Le sel joue un rôle essentiel dans la conservation des produits de charcuterie puisqu’il inhibe le développement bactérien. Or les recommandations nutritionnelles visent à réduire les teneurs en sel dans les denrées alimentaires. Les objectifs de ce projet de thèse étaient (1) de caractériser la communauté bactérienne des chipolatas et le phénomène d’altération sous l’effet d’une réduction de sel et (2) de corréler la dégradation organoleptique des produits aux modifications de la communauté bactérienne.Nous avons tout d’abord caractérisé l’altération des chipolatas par des mesures sensorielles et physico-chimiques. Les travaux démontrent que l’intensité de l’altération est plus importante quand la teneur en sel est réduite et plus particulièrement lorsque les chipolatas sont conditionnées sous atmosphère modifiée. L’altération est caractérisée par la production d’odeurs soufrées, aigres et rances, une diminution du pH des chipolatas et une augmentation de la production d’exsudat.Parallèlement, nous avons décrit la diversité bactérienne des chipolatas altérées par analyse des ARNr 16S bactériens et l’abondance des espèces bactériennes a été quantifiée par qPCR. Par ces méthodes, nous avons pu distinguer la population dominante de la population sous-dominante. La baisse de sel entraine un déséquilibre d’abondance entre ces deux populations et ce déséquilibre résulte non pas de l’augmentation des espèces dominantes mais d’une diminution d’abondance des espèces sous-dominantes.Pour comprendre le rôle respectif de ces populations bactériennes, nous avons analysé leurs activités métaboliques par approche RNAseq. Les travaux montrent une forte activité métabolique des espèces sous-dominantes. Lorsque le sel est en plus faible concentration, l’expression des gènes de Serratia spp. impliqués dans la fermentation du pyruvate pour produire de l’éthanol, du CO2 et de l’acétate est plus importante. La production d’acétate par cette espèce bactérienne peut être reliée aux défauts d’altération observés (baisse de pH, production d’exsudat, odeur aigre).Ces travaux démontrent que le sel impacte la communauté bactérienne des chipolatas (abondance et activités métaboliques) et que cette perturbation compromet la qualité organoleptique des produits. / Salt content plays a key role in meat product preservation since it inhibits bacterial growth. However, dietary guidelines aim to reduce salt content in food. The objectives of this study were (1) to characterize the bacterial community of raw pork sausages and the spoilage phenomenon of these products under salt reduction conditions and (2) to correlate the organoleptic deterioration of the products to modifications in bacterial community.We first characterized the raw pork sausages spoilage by sensory and physicochemical analysis. The work demonstrates that spoilage intensity is greater under a reduced salt content, particularly when sausages are packaged under modified atmosphere. The spoilage is characterized by the production of sulfur, sour and rancid off-odors, a decrease in pH of the sausages and an increase of exudate production.At the same time, we described the bacterial diversity of spoiled sausages through 16S rRNA analysis. Abundance of bacterial species was quantified by qPCR. With these methods, we were able to distinguish the dominant population from the subdominant population. Reducing salt content causes an abundance imbalance between these two populations. This imbalance does not result from an increase of the dominant species; it results from a decrease in abundance of subdominant species.To understand the roles of these bacterial populations, we analyzed their metabolic activities by RNA-Seq approach. The works highlight a high metabolic activity of the subdominant species. When the salt concentration is lowest, the expression of Serratia sp. genes involved in the fermentation of pyruvate to produce ethanol, CO2 and acetate is most important. The acetate production may be connected to the spoilage defaults observed (decrease in pH, exudate production and sour off-odors).These studies reveal that salt reduction impacts the bacterial community of raw pork sausages (abundance and metabolic activities) and this disruption compromises the organoleptic quality of the products.

The traditional aluminum production process (Hall-Héroult process) involves electrolyzing the alumina dissolved in the molten cryolite salt. This process is energy intensive and emits massive amounts of CO2 and other greenhouse gases. The market demand of aluminum and the environmental impact of the current aluminum production process justify research and development of alternative electrolytic processes for aluminum production that can both reduce the cost and eliminate adverse environment impacts. Solid oxide membrane (SOM) based electrolysis process is an innovative technology that has been demonstrated to successfully produce many energy-intensive metals directly from their oxides in an efficient, economical and environmentally sound way. During the SOM electrolysis process, an oxygen-ion-conducting SOM tube made of ytteria-stabilized zirconia (YSZ) separates the pre-selected molten flux with dissolved metal oxide from the inert anode assembly inside the YSZ tube. When the applied DC potential between the cathode and the anode exceeds the dissociation potential of desired metal oxide, the metal is reduced at the cathode while oxygen ions migrate through the YSZ membrane and are oxidized at the anode. Employing the inert anode allows the oxygen to be collected at the anode as a value added byproduct. In this work, a zero-direct-carbon-emission aluminum production process utilizing SOM electrolysis is presented. The molten flux used in the electrolysis process is optimized through careful measurements of its physio-chemical properties. The liquidus temperature, volatilization rate, alumina solubility, aluminum solubility, YSZ membrane degradation rate and electrical conductivity of various flux compositions were measured, and the flux chosen for SOM electrolysis was a eutectic MgF2-CaF2 system containing optimized amounts of YF3, CaO and Al2O3. Laboratory scale SOM electrolysis employing the inert anode were performed at 1100 ~ 1200oC to demonstrate the feasibility of producing and collecting aluminum while producing pure oxygen as a byproduct. The aluminum product was characterized by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). An equivalent circuit model for the electrolysis process was developed in order to identify the polarization losses in the SOM electrolysis cell. / 2016-12-21T00:00:00Z

Ce manuscrit présente la dynamique des dépôts évaporitiques du bassin de Sivas en Turquie et évalue l’impact diagénétique de ces évaporites sur les analogues de réservoirs gréseux. Cette étude s’effectue dans un bassin d’avant-pays ayant la spécificité d’avoir enregistré une intense tectonique salifère, marquée notamment par la présence de mini-bassins oligo-miocènes. Les résultats présentés s’appuient sur des relevés cartographiques de terrain, des descriptions sédimentaires ainsi que sur des analyses pétrographiques et géochimiques.Les premières évaporites du bassin se forment à l’Eocène supérieur lorsque l’avant-pays perd progressivement sa connexion avec le domaine marin, en conséquence de la propagation de la chaine de plis et de chevauchements. La fermeture océanique s’accompagne d’une diminution drastique des apports clastiques. Les faciès turbiditiques évoluent alors vers des dépôts argilo-carbonatés propres à un bassin affamé et anoxique. Les évaporites commencent par précipiter dans des bassins en piggy-back précocement isolés du reste de l’avant-pays. Par surrection tectonique, ces dépôts subissent un démantèlement gravitaire qui induit des accumulations de gypses détritiques au front de la chaîne. Avec l’augmentation des conditions de salinité de l’ensemble du bassin, des plateformes évaporitiques s’établissent ensuite sur les domaines peu profonds et nourrissent en fond de bassin des turbidites de gypse. Enfin, dans un plan d’eau devenu peu profond, l’essentiel de l’avant pays est comblé par de la halite aujourd’hui lessivée en surface. Tout au long de l’Oligo-Miocène, les évaporites éocènes induisent des déformations halocinétiques. Les sels diapiriques sont alors dissous et recyclés sous forme de dépôts gypsifères qui précipitent en domaine continental, au sein d’environnements sebkhaïques à lacustres peu profonds. Ces évaporites de seconde génération ont pu connecter différents émissaires diapiriques pour constituer ce que nous nommons « une canopée resédimentée ». Les sulfates recyclés se sont également accumulés sur des émissaires diapiriques en cours de déflation pour ainsi former de véritables mini-bassins évaporitiques secondaires encapsulés. Sur toute la bordure nord du bassin, et en continuité latérale d’une canopée salifère, les évaporites recyclées ont formé des accumulations majeures de gypse sélénitique lacustre.L’étude diagénétique des grès continentaux de mini-bassins montre une paragenèse ayant été contrôlée au premier ordre par la composition minéralogique des grains détritiques. Ainsi, dans les grès fortement polygéniques, des fluides salins et alcalins probablement dérivés du lessivage des émissaires diapiriques ont interagi avec les grains réactifs pour induire la précipitation précoce de ciments analcitiques. Ces derniers paraissent également avoir été favorisés dans les mini-bassins isolés hydrographiquement par des reliefs diapiriques. Plus localement, des phénomènes de gypsification se sont produits au niveau de dépôts faillés ou fracturés et positionnés à proximité immédiate de structures salifères. Les fluides salins impliqués circulaient par l’intermédiaire de la porosité créée par l’endommagement tectonique.L’ensemble des résultats présentés trouvent des analogies avec d’autres bassins salifères, actuels ou anciens, affectés par des déformations halocinétiques en contexte continental (e.g. le bassin Précaspien, le bassin du Zechstein ou le Great Kavir en Iran). / This manuscript focuses on the various evaporitic systems of the Sivas Basin (Turkey) and assesses the diagenetic impact of saline fluid flow on silicoclastic reservoir analogues. This study takes place in a foreland basin that has the peculiarity of having recorded halokinetic deformations, as evidenced by outcropping Oligo-Miocene mini-basins structures. The results are based on geological field mapping and sedimentary descriptions complemented by petrographic and geochemical analyses.The first evaporites of the basin precipitated during the Late Eocene when the foreland progressively lost its connection with the oceanic domain, as a result of the northward propagation of the fold-and-thrust-belt. Such event first resulted in sediment-starved conditions, with siliciclastic turbidites grading to muddy- and organic-rich facies. The evaporites then formed in early isolated piggy-back basins and were subsequently reworked in the foredeep by tectonically-induced gravitational collapses. With increasing saline conditions, evaporitic platforms developed in shallow-water domains of the foreland, and fed gypsum turbidites in the deep-water setting. Finally, after the general establishment of shallow-water hypersaline conditions, most of the available space was filled by halite deposits, nowadays entirely dissolved at the surface.During the Oligo-Miocene, Eocene evaporites induced halokinetic deformations. The diapiric salts were then recycled as gypsiferous deposits precipitated in sabkha to shallow-water lacustrine setting within salt-walled mini-basins. Such evaporitic deposits of second-generation were able to connect different diapiric structures, forming what we define as a “resedimented canopy”. The recycled evaporites also accumulated in depleting diapiric stems, resulting in the development of peculiar encased evaporitic mini-basins. Finally, along the northern border of the basin, the recycled evaporites formed massive accumulations of lacustrine selenitic gypsum southward connected to a spreading salt canopy.The diagenetic study of Oligocene continental sandstones emplaced within mini-basins highlights a paragenesis controlled at first order by the detrital composition. For instance, in the less sorted sandstones, saline-alkaline fluids, probably resulting from the leaching of diapiric salts, interacted with reactive grains to produce analcitic cements at shallow burial. These cements also seem to have been favored in mini-basins that were hydrographically isolated by diapiric reliefs. More locally, in fractured to faulted sandstones close from a diapiric structures, the porosity has been early to lately occluded by gypsum cements. The saline fluids inducing such cementation were fed by the diapiric evaporites, and reached the reservoirs through the fracture or fault-related porosity.All of these results may find relevant analogies with other ancient or present-day evaporitic basins affected by halokinetic deformation in continental setting (e.g. the Precaspian Basin, the Zechstein Basin or the Great Kavir in Iran).

Dans les cellules végétales, les canaux et les transporteurs anioniques sont essentiels pour les fonctions clés telles que la nutrition, l'homéostasie ionique et la tolérance aux stress biotiques ou abiotiques. Chez Arabidopsis thaliana, les membres de la famille CLC (pour ChLoride Channel), situés sur le tonoplaste, sont requis pour l'homéostasie du nitrate (AtCLCa et AtCLCb) ou impliqués dans la tolérance au sel (AtCLCc).Dans mon travail de thèse, j’ai identifié et caractérisé un canal chlorure, AtCLCg, chez A. thaliana. L'étude de la protéine fusion AtCLCg::GFP a révélé que cette protéine est localisée sur le tonoplaste. Deux lignés mutants indépendants d’insertion ADN-T, atclcg ont été sélectionnés. Les études physiologiques sur ces deux lignés ont démontré qu’AtCLCg joue un rôle dans le passage de chlorure mais pas dans l'homéostasie du nitrate au travers du tonoplaste. En effet, aucune différence de contenu en nitrate (NO3-) racinaire et foliaire n’a été observée entre le sauvage et les mutants dans nos conditions. Par contre, les plantes mutantes présentent un phénotype par rapport au sauvage lorsqu'elles se développent sur milieu de croissance contenant 75 mM NaCl: (i) une diminution de 20% de la masse fraîche ; (ii) une diminution de 16% de la longueur de racines primaires et une réduction de 19% du nombre de racines secondaires ; (iii) une sur-accumulation de 21% et 26% de chlorure et sulfate foliaire, respectivement. Ces phénotypes sont abolis chez les lignés complétées avec 35S::AtCLCg. De plus, les mutants atclcg présentent un phénotype similaire à la présence de 75 mM KCl, mais aucune différence n'est détectée en réponse à 140 mM mannitol. Ce résultat suggère que le phénotype d'hypersensibilité des mutants atclcg dépend du chlorure et non du l'effet osmotique du stress salin.Sachant qu’AtCLCg et AtCLCc partagent un haut degré d'homologie, environ 75% d'identité au niveau des protéines, et que les deux sont impliquées dans la réponse au stress salin de la plante, nous avons généré le double mutant atclcc/atclcg. L’analyse phénotypique a montré que le double mutant ne présente pas un phénotype additif sur milieu de stress 75 mM NaCl. En parallèle, l'analyse de l'expression des gènes a montré qu’AtCLCg est réprimé dans le fond mutant atclcc, et inversement. Par ailleurs, l'analyse de l'expression de gène rapporteur démontre que PAtCLCg::GUS est fortement exprimé dans les cellules du mésophylle alors qu’une forte expression de PAtCLCc::GUS dans les cellules de garde et le pollen est observé. Ainsi, l’ensemble de ces résultats montrent que ces deux protéines AtCLCc et AtCLCg sont impliquées dans la réponse au stress salin de la plante, mais elles n’ont pas de fonction redondante. / In plant cells, anion channels and transporters are essential for key functions such as nutrition, ion homeostasis and, resistance to biotic or abiotic stresses. In Arabidopsis thaliana, members of the ChLoride Channel (CLC) family located on the tonoplast have been shown to be required for nitrate homeostasis (AtCLCa, AtCLCb) or involved in salt tolerance (AtCLCc). In this study, we identified and characterized the chloride channel AtCLCg in A. thaliana. Use of an AtCLCg:GFP fusion revealed the localization of this protein on the tonoplast. Studies on the disruption of the AtCLCg gene by a T-DNA insertion in two independent lines demonstrated that AtCLCg is involved in response to salt stress and not in nitrate homeostasis in our conditions. Although no difference in shoot and root NO3- content is observed, mutant plants show a phenotype compared to wild-type when they are grown on 75 mM NaCl: (i) a decrease by 20% of total plant fresh weight; (ii) a diminution by 16% of primary root length and a reduction by 19% of secondary root number; (iii) an over-accumulation of chloride and sulfate in shoots by 21% and 26% respectively. These phenotypes are abolished in complemented lines with 35S::AtCLCg. atclcg mutants show a similar phenotype in the presence of 75 mM KCl, but no difference is detected in response to 140 mM mannitol. This result suggests that the hypersensitivity phenotype of atclcg mutant depends on the ionic component and not on osmotic effect of salt stress.Knowing that AtCLCg and AtCLCc share a high degree of homology, approximately 75% of identity at protein level, and both are involved in response to salt stress, we generated a clcc/clcg double mutant. Phenotypic analysis showed that the two KO mutations do not have additive effect under salt stress of 75 mM NaCl. In parallel, gene expression analysis showed that AtCLCg is repressed in the clcc mutant background, and conversely. Expression analysis of reporter gene displayed a different pattern for PAtCLCg::GUS, strongly expressed in mesophyll cells, compared with a strong expression of PAtCLCc::GUS in guard cells and pollen. Altogether these results demonstrate that both AtCLCc and AtCLCg are involved in response to salt stress but they are not functionally redundant.

Salt hydrates have the potential to be used in heat storage as both phase-change materials (PCMs) and thermochemical materials (TCMs). These materials offer advantages over traditional heat storage methods due to their high energy densities. However, both domestic and industrial applications require thousands of thermal cycles and there are often many issues that need to be overcome before these materials can be used reliably for heat storage. One of the major issues with using salt hydrates as PCMs is incongruency - the formation of anhydrous phases during melting. In this research, the mechanisms of the action of polymers to prevent incongruency in sodium acetate trihydrate have been investigated. A new polymorph of anhydrous sodium acetate, Form IV, was obtained in the presence of the polymer. This polymorph crystallises as long, blade-shaped crystals, thereby increasing the surface area to volume ratio. Indexing of the crystal faces revealed that every face had Na+ or the oxygen atoms of the acetate ion near or on the surface, as opposed to hydrophobic methyl groups found on the faces of the anhydrous salt grown without polymer. These two factors are believed to significantly increase the dissolution kinetics. This technique has the potential to be used for screening polymers to reformulate other salt hydrates that display incongruent behaviour. Eutectic compositions of NaCl and KCl with strontium hydroxide octahydrate were investigated as a potential means to prevent the incongruency of this PCM. However, degradation was observed with thermal cycling. Variable temperature PXRD studies discovered a new Sr(OH)2 hydrate when heating above 75 °C - Sr(OH)2. ⅓H2O. The recrystallisation of the octahydrate from the new phase was slow with incomplete conversion, explaining the degradation with continuous cycling. The effect of addition of NaCl and KCl to congruent barium hydroxide octahydrate was also investigated. On heating, a phase transition was observed, but the samples remained solid. Variable temperature PXRD investigations discovered that this was due to the formation of the salt hydrate, Ba(OH)Cl.2H2O. This hydrate melted at 110 °C, showing its potential as a high temperature PCM. The dehydration pathways of magnesium sulfate heptahydrate were investigated. In-situ PXRD studies showed that changing the heating rate changed the intermediates present during the dehydration. The fast dehydration rate saw both the known phases of trihydrate and 2.5 hydrate form as the dehydration product of the tetrahydrate. These both then dehydrated to the known dihydrate. This differed when the slower heating rate was used, as the trihydrate was the only product of dehydration from the tetrahydrate. The trihydrate then proceeded to dehydrate to a new phase. This was found to be a new polymorph of the dihydrate, β-MgSO4.2H2O. Dehydration of MgSO4.7H2O with 50 mol% NaCl was also performed. Loeweite, Na12Mg7(SO4)13.15H2O, a dication sulfate hydrate, was formed as the major intermediate. This mixture showed advantages over the pure MgSO4.7H2O as dehydration to the monohydrate took less time and occurred at a lower temperature. There were also three fewer intermediate phases before dehydration to the monohydrate. Suspension and encapsulation materials were used in order to overcome the major issue of agglomeration with magnesium sulfate. Liquid water was ruled out as a viable hydration medium. Apparatus was developed to test humidity cycling, which allowed the effects of dehydration time and temperature to be investigated, as well testing a range of different formulations.

Future nuclear fission reactors (GEN IV) are designed to include fast breeder reactor technologies, which can accept transuranics (elements heavier than uranium) as fuel. This has the potential of being more fuel efficient but requires the closing of the nuclear fuel cycle: full recycling of existing and newly generated nuclear waste to extract uranium and transuranic elements which can be reused as fuel. In the UK a system being investigated is electrochemical pyroprocessing which uses molten LiCl-KCl eutectic (LKE), which aims to recover uranium by electrodeposition on an inert (steel) electrode and the transuranics by electrodeposition as alloys with an active metal electrode (bismuth, cadmium or aluminium). Of the three active metal candidates, aluminium has the best separation efficiency of actinides and lanthanides, which is important as lanthanides are neutron poisons and so are not to be extracted. The development of pyroprocessing requires fundamental understandings of electrochemical alloy formation, as well as on-line monitoring tools to ensure the reprocessing occurs safely and efficiently. To that end, this thesis investigates cerium-aluminium alloying (a non-radioactive model system for plutonium-aluminium) on macro- and microelectrodes to understand the limiting factors during the alloying reaction at each electrode scale and also the circumstances under which the Ce3+ concentration can be reliably determined for on-line monitoring. On a bulk aluminium macroelectrode one cerium-aluminium alloying reaction was observed. This reaction was kinetically limited by the phase change from cerium insertion into the aluminium, and resulted in lattice expansion and progressive roughening of the electrode surface. These factors made it difficult to reliably calculate the Ce3+ concentration. Li+ from the solution was also able to reduce and form alloys with aluminium, approximately 0.3 V more negative than the first cerium-aluminium alloying peak. Since lithium atoms are smaller than cerium, and there is an abundance of Li+ in the salt, lithium-aluminium alloy was found to form preferentially to cerium-aluminium alloy at these more negative potentials. By co-depositing Al3+ and Ce3+ together on a tungsten electrode which is inert under these conditions (it does not alloy), the kinetic barrier to alloy formation by cerium insertion was decreased, which is beneficial to studying the thermodynamics of alloying. Studies of pure aluminium plating and pure cerium plating showed each individual reaction was diffusion limited, with an increased contribution of convection to the mass transport at slow scan rates. Co-deposition on macroelectrodes with a low ratio of [CeCl3]:[AlCl3] showed only one cerium-aluminium alloying peak. The co-deposition currents, and ratio of oxidation peaks charges, showed that co-deposition was occurring with both species under diffusion control, resulting in an amorphous alloy with a Ce:Al ratio that smoothly varied with the [CeCl3]:[AlCl3] ratio. This was in contrast to the alloying behaviour of cerium with liquid bismuth, in which co-deposition occurred at specific ratios determined by the crystal phases that could be formed at the applied potentials, with higher co-deposition ratios being achieved at more negative potentials. Co-deposition on macroelectrodes with a high ratio of [CeCl 3]:[AlCl3] could result in up to five cerium-aluminium alloy peaks, corresponding to all five CexAly crystalline phases predicted by the phase diagram. This phase change from amorphous to crystalline was promoted by the high Ce:Al ratio in the amorphous alloy resulting from the high [CeCl3]:[AlCl3] ratio and by plating pure cerium on the surface, which could then insert into the alloy. Charge analysis of these peaks confirmed the expected stoichiometries of the crystal phase from these in-situ measurements which is important for rapid analysis, whereas all previous literature has relied on ex-situ techniques which cooled the alloy, possibly changing its composition and structure. In all circumstances of alloy formation on macroelectrodes, the rate of reduction of Ce3+ was time dependent and sensitive to convection. This significantly complicated analysis of the electrochemical signal, making it very difficult to reliably calculate the concentration of Ce3+, which is required for on-line monitoring. Co-deposition on in-house microfabricated tungsten microelectrodes resulted in steady state currents for both pure aluminium deposition and cerium-aluminium co-deposition (up to the beginning of lithium-aluminium alloying). Thus, unlike on macroelectrodes, the deposition rate occurred at the flux ratio of each species from solution and only one oxidation peak was observed corresponding to the amorphous cerium-aluminium phase, even at high [CeCl3]:[AlCl3] ratios. The steady state alloying current meant that calculating the Ce3+ concentration was relatively simple from co-deposition on microelectrodes. Co-deposition was highly beneficial for studying alloying, however to avoid the addition of Al3+ to the molten salt, in-house microfabricated thin film aluminium microelectrodes were also used to study alloying. Alloying on microfabricated thin film aluminium microelectrodes was hampered by the formation of a native aluminium oxide layer, which prevented cerium insertion into the aluminium. The oxide layer could be disrupted by reduction of lithium, which showed steady state currents (albeit with significant capacitance) could be achieved for alloying by cerium insertion. However, the full surface area of the microelectrode could not be attained and all microelectrodes lost their aluminium layer after multiple lithiation/de-lithiation cycles. These devices need further development to overcome the oxide layer, or prevent its formation, in order to study alloying in greater detail with aluminium microelectrodes to fully realise their advantages for sensing and monitoring in pyroprocessing.

O trabalho foi conduzido na EEA-UFRGS, em Eldorado do Sul/RS no período de setembro de 2014 a maio de 2015 com o objetivo de avaliar a importância relativa da estrutura da vegetação e das variáveis abióticas (posição das cercas, da água, da porteira e do sal) sobre o pastejo de novilhas em campo nativo e avaliar se a introdução de sal em pontos estratégicos muda o uso relativo do espaço no ambiente de pastejo, por novilhas em campo nativo do bioma Pampa. Foi utilizada uma área onde é conduzido um ensaio de longa duração onde a pastagem natural é manejada sob níveis de oferta de forragem (kg de maté ria seca . kg de peso vivo-1) há 30 anos, sendo que para este experimento foram utilizadas as ofertas de 2, 3, 4 e 2-3 (2 durante a primavera e 3 no restante do ano). Novilhas de 12 meses foram monitoradas com GPS em intervalos de 2 minutos, gerando mapas de utilização da área. Foram identificadas áreas subutilizadas, onde foram inseridos blocos de sal de maneira estratégica. Foram feitas avaliações com o objetivo de caracterizar a estrutura da vegetação antes e depois da colocação do sal nos piquetes. Através de modelo linear foi analisada a influência dos fatores bióticos - altura da vegetação, biomassa do estrato inferior e entouceiramento - e abióticos - água, cercas e sal - no pastejo antes e depois da introdução do sal. Para todos os fatores (água, cerca, altura da vegetação, biomassa e entouceiramento) houve influência muito significativa (P < 0,001), em efeito simples ou quadrático, antes do uso do sal. Após a colocação do sal houve também influência muito significativa (P < 0,001) de todos fatores. O efeito da interação do tratamento (sal estratégico) com sal foi pouco significativa (P < 0,010), bem como para a interação com biomassa (P < 0,045). Os fatores bióticos não são fixos, sofrendo alteração não apenas do pastejo, mas também das condições climáticas, assim como estas interferem no comportamento animal. Nos mapas de vegetação podemos ver diminuições de entouceiramento, no entanto quando analisada a estrutura da vegetação não modificou com o uso estratégico do sal, isso pode ter ocorrido pelo curto período do experimento, que não foi suficiente para alterar a vegetação. Estudos com maior tempo de observação são necessários para avaliar o efeito da mudança de pontos atrativos na vegetação. / The study was conducted in the EEA-UFRGS, in Eldorado do Sul / RS from September 2014 to May 2015 in order to assess the relative importance of the structure of vegetation and abiotic variables (position of the fences, the water, gate and salt) on the grazing heifers in native pasture and assess whether the introduction of salt at strategic points changes the relative use of space in the grazing area for heifers in native pasture un the Pampa biome. An area where it is conducting a long-term experiment where natural pasture is managed under herbage allowance levels was used (kg dry matter. kg live weight -1) since 30 years, and for this experiment were used the treatments 2, 3, 4 and 2-3 (2 during spring and 3 the rest of the year). Heifers with 12 months were monitored with GPS using 2-minute intervals, generating maps of use of the area. Were identified underutilized areas, where salt blocks were placed strategically. Evaluations were made in order to characterize the vegetation structure before and after putting salt on the paddocks. Through linear model was analyzed the influence of biotic - vegetation height, lower stratum biomass and tussocks - and abiotic factors - water, fences and salt - in grazing before and after the introduction of salt. For all factors (water, fence, vegetation height, biomass and tussocks) was very significant influence (p <0.001), in single or quadratic effect, before use of the salt. After placing the salt was also very significant influence (p <0.001) for all factors. The effect of the interaction of treatment (strategic salt) with salt was low significant (P <0.010), as well as interaction with biomass (P <0.045). Biotic factors are not fixes, suffering not only change the grazing, but also the weather, as these interfere in animal behavior. In vegetation maps can see tussocks decreases, however when analyzing the vegetation structure did not change with the strategic use of salt, this may be due to the short period of the experiment, which was not enough to change the vegetation. Studies with more observation time is needed to evaluate the effect of changing attractive points in the vegetation.

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Submitted by Mario BC (mario@bc.ufrpe.br) on 2017-02-15T13:51:50Z No. of bitstreams: 1 Maria Isabel Leite da Silva.pdf: 1411757 bytes, checksum: d3a9e59e473802e999997d511c7d2197 (MD5) / Made available in DSpace on 2017-02-15T13:51:50Z (GMT). No. of bitstreams: 1 Maria Isabel Leite da Silva.pdf: 1411757 bytes, checksum: d3a9e59e473802e999997d511c7d2197 (MD5) Previous issue date: 2015-11-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Salt stress is a present threat to agricultural production, especially where irrigation makes it necessary for forage crops for animal feed. To minimize this problem, an alternative that has been identified as promising is the use of silicon (Si) via fertilizer, due to the addition of this mineral increase tolerance to salinity of poaceae. Thus, the objective was to evaluate the effect of silicon fertilization on the growth and chemical- bromatological composition of Brachiaria brizantha cv. MG5 in salt stress conditions, using four concentrations of sodium chloride (0, 20, 40 and 60 mmol L-1, equivalent to the electrical conductivity 0, 3.9, 7.5 and 10.9 dS m-1, respectively), and silicon concentrations (0, 1, 2, 3 and 4 mmol L-1) in the nutrient solution, and three cutting times. The experiment was completely randomized in a factorial 4 x 5 x 3 with four replications, where the experimental plot was represented by a pot containing a plant. In the biggest changes in chemical-bromatological composition were due to the sodium chloride concentration in the solution three cuts made. In the three studied cuts the high concentrations of sodium chloride accelerated senescence, reduced growth and nutritive value of Brachiaria brizantha cv. MG5. The concentration of 4 mmol L-1 Si minimized the deleterious effects of sodium chloride in the regrowth of Brachiaria brizantha cv. MG5 in the last two cuts, improving growth. However, the applications of silicon levels were not sufficient to mitigate the deleterious effects of sodium chloride in nutritional value and dry matter production of Brachiaria brizantha cv. MG5 in the three cuts. / O estresse salino é uma ameaça presente na produção agrícola, especialmente onde a irrigação se faz necessária para o cultivo de forragem para a alimentação animal. Para minimizar tal problema, uma alternativa que vem sendo apontada como promissora é o uso do silício (Si) via adubação, em virtude da adição deste mineral aumentar a tolerância das poáceas à salinidade. Dessa forma, objetivou-se avaliar o efeito da adubação silicatada sobre o crescimento e a composição químico-bromatológica da Brachiaria brizantha cv. MG5 em condições de estresse salino, utilizando-se quatro concentrações de cloreto de sódio (0; 20; 40 e 60 mmol L-1, equivalentes às condutividades elétricas 0; 3,9; 7,5 e 10,9 dS m-1, respectivamente) e cinco concentrações de Si (0; 1; 2; 3 e 4 mmol L-1) na solução nutritiva, e três épocas de corte. O experimento foi em delineamento inteiramente casualizado em esquema fatorial 4 x 5 x 3, com quatro repetições, onde a parcela experimental foi representada por um vaso contendo uma planta. Nos três cortes realizados as maiores alterações da composição química-bromatológica ocorreram em função das concentrações do cloreto de sódio na solução. As concentrações altas de cloreto de sódio aceleraram a senescência, reduziram o crescimento e o valor nutritivo da Brachiaria brizantha cv. MG5. A concentração de 4 mmol L-1 de Si minimizou os efeitos deletérios do cloreto de sódio na rebrota da Brachiaria brizantha cv. MG5 nos dois últimos cortes, melhorando o crescimento. No entanto, as aplicações dos níveis de silício não foram suficientes para atenuar os efeitos deletérios do cloreto de sódio no valor nutritivo e na produção de massa seca da Brachiaria brizantha cv. MG5 nos três cortes estudados.