Finding a common language in describing and interpreting multivariate data associated with rehabilitation and disturbance ecology, has became a major challenge. The main objective of this study is to find and evaluate mathematical models to describe ecosystem change based on selected indicators of change. Existing data from a previous rehabilitation project on Hendrina Power Station (Mpumalanga, South Africa) was used as a database for this study and this study aims to report on the development of models concentrating on radar graphs and a model based on matrix mathematics. The main groups of organisms selected for the construction of models, were vegetation, soil mesofauna and ant species. The datasets were limited to some indicative species and their mean abundances were determined. The grids that were used were randomly chosen and the models were constructed. Radar graphs were constructed to model the suite of species identified, through a sensitivity analysis, to indicate possible rehabilitation success over time and was applied to the different rehabilitation ages. The surface areas under the radar graphs were determined and compared for the different rehabilitation ages in the same year of survey. Correlation graphs were drawn between the surface area and the rehabilitation ages. These graphs did not indicate much relevance in indicating rehabilitation success, but the radar graphs proved to be good indicators of change in abundance of the selected species over time. iv The vegetation species, Eragrostis curvula, was the only species that showed a strong significant positive relationship with rehabilitation age and could be considered a good rehabilitation species and indicator of rehabilitation success. After the evaluation of this model, Eragrostis curvula, and two additional ant species, Tetramorium setigerum and Lepisiota laevis, were added. These species that were added, showed an increase in abundance over time, as found in a previous study. These radar graphs also did not indicate much relevance and it can be concluded that the radar graphs can only be used for a visual representation of the changes in abundance of the relevant species over time. This study also refers to a matrix model. This model focused on the interactions between the different variables selected. The percentage carbon in the soil were also added to the list of species. Model fitting graphs were constructed and correlations were drawn between the species that had significant values in the interaction table. This model could be useful for future studies, but more data and replication is necessary, over a longer period of time. This will serve to eliminate possible shortcomings of the model. / Thesis (M. Environmental Science (Biodiversity and Conservation Biology))--North-West University, Potchefstroom Campus, 2007.

Finding a common language in describing and interpreting multivariate data associated with rehabilitation and disturbance ecology, has became a major challenge. The main objective of this study is to find and evaluate mathematical models to describe ecosystem change based on selected indicators of change. Existing data from a previous rehabilitation project on Hendrina Power Station (Mpumalanga, South Africa) was used as a database for this study and this study aims to report on the development of models concentrating on radar graphs and a model based on matrix mathematics. The main groups of organisms selected for the construction of models, were vegetation, soil mesofauna and ant species. The datasets were limited to some indicative species and their mean abundances were determined. The grids that were used were randomly chosen and the models were constructed. Radar graphs were constructed to model the suite of species identified, through a sensitivity analysis, to indicate possible rehabilitation success over time and was applied to the different rehabilitation ages. The surface areas under the radar graphs were determined and compared for the different rehabilitation ages in the same year of survey. Correlation graphs were drawn between the surface area and the rehabilitation ages. These graphs did not indicate much relevance in indicating rehabilitation success, but the radar graphs proved to be good indicators of change in abundance of the selected species over time. iv The vegetation species, Eragrostis curvula, was the only species that showed a strong significant positive relationship with rehabilitation age and could be considered a good rehabilitation species and indicator of rehabilitation success. After the evaluation of this model, Eragrostis curvula, and two additional ant species, Tetramorium setigerum and Lepisiota laevis, were added. These species that were added, showed an increase in abundance over time, as found in a previous study. These radar graphs also did not indicate much relevance and it can be concluded that the radar graphs can only be used for a visual representation of the changes in abundance of the relevant species over time. This study also refers to a matrix model. This model focused on the interactions between the different variables selected. The percentage carbon in the soil were also added to the list of species. Model fitting graphs were constructed and correlations were drawn between the species that had significant values in the interaction table. This model could be useful for future studies, but more data and replication is necessary, over a longer period of time. This will serve to eliminate possible shortcomings of the model. / Thesis (M. Environmental Science (Biodiversity and Conservation Biology))--North-West University, Potchefstroom Campus, 2007.

Shorebirds are increasingly threatened by introduced predators, invasive grasses, and human disturbance. Matrix models can be used to predict population growth and assess management options. The Pacific coast population of the western snowy plover, Charadrius alexandrinus nivosus, is listed as threatened under the Endangered Species Act, largely due to high rates of nest predation. A matrix model for the entire Pacific coast metapopulation of western snowy plovers was published in 1999 by Nur et al., but population growth has not been comprehensively reassessed since, even after development of a recovery plan (USFWS 2007) and extensive management intervention. I built and analyzed a matrix model for one subpopulation of western snowy plovers previously considered a sink habitat—Recovery Unit 2 in northern California, comprising Humboldt, Mendocino, and Del Norte counties. Based on my model, growth rate (lambda) is 1.05—countering a previous finding that Recovery Unit 2 is a sink—compared to 1.036 for the Nur et al. (1999) metapopulation model. I found that sensitivities and elasticities for each vital rate were similar between the two models; adult survival had the greatest effect on lambda, followed by juvenile survival, and fecundity had the least effect. Even though fecundity was lower for my model than Nur et al.’s (1999), adult survival was higher, which had a larger impact on population growth. In terms of management strategies, predator control, habitat restoration, and restriction of human activity should continue as outlined in the recovery plan, so as to continue the trend of positive growth for the coastal breeding population. Future directions involve performing population viability analyses for other recovery units to reassess the state of western snowy plovers compared to 1999.

Cette thèse concerne deux sujets différents: une étude d'une classe de modèles matriciels qui sont pertinents pour l'holographie, et le calcul d'observables dans une théorie superconforme N = 2 grâce à la technique de la localisation supersymétrique. Le premier sujet traite de modèles matriciels avec symétrie U(N)xO(D) qui ont été introduits récemment. Dans ces modèles, appelés modèles de matrices-vecteurs, il a été montré qu'il est possible de définir une limite de grand D qui conduit à un développement en diagrammes planaires resommable. De plus, ils contiennent des champs et des symétries inspirés de la théorie des cordes et il a été montré qu'un de ces modèles présente les mêmes propriétés physiques que le modèle SYK, dont la connexion avec l'holographie est bien connue. Dans cettethèse, l'étude de ces modèles matriciels est étendue en considérant plusieurs généralisations de la littérature existante. L'étude de modèles avec des termes d'interaction multi-traces et avec une symétrie réduite, et le calcul des observables multi-traces, sont considerés. De plus, plusieurs problèmes concernant la construction de modèles sont pris en considération. Enfin, une analyse approfondie des modèles de matrices-vecteurs fermioniques avec des termes d'interaction quartique est effectuée. Dans le cadre de la localisation supersymétrique, la seconde partie de la thèse se concentre sur le calcul des observables dans la QCD superconforme N = 2 (SCQCD) en 4 dimensions avec symétrie de jauge SU(N). Pour commencer, les résultats connus concernant le calcul de corrélateurs d'opérateurs chiraux et les valeurs moyennes de boucles de Wilson circulaires en utilisant la technique de la localisation supersymétrique sont présentés. La contribution originale de cette partie concerne le calcul de corrélateurs entre opérateurs chiraux et boucles de Wilson circulaires. Le calcul est organisé comme suit: d'abord, les observables sont calculées à travers le modèle matriciel résultant de la procédure de localisation. Ensuite, les résultats du modèle matriciel sont testés par rapport au calcul utilisant la théorie quntique des champs perturbative. Ce calcul esteffectué en prenant la différence entre l'observable calculée dans N = 2 SCQCD et la même observable calculée dans N = 4 super Yang-Mills. Ceci réduit considérablement le nombre de diagrammes de Feynman qui contribuent au corrélateur, ce qui permet d'effectuer des contrôles perturbatifs jusqu'à deux boucles. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

L’eau est vitale dans toutes les économies. C’est à cause de son rôle prépondérant pour la survie que les tensions politiques autour des basins et des fleuves internationaux tendent à être particulièrement très épineuses. Actuellement, la mauvaise répartition de cette ressource pose un sérieux problème du fait qu’elle est gérée en fonction de stratégies politiques et non en fonction des réalités hydrologiques régionales. Nous expliquons à l’aide de la « Enhanced Power Matrix Model » (La Matrice de FREY et NAFF améliorée) que les tensions autour des bassins et des fleuves au Moyen – Orient n’aboutiront pas à des conflits armés mais à une situation de non guerre et de non paix, très peu propice à la coopération. Pour sortir de cette situation de blocage, nous proposons aux décideurs politiques et aux négociateurs, sur base de l’article 6 de la Convention de New York de 1997 sur « les cours d’eau internationaux à d’autres usages que la navigation », un modèle de répartition de la ressource hydrique entre les différents riverains d’un cours d’eau international. Face à cette situation, beaucoup de pays de la région tentent de mettre de façon unilatérale des modèles de gestion macroéconomique : réduction de la demande ou l’augmentation de l’offre de l’eau. Ces modèles se heurtent à des obstacles de nature économique, politique, sociologique et culturelle. Dans un objectif de conception de nouveaux modèles de gestion de l’eau, nous proposons un modèle coopératif, les projets de transfert inter – bassin, pour faire face à la mauvaise répartition de cette ressource au Moyen – Orient. Nous appuyons sur la méthodologie multicritère d’aide à la décision pour opérationnaliser l’article 6 de la Convention de New York et pouvoir comparer les différents projets de transfert inter - bassin. Cette méthodologie fait appel à un logiciel d’aide à la décision « Décision Lab 2000 ». Le commentaire des résultats fournis par ce logiciel nous a permit de tirer l’enseignement suivant : seuls les projets qui présentent une faisabilité politique élevée arrivent en tête de classement. Ce qui nous fait dire que la question de l’eau au Moyen – Orient est, avant tout, une question politique.

We reinvestigate the validity of mapping the problem of two onsite interacting particles in a random potential onto an effective random matrix model. To this end we first study numerically how the non-interacting basis is coupled by the interaction. Our results indicate that the typical coupling matrix element decreases significantly faster with increasing single-particle localization length than is assumed in the random matrix model. We further show that even for models where the dependency of the coupling matrix element on the single-particle localization length is correctly described by the corresponding random matrix model its predictions for the localization length can be qualitatively incorrect. These results indicate that the mapping of an interacting random system onto an effective random matrix model is potentially dangerous. We also discuss how Imry's block-scaling picture for two interacting particles is influenced by the above arguments.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第22997号 / 理博第4674号 / 新制||理||1670(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 國友 浩, 教授 杉本 茂樹, 教授 田中 貴浩 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

The aim of this thesis is to define and study harvesting models of fish populations. These models are applied to particular fish species e.g., haddock and cod. The thesis is divided into five chapters: The first chapter is considered as an introductory one. In it, basics of fish biology and the recruitment process are defined. Two simple recruitment models known by the names Ricker and Beverton-Holt are used. In the second chapter the generalized Leslie model or Usher model is introduced. In section 2.2, some matrix theory is presented. For this matrix model, the net reproductive number is defined and studied in section 2.3. It turns out to be more useful than the spectral radius. In section 2.4, this study is extended to nonlinear matrix models. The nonlinearity, however, is defined only by the recruitment process. This allows to determine the equilibrium components. Finally section 2.5, the local stability of nonlinear matrix models is analyzed. Harvesting of such general matrix model is defined in chapter 3. We distinguish three different harvesting models (selective, net and semicontinuous harvesting models). In chapter 4, these harvesting models are then applied to concrete fish populations and analyzed with respect to its various parameters. In chapter 5, the stability is studied again along the lines of the paper of Levin, Goodyear [18]. The key results in this study are: 1) The maximum sustainable yields for selective harvesting and net harvesting are rather close. 2) Semicontinuous harvesting is more realistic harvesting models. 3) From a quantitative point of view, the choice of the recruitment function is important. 4) Harvesting process increases mortality and stability when we used Ricker recruitment model. 5) Stability of populations always holds if we use Beverton-Holt recruitment model.

Anthropogenic pressures have caused changes in both the mean and variance of environmental conditions, with associated effects on the demography of natural populations. The demographic effects of environmental change can manifest through direct (i.e., physiological) or indirect pathways (i.e., through shifts in species interactions). For many populations, environmental change will affect multiple life cycle stages simultaneously, thereby altering vital rate correlation structures with potentially important impacts on evolutionary fitness. The effects of environmental change will also often be habitat-specific, particularly when species interactions modify demographic sensitivity to climate. As a result, the effects of climate change are likely to vary across a species range, with important implications for range expansion and population viability. In chapter 2, I examine the effects of joint vital rate responses to environmental drivers on the evolution of life histories in variable environments. I show that vital rate covariation, generated when multiple vital rates respond to a shared environmental driver, can fundamentally alter evolutionary selection pressures. Negative vital rate covariation promotes the evolution of demographic lability (stronger demographic responsiveness), while positive covariation promotes buffering (weaker demographic responsiveness), altering the range of life histories over which the evolution of buffered and labile vital rates are a predicted evolutionary outcome. By identifying the life histories for which selection pressures are most sensitive to environmentally-driven vital rate covariation, this study provides a richer understanding of both life history evolution and the capacity of species to cope with ongoing changes to contemporary environments. In chapter 3, I use a long-term study of lesser snow geese to test the hypothesis that demographic and developmental responses to climate will be weakest in habitats where resource diversity is greatest. I find support for this hypothesis, and my results indicate that gosling demography is much more responsive to climate in recently colonized, freshwater habitats where landscape diversity and gosling diet diversity is low. These results underscore the potential importance of accounting for biotic interactions when predicting spatio-temporal responses to climate. In chapter 4, I quantify the consequences of observed climate change for lesser snow goose population dynamics across habitats. I find that climate change increases population growth in all habitats, but that such increases are disproportionately large in novel inland freshwater habitats. These results suggest that in a warmer and more variable climate, the breeding range and population growth of lesser snow geese is likely to increase, counteracting current management efforts to reduce overabundant populations.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18786号 / 理博第4044号 / 新制||理||1582(附属図書館) / 31737 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 川合 光, 教授 畑 浩之, 教授 田中 貴浩 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM