Orientador: Wilson Castro Ferreira Junior / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica / Made available in DSpace on 2018-08-22T04:48:33Z (GMT). No. of bitstreams: 1 LouVega_Salvador_D.pdf: 14692586 bytes, checksum: f745ca7fb3da3cfa09dfb8a8dd9f37bb (MD5) Previous issue date: 2013 / Resumo: Apresentamos um modelo integro - recursivo para a dispersão de uma planta que acopla uma dinâmica de reprodução, com efeito, Allee e uma dinâmica de dispersão em um meio heterogêneo. Propomos um modelo de difusão e sedimentação para derivar núcleos de dispersão teóricos, que representem o padrão de dispersão de sementes gerado por pássaros frugívoros em um meio heterogêneo. O núcleo gerado através do modelo _e capaz de reproduzir o padrão espacial de agregação de sementes gerado pelos pássaros frugívoros sob condições naturais. Enquanto _a dinâmica de reprodução, consideramos um efeito Allee devido à limitação de pólen, que reduz a produção de sementes. Introduzimos o efeito Allee através de uma função de probabilidade que depende da densidade local de plantas. Analisa-se o comportamento da expansão da planta, e estima-se a velocidade média de expansão. O modelo mostra uma invasão através de pulsos, que atribuímos ao efeito Allee e ao comportamento de dispersão da planta / Abstract: We present an integro-difference model for a plant dispersal, which couples a reproductive dynamic with Allee effect and dispersal dynamic in a heterogeneous environment. We propose diffusion and settling model to derive theoretical dispersal kernels that represent the seed dispersal pattern generated by frugivores birds in a heterogeneous environment. The dispersal kernel derived through the model is able to reproduce the aggregate seed dispersal pattern generated by the frugivores birds under field conditions. As for the reproductive dynamic, we consider an Allee effect due to pollen limitation, which reduces seed production. We introduce the Allee effect through a probability function, which depends on the local plant density. The plant expansion behavior is analyzed, and the average expansion speed is estimated. The model shows a pulsed invasion, which we attribute to the Allee effect and the plant dispersal behavior / Doutorado / Matematica Aplicada / Doutor em Matemática Aplicada

Graduation date: 1998

Invasive alien plants have widespread ecological and socioeconomic impacts throughout many parts of the world, including Swaziland where the government declared them a national disaster. Control of these species requires knowledge on the invasion ecology of each species including how they interact with the invaded environment. Species distribution models are vital for providing solutions to such problems including the prediction of their niche and distribution. Various modelling approaches are used for species distribution modelling albeit with limitations resulting from statistical assumptions, implementation and interpretation of outputs. This study explores the usefulness of Bayesian networks (BNs) due their ability to model stochastic, nonlinear inter-causal relationships and uncertainty. Data-driven BNs were used to explore patterns and processes influencing the spatial distribution of 16 priority invasive alien plants in Swaziland. Various BN structure learning algorithms were applied within the Weka software to build models from a set of 170 variables incorporating climatic, anthropogenic, topo-edaphic and landscape factors. While all the BN models produced accurate predictions of alien plant invasion, the globally scored networks, particularly the hill climbing algorithms, performed relatively well. However, when considering the probabilistic outputs, the constraint-based Inferred Causation algorithm which attempts to generate a causal BN structure, performed relatively better. The learned BNs reveal that the main pathways of alien plants into new areas are ruderal areas such as road verges and riverbanks whilst humans and human activity are key driving factors and the main dispersal mechanism. However, the distribution of most of the species is constrained by climate particularly tolerance to very low temperatures and precipitation seasonality. Biotic interactions and/or associations among the species are also prevalent. The findings suggest that most of the species will proliferate by extending their range resulting in the whole country being at risk of further invasion. The ability of BNs to express uncertain, rather complex conditional and probabilistic dependencies and to combine multisource data makes them an attractive technique for species distribution modeling, especially as joint invasive species distribution models (JiSDM). Suggestions for further research are provided including the need for rigorous invasive species monitoring, data stewardship and testing more BN learning algorithms. / Environmental Sciences / D. Phil. (Environmental Science)

Les forêts tropicales renferment des peuplements arborescents dont la gestion et l’aménagement nécessitent des connaissances sur leur organisation spatiale et leur dynamique. Les analyses de la structure spatiale des espèces arborescentes peuvent être utilisées en forêts naturelles pour identifier les mécanismes sous-jacents qui structurent les peuplements forestiers afin d’améliorer la compréhension des relations entre les espèces. Cette étude a été menée dans la Réserve Forestière de Yoko (RFY) aux environs de Kisangani à l’est de la RD Congo (R.D.C). Elle consiste à analyser la structure spatiale horizontale des espèces les plus abondantes et à tenter d’identifier, à l’échelle locale, les facteurs et/ou processus écologiques potentiellement explicatifs pour en retirer des enseignements utiles à la gestion des massifs forestiers situés à proximité de Kisangani. <p>Pour ce faire, une parcelle d’échantillonnage de 25 ha (500m 500m) a été délimitée dans le bloc sud de la RFY constitué d’une végétation ligneuse mixte et semi-décidue. Un inventaire forestier a permis d’analyser la composition floristique et structurale de la zone. Trois techniques (ou modèles statistiques) relevant de l’écologie spatiale pour l’analyse de la structure horizontale des espèces ont été utilisées :la méthode du voisin le plus proche de Clark & Evans (1954), la méthode d’échantillonnage aléatoire de Hines & Hines (1979), ces deux méthodes reposant sur une analyse à échelle unique de la parcelle d’étude, et la méthode de Ripley (1977) permettant non seulement une analyse multi-échelle mais aussi l’étude des relations intra et interspécifiques. Concernant ce point précis, les arbres ont été catégorisés en trois stades de développement sur la base de leurs diamètres (les jeunes, les immatures et les adultes). Une analyse comparative et théorique des trois méthodes a été effectuée. <p>Un total de 169 espèces appartenant à 36 familles dont 114 genres ont été identifiées, et la famille des Fabaceae dont la majorité des espèces appartiennent à la sous famille des Caesalpinioideae est apparue prépondérante. Trois espèces se sont révélées les plus abondantes et les plus représentatives du peuplement, et ont pour cette raison fait l’objet de toutes les analyses :Gilbertiodendron dewevrei J. Léonard (De Wild), Scorodophloeus zenkeri Harms et Uapaca guineensis Mull. Arg. Elles ont toutes les trois montré une structure agrégée, et cela à toutes les échelles d’analyse. Les agrégats observés présentent un rayon d’environ 25 m de distance. L’analyse en fonction du diamètre a indiqué une structure agrégée pour les plus petits diamètres et régulière pour les plus grands, et que l’agrégation diminue avec le diamètre. Les résultats montrent également que les structures spatiales observées dépendent de l’échelle d’analyse considérée et de la méthode utilisée. La méthode de Clark & Evans est sensible à la variation de l’étendue. À cet égard, l’échantillonnage aléatoire de Hines & Hines est apparu plus adaptée que celui de Clark & Evans. Les fonctions de Ripley et dérivées sont des outils efficaces et apportent plus d’information. Les analyses ont montré des associations positives entre G. dewevrei et S. zenkeri, ainsi qu’entre G. dewevrei et U. guineensis. Par contre, une indépendance a été constatée entre S. zenkeri et U. guineensis. Il apparaît également que les jeunes sont associés positivement aux adultes supposés reproducteurs, et que les immatures sont indépendants par rapport aux adultes. La dispersion faible ou limitée des graines à proximité des arbres parents en est le principal facteur endogène responsable. Ce facteur explique également les associations positives entre les jeunes et les adultes de la même espèce. La compétition entre des individus pour les besoins en espace, en lumière ou en nutriments dans le sol, explique la structure régulière observée ainsi que l’indépendance des immatures envers les adultes. La dispersion limitée n’est cependant pas le seul facteur explicatif de l’agrégation spatiale des arbres, d’autres facteurs tels que l’hétérogénéité environnementale (sol, topographie,…) ou la perturbation sont vraisemblablement aussi impliqués. La perturbation anthropique ou naturelle est un processus écologique qui devrait avoir joué un rôle déterminant dans l’organisation spatiale des communautés de la forêt. Combinée au phénomène de masting, aux effets de Janzen-Connell et aux ectomycorhizes, elle est très probablement à la base des structures spatiales et des relations spatiales observées entre les espèces de la RFY. / Tropical forests contain tree-stands with management and planning requires knowledge of their spatial organization and dynamics. Analyses of the spatial structure of tree species can be used in natural forests to identify the underlying mechanisms that structure of forest stands to improve the understanding of the relationships between species. This study was conducted in the Yoko Forest Reserve (YFR) around Kisangani in eastern DR Congo (DRC). It is to analyze the horizontal spatial structure of the most abundant species and to try to identify, on a local scale, factors and / or potentially explicative ecological processes to draw valuable lessons for the management of forest areas nearby Kisangani. <p>To do this, a sample plot of 25 ha (500m x 500m) was delineated in the southern block of the YFR consists of a mixed woody vegetation and semi-deciduous. A forest inventory was used to analyze the floristic and structural composition of the area. Three techniques (or statistical models) under spatial ecology for the analysis of the horizontal structure of the species were used: the nearest neighbor method of Clark & Evans (1954), the random sampling method Hines & Hines (1979), these two methods based on a single scale analysis of the study plot, and the method of Ripley (1977) allows not only a multi-scale analysis, but also the study of intra- and inter-relationships. Regarding this point, the trees were categorized into three stages of development on the basis of their diameters (young, immature and adult). A comparative and theoretical analysis of the three methods was performed. <p>A total of 169 species belonging to 36 families with 114 genera have been identified and the family Fabaceae which the majority of species belong to the subfamily Caesalpinioideae appeared decisive. Three species have proved the most abundant and the most representative of the stand, and for this reason the subject of all analyzes Gilbertiodendron dewevrei J. Léonard (De Wild) Scorodophloeus zenkeri Harms and Uapaca guineensis Mull. Arg. They all three showed an aggregated structure, and that all scales of analysis. Observed aggregates have a radius of about 25 m distance. The analysis based on the diameter indicated an aggregated structure for smaller diameters and regular for larger and that aggregation decreases with diameter. The results also show that the observed spatial structures depend on the considered analysis of scale and the method used. The method of Clark & Evans is sensitive to the variation in the extent. In this regard, the random sampling of Hines & Hines appeared more suitable than that of Clark & Evans. Ripley's functions and derivatives are effective tools and provide more information. Analyses showed positive associations between G. dewevrei and S. zenkeri, and between G. dewevrei and U. guineensis. By against, independence was found between S. zenkeri and U. guineensis. It also appears that young people are positively associated with the supposed breeding adults and immatures are independent compared to adults. The low or limited seed dispersal near parent trees is the main endogenous factor responsible. This factor also explains the positive associations between youth and adults of the same species. The competition between individuals to space requirements, light or nutrients in the soil, explains the observed regular structure and the independence of immature towards adults. Limited dispersal, however, is not the only factor explaining the spatial aggregation trees, other factors such as environmental heterogeneity (soil, topography, ) or disturbance are probably also involved. Anthropogenic or natural disturbance is an environmentally friendly process that should have played a decisive role in the spatial organization of forest communities. Combined with masting phenomenon, the effects of Janzen-Connell and Ectomycorrhizae, it is very probably the basis of spatial structures and spatial relationships observed between species of the YFR.<p><p> / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished