sur-Saulx (Meuse). Il est important de noter que nous utiliserons les isotopes du bore (11B et 10B) afin de comprendre la dynamique de son cycle biogéochimique ainsi que les échelles de temps des échanges ayant lieu entre les différents compartiments environnementaux. Au final, cette thèse se divise en quatre parties distinctes : 1. Une première partie de développement analytique, visant à la mise en place, l’extraction, la purification et la mesure du bore et de ses isotopes au sein des matrices végétales. 2. Une seconde partie focalisée sur les origines et mécanismes qui contrôlent les apports atmosphériques dissous et particulaires sur le site atelier de Montiers. 3. La troisième partie vise à établir les différents transferts de bore dans le système sol plante sur deux sols distincts : un rendisol, basique ainsi qu’un alocrisol, acide. Le but de cette démarche est d’évaluer dans un premier temps l’influence des composantes du cycle biogéochimique sur les transferts de bore puis, dans un second temps, d’évaluer l’influence des propriétés d’un sol sur la dynamique du cycle biogéochimique d’un écosystème. 4. La dernière partie vise à établir un modèle d'évolution du bore et de ses isotopes dans le système sol-plante. Ce modèle est principalement basé sur les observations réalisées durant l'année 2012 / This thesis aims at establishing and understanding the biogeochemical cycle of boron and its isotopes within a forest ecosystem. In that context, many questions remain concerning the dynamics of boron within terrestrial ecosystems: • What are the major sources of boron? • What type of transfer occurs between the compartments of the environment? • What mechanisms are controlling those transfers? In order to establish this biogeochemical cycle, we quantified the different stocks (vegetation, humus and soil) and fluxes (atmospheric dust and dissolved deposition, throughfalls, stemfloxs, litterfall and drainage) of boron in the study site of Montiers. The use of boron isotopes will give us insight concerning the mechanisms controlling the dynamics of boron. This thesis is divided in 4 main parts: 1. The first part aims at establishing a new method of extraction, purification and measurement of boron and its isotopes within vegetation samples. 2. The second part focuses on the sources and mechanisms controlling boron within atmospheric dust and dissolved deposition on the study site of Montiers. 3. The third part aims at establishing the stocks and fluxes of boron on two distinct soils: a rendisoil (basic pH) and an alocrisoil (acid pH). The goal is to determine the influence of different soil properties on boron dynamics within its biogeochemical cycle. 4. The last part aims at establishing a model of boron and boron isotopes dynamics in the soil plant system. This model is mainly based of the measurement made in 2012