Southern Louisiana is experiencing a dramatic loss of freshwater wetlands as a result of natural and man-made changes in the landscape. Multitempral remotely sensed data were used to examine the impact of the Caernarvon Freshwater Diversion Structure, built in 1991 to divert water to Breton Sound. Satellite imagery data covering the period from 1974 to 2006 were analyzed by computing several spectral indices including NDVI, VI, IR/R, Sqrt IR/R, T-NDVI, and NDWI, as well as principle component analysis. The resulting enhanced images were classified into two classes, vegetation or open water. The ratios of vegetation to open water were then calculated and the changes graphed over the 1974-2006 timeframe. The results indicated that despite the infusion of freshwater, the open water portion of the Breton Sound area continued to expand, indeed the expansion rate increased from approximately 0.25% per year before construction of Caernarvon to 0.45% per year after construction.

Wheat consumption has become more widespread and is increasing in South Africa especially in the urban areas. The wheat industry contributes four billion rands to the gross value of agriculture and is a source of employment to approximately 28 000 people. Wheat yield forecasting is crucial in planning for imports and exports depending on the expected yields and wheat health monitoring is important in minimizing crop losses. However, current crop surveying techniques used in South Africa rely on manual field surveys and aerial surveys, which are costly and not timely (after harvest). This research focuses on wheat health monitoring and wheat yield prediction using remote sensing, which is a cost effective, reliable and time saving alternative to manual surveys. Hence, the research objectives were: (i) to identify remotely sensed spectral indices that comprehensively describe wheat health status. (ii) Develop an Normalized Difference Vegetation Index (NDVI) based wheat yield forecasting model and (iii) to evaluate the impact of selected agrometeorological parameters on the NDVI based forecasting model. Landsat 8 images were used for determining spectral indices suitable for wheat health monitoring by relating the spectral indices to the land surface temperature. Results show that the Normalized Difference Water Index (R2 between 0.65 and 0.89) and NDVI (R2 between 0.36 and 0.62) were the most suitable indices for wheat health status monitoring. Whereas, the Normalized Difference Moisture Index (R2 between 0.53 and 0.79) and the Green Normalized Difference Vegetation Index (R2 between 0.28 and 0.41) were found to be less suitable for wheat health monitoring. Moderate Resolution Spectroradiometer (MODIS) derived NDVI for fourteen years was used to build and test a wheat yield forecasting model. The model was significant with an R2 value of 0.73, a p-value of 0.00161 and an RMSE of 0.41 tons ha-1. The study established that the period 30 days before harvest during the anthesis growth stage, is the best period to use the linear regression model for wheat yield forecasting. Satellite derived agrometeorological parameters such as: soil moisture, evapotranspiration and land surface temperature were added to the NDVI based model to form a multi-linear regression model. The addition of these parameters to the NDVI model improved it from an R2 of 0.73 to an R2 of 0.82. Through the use of a correlation matrix, the NDVI (r=0.88) and evapotranspiration (r=0.58) were highly correlated to wheat yield as compared to soil moisture (r=0.27) and land surface temperature (r=-0.02). This research provided evidence that remote sensing can be used at acceptable levels of accuracy for wheat monitoring and wheat yield predictions compared to manual field surveys which are costly and time consuming. / Dissertation (MSc)--University of Pretoria, 2017. / Agricultural Research Council / National Research Foundation / Spatial Business IQ / GeoTerra Images / University of Pretoria / Geography, Geoinformatics and Meteorology / MSc / Unrestricted

Este trabalho apresenta as medidas das taxas de reação nuclear ao longo da direção radial da pastilha combustível por irradiação e posterior espectrometria gama de um fino disco de UO2 com enriquecimento de 4,3% no reator IPEN/MB- 01. A partir de sua irradiação, a taxa de captura radioativa e de fissão foram medidas em função do raio do disco utilizando um detector HPGe. Colimadores de chumbo foram utilizados para esse fim. O disco de UO2 é inserido no interior de uma vareta combustível desmontável e esta é então colocada na posição central do núcleo do reator IPEN/MB-01 e irradiada durante uma hora sob um fluxo de nêutrons de aproximadamente 9 x 108 n/cm2s. Na espectrometria gama, 10 colimadores com diâmetros diferentes foram utilizados, consequentemente, as reações nucleares de captura radioativa que ocorrem nos átomos de 238U e as fissões que ocorrem em ambos 235U e 238U são mensuradas em função de 10 regiões distintas do disco combustível. Correções de eficiência geométrica devido à introdução dos colimadores no sistema de detecção HPGe foram estimados usando o código MCNP-4C. Alguns valores calculados da taxa de reação nuclear de captura radioativa e fissão obtidos pela metodologia de Monte Carlo, utilizando o código MCNP-4C, são apresentados e comparados aos dados experimentais apresentando boa concordância. Além de taxas de reação nuclear, os índices espectrais 28ρ e 25δ foram obtidos para cada raio do disco combustível. / This work presents the measurements of the nuclear reaction rates along the radial direction of the fuel pellet by irradiation and posterior gamma spectrometry of a thin slice of fuel pellet of UO2 with 4,3% enrichment. From its irradiation the rate of radioactive capture and fission have been measured as a function of the radius of the pellet disk using a HPGe detector. Lead collimators has been used for this purpose. Simulating the fuel pellet in the pin fuel of the IPEN/MB-01 reactor, a thin UO2 disk is used. This disk is inserted in the interior of a dismountable fuel rod. This fuel rod is then placed in the central position of the IPEN/MB-01 reactor core and irradiated during 1 hour under a neutron flux of around 9 x 108 n/cm2s. For gamma spectrometry 10 collimators with different diameters have been used, consequently, the nuclear reactions of radioactive capture that occurs in atoms of 238U ans fissions that occur on both 235U and 238U are measured in function of 10 different region (diameter of collimator) of the fuel pellet disk. Corrections in the geometric efficiency due to introduction of collimators on HPGe detection system were estimated using photon transport of MCNP-4C code. Some calculated values of nuclear reaction rate of radioactive capture and fission along of the radial direction of the fuel pellet obtained by Monte Carlo methodology, using the MCNP-4C code, are presented and compared to the experimental data showing very good agreement. Besides nuclear reaction rates, the spectral indices 28ρ and 25δ have been obtained at each different radius of the fuel pellet disk.

Este trabalho apresenta as medidas das taxas de reação nuclear ao longo da direção radial da pastilha combustível por irradiação e posterior espectrometria gama de um fino disco de UO2 com enriquecimento de 4,3% no reator IPEN/MB- 01. A partir de sua irradiação, a taxa de captura radioativa e de fissão foram medidas em função do raio do disco utilizando um detector HPGe. Colimadores de chumbo foram utilizados para esse fim. O disco de UO2 é inserido no interior de uma vareta combustível desmontável e esta é então colocada na posição central do núcleo do reator IPEN/MB-01 e irradiada durante uma hora sob um fluxo de nêutrons de aproximadamente 9 x 108 n/cm2s. Na espectrometria gama, 10 colimadores com diâmetros diferentes foram utilizados, consequentemente, as reações nucleares de captura radioativa que ocorrem nos átomos de 238U e as fissões que ocorrem em ambos 235U e 238U são mensuradas em função de 10 regiões distintas do disco combustível. Correções de eficiência geométrica devido à introdução dos colimadores no sistema de detecção HPGe foram estimados usando o código MCNP-4C. Alguns valores calculados da taxa de reação nuclear de captura radioativa e fissão obtidos pela metodologia de Monte Carlo, utilizando o código MCNP-4C, são apresentados e comparados aos dados experimentais apresentando boa concordância. Além de taxas de reação nuclear, os índices espectrais 28ρ e 25δ foram obtidos para cada raio do disco combustível. / This work presents the measurements of the nuclear reaction rates along the radial direction of the fuel pellet by irradiation and posterior gamma spectrometry of a thin slice of fuel pellet of UO2 with 4,3% enrichment. From its irradiation the rate of radioactive capture and fission have been measured as a function of the radius of the pellet disk using a HPGe detector. Lead collimators has been used for this purpose. Simulating the fuel pellet in the pin fuel of the IPEN/MB-01 reactor, a thin UO2 disk is used. This disk is inserted in the interior of a dismountable fuel rod. This fuel rod is then placed in the central position of the IPEN/MB-01 reactor core and irradiated during 1 hour under a neutron flux of around 9 x 108 n/cm2s. For gamma spectrometry 10 collimators with different diameters have been used, consequently, the nuclear reactions of radioactive capture that occurs in atoms of 238U ans fissions that occur on both 235U and 238U are measured in function of 10 different region (diameter of collimator) of the fuel pellet disk. Corrections in the geometric efficiency due to introduction of collimators on HPGe detection system were estimated using photon transport of MCNP-4C code. Some calculated values of nuclear reaction rate of radioactive capture and fission along of the radial direction of the fuel pellet obtained by Monte Carlo methodology, using the MCNP-4C code, are presented and compared to the experimental data showing very good agreement. Besides nuclear reaction rates, the spectral indices 28ρ and 25δ have been obtained at each different radius of the fuel pellet disk.

Dans le contexte des changements climatiques prévisibles et d'une demande évaporative accrue vis à vis des cultures, ce travail de thèse vise à évaluer la variabilité génétique du pommier pour sa réponse à la contrainte hydrique. Cette évaluation est d'un intérêt certain pour l'amélioration future de l'espèce, qu'il s'agisse de mieux tolérer le stress pouvant résulter d'une sécheresse temporaire du sol, ou d'une efficience accrue d'utilisation de l'eau. Les méthodes de phénotypage actuellement disponibles pour l'étude de la réponse à la contrainte hydrique ne permettent pas un haut débit de mesure compatible avec les comparaisons simultanées entre de nombreux individus. En conséquence, ce travail de thèse s'est focalisé sur l'application de l'imagerie multi-spectrale aéroportée comme outil de phénotypage à haut débit en condition de plein champ et sur l'évaluation de sa pertinence pour l'analyse quantitative des réponses à la contrainte hydrique et la recherche des déterminismes génétiques associés. Les essais ont été réalisés sur une population hybride de pommiers (croisement Starkrimson x Granny Smith) âgée de 4 ans au début de l'étude, implantée dans le sud de la France. A partir d'images acquises dans les longueurs d'onde du visible, du proche infrarouge et de l'infrarouge thermique, à une résolution spatiale proche de 30cm, différents indices de végétation et de stress ont été calculés permettant d'apprécier la vigueur des arbres et leur transpiration. La prise en compte, dans des modèles linéaires mixtes, de six dates d'expérimentation, couvrant deux campagnes d'acquisitions, et de régimes d'irrigation différenciés sur la population a permis de mettre en évidence l'héritabilité des indices phénotypiques et conduit à la détection de nombreux QTLs. 18 QTLs se sont révélés indépendants de la date d'acquisition. Pour quatre de ces QTLs, dits adaptatifs, c'est-à-dire exprimés en conditions de stress, un certain nombre de gènes candidats potentiellement impliqués dans les réponses précoces responsables de la régulation stomatique ont été identifiés. / In the context of foreseen climate changes and higher evaporative demand in crops, this PhD work is aiming at assessing the apple tree variability in response to hydric constraints. This could be of great interest for future breeding programs in this species, either in respect to temporary abiotic stress tolerance, or looking at a better water use efficiency. Phenotyping methods presently available for evaluating the plant response to hydric constraints do not allow the high-throughput that could be compatible with simultaneous comparison of a high number of individuals. As a consequence, this thesis focused on the application of airborne multispectral imagery as a tool for high-throughput field phenotyping, and it assessed the relevancy of this method for quantitative analysis of response to drought and further dissection of associated genetic determinisms. Trials were realized on a segregating hybrid apple population (Starkrimson x Granny Smith cross), 4-year old at the beginning of study, installed in the South of France. Images acquired in visible, near infrared and thermal infrared, with a spatial resolution close to 30cm, were the calculation basis of various vegetation and stress indices, allowing estimation of individual tree vigor and transpiration. Linear mixed models taking account of six flight dates, covering two acquisition campaigns and including two contrasted irrigation regimes over the apple population, made it possible to highlight the heritability of phenotypic indices and to perform numerous QTLs mapping. Eighteen QTLs were revealed independently from the acquisition date. Out of this QTLs set, a further analysis on 4 of them, which were adaptative i.e. expressed in stress conditions, allowed first identification of putative candidate genes potentially involved in the early stomatal closure.

Tesis por compendio / [ES] Los humedales son uno de los ecosistemas que reciben mayor atención por parte de la comunidad científica. Su importancia se puede explicar teniendo en cuenta que ayudan a mitigar los efectos de inundaciones, pueden actuar como filtros de agua y constituyen hábitats de valiosas especies de fauna y flora. En los últimos años este tipo de ambientes están cada vez más amenazados como consecuencia de la contaminación, alteraciones de los niveles de agua asociadas a los efectos del cambio climático y usos antrópicos, introducción de especies invasoras y los efectos negativos de algunos cambios de usos del suelo y determinadas prácticas asociados a ellos (agrícolas, pastoreo y urbanización). Para analizar estos ecosistemas, la teledetección se presenta como una herramienta con alto potencial que permite identificar, evaluar y monitorizar estos espacios. En esta tesis se utilizaron imágenes Sentinel-2A/B, Landsat-5 TM y Landsat-8 OLI para extraer láminas de agua libre en dos entornos: humedales mediterráneos costeros (Prat Cabanes-Torreblanca, Marjal de Sagunto, Marjal de La Safor y Marjal Pego-Oliva) y el humedal de llanura aluvial situado en el centro de España las Tablas de Daimiel. Para ello, se realizó un análisis de siete índices de agua (NDWI, mNDWI, Cedex, Re-NDWI, Awei(sh), AWEI (nsh) y B_Blue) y de umbrales para obtener la cartografía de las masas de agua libre en estos espacios. El objetivo principal es definir el índice y el umbral que permitan un uso más amplio de la metodología para su aplicación en otras zonas húmedas. También se utilizó información LiDAR (Laser Imaging Detection and Ranging) en el humedal de La Safor para analizar los efectos de la superficie inundada en diferentes usos del suelo. La evaluación de los resultados se realizó a partir de la validación con un conjunto de muestras obtenidas a partir de imágenes de elevada resolución espacial. Se calcularon la fiabilidad global y el índice kappa en los humedales analizados para distintas fechas y sensores. En el caso de los humedales costeros, el índice de agua NDWI con un umbral de ¿0,30 proporcionó los resultados con mayor precisión obteniendo un valor promedio de 0,89 en fiabilidad global. En el caso del humedal de las Tablas de Daimiel, se seleccionaron el índice MNDWI y umbral ¿0,15 para imágenes Landsat-5 (fiabilidad global 0,88), el índice MNDWI y umbral ¿0,25 para imágenes Landsat-8 (fiabilidad global 0,99) y el índice NDWI y umbral ¿0,20 (fiabilidad global 0,99) en el caso de imágenes Sentinel-2A/B. En el humedal de las Tablas de Daimiel se realizó un análisis temporal desde el año 2000 al 2021 que permitió calcular las anomalías de la superficie de agua, de la precipitación, del nivel piezométrico y del caudal hidrológico. Esta reconstrucción temporal también permitió comparar los resultados derivados a partir de las imágenes Sentinel-2A/B y de las imágenes Landsat 8. Se realizó un análisis de correlación entre los índices de anomalías calculados, que revela una correlación no significativa entre las anomalías precipitación y de superficie de agua. Mientras que el índice de anomalías de superficie de agua si presentó una correlación estadísticamente significativa con los índices de anomalía de caudal y de niveles piezométricos. En cuanto al análisis comparativo entre las imágenes Landsat-8 y Sentinel-2 se obtuvo una relación lineal entre la superficie de agua estimada por ambos sensores con un valor de R2 = 0,87. No obstante, la mayor resolución espacial de Sentinel-2 permite detectar masas de agua más pequeñas contribuyendo a un mejor análisis de los patrones de variabilidad en el área de estudio. La información derivada de esta tesis presenta una aplicabilidad de interés medioambiental para el seguimiento del estado de los humedales ayudando a adaptar planes de gestión que conduzcan a un estado de conservación adecuado. / [CA] Els aiguamolls són un dels ecosistemes que reben major atenció per part de la comunitat científica. La seua importància es pot explicar tenint en compte que ajuden a mitigar els efectes d'inundacions, poden actuar com a filtres d'aigua i constitueixen hàbitats de valuoses espècies de fauna i flora. En els últims anys aquest tipus d'ambients estan cada vegada més amenaçats a conseqüència de la contaminació, alteracions dels nivells d'aigua associades a l'efecte del canvi climàtic i usos antròpics, introducció d'espècies invasores i els efectes negatius d'alguns canvis d'usos del sòl i determinades pràctiques associades a ells (agrícoles, pasturatge i urbanització). Per a analitzar aquests ecosistemes, la teledetecció es presenta com una eina amb alt potencial que permet identificar, avaluar i monitorar aquests espais. En aquesta tesi es van utilitzar imatges Sentinel-2A/B, Landsat-5 TM i Landsat-8 OLI per a extraure làmines d'aigua lliure en dos entorns: aiguamolls mediterranis costaners (Prat Cabanes-Torreblanca, Marjal de Sagunt, Marjal de La Safor i Marjal Pego-Oliva) i l'aiguamoll de plana al·luvial situat en el centre d'Espanya les Taules de Daimiel. Per a això, es va realitzar una anàlisi de set índexs d'aigua (NDWI, mNDWI, Cedex, Re-NDWI, Awei (sh), AWEI (nsh) i B_Blue) i de llindars per a obtindre la cartografia de les masses d'aigua lliure en aquests espais. L'objectiu principal és definir l'índex i el llindar que permeten un ús més ampli de la metodologia per a la seua aplicació en altres zones humides. També es va utilitzar informació LiDAR (Laser Imaging Detection and Ranging) en l'aiguamoll de La Safor per a analitzar els efectes de la superfície inundada en diferents usos del sòl. L'avaluació dels resultats es va realitzar a partir de la validació amb un conjunt de mostres obtingudes a partir d'imatges d'elevada resolució espacial. Es van calcular la fiabilitat global i l'índex kappa en els aiguamolls analitzats per a diferents dates i sensors. En el cas dels aiguamolls costaners, l'índex d'aigua NDWI amb un llindar de ¿0,30 va proporcionar els resultats amb major precisió obtenint un valor mitjà de 0,89 en fiabilitat global. En el cas de l'aiguamoll de les Taules de Daimiel, es van seleccionar l'índex MNDWI i llindar ¿0,15 per a imatges Landsat-5 (fiabilitat global 0,88), l'índex MNDWI i llindar ¿0,25 per a imatges Landsat-8 (fiabilitat global 0,99) i l'índex NDWI i llindar ¿0,20 (fiabilitat global 0,99) en el cas d'imatges Sentinel-2A/B. En l'aiguamoll de les Taules de Daimiel es va realitzar una anàlisi temporal des de l'any 2000 al 2021 que va permetre calcular les anomalies de la superfície d'aigua, de la precipitació, del nivell piezomètric i del cabal hidrològic. Aquesta reconstrucció temporal també va permetre comparar els resultats derivats a partir de les imatges Sentinel-2A/B i de les imatges Landsat 8. Es va realitzar una anàlisi de correlació entre els índexs d'anomalies calculats, que revela una correlació no significativa entre les anomalies precipitació i de superfície d'aigua. Mentre que l'índex d'anomalies de superfície d'aigua si va presentar una correlació estadísticament significativa amb els índexs d'anomalia de cabal i de nivells piezomètrics. Quant a l'anàlisi comparativa entre les imatges Landsat-8 i Sentinel-2 es va obtindre una relació lineal entre la superfície d'aigua estimada per tots dos sensors amb un valor de R2 = 0,87. No obstant això, la major resolució espacial de Sentinel-2 permet detectar masses d'aigua de menor grandària contribuint a una millor anàlisi dels patrons de variabilitat en l'àrea d'estudi. La informació derivada d'aquesta tesi presenta una aplicabilitat d'interés mediambiental per al seguiment de l'estat dels aiguamolls ajudant a adaptar plans de gestió que condueixen a un estat de conservació adequat. / [EN] Wetlands are one of the ecosystems that receive the most attention from the scientific community. Their importance can be explained by the fact that they help mitigate the effects of flooding, can act as water filters, and provide habitats for valuable species of fauna and flora. In recent years, these types of environments are increasingly threatened as a result of pollution, alterations in water levels associated with the effects of climate change and anthropic uses, the introduction of invasive species and the negative effects of some changes in land use and certain practices associated with them (agriculture, grazing and urbanization). To analyze these ecosystems, remote sensing is presented as a tool with high potential to identify, evaluate and monitor these areas. In this thesis, Sentinel-2A/B, Landsat-5 TM and Landsat-8 OLI images were used to extract free water bodies in two environments: coastal Mediterranean wetlands (Prat Cabanes-Torreblanca, Marjal de Sagunto, Marjal de La Safor and Marjal Pego-Oliva) and the alluvial plain wetland located in the center of Spain, the Tablas de Daimiel. For this purpose, an analysis of seven water indices (NDWI, mNDWI, Cedex, Re-NDWI, Awei (sh), AWEI (nsh) and B_Blue) and thresholds were carried out to obtain the mapping of free water bodies in these areas. The main objective is to define the index and threshold that allow a wider use of the methodology for its application in other wetlands. LiDAR (Laser Imaging Detection and Ranging) information was also used in La Safor wetland to analyze the effects of the flooded surface on different land uses. The evaluation of the results was carried out based on the validation with a set of samples obtained from high spatial resolution images. The overall accuracy and the kappa index were calculated for the wetlands analyzed for different dates and sensors. In the case of the coastal wetlands, the NDWI water index with a threshold of ¿0.30 provided the most accurate results with an average value of 0.89 in global accuracy. In the case of Las Tablas de Daimiel wetland, the MNDWI index and threshold ¿0.15 were selected for Landsat-5 images (overall accuracy 0.88), the MNDWI index and threshold ¿0.25 for Landsat-8 images (overall accuracy 0.99) and the NDWI index and threshold ¿0.20 (overall accuracy 0.99) in the case of Sentinel-2A/B images. In Las Tablas de Daimiel wetland, a temporal analysis was carried out from 2000 to 2021 to calculate the anomalies of the water surface, precipitation, piezometric level and hydrological flow. This temporal reconstruction also made it possible to compare the results derived from Sentinel-2A/B images and Landsat 8 images. A correlation analysis was performed between the calculated anomaly indices, which revealed a non-significant correlation between the precipitation and water surface anomalies. However, the water surface anomaly index did show a statistically significant correlation with the flow anomaly and piezometric level indexes. As for the comparative analysis between Landsat-8 and Sentinel-2 images, a linear relationship was obtained between the water surface estimated by both sensors with a value of R2 = 0.87. However, the higher spatial resolution of Sentinel-2 allows the detection of smaller water masses contributing to a better analysis of the variability patterns in the study area. The information derived from this thesis presents an application of environmental interest for monitoring the state of wetlands helping to adapt management plans that lead to an adequate conservation status. / Pena Regueiro, J. (2023). Monitorización de cambios en la lámina libre de agua en humedales mediante teledetección [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/196109 / Compendio