The objective of this dissertation is to extend the use of spatial predictive modelling for use by biosecurity agencies to help prevent the introductions of new and emerging invasive plants (i.e., pests). A critical review of international and national policy instruments found that they did not effectively articulate how spatial predictive modelling could be incorporated into the biosecurity toolbox. To determine how spatial predictive modelling could be extended I modelled the potential distribution of Tamarix and Lythrum salicaria in Prairie Canada using a genetic algorithm. New seasonal growth data was used to interpolate a growing degree-day’s risk surface for L. salicaria. Models were developed using suites of predictive variables as well as different data partitioning methods and evaluated using different performance measures. Expert evaluation was found to important in final model selection. The results indicated that both invasive plants have yet to reach their potential distribution in Prairie Canada. The spatial models can be used to direct risk-based surveillance efforts and to support biosecurity policy decisions. The results of this dissertation conclude that spatial predictive modelling is an informative tool that needs to be incorporated into the biosecurity toolbox. A phytosanitary standard is proposed to guide toolbox development.

The objective of this dissertation is to extend the use of spatial predictive modelling for use by biosecurity agencies to help prevent the introductions of new and emerging invasive plants (i.e., pests). A critical review of international and national policy instruments found that they did not effectively articulate how spatial predictive modelling could be incorporated into the biosecurity toolbox. To determine how spatial predictive modelling could be extended I modelled the potential distribution of Tamarix and Lythrum salicaria in Prairie Canada using a genetic algorithm. New seasonal growth data was used to interpolate a growing degree-day’s risk surface for L. salicaria. Models were developed using suites of predictive variables as well as different data partitioning methods and evaluated using different performance measures. Expert evaluation was found to important in final model selection. The results indicated that both invasive plants have yet to reach their potential distribution in Prairie Canada. The spatial models can be used to direct risk-based surveillance efforts and to support biosecurity policy decisions. The results of this dissertation conclude that spatial predictive modelling is an informative tool that needs to be incorporated into the biosecurity toolbox. A phytosanitary standard is proposed to guide toolbox development.

This study was conducted to investigate the requirements for the spatial modelling of current and future water demand in the Berg River Water Management Area in the Western Cape of South Africa in order to produce a prototype model from which annual water requirements could be computed and spatially visualised. To accomplish this the spatial distribution of water demand within the study area was first investigated. The data required to perform spatial water demand modelling of diverse land uses and socio-economic activities were evaluated. Finally, the question of improving spatial water demand modelling at the catchment scale was considered from both a systems design and a technical perspective. The resulting model consists of two main modules; one performing a rudimentary monthly soil water balance to obtain monthly and annual irrigation requirements, and another applying preconfigured determinant layers derived from land use to town zone layers in order to determine annual urban water use intensities per areal unit. The resulting model prototype follows a sequential workflow based on a series of components that combine to produce a spatial overview of water use intensity within the study area. Water demand was found to be predominantly irrigated agriculture in the upper reaches of the Berg (mainly wine grape) and was found to be dominated by intensive industrial users in the central and lower reaches. The model was designed so that new data could be introduced in order to expand the system where required, as well as allowing for updated datasets to be incorporated as they become available. Due to the uncertainties inherent in the modelling and approximation of real world phenomena, the importance of establishing a set of structured, stable, predefined user requirements and system specifications were noted as a fundamental requirement for improving model development and design efficiency and ensuring model validity. It was further found that incorporating additional datasets, covering parameters related to the system, may serve to improve model accuracy, but could easily lead to compounded errors if not correctly parameterised or adequately validated.

No description available.

As the largest carbon reservoir in ecosystems, soil accounts for more than twice as much carbon storage as that of vegetation biomass or the atmosphere. The goal of this study is to examine spatial patterns of soil organic carbon (SOC) in Canadian forest area at an eco-region scale and to explore its relationship with different ecological variables. In this study, the first Canadian forest soil database published in 1997 by the Canada Forest Service was analyzed along with other long-term eco-climatic data (1961 to 1991) including precipitation, air temperature, Normalized Difference Vegetation Index (NDVI), slope, aspect, and elevation. Additionally, an eco-region framework established by the Environment Canada was adopted in this study for SOC distribution assessment. Exploratory spatial data analysis techniques, with an emphasis on spatial autocorrelation analysis, were employed to explore how forest SOC was spatially distributed in Canada. Correlation analysis and spatial regression analysis were applied to determine the most dominant ecological factors influencing SOC distribution in different eco-regions. At the national scale, a spatial error model was built up to adjust for spatial effects and to estimate SOC patterns based on ecological and ecosystem property factors. Using the significant variables derived in the spatial error model, a predictive SOC map in Canadian forest area was generated. Findings from this study suggest that high SOC clusters tend to occur in coastal areas, while low SOC clusters occur in western boreal eco-region. In Canadian forest area, SOC patterns are strongly related to precipitation regimes. Although overall SOC distribution is influenced by both climatic and topographic variables, distribution patterns are shown to differ significantly among eco-regions, thus verifying the eco-region classification framework for SOC zonation mapping in Canada.

In Tanzania, approximately 76% of the drinking water supplies is dependent on groundwater sources. However, the groundwater in north Tanzania is susceptible to contamination by arsenic and fluoride. This study examines the spatial analysis of arsenic and fluoride mobilization in groundwater around Mount Meru, located in northern Tanzania. The study area covers approximately 1,450 Km2 around Mount Meru in Arusha region, Tanzania. The statistical analysis was performed in IBM SPSS Statistics version 28.0.0.0 to interpret data and unveil the correlation and trends between chemical elements in 11 springs and in 17 wells.  The geochemical modelling software, Visual MINTEQ ver.3.1. have been used to simulate chemical elements in springs and wells in the study area to predict the chemical species, saturation indices, and adsorption efficiency of arsenic to goethite and of fluoride to gibbsite. Moreover, the spatial analysis was done using ArcGIS Desktop 10.8.2 and Geoda 1.20.0.22 software to identify the hotspots areas and to connect spatial patterns of arsenic and fluoride distribution within the study area. The statistical analysis revealed a positive correlation between arsenic and pH in springs. The Na-Cl-HCO3 water type was found in springs, with increased F- concentration in groundwater. The results of geochemical modelling confirmed that more undersaturated values for F- minerals were observed in springs than in wells, which were likely influenced by the fluoride adsorption to gibbsite surface. It was observed that initial concentration and increase of adsorbent dose promoted adsorption efficiency of arsenic and fluoride on goethite and gibbsite, respectively, between pH 4 and pH 6. However, the increase in pH value hinders adsorption efficiency. Moreover, the highest adsorption efficiency was observed at adsorbent dose of 0.05 g/L of goethite for arsenic adsorption, and at adsorbent dose 6.6 g/L and 10 g/L of gibbsite for fluoride adsorption. The spatial analysis results showed that the concentration of fluoride was high in the northeast and eastern part of the study area, where the low elevation area is composed of Tertiary and Quaternary volcanic rocks and debris avalanche deposits. In contrast, the southwestern part of the study area had comparatively low fluoride concentrations, which could be attributed to the less permeable nature of the Tertiary and Quaternary unconsolidated soil. The geological map revealed that the study area is composed of pyroclastic rocks and basic igneous rocks, which predict the presence of fluoride rich minerals such as apatite and fluorapatite. The spatial distribution of arsenic and fluoride in springs and wells revealed that the hotspots groundwater sources such as S5, S6, S7and W3, W4, W5, W6 were in low elevated areas that accumulated from the mobilization of dissolved arsenic and fluoride species from high recharge altitude, groundwater interaction with arsenic and fluoride bearing minerals and agricultural areas. The findings of this study can be useful to the future researchers and local authorities to know about high risky sources of groundwater for better managing and mitigating the risks associated with arsenic and fluoride contamination in Mount Meru groundwater aquifers. / I Tanzania är cirka 76 % av dricksvatten försörjning beroende av grundvattenkällor. Grundvattnet i norra Tanzania är dock känsligt för kontaminering av arsenik och fluor. Denna studie undersöker den rumsliga analysen av arsenik- och fluoridmobilisering i grundvatten runt Mount Meru, beläget i norra Tanzania. Studieområdet omfattar cirka 1 450 km2 runt Mount Meru i Arusha-regionen, Tanzania. Den statistiska analysen utfördes i IBM SPSS Statistics version 28.0.0.0 för att tolka data och avslöja korrelationen och trenderna mellan kemiska grundämnen i 11 källor och i 17 brunnar. Programvaran för geokemisk modellering, Visual MINTEQ ver.3.1. har använts för att simulera kemiska element i källor och brunnar i studieområdet för att förutsäga de kemiska arterna, mättnadsindexen och adsorptionseffektiviteten för arsenik till goetit och av fluorid till gibbsit. Dessutom gjordes den rumsliga analysen med hjälp av mjukvaran ArcGIS Desktop 10.8.2 och Geoda 1.20.0.22 för att identifiera hotspot-områdena och för att koppla samman rumsliga mönster av arsenik- och fluoriddistribution inom studieområdet. Den statistiska analysen visade en positiv korrelation mellan arsenik och pH i fjädrar. Vattentypen Na-Cl-HCO3 hittades i källor, med ökad F- koncentration i grundvattnet. Resultaten av geokemiska modelleringar bekräftade att fler undermättade värden för F-mineraler observerades i källor än i brunnar, vilka troligen påverkades av fluoridadsorptionen till gibbsitytan. Det observerades att initial koncentration och ökning av adsorbentdos främjade adsorptionseffektiviteten av arsenik och fluorid på goetit respektive gibbsit mellan pH 4 och pH 6. Ökningen i pH-värde hindrar emellertid adsorptionseffektiviteten. Dessutom observerades den högsta adsorptionseffektiviteten vid adsorbentdosen på 0,05 g/L goetit för arsenikadsorption och vid adsorbentdosen 6,6 g/L och 10 g/L gibbsit för fluoridadsorption. De rumsliga analysresultaten visade att koncentrationen av fluorid var hög i den nordöstra och östra delen av studieområdet, där låghöjdsområdet är sammansatt av tertiära och kvartära vulkaniska bergarter och avfall av lavinavlagringar. Däremot hade den sydvästra delen av studieområdet jämförelsevis låga fluoridkoncentrationer, vilket kan tillskrivas den mindre permeabla naturen hos den tertiära och kvartära okonsoliderade marken. Den geologiska kartan avslöjade att studieområdet består av pyroklastiska bergarter och grundläggande magmatiska bergarter, som förutsäger närvaron av fluorrika mineraler som apatit och fluorapatit. Den rumsliga fördelningen av arsenik och fluor i källor och brunnar avslöjade att hotspots grundvattenkällor som S5, S6, S7 och W3, W4, W5, W6 låg i lågt upphöjda områden som ackumulerades från mobiliseringen av löst arsenik och fluorarter från hög uppladdning höjd över havet, grundvatteninteraktion med arsenik- och fluorhaltiga mineraler och jordbruksområden. Resultaten av denna studie kan vara användbara för framtida forskare och lokala myndigheter att veta om högriskfyllda grundvattenkällor för att bättre hantera och mildra riskerna förknippade med arsenik och fluoridkontamination i Mount Meru grundvattenakviferer.

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2016-02-29T12:41:37Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) PDF - Gustavo Correia de Moura.pdf: 4048269 bytes, checksum: 93440f590dbf6da5c94a68be759a0082 (MD5) / Approved for entry into archive by Secta BC (secta.csu.bc@uepb.edu.br) on 2016-03-10T15:14:56Z (GMT) No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) PDF - Gustavo Correia de Moura.pdf: 4048269 bytes, checksum: 93440f590dbf6da5c94a68be759a0082 (MD5) / Made available in DSpace on 2016-03-10T15:14:56Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) PDF - Gustavo Correia de Moura.pdf: 4048269 bytes, checksum: 93440f590dbf6da5c94a68be759a0082 (MD5) Previous issue date: 2015-08-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This study aimed to analyze the drivers factors of biomass, functional diversity and fatty acids of the zooplankton community in two tropical estuaries with different trophic states (Mamanguape and Paraíba do Norte), located in Northeastern Brazil. The study was divided into two manuscripts which were sampled in dry and rainy season, as follows: Nov/2013 to Jul/2014, for the first manuscript and Dec/2014 and Jul/2014 to the second manuscript, respectively. Four sample zones were selected along each estuary and in each one were selected three sites where at each site three biotic samples (zooplankton community) and abiotic (environmental variables) were sampled. The fatty acid profiles were obtained from gas chromatography techniques from selected copepod species. In the first study, we tested whether the estuarine connectivity, the phylogenetic relationships and the local environmental conditions are the main drivers of the pattern of distribution of biomass and functional diversity of the zooplankton community. It was observed that these three components are sufficient to explain the variation in Mamanguape estuary that is located in a conservation area, and different than is commonly expected, the connectivity can provide greater explicability for the community distribution, when compared to the environmental conditions. However, the three components used were not sufficient to explain the variation in Paraíba do Norte estuary which is influenced by anthropogenic impacts. The study shows the importance of spatial variable to assess the drivers factors of biomass and functional diversity of the zooplankton community, as this part of the analysis the effects of dispersal ability of species and the physical forces acting on the system. Moreover, a thorough investigation is needed to clarify the factors that determine and shape the zooplankton communities in high impacted tropical systems. In the second study, we tested whether the profiles of fatty acids can reveal spatial and temporal changes in diet of copepods, and therefore can be used as indicators of the trophic status of estuaries. It was observed that the fatty acid composition of zooplanktonic organisms revealed seasonal and temporal variations in trophic ecology of copepods in both tropical estuaries. In addition, the profiles of fatty acids were able to reveal differences in the quality of potential food sources in the two estuaries with different levels of anthropogenic impact, with a lower quality of food sources in the most impacted system (Paraíba do Norte estuary). In this study the profiles of fatty acids were sensitive to natural and anthropogenic stresses, being a fast tool to assess the trophic status of tropical estuaries. / O presente estudo teve por objetivo analisar os fatores direcionadores da biomassa, diversidade funcional e ácidos graxos da comunidade zooplanctônica em dois estuários tropicais com diferentes estados tróficos (Mamanguape e Paraíba do Norte), localizados no Nordeste do Brasil. O estudo foi dividido em dois manuscritos os quais tiveram amostragens realizadas no período de seca e cheia, sendo: nov/2013 e jul/2014, para o primeiro manuscrito e dez/2014 e jul/2014 para o segundo manuscrito, respectivamente. Foram selecionados quatro zonas amostrais ao longo de cada estuário e em cada uma foram selecionados três pontos onde em cada ponto três amostras bióticas (comunidade zooplanctônica) e abióticas (variáveis ambientais) foram coletadas. Os perfis de ácidos graxos foram obtidos à partir de técnicas de cromatografia gasosa das espécies de copépodes selecionados. No primeiro estudo, foi testado se a conectividade estuarina, as relações filogenéticas e as condições ambientais locais são os principais direcionadores do padrão de distribuição da biomassa e diversidade funcional da comunidade zooplanctônica. Observou-se que esses três componentes são suficientes para explicar a variação no estuário Mamanguape que se localiza em uma área de conservação, e que diferente do que é comumente esperado, a conectividade pode apresentar uma explicabilidade maior na distribuição da comunidade, quando comparada às condições ambientais. No entanto, os três componentes utilizados não foram suficientes para explicar a variação no estuário Paraíba do Norte o qual sofre a influência de impactos antrópicos. O estudo mostra a importância da variável espacial para avaliar os fatores direcionadores da biomassa e diversidade funcional da comunidade zooplanctônica, visto que esta integra à análise os efeitos da capacidade de dispersão das espécies e das forças físicas que atuam no sistema. Além disso, uma investigação aprofundada é necessária para esclarecer os fatores que determinam e moldam as comunidades zooplanctônicas em sistemas tropicais muito impactados. No segundo estudo, foi testado se os perfis de ácidos graxos podem revelar mudanças espaciais e temporais na dieta de copépodos, e por conseguinte, possam ser usados como indicadores do estado trófico dos sistemas estuarinos. Foi possível observar que a composição de ácidos gráxos dos organismo zooplanctônicos revelaram variações sazonais e temporal na ecologia trófica dos copépodos nos dois estuários tropicais. Além disso, os perfis de ácidos gráxos foram capazes de revelar diferenças na qualidade das potenciais fontes de alimento nos dois estuários com diferentes níveis de impacto antrópico, com uma menor qualidade de fontes alimentares presente no sistema mais impactado (estuário do Paraíba do Norte). Nesse estudo os perfis de ácidos gráxos foram sensíveis à estresses naturais e antrópicos, mostrando ser uma ferramenta rápida para avaliar o estado trófico de estuários tropicais.

Afin de quantifier les risques d’invasion chez le goujon Asiatique Pseudorasbora parva, un petit cyprinidae d’eau douce, j’ai tout d’abord testé une approche corrélative de modélisation de la niche climatique dans laquelle j’ai intégré un proxy relatif à la probabilité d’introduction. Cette approche s’appuie sur des assomptions relatives à l’adaptation des organismes aux conditions environnementales locales ou régionales. J’ai ensuite comparé la niche climatique mesurée de deux lignées génétiques majeures à la fois dans les aires natives et envahies. Puis dans un second temps, par une approche expérimentale j’ai comparé la réponse aux variations de température, des traits d’histoire de vie de populations vivant dans des zones climatiques contrastées. Finalement, je me suis intéressé à la dispersion des goujons Asiatiques afin de mieux comprendre si les populations situées sur les fronts d’invasions avaient des capacités de colonisation plus importante. J’ai donc quantifié et comparé le long d’un gradient d’invasion, le potentiel de dispersion des individus ainsi que des traits pouvant y être liés (activité et morphologie). L’étude des risques d’invasions a montré que de nombreuses zones – au delà des zones déjà envahies - étaient climatiquement favorables au goujon Asiatique. C’était le cas en particulier pour certaines zones comme l’Australie, l’Amérique du Sud et du Nord, indiquant que l’invasion de cette espèce pourrait encore s’étendre. Après avoir pris en compte les probabilités d’introduction, cette étude a montré que l’Amérique du Nord était la zone la plus à risques. Par contre, la niche climatique entre les différentes lignées dans les zones géographiques envahies est très similaire, ce qui laisse à penser qu’il n’y a pas de patrons d’adaptation locale chez cette espèce. Pour autant, la niche climatique observée dans la zone envahie est très différente de celle observée dans la zone native, ce qui suggère un shift climatique important au cours de l’invasion. Les réponses thermiques des traits d’histoire de vie du goujon Asiatique testés expérimentalement n’ont pas varié significativement entre les populations originaires de conditions climatiques continentales et maritime-tempérées. Par exemple, l’effort reproductif global des femelles n’a pas varié entre les températures testées (15-25°C) mais la stratégie temporelle de reproduction a beaucoup varié. L’effort reproductif était plus cours et plus intense à forte température, alors qu’il était plus étalé et avec des pics reproductifs moins forts à faible température. Pour ailleurs, il semble qu’il existe un gradient morphologique fort entre les populations situées à différentes distances du front d’invasion ce qui suggère une forte plasticité morphologique mais qui ne serait pas liée à la capacité de dispersion de ces populations. En effet, cette dernière ne variant pas significativement le long du gradient d’invasion. La capacité de dispersion serait principalement liée à la taille du corps de goujon Asiatique, les individus les plus grands ayant une probabilité plus élevée de disperser.Bien que les prédictions générales du modèle de niche puissent être affectées par de potentielles adaptations à l’échelle de la population ou de la lignée évolutive, les résultats suggèrent qu’une certaine incertitude liée à ces prédictions persiste puisque la distribution native ne prédisait que très mal la distribution actuelle dans les zones envahies. Par ailleurs, mes travaux expérimentaux à plus fine échelle suggèrent que cette espèce est extrêmement adaptable et tolère une large gamme environnementale, ce qui pourrait expliquer son caractère invasif. Les connaissances produites au cours de cette thèse constituent donc des ressources extrêmement pertinentes pour développer des stratégies de gestion visant à contrôler les invasions futures du goujon Asiatique. / In this thesis I set out to quantify the risk of invasion from the invasive freshwater fish, Pseudorasbora parva, at a global extent, using traditional correlative ecological niche modelling approaches with the integration of surrogate data representing introduction likelihood (Chapter I). These correlative approaches rely upon key assumptions relating to the presence or absence of local or regional adaptations, and so I subsequently tested for evidence of such adaptations in genetic lineages and in individual populations. This was achieved through analyzing climatic niche differentiation of key genetic lineages in the native and invasive ranges (Chapter II) and by conducting lab experiments comparing thermal responses of important life history traits in populations from contrasting climates (Chapter III). The initial risk assessment did not account for a key factor in invasions; namely, natural dispersal. Natural dispersal has been observed to be subject to selection in vanguard populations of invasive species, and adaptation of dispersal traits can infer additional invasive vigor, allowing the species to spread across the landscape quicker. For this reason, I quantified dispersal, activity and morphological differences, often associated with differential dispersal ability, in populations along a distance-gradient from an invasion front, in order to identify if P. parva is capable of such adaptations.The initial risk mapping study showed that large areas, beyond the current distribution of the species, are climatically suitable. These areas are mainly in North and South America, Australia and New Zealand, and constitute significant scope for spread and impact of this species. When introduction likelihood was included, N. America appears most at risk. I found no evidence to suggest that native genetic lineages represented local adaptations to their respective native climates - there was little or no differentiation of the lineages’ climatic niches in the invasive range. It was also apparent, from the niche comparisons, that the climatic niche in the invaded range constituted a significant shift, compared to the native range. The thermal responses of P. parva life history traits did not differ significantly between populations from a strongly seasonal continental climate and a mild temperate maritime climate. The overall reproductive output of females did not vary according to breeding season temperature, however, temporal reproductive strategy showed a strong response, with lower temperatures inducing a protracted breeding season and higher temperatures inducing rapid and intense reproductive output. The dispersal and morphology-related study identified a strong gradient of morphological change, corresponding with distance from invasion front. This demonstrates a high degree of plasticity in P. parva’s morphology in an invasion context, however this was not linked to either dispersal or activity levels, neither of which was significantly linked to distance from invasion front. Dispersal was best explained by body size, with larger fish more likely to disperse further.Whilst I found no evidence to suggest that the model predictions (Chapter I) were hampered by differentiation at either lineage or population levels, the findings of Chapter II do highlight the uncertainties surrounding the degree of conservatism in such predictions, mainly owing to the fact that past, native, distribution did not accurately predict the current invaded distribution. The results of Chapters II-IV show broad tolerances and great plasticity in P. parva, which likely underpin this species success as a pan-continental invader. The knowledge produced in this thesis provides a useful new resource for the development of management strategies for P. parva and could be usefully enhanced by the additional of analogous studies on native populations, which could help elucidate the source of the observed plasticity.

Les espaces montagnards représentent des zones à forts enjeux environnementaux, économiques, sociaux voire culturels. Les changements d’occupation et d’usage du sol qui s’y tiennent, qu’ils soient d’origine anthropiques ou non, ont engendré, au cours des dernières décennies, des dynamiques significatives d’enfrichement et de reforestation dans les Pyrénées françaises. Les tendances en cours laissent présager que ces dynamiques vont s’amplifier à l’avenir. Si ces dynamiques sont étroitement liées au déclin des activités agro-sylvo-pastorales, la localisation des zones potentiellement concernées constitue un réel enjeu pour les gestionnaires et les acteurs locaux. Dans une perspective de gestion à moyen ou long terme des espaces montagnards, il est aujourd’hui essentiel de pouvoir leur fournir une vision quantifiée des futurs possibles de leur territoire afin d’éclairer leurs décisions. L’objectif de ce travail est de construire des scénarios prospectifs spatialisés à trois échelles différentes et emboîtées (régionale, locale et micro-locale) afin d’identifier les espaces les plus vulnérables aux changements d’occupation et d’usage du sol et d’analyser l’influence des échelles spatiales et des approches de modélisation sur leur localisation. La démarche méthodologique s’articule autour de quatre étapes. La première étape consiste à identifier les approches de modélisation prospective qui sont privilégiées selon les échelles spatiales considérées. La seconde étape vise à construire « la base » des scénarios. La troisième étape consiste à produire les scénarios prospectifs spatialisés à chacune des échelles spatiales, selon des démarches de modélisation adaptées et des facteurs explicatifs pertinents, afin de simuler l’évolution possibles des paysages montagnards et d’identifier les espaces les plus vulnérables aux processus d’enfrichement et de reforestation. Enfin, la dernière étape consiste à analyser l’influence des échelles et des approches de modélisation au sein des travaux de prospective. Les scénarios prospectifs spatialisés ont permis (i) de quantifier et de spatialiser les impacts possibles de contextes socio-économiques et environnementaux contrastés sur les changements d’occupation et d’usage du sol et (ii) d’identifier les espaces les plus vulnérables aux changements à chacune des échelles considérées. Le croisement des scénarios produits a également permis d’évaluer l’incertitude spatiale des changements liée au futur. Les modèles pattern-based, utilisés à l’échelle régionale et locale, tendent à sous-estimer les changements par rapport au modèle process-based appliqué à l’échelle micro-locale. Au final, l’approche multi-scalaire a permis : d’apporter des connaissances sur le fonctionnement du système pyrénéen, voire de combler des lacunes quant aux données disponibles, qu’une approche mono-scalaire n’aurait pas produites ; de cibler les espaces les plus propices aux changements et d’établir un degré de confiance quant aux approches de modélisation choisies dans le but d’éclairer les politiques et stratégies de gestion. / Mountain areas exhibit high environmental, economic, social or cultural values. Land use and cover changes (LUCC), whether or not from anthropogenic origin, have led to significant encroachment and reforestation dynamics over the last decades in the French Pyrenees. Current trends suggest that these dynamics will amplify in the future. If they are closely related to the decline of agropastoral and forestry activities, the location of potentially affected areas is of great importance for managers and local stakeholders. For medium to long-term management perspectives, it is now essential to provide a quantified vision of possible futures of their territory to help in the definition of sustainable strategies. The objective of this work is to spatialize future scenarios at three different scales (regional, local and micro-local) to identify the most vulnerable areas to LUCC and analyze the influence of spatial scales and modeling approaches on their location. The methodology is based on four stages. The first step is to identify prospective modelling approaches that are preferred according to the considered spatial scales. The second step is to provide the knowledge for building scenarios. The third step is to simulate future scenarios at each spatial scales to identify the most vulnerable areas to encroachment and reforestation. The last step is to analyze the influence of scales and modeling approaches in the prospective framework. Spatially explicit scenarios allow to (i) quantify and assess possible impacts of contrasting socio-economic and environmental contexts on LUCC, and (ii) identify the most vulnerable areas to encroachment and reforestation for each considered spatial scale. Moreover, the combination of scenarios allows to evaluate the spatial uncertainty, regrouping the inherent and the ensemble uncertainties, related to future LUCC. The pattern-based models used at the regional and local levels tend to underestimate LUCC compared to the process-based model used. Finally, the multi-scale approach allowed to provide knowledge on the Pyrenean land system that a single scale approach would not have provided, to target the areas at stake regarding future LUCC and to establish a degree of confidence in the adopted modeling approaches in order to help in the definition and assessment of land use policies and strategies.

Species conservation initiatives play an important role in ecological studies. Occupancy models have been a useful tool for ecologists to make inference about species distribution and occurrence. Bayesian methodology is a popular framework used to model the relationship between species and environmental variables. In this dissertation we develop a Gibbs sampling method using a logit link function in order to model posterior parameters of the single-season spatial occupancy model. We incorporate the widely used Intrinsic Conditional Autoregressive (ICAR) prior model to specify the spatial random effect in our sampler. We also develop OccuSpytial, a statistical package implementing our Gibbs sampler in the Python programming language. The aim of this study is to highlight the computational efficiency that can be obtained by employing several techniques, which include exploiting the sparsity of the precision matrix of the ICAR model and also making use of Polya-Gamma latent variables to obtain closed form expressions for the posterior conditional distributions of the parameters of interest. An algorithm for efficiently sampling from the posterior conditional distribution of the spatial random effects parameter is also developed and presented. To illustrate the sampler's performance a number of simulation experiments are considered, and the results are compared to those obtained by using a Gibbs sampler incorporating Restricted Spatial Regression (RSR) to specify the spatial random effect. Furthermore, we fit our model to the Helmeted guineafowl (Numida meleagris) dataset obtained from the 2nd South African Bird Atlas Project database in order to obtain a distribution map of the species. We compare our results with those obtained from the RSR variant of our sampler, those obtained by using the stocc statistical package (written using the R programming language), and those obtained from not specifying any spatial information about the sites in the data. It was found that using RSR to specify spatial random effects is both statistically and computationally more efficient that specifying them using ICAR. The OccuSpytial implementations of both ICAR and RSR Gibbs samplers has significantly less runtime compared to other implementations it was compared to.