The use of satellite and airborne remote sensing data to predict foliar macronutrients and pigments for a boreal mixedwood forest composed of black and white spruce, balsam fir, northern white cedar, white birch, and trembling aspen was investigated. Specifically, imaging spectroscopy (IS) and light detection and ranging (LiDAR) are used to model the foliar N:P ratio, macronutrients (N, P, K, Ca, Mg) and chlorophyll. Measurement of both foliar macronutrients and foliar chlorophyll provide critical information about plant physiological and nutritional status, stress, as well as ecosystem processes such as carbon (C) exchange (photosynthesis and net primary production), decomposition and nutrient cycling. Results show that airborne and spaceborne IS data explained approximately 70% of the variance in the canopy N:P ratio with predictions errors of less than 8% in two consecutive years. LiDAR models explained more than 50% of the variance in the canopy N:P ratio with similar predictions errors. Predictive models using spaceborne Hyperion IS data were developed with adjusted R2 values of 0.73, 0.72, 0.62, 0.25, and 0.67 for N, P, K, Ca and Mg, respectively. The LiDAR model explained 80% of the variance in canopy Ca concentration with an RMSE of less than 10%, suggesting strong correlations between forest height and Ca. Two IS derivative indices emerged as good predictors of chlorophyll across time and space. When the models of these two indices with the same parameters as generated from Hyperion data were applied to other years' data for chlorophyll concentration prediction, they could explain 71, 63 and 6% and 61, 54 and 8 % of the variation in chlorophyll concentration in 2002, 2004 and 2008, respectively with prediction errors ranging from 11.7% to 14.6%. Results demonstrate that the N:P ratio, N, P, K, Mg and chlorophyll can be modeled by spaceborne IS data and Ca can only be predicted by LiDAR data in the canopy of this forest. The ability to model the N:P ratio and macronutrients using spaceborne Hyperion data demonstrates the potential for mapping them at the canopy scale across larger geographic areas and being able to integrate them in future studies of ecosystem processes. / Ph. D.

A mineração causa graves impactos ambientais, sendo o solo um dos componentes do meio físico mais vulnerável durante a exploração das jazidas. O ciclo do N tem sido bastante estudado, entretanto, pouco se sabe sobre a trajetória de recuperação da sua ciclagem em florestas restauradas após a mineração de bauxita. O objetivo foi investigar de que maneira o processo de restauração florestal em área minerada para extração de bauxita interfere na ciclagem do nitrogênio no sistema solo-planta-serapilheira. Para tanto, foram mensurados nesses compartimentos a disponibilidade de N, suas razões N:P e a abundância natural do isótopo estável de N (?15N). As hipóteses propostas foram: \"A restauração florestal, conduzida pelo uso de técnicas de engenharia ecológica, plantio de espécies arbóreas nativas e adição de topsoil é suficiente para aumentar a disponibilidade de N no ecossistema\", e \"Áreas mineradas em processo de restauração florestal, com o avanço da sucessão ecológica, podem desenvolver uma dinâmica na ciclagem de N próxima ao ecossistema de referência, apresentando valores de concentrações desse nutriente nos seus compartimentos (solo-planta-serapilheira) semelhantes a esse ecossistema\". O estudo foi conduzido no município de Poços de Caldas/MG, sendo considerados três tratamentos: floresta nativa, área restaurada há aproximadamente 06 anos e área restaurada há 24 anos, com seis repetições para cada. O delineamento utilizado foi o inteiramente casualizado, no esquema de parcelas subdivididas. O ciclo do N não foi recuperado nas florestas em restauração. Entretanto, há uma tendência de a ciclagem desse elemento assemelhar-se a da floresta nativa, conforme o avanço da sucessão ecológica. Deste modo, ambas as hipóteses propostas foram confirmadas, sendo a utilização de técnicas de engenharia ecológica, plantio adensado de espécies nativas e a adição de topsoil, os principais responsáveis pelos resultados / Mining causes serious environmental impacts and the soil is the most vulnerable component of the physical environment during the exploitation of deposits. The N cycle has been extensively studied, however, little is known about the recovery trend of its cycling in forests restored after bauxite mining. The aim was to investigate how the forest restoration process in bauxite mined area interferes in the nitrogen cycling in the soil-plant-litter system. Therefore, we measured the availability of N, the N:P ratios and the natural abundance of N stable isotope (?15N) in these compartments. The hypotheses proposed were: \"Forest restoration, driven by the use of ecological engineering techniques, planting of native tree species and addition of topsoil is sufficient to increase the availability of N in the ecosystem\", and \"Mined areas in forest restoration process, with the advancement of ecological succession, can develop a dynamics in N cycling resembling to that of the reference ecosystem, presenting values of concentrations of this nutrient in their compartments (soil-plant-litter) similar to this ecosystem. The study was conducted in Poços de Caldas county, Minas Gerais state, Brazil, considering three treatments: native forest, area restored for approximately 06 years and a restored area for 24 years with six repetitions for each. The design was completely randomized in a split plot. The N cycle has not been recovered in forest restoration. However, there is a tendency of N cycling resemble that of the native forest as the advancement of ecological succession. Thus, both hypotheses were confirmed, and the use of ecological engineering techniques, dense planting of native species and the addition of topsoil, were the main responsible for these results

A mineração causa graves impactos ambientais, sendo o solo um dos componentes do meio físico mais vulnerável durante a exploração das jazidas. O ciclo do N tem sido bastante estudado, entretanto, pouco se sabe sobre a trajetória de recuperação da sua ciclagem em florestas restauradas após a mineração de bauxita. O objetivo foi investigar de que maneira o processo de restauração florestal em área minerada para extração de bauxita interfere na ciclagem do nitrogênio no sistema solo-planta-serapilheira. Para tanto, foram mensurados nesses compartimentos a disponibilidade de N, suas razões N:P e a abundância natural do isótopo estável de N (?15N). As hipóteses propostas foram: \"A restauração florestal, conduzida pelo uso de técnicas de engenharia ecológica, plantio de espécies arbóreas nativas e adição de topsoil é suficiente para aumentar a disponibilidade de N no ecossistema\", e \"Áreas mineradas em processo de restauração florestal, com o avanço da sucessão ecológica, podem desenvolver uma dinâmica na ciclagem de N próxima ao ecossistema de referência, apresentando valores de concentrações desse nutriente nos seus compartimentos (solo-planta-serapilheira) semelhantes a esse ecossistema\". O estudo foi conduzido no município de Poços de Caldas/MG, sendo considerados três tratamentos: floresta nativa, área restaurada há aproximadamente 06 anos e área restaurada há 24 anos, com seis repetições para cada. O delineamento utilizado foi o inteiramente casualizado, no esquema de parcelas subdivididas. O ciclo do N não foi recuperado nas florestas em restauração. Entretanto, há uma tendência de a ciclagem desse elemento assemelhar-se a da floresta nativa, conforme o avanço da sucessão ecológica. Deste modo, ambas as hipóteses propostas foram confirmadas, sendo a utilização de técnicas de engenharia ecológica, plantio adensado de espécies nativas e a adição de topsoil, os principais responsáveis pelos resultados / Mining causes serious environmental impacts and the soil is the most vulnerable component of the physical environment during the exploitation of deposits. The N cycle has been extensively studied, however, little is known about the recovery trend of its cycling in forests restored after bauxite mining. The aim was to investigate how the forest restoration process in bauxite mined area interferes in the nitrogen cycling in the soil-plant-litter system. Therefore, we measured the availability of N, the N:P ratios and the natural abundance of N stable isotope (?15N) in these compartments. The hypotheses proposed were: \"Forest restoration, driven by the use of ecological engineering techniques, planting of native tree species and addition of topsoil is sufficient to increase the availability of N in the ecosystem\", and \"Mined areas in forest restoration process, with the advancement of ecological succession, can develop a dynamics in N cycling resembling to that of the reference ecosystem, presenting values of concentrations of this nutrient in their compartments (soil-plant-litter) similar to this ecosystem. The study was conducted in Poços de Caldas county, Minas Gerais state, Brazil, considering three treatments: native forest, area restored for approximately 06 years and a restored area for 24 years with six repetitions for each. The design was completely randomized in a split plot. The N cycle has not been recovered in forest restoration. However, there is a tendency of N cycling resemble that of the native forest as the advancement of ecological succession. Thus, both hypotheses were confirmed, and the use of ecological engineering techniques, dense planting of native species and the addition of topsoil, were the main responsible for these results

Les conditions de culture de microalgues autotrophes en système ouvert associant microalgues / bactéries ont été étudiées au cours de ce travail de thèse. L'objectif était de développer un procédé de valorisation des nutriments (N, P) contenus dans la phase liquide des digestats issus de méthanisation agricole. Dans un premier temps, une synthèse sur les filières de méthanisation suivi d'un état de l'art sur les microalgues et leurs conditions de culture ont permis de mettre en évidence les principaux paramètres d'influence spécifiques à l'influent étudié, tels que la coloration, et les interactions avec les processus de nitrification/dénitrification. Ainsi, dans le but de mieux comprendre les mécanismes et d'évaluer les impacts des paramètres principaux, un pilote de laboratoire composé de 6 réacteurs de 2,5 litres a été conçu et des analyses spécifiques ont été développées au laboratoire. A partir de ces outils, l'effet de la couleur et de la lumière sur la pénétration de la lumière et sur la croissance algale a été quantifié. Ensuite, l'influence du ratio N/P du milieu a été testée, ce qui a permis de mettre en exergue le stockage du phosphore par les microalgues, leur permettant de continuer leur croissance lorsque le phosphore du milieu est épuisé. Par la suite, le transfert du dioxyde de carbone et son impact sur la croissance des microalgues ont été étudiés. La productivité algale est fonction de la quantité de CO2 fournie à la culture et chute à 0 sans injection. Enfin, l'étude du temps de séjour des solides et de leur fréquence d'extraction a révélé que la nitrification-dénitrification est un mécanisme important d'élimination de l'azote dans une culture algale en continu et en système ouvert. Il peut même s'avérer prédominant par rapport à l'assimilation de l'azote par les microalgues dans certaines conditions. La proportion de chacun de ces processus peut néanmoins être contrôlée par ces paramètres. Ces expérimentations ont par ailleurs permis de mieux comprendre les interactions entre microalgues et bactéries nitrifiantes ainsi que la prédominance des genres d'algues en fonction des conditions de culture. Les microalgues sont de meilleures compétitrices sur le phosphore que les bactéries nitrifiantes. De plus, lorsque le phosphore n'est pas limitant, la nitrification est réduite en proportion de la productivité algale. En cas de limitation en phosphore et avec une faible lumière disponible, les genres d'algues qui se sont montrés dominants sont Scenedesmus sp. et Chlorella sp. Respectivement. Les essais expérimentaux ont été complétés par le développement ou l'adaptation de modèles biocinétiques capables de représenter la croissance algale et l'épuration assez fidèlement. A partir de cette modélisation, différentes configurations ont été simulées pour dimensionner un lagunage algal à haut rendement et ainsi mieux comprendre et apprécier la faisabilité d'une culture algale pour extraire les nutriments des digestats. / The culture conditions of autotrophic microalgae in open system associating microalgae/bacteria were studied in this thesis. The objective was to develop a process to valorize nutrients (N, P) contained in the liquid phase of digestate coming from agricultural methanization. First, a synthesis of anaerobic digestion process followed by a state of art on microalgae and their culture conditions allowed to highlight the main parameters specific to the studied influent, such as coloration, and the interactions with nitrification-denitrification processes. To better understand the mechanisms and study the impact of the main parameters, a laboratory-scale pilot composed of six 2.5L-reactors was designed and specific analyses were developed at the laboratory. With the help of those tools, effects of color and light on light penetration and on microalgae growth were quantified. Then, the study of the N:P ratio of the medium allowed to highlight the phosphorus storage by microalgae, allowing them to continue their growth while the phosphorus of the medium was depleted. Thereafter, the carbon dioxide transfer and its impact on microalgae growth were studied. The algal productivity is a function of the quantity of provided CO2 into the culture and fall to zero without injection. Finally, the study of solid retention time and extraction rate revealed that nitrification-denitrification is an important mechanism for nitrogen removal in a continuous algae culture in open system. This mechanism may even be predominant compared to nitrogen assimilation by microalgae under certain conditions. The proportion of each of these processes may still be controlled by these parameters. These experiments have also provided insight into the interactions between microalgae and nitrifying bacteria and the predominance of algae genera depending on culture conditions. Microalgae are better competitors on phosphorus than nitrifying bacteria. Furthermore, in non-limiting phosphorus conditions, nitrification is reduced in proportion to algal productivity. Scenedesmus and Chlorella proved to be dominant respectively when phosphorus and light are limiting. The experimental trials were completed by the development or the adaptation of biokinetic models able to represent quite accurately microalgae growth and nitrogen removal. From this model, different configurations were simulated to design high rate algal pond and assess the feasibility of the algal culture to extract nutrients from digestate.

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