No description available.

Rubisco activase operates as the chaperone responsible for maintaining the catalytic competency of Ribulose 1,5-bisphophate carboxylase oxygenase (Rubisco) in plants. Rubisco is notoriously inefficient, rapidly self-inactivating under physiological conditions. Rubisco activase uses the power released from the hydrolysis of ATP to power a conformational change in Rubisco, reactivating it. Rubisco activase has been previously shown to form a large range of species in solution; however, little has been done to relate the size of oligomeric species and physiological activity. In this thesis data is presented from a range of biophysical techniques including analytical ultracentrifugation, static light scattering, and small angle X-ray scattering combined with activity assays to show a strong relationship between oligomeric state and activity. The results suggest that small oligomers comprising 2-4 subunits are sufficient to attain full specific activity, a highly unusual property for enzymes from the AAA+ family. Studies utilising a number of Rubisco activase variants enabled the determination of how Rubisco and Rubisco activase may interact within a plant cell. A detailed characterisation of the α-, β-, and a mixture of isoforms further broadened our knowledge on the oligomerisation of Rubisco activase. Of particular importance was the discovery of a thermally stable hexameric Rubisco activase variant. It is hoped that these findings may contribute to development of more heat tolerant Rubisco activase and lead research into more drought resilient crop plants.

Abstract The ubiquity of the Calvin-Benson-Bassham cycle (CBB) amongst autotrophic organisms suggests that it provides an advantage over a wide range of environmental conditions. However, in some habitats, such as hydrothermal vents, the reductive citric acid cycle (rCAC) is an equally predominant carbon fixation pathway. It has been suggested that the CBB cycle poses a disadvantage under certain circumstances due to being more energetically demanding compared to other carbon fixation pathways. The purpose of this study was to compare the relative metabolic cost of cell biosynthesis by an autotrophic cell using either the CBB cycle or the rCAC. For both pathways, the energy, in ATP, required to synthesize the macromolecules (DNA, RNA, protein, and cell envelope) for one gram of biomass was calculated, beginning with CO2. Two sulfur-oxidizing chemolithoautotrophic proteobacteria, Thiomicrospira crunogena XCL-2, and Sulfurimonas autotrophica were used to model the CBB cycle and rCAC, respectively while Escherichia coli was used to model both pathways because it has had its cell composition extremely well-characterized. Since these organisms have had their genomes sequenced, it was possible to reconstruct the biochemical pathways necessary for intermediate and macromolecule synthesis. Prior estimates, based solely on the ATP cost of pyruvate biosynthesis, suggested that the cellular energetic expense for biosynthesis from the CBB cycle was more than that from the rCAC. The results of this study support this conclusion; however the difference in expense between the two pathways may not be as extreme as suggested by pyruvate synthesis. Other factors, such as oxygen sensitivity, may act in concert with energetic expense in contributing to the selective advantages between different autotrophic carbon fixation pathways.

Les premières formes de vie sur Terre seraient apparues durant l’Archéen, il y a 4 à 2,5 milliards d’années. Durant cette période, les océans et l’atmosphère étaient anoxiques. Vers la fin de cet éon, la concentration en dioxygène a brusquement augmenté grâce à la photosynthèse, contribuant à la Grande Oxygénation de la Terre. Toutefois, en raison de la rareté des microorganismes fossiles connus, les métabolismes actifs à cette époque restent mal compris. Le fractionnement des isotopes stables du carbone est souvent utilisé comme un critère de biogénicité et pour l’appréciation des voies métaboliques présentes. Ces fractionnements peuvent être le résultat d’au moins six à huit voies de fixation du carbone. Pour étudier l’histoire évolutive des voies de fixation du carbone et de déterminer leur ordre d’émergence, j’ai appliqué une approche phylogénomique sur l’importante diversité microbienne récemment découverte. Le but était d’identifier les voies responsables des signatures isotopiques du carbone datant de l’éon Archéen inférieur (>3,2 milliards d’années). Le premier chapitre constitue une revue récente sur la diversité, l’écologie et l’évolution des Archaea. J’ai construit une phylogénie de référence des Archaea, robuste et incluant un nombre important de nouveaux génomes. Cette phylogénie m’a permis de mettre en évidence de nouveaux clades d’Archaea pour lesquels j’ai proposé des nouveaux noms. De plus, j’ai examiné la distribution des gènes marqueurs classiquement utilisés dans la taxonomie des Archaea. Dans le chapitre 2, j’ai assemblé différents jeux de données pour construire des phylogénies de référence pour les bactéries. Ceci m’a permis de discuter la classification au sein de ce domaine et la position de quelques groupes proches de la racine. Ces phylogénies des Archaea et Bacteria m’ont servi de cadre pour retracer l’évolution des voies de fixation du carbone. J’ai ensuite étudié la voie de Wood-Ljungdahl (WL) qui est considérée comme la forme la plus ancienne de fixation du carbone mais dont les origines restent encore controversées. J’ai assemblé des banques de données locales englobant 6400 génomes et couvrant toute la diversité connue des archées et des bactéries. Ces banques ont été utilisées pour des recherches exhaustives des homologues des enzymes de la branche carbonyle (chapitre 3) et méthyle basée sur la tétrahydrométhanoptérine (H4MPT; chapitre 4) de la voie de WL. Ces analyses m’ont permis d’inférer la présence d’une forme fonctionnelle de la branche carbonyle chez LUCA (Last Universal Common Ancestor). Cette voie a ensuite été héritée verticalement chez les archées et bactéries en gardant la co-localisation de ses gènes, à l’exception de quelques rares transferts intra et inter-domaines. La branche méthyle-H4MPT semble être apparue chez les archées puis transférée aux bactéries chez lesquelles elle serait impliquée dans la syntrophie ou l’assimilation du carbone. A la suite de gains et de pertes de gènes au sein de cette branche, elle a ensuite été successivement adaptée pour la méthylotrophie anaérobie, la détoxification du formaldéhyde, et la méthylotrophie aérobie. Ces résultats indiquant l’origine de la voie de WL à l’Archéen m’ont permis d’interpréter les signatures isotopiques du carbone et d’apporter des éléments sur la composition de l’atmosphère à la fin de cet éon. Enfin, dans le chapitre 5, j’ai étudié l’histoire évolutive des autres voies de fixation du carbone (Calvin-Benson-Bassham, Reductive Hexulose Phosphate, reverse Krebs, 3-hydroxypropionate bicycle, 3-hydroxypropionate/4-hydroxybutyrate, dicarboxylate/4-hydroxybutyrate). Mes résultats préliminaires m’ont permis de discuter la présence possible de ces voies pendant l’Archéen. / Life on Earth emerged during the Archean Eon (4-2.5 billion years ago). At the time the oceans and atmosphere were anoxic, and oxygen rose at the end of the Eon as a result of oxygenic photosynthesis, in what is known as the Great Oxygenation Event. Anaerobic microorganisms and metabolisms are expected to have operated at the time. However, the specifics are poorly understood, since the fossil record is scarce. The fractionation of stable carbon isotopes is often used as a criterion of biogenicity but also to interpret possible metabolic processes. Such fractionations can arise from at least six to eight different carbon fixation pathways. I took advantage of the newly available microbial diversity, and applied a phylogenomic approach to elucidate the evolutionary history of carbon fixation pathways, and determine their relative order of emergence. The aim was to deduce which ones would have been responsible for the isotopic signatures in the lower Archean (before 3.2 billion years). In the first Chapter, I reviewed the recent literature on the diversity, ecology, and evolution of Archaea. I constructed a well-resolved reference phylogeny taking into account all the novel lineages, for which genomic information has recently become available. I assigned names to some of them, as well as to some of the taxonomic units that were recovered from the phylogeny. Then I examined the distribution of genes that have been used in the past as taxonomic markers for the Archaea. Similarly, in Chapter 2, I constructed well-resolved bacterial phylogenies using different datasets, and used them to map the distribution of potential marker genes. I then discussed the taxonomic classification of Bacteria above phylum level, and the position of some possibly deep-branching phyla. From these endeavors, I gleaned highly resolved phylogenies of Bacteria and Archaea which were then used to map the evolution of carbon fixation pathways. Next, I analyzed the evolution of the Wood-Ljungdahl pathway. It is believed to be the most ancient form of carbon fixation but its origins have been controversial. I assembled local databanks of over 6400 genomes of Bacteria and Archaea encompassing all their known diversity. These were used to perform exhaustive homology searches for the components of the carbonyl (Chapter 3) and tetrahydromethanoperin (H4MPT; Chapter 4) methyl branches. A functional form of the carbonyl branch was found to date back to the Last Universal Common Ancestor. It was then inherited mostly vertically across Bacteria and Archaea with its genes remaining co-localized, except for a few rare intra and interdomain transfers. The H4MPT branch seems to have originated in Archaea and was subsequently transferred to Bacteria where its original role was probably related with hydrogen syntrophy or as a carbon assimilation electron sink. Afterward, through gene gains and losses linking the branch with other pathways, it came to be used in anaerobic methylotrophy and formaldehyde detoxification, and finally in aerobic methylotrophy. These results highlight a presence of the Wood-Ljungdahl pathway throughout the Archean, and also allow me to discuss possible inferences on the composition of the atmosphere and the interpretation of some late Archean carbon isotopic signatures.Finally, in Chapter 5, I attempt to determine the earliest possible origin for the remaining carbon fixation pathways (Calvin-Benson-Bassham, Reductive Hexulose Phosphate, reverse Krebs, 3-hydroxypropionate bicycle, 3-hydroxypropionate/4-hydroxybutyrate, dicarboxylate/4-hydroxybutyrate), by studying the evolution of their marker genes. I managed to deduce some possible constraints about the presence of these pathways in the Archean. My results contribute to expanding our knowledge on early life, the Last Universal Common Ancestor, and the evolution of carbon fixation. They also shed light on the processes on the Archean Earth from the perspective of microbial evolution.

No description available.

No description available.

O projeto estudou a potencialidade de seqüestrar carbono em solos arenosos de Cerrado sob pastagens. O enfoque principal consistiu em deduzir quantas toneladas por hectare podem ser seqüestradas em função de um melhor manejo. Para tanto escolheram-se quatro pastagens com as mesmas características pedológicas, climáticas e topográficas, possibilitando explicar as diferenças nos estoques de carbono no solo por seus diferentes manejos e níveis de produtividade. As pastagens encontram-se na parte ocidental da bacia do rio Piracicaba (SP). Nessa região, as pastagens constituem o uso dominante da terra e são cultivadas principalmente em solos arenosos do tipo Neossolos Quartzarênicos (RQ). Após a fase de seleção, as quatro pastagens foram caracterizadas de acordo com os estoques de carbono no solo (0-50cm) e suas respectivas produtividades. A produtividade das pastagens foi determinada pelos seguintes parâmetros: (i) índice de área foliar (IAF), (ii) taxa de crescimento da biomassa vegetal, (iii) peso da biomassa vegetal e (iv) peso radicular. Investigou-se a correlação entre os estoques de carbono no solo e cada parâmetro de produtividade de cada pastagem estudada. Avaliou-se também o nível de produtividade em relação ao histórico de manejo do pasto. Os resultados indicam uma boa correlação entre a produtividade de pasto e seu estoque de carbono no solo. Especialmente o parâmetro de produtividade IAF revelou uma boa correlação com os estoques de carbono no solo (r = 0,97). O segundo objetivo do projeto era investigar a aplicabilidade de técnicas de sensoriamento remoto para mapear a potencialidade de seqüestrar carbono no solo. Para os fins da pesquisa, considerou-se que o pasto estudado que apresentou o maior estoque de carbono (e também maior produtividade) no solo possui o estoque máximo possível sob as condições climáticas, pedológicas e topográficas encontradas nas áreas de estudo. Calculou-se a diferença do estoque entre a pastagem com o maior estoque de carbono no solo e as três outras pastagens. A diferença no estoque representa a potencialidade de as pastagens estocarem mais carbono. O potencial de seqüestro de carbono total no pasto mais degradado (Descalvado) representa um aumento de 70,0% (22,41 Mg ha -1 ), de 30,8% (12,81 Mg ha -1 ) no pasto significativamente degradado (Bondade) e de 4,9% (7,7 Mg ha -1 ) no pasto moderadamente degradado (Barreiro Rico). Como as quatro pastagens só diferem no tipo de manejo no que se refere aos parâmetros determinantes da estocagem, as diferenças no estoque são diretamente ligadas ao manejo. O estoque de carbono no solo é uma informação subterrestre e portanto não pode ser investigado diretamente por bandas espectrais do espectro óptico, as quais não penetram a superfície terrestre. Portanto, como este projeto comprovou uma boa correlação entre a produtividade e os estoques de carbono no solo sob pastagens na região estudada, tentou-se mapear os estoques de carbono por meio das produtividades das pastagens. Para esse fim, estabeleceu-se uma classificação radiométrica de produtividade de pasto. Seis bandas do sensor ETM+, além do NDVI, (Normalized Difference Vegetation Index) foram processadas em todas as combinações de entrada possíveis (120) para duas classificações supervisionadas (Máxima Verossimilhança e Rede Neural Propagação Posterior). Para determinar quais são as melhores combinações de entradas de bandas para fins de discriminação da produtividade de pasto em diferentes níveis, usou-se uma matriz de erro. O melhor resultado, com a entrada das bandas B2 B5 B7 NDVI, revelou uma exatidão de 64,79% ao classificar corretamente duas classes de produtividade de pasto (alta/baixa). Essa exatidão foi considerada insuficiente. Entretanto, efetuou-se uma análise radiométrica das pastagens por espectro, que revelou uma melhor separabilidade espectral da produtividade no espectro do infravermelho médio do que no espectro visível ou infravermelho próximo. Foram realizadas também análises de regressão entre a reflectância das quatro pastagens para cada espectro e seus respectivos estoques de carbono, para investigar correlações diretas entre o comportamento espectral das pastagens e os estoques de carbono no solo. O espectro vermelho (r = 0,96 ) e infravermelho médio I (r = 0,944) possuem uma correlação significativa com o estoque de carbono no solo. Resumindo, conclui-se que existe uma boa correlação entre o manejo (produtividade) de pasto e o estoque de carbono no solo. Constatou-se que a imagem de satélite utilizada (Landsat 7) não tem uma resolução espacial/espectral suficiente para separar com uma exatidão adequada os diferentes níveis de produtividade de pasto. Entretanto, existe boa separabilidade dos diferentes níveis de produtividade no espectro infravermelho médio. A investigação da correlação direta entre o comportamento espectral das pastagens e o estoque de carbono obteve resultados significativos nos espectros de vermelho (630 – 690nm) e infravermelho médio I (1550 – 1750nm). Portanto, no âmbito do sensoriamento remoto, recomenda-se investigar se é possível mapear estoques de carbono no solo diretamente por meio da reflectância espectral das pastagens ou por meio do Índice de Área Foliar, que pode ser deduzido por meio do NDVI em imagens de satélite. / The project studied the potential for soil carbon sequestration in pastures growing on sandy soils in the Cerrado region and for the application of remote sensing techniques for estimating carbon sequestration levels. The main focus was deducing how many tons per hectare could be sequestered if better pasture management techniques were adopted. Four pastures with identical pedological, climate and topographical characteristics were chosen, so that the discrepancies in carbon stock levels in the soil could be interpreted in light of their different types of management and productivity levels. The pastures are located in the western part of the Piracicaba basin, in São Paulo State, Brazil. The dominant land use in this region is pasture on sandy soils, classified as Neossolos Quartzarênicos (RQ), according to Brazilian soil classification. After the selection phase, the four pastures were classified according to their soil carbon stocks (0-50cm layer) and their respective productivity levels. Pasture productivity was determined by the following parameters: (i) leaf area index (LAI), (ii) biomass growth rate, (iii) dry matter weight and (iv) root stocks. The correlation between soil carbon stocks and each of the productivity parameters was investigated. The productivity levels were also studied in relation to the pasture management history of each of the selected pastures. The results indicate a good correlation between the productivity level of the pastures and their carbon stocks in the soil. The LAI parameter showed a particularly good correlation with soil carbon stocks (r= 0,97). The second objective of the project was investigating the applicability of remote sensing techniques to map the potential for soil carbon sequestration. For the purposes of this study, the pasture with the highest soil carbon stocks (and higher productivity) was considered to represent the maximum stock possible under the climate, pedological and topography conditions found in the region of the study. The difference between the stock in the highest stock pasture and the three other pastures was calculated. This difference represents the potential for increasing carbon sequestration. The total soil carbon sequestration potential in the most degraded pasture (Descalvado) is equivalent to a 70,0% increase (22.41 Mg ha -1 ) from current levels. In the significantly degraded pasture (Bondade), the potential amounted to 30.08% (12.81 Mg ha -1 ) and to 4.9% (22.41Mg ha -1 ) in the moderately degraded pasture (Barreiro Rico). Since the only determinant parameter for soil carbon sequestration these pasture do not have in common is the type of management, the differences in stock levels are directly related to their type of management. Soil carbon stock levels are a subterraneous type of information, and thus cannot be examined through direct use of optical spectrum bands, which cannot go through the soil. Therefore, and taking into consideration that this study demonstrated a good correlation between productivity and soil carbon stocks in the pastures of the sample, the author attempted to map carbon stocks through pasture productivity. To this end, a radiometric classification of pasture productivity was established. Six spectral bands from the ETM+ satellite sensor and the Normalized Difference Vegetation Index (NDVI) were processed in all possible entry band combinations for two supervised classifications (Maximum Likelihood and Back Propagation). An error matrix was subsequently used to determine the best band combinations for distinguishing pasture productivity levels (two classes). The best result (B2 B5 B7 NDVI) revealed an overall accuracy of 64,79% in the classification of two classes of productivity, which is considered insufficient. Nevertheless, a spectrum radiometric analysis of the pastures was conducted, which showed better separability in the medium infrared spectrum than in the visible or near infrared spectrum. Regression analyses were performed between the reflectance of the four pastures under each spectrum and their respective soil carbon stocks levels, with the purpose of investigating whether there are any direct correlations between the spectral behavior of the pastures and the soil carbon stocks levels. The red (r=0.95) and middle infrared (r=0,944) spectra were demonstrated to have a significant correlation with soil carbon stocks. The author concludes that there is a good correlation between pasture management (productivity) and soil carbon stocks. It has also been determined that the satellite image used in this study (Landsat 7) does not have an adequate spacial and spectral resolution for accurately separating different productivity levels. However, good separability of productivity levels was shown in the middle infrared spectrum. The evaluation of a direct correlation between the spectral behavior of the pastures and their respective soil carbon stock levels obtained significant results in the red (690nm) and near infrared (1550- 1750nm) spectra. Therefore, it is recommended to investigate carbon soil stock mapping by remote sensing techniques directly through the spectral reflectance of pastures in the red and middle infrared spectra or indirectly through the LAI, which can be deduced through the NDVI in satellite images.

This thesis is composed of two problems. The first is a systems level analysis of the carbon concentrating mechanism in cyanobacteria. The second presents a theoretical analysis of femtosecond laser melting for the purpose of hyperdoping silicon with sulfur. While these systems are very distant, they are both relevant to the development of alternative energy (production of biofuels and methods for fabricating photovoltaics respectively). Both problems are approached through analysis of the underlying diffusion equations.

Submitted by Jos? Henrique Henrique (jose.neves@ufvjm.edu.br) on 2018-06-25T20:55:36Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) demerson_luiz_almeida_barbosa.pdf: 1831298 bytes, checksum: 82c8ae9507b56ac9f73a9ab0bb6fec79 (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2018-07-18T12:37:53Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) demerson_luiz_almeida_barbosa.pdf: 1831298 bytes, checksum: 82c8ae9507b56ac9f73a9ab0bb6fec79 (MD5) / Made available in DSpace on 2018-07-18T12:37:54Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) demerson_luiz_almeida_barbosa.pdf: 1831298 bytes, checksum: 82c8ae9507b56ac9f73a9ab0bb6fec79 (MD5) Previous issue date: 2017 / Funda??o de Amparo ? Pesquisa do estado de Minas Gerais (FAPEMIG) / Os sistemas integrados de produ??o s?o uma possibilidade para otimiza??o do cultivo sustent?vel no semi?rido mineiro, principalmente em rela??o ?s ?reas de pastagens degradadas. Objetivou-se com esse trabalho analisar quantitativamente e qualitativamente o crescimento, a produ??o e o estoque de carbono (C) de dois gen?tipos de eucalipto em sistema de integra??o lavoura-pecu?ria-floresta (iLPF) implantado no norte de Minas Gerais. Essa pesquisa foi realizada na Fazenda da Barra, munic?pio de Francisco S?, entre dezembro de 2012 e novembro de 2016. Foi conduzida em ?rea experimental de 3,2 ha subdividida em dois tratamentos com Eucalyptus cloeziana e o h?brido urograndis. O sistema foi consorciado com sorgo e capim-marandu, com espa?amentos em renques duplos (2 x 3m) x 14 metros. Em cada tratamento foram estabelecidas 12 parcelas de 336 m2 distribu?das aleatoriamente, com inclus?o de 24 ?rvores/parcela. Foram avaliadas taxas de sobreviv?ncia, di?metro na altura do solo, di?metro na altura do peito e altura total das ?rvores, al?m de danos e debilidades. Tamb?m foram analisados volume, biomassa, fixa??o de C e sequestro de di?xido de C (CO2). Os dados foram submetidos ? an?lise de vari?ncia e de matriz de correla??o. Os resultados indicaram que a abelha arapu? e o cupim foram os principais fatores bi?ticos causadores dos danos e debilidades nos eucaliptos cloeziana e urograndis, respectivamente. O crescimento e volume dos gen?tipos foram estatisticamente diferentes para os 450, 630, 1.020 e 1.320 dias ap?s o transplantio. O urograndis, embora tenha apresentado menor taxa de sobreviv?ncia (66,7%), obteve maior volume (23,4920 m3 ha-1) e resist?ncia ao per?odo de seca. No entanto, o E. cloeziana apresentou maior taxa de sobreviv?ncia (80,6%) e menor volume (9,2974 m3 ha-1). Os incrementos correntes anuais para biomassa foram maiores no urograndis (5.673,36 kg ha-1) em rela??o ao cloeziana (3.166,04 kg ha-1). Dessa maneira, o eucalipto urograndis foi o gen?tipo que apresentou maior fixa??o de C (5,53 t ha-1) e sequestro de CO2 (20,30 t ha-1) no sistema de integra??o lavoura-pecu?ria-floresta avaliado. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Ci?ncia Florestal, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017. / Integrated production systems are cited as a possibility for optimization of sustainable cultivation in the semi-arid region of Minas Gerais, especially in relation to degraded pasture areas. The objective of this work was to analyze quantitatively and qualitatively the growth, production and carbon stocks of two eucalyptus genotypes cultivated in an integrated crop-livestock-forest (ICLF) system in the north of Minas Gerais State, Brazil. This research was carried out at Fazenda da Barra, municipality of Francisco S?, between December 2012 and November 2016. It was conducted in a 3.2 ha experimental area subdivided into two treatments with Eucalyptus cloeziana and the urograndis hybrid. The system was intercropped with sorghum and marandu grass, with spacing in double rows (2 x 3m) x 14 m. In each treatment, 12 plots of 336 m2 were randomly distributed, including 24 trees/plot. Survival rates, diameter at soil height, diameter at breast height and total height of trees, as well as damage and weakness, were evaluated. Volumetric and biomass production, carbon (C) fixation and C dioxide sequestration (CO2) were also analyzed. Data were submitted to analysis of variance and correlation matrix. The results indicate that the ?arapu?? (Trigona spinipes) bee and the termite were the main biotic factors to the damages and weaknesses in eucalyptus cloeziana and urograndis, respectively. The growth and volumetric production of the genotypes were statistically different for the 450, 630, 1020 and 1,320 days after transplanting. Urograndis, although reaching the higher mortality rate (66.7%), had the higher volumetry production (23.4920 m3 ha-1) and resistance to the dry seasons. However, E. cloeziana had a higher survival rate (80.6%) and lower volumetric production (9.2974 m3 ha-1). The mean annual increment for biomass were higher in urograndis (5,673.36 kg ha-1) than in cloeziana (3,166.04 kg ha-1). Thus, eucalyptus urograndis was the genotype that presented higher C fixation (5.53 t ha-1) and CO2 sequestration (20.30 t ha-1) in the ICLF system evaluated.

O projeto estudou a potencialidade de seqüestrar carbono em solos arenosos de Cerrado sob pastagens. O enfoque principal consistiu em deduzir quantas toneladas por hectare podem ser seqüestradas em função de um melhor manejo. Para tanto escolheram-se quatro pastagens com as mesmas características pedológicas, climáticas e topográficas, possibilitando explicar as diferenças nos estoques de carbono no solo por seus diferentes manejos e níveis de produtividade. As pastagens encontram-se na parte ocidental da bacia do rio Piracicaba (SP). Nessa região, as pastagens constituem o uso dominante da terra e são cultivadas principalmente em solos arenosos do tipo Neossolos Quartzarênicos (RQ). Após a fase de seleção, as quatro pastagens foram caracterizadas de acordo com os estoques de carbono no solo (0-50cm) e suas respectivas produtividades. A produtividade das pastagens foi determinada pelos seguintes parâmetros: (i) índice de área foliar (IAF), (ii) taxa de crescimento da biomassa vegetal, (iii) peso da biomassa vegetal e (iv) peso radicular. Investigou-se a correlação entre os estoques de carbono no solo e cada parâmetro de produtividade de cada pastagem estudada. Avaliou-se também o nível de produtividade em relação ao histórico de manejo do pasto. Os resultados indicam uma boa correlação entre a produtividade de pasto e seu estoque de carbono no solo. Especialmente o parâmetro de produtividade IAF revelou uma boa correlação com os estoques de carbono no solo (r = 0,97). O segundo objetivo do projeto era investigar a aplicabilidade de técnicas de sensoriamento remoto para mapear a potencialidade de seqüestrar carbono no solo. Para os fins da pesquisa, considerou-se que o pasto estudado que apresentou o maior estoque de carbono (e também maior produtividade) no solo possui o estoque máximo possível sob as condições climáticas, pedológicas e topográficas encontradas nas áreas de estudo. Calculou-se a diferença do estoque entre a pastagem com o maior estoque de carbono no solo e as três outras pastagens. A diferença no estoque representa a potencialidade de as pastagens estocarem mais carbono. O potencial de seqüestro de carbono total no pasto mais degradado (Descalvado) representa um aumento de 70,0% (22,41 Mg ha -1 ), de 30,8% (12,81 Mg ha -1 ) no pasto significativamente degradado (Bondade) e de 4,9% (7,7 Mg ha -1 ) no pasto moderadamente degradado (Barreiro Rico). Como as quatro pastagens só diferem no tipo de manejo no que se refere aos parâmetros determinantes da estocagem, as diferenças no estoque são diretamente ligadas ao manejo. O estoque de carbono no solo é uma informação subterrestre e portanto não pode ser investigado diretamente por bandas espectrais do espectro óptico, as quais não penetram a superfície terrestre. Portanto, como este projeto comprovou uma boa correlação entre a produtividade e os estoques de carbono no solo sob pastagens na região estudada, tentou-se mapear os estoques de carbono por meio das produtividades das pastagens. Para esse fim, estabeleceu-se uma classificação radiométrica de produtividade de pasto. Seis bandas do sensor ETM+, além do NDVI, (Normalized Difference Vegetation Index) foram processadas em todas as combinações de entrada possíveis (120) para duas classificações supervisionadas (Máxima Verossimilhança e Rede Neural Propagação Posterior). Para determinar quais são as melhores combinações de entradas de bandas para fins de discriminação da produtividade de pasto em diferentes níveis, usou-se uma matriz de erro. O melhor resultado, com a entrada das bandas B2 B5 B7 NDVI, revelou uma exatidão de 64,79% ao classificar corretamente duas classes de produtividade de pasto (alta/baixa). Essa exatidão foi considerada insuficiente. Entretanto, efetuou-se uma análise radiométrica das pastagens por espectro, que revelou uma melhor separabilidade espectral da produtividade no espectro do infravermelho médio do que no espectro visível ou infravermelho próximo. Foram realizadas também análises de regressão entre a reflectância das quatro pastagens para cada espectro e seus respectivos estoques de carbono, para investigar correlações diretas entre o comportamento espectral das pastagens e os estoques de carbono no solo. O espectro vermelho (r = 0,96 ) e infravermelho médio I (r = 0,944) possuem uma correlação significativa com o estoque de carbono no solo. Resumindo, conclui-se que existe uma boa correlação entre o manejo (produtividade) de pasto e o estoque de carbono no solo. Constatou-se que a imagem de satélite utilizada (Landsat 7) não tem uma resolução espacial/espectral suficiente para separar com uma exatidão adequada os diferentes níveis de produtividade de pasto. Entretanto, existe boa separabilidade dos diferentes níveis de produtividade no espectro infravermelho médio. A investigação da correlação direta entre o comportamento espectral das pastagens e o estoque de carbono obteve resultados significativos nos espectros de vermelho (630 – 690nm) e infravermelho médio I (1550 – 1750nm). Portanto, no âmbito do sensoriamento remoto, recomenda-se investigar se é possível mapear estoques de carbono no solo diretamente por meio da reflectância espectral das pastagens ou por meio do Índice de Área Foliar, que pode ser deduzido por meio do NDVI em imagens de satélite. / The project studied the potential for soil carbon sequestration in pastures growing on sandy soils in the Cerrado region and for the application of remote sensing techniques for estimating carbon sequestration levels. The main focus was deducing how many tons per hectare could be sequestered if better pasture management techniques were adopted. Four pastures with identical pedological, climate and topographical characteristics were chosen, so that the discrepancies in carbon stock levels in the soil could be interpreted in light of their different types of management and productivity levels. The pastures are located in the western part of the Piracicaba basin, in São Paulo State, Brazil. The dominant land use in this region is pasture on sandy soils, classified as Neossolos Quartzarênicos (RQ), according to Brazilian soil classification. After the selection phase, the four pastures were classified according to their soil carbon stocks (0-50cm layer) and their respective productivity levels. Pasture productivity was determined by the following parameters: (i) leaf area index (LAI), (ii) biomass growth rate, (iii) dry matter weight and (iv) root stocks. The correlation between soil carbon stocks and each of the productivity parameters was investigated. The productivity levels were also studied in relation to the pasture management history of each of the selected pastures. The results indicate a good correlation between the productivity level of the pastures and their carbon stocks in the soil. The LAI parameter showed a particularly good correlation with soil carbon stocks (r= 0,97). The second objective of the project was investigating the applicability of remote sensing techniques to map the potential for soil carbon sequestration. For the purposes of this study, the pasture with the highest soil carbon stocks (and higher productivity) was considered to represent the maximum stock possible under the climate, pedological and topography conditions found in the region of the study. The difference between the stock in the highest stock pasture and the three other pastures was calculated. This difference represents the potential for increasing carbon sequestration. The total soil carbon sequestration potential in the most degraded pasture (Descalvado) is equivalent to a 70,0% increase (22.41 Mg ha -1 ) from current levels. In the significantly degraded pasture (Bondade), the potential amounted to 30.08% (12.81 Mg ha -1 ) and to 4.9% (22.41Mg ha -1 ) in the moderately degraded pasture (Barreiro Rico). Since the only determinant parameter for soil carbon sequestration these pasture do not have in common is the type of management, the differences in stock levels are directly related to their type of management. Soil carbon stock levels are a subterraneous type of information, and thus cannot be examined through direct use of optical spectrum bands, which cannot go through the soil. Therefore, and taking into consideration that this study demonstrated a good correlation between productivity and soil carbon stocks in the pastures of the sample, the author attempted to map carbon stocks through pasture productivity. To this end, a radiometric classification of pasture productivity was established. Six spectral bands from the ETM+ satellite sensor and the Normalized Difference Vegetation Index (NDVI) were processed in all possible entry band combinations for two supervised classifications (Maximum Likelihood and Back Propagation). An error matrix was subsequently used to determine the best band combinations for distinguishing pasture productivity levels (two classes). The best result (B2 B5 B7 NDVI) revealed an overall accuracy of 64,79% in the classification of two classes of productivity, which is considered insufficient. Nevertheless, a spectrum radiometric analysis of the pastures was conducted, which showed better separability in the medium infrared spectrum than in the visible or near infrared spectrum. Regression analyses were performed between the reflectance of the four pastures under each spectrum and their respective soil carbon stocks levels, with the purpose of investigating whether there are any direct correlations between the spectral behavior of the pastures and the soil carbon stocks levels. The red (r=0.95) and middle infrared (r=0,944) spectra were demonstrated to have a significant correlation with soil carbon stocks. The author concludes that there is a good correlation between pasture management (productivity) and soil carbon stocks. It has also been determined that the satellite image used in this study (Landsat 7) does not have an adequate spacial and spectral resolution for accurately separating different productivity levels. However, good separability of productivity levels was shown in the middle infrared spectrum. The evaluation of a direct correlation between the spectral behavior of the pastures and their respective soil carbon stock levels obtained significant results in the red (690nm) and near infrared (1550- 1750nm) spectra. Therefore, it is recommended to investigate carbon soil stock mapping by remote sensing techniques directly through the spectral reflectance of pastures in the red and middle infrared spectra or indirectly through the LAI, which can be deduced through the NDVI in satellite images.