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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
481

Quantifying landscape anthropisation patterns: concepts, methods and limits / Quantification de la structure spatiale de l'anthropisation des paysages: concepts, méthodes et limites

Vranken, Isabelle 24 February 2015 (has links)
Since human beings began to use and shape the land, their influence on their<p>environment has kept on growing so that little or no ecosystem in the world is now<p>considered as untouched. This induces pressures on ecosystem health and land scarcity.<p>Africa is of particular concern because it still presents broad undisturbed zones and<p>key ecosystem services, despite being submitted to increasing anthropogenic pressures.<p>Landscape ecology appears suitable for the study of such phenomena, thanks to its spacebased<p>integrative nature and geographical level of focus. It studies the impact of spatial<p>pattern transformation — especially heterogeneity and its components — on ecological<p>processes and provides powerful analytical tools of landscape anthropisation.<p>The main objective of this thesis is to organise the concepts and methods, from<p>landscape ecology and related disciplines, into a consistent logic, to pinpoint missing<p>analytical frameworks for response-oriented anthropisation assessment, and to apply them<p>to African cases to explore the spatial patterns of anthropisation. In order to address<p>landscape anthropisation, we assemble diverse disciplines into a logical network (DPSIR).<p>The new theoretical framework is tested on Lubumbashi (DRC). In order to address<p>spatial patterns, we first evaluate the thermodynamic connection of the term entropy in<p>landscape ecology: spatial heterogeneity, unpredictability and scale influence. Then, based<p>on 20 landscapes, we highlight the complex relationship between spatial heterogeneity<p>and landscape anthropisation. We finally use the modelled relationships to test the<p>anthropogenic origin of the spatial pattern of a land cover class in Lubumbashi.<p>The main results of this research show that several concepts are used to describe different<p>aspects of anthropisation and that its quantification strongly depends on the reference states.<p>Data formats can be combined into a new assessment method ensuring more precision<p>and comparability, but a good field knowledge is required. As for heterogeneity, the<p>existing definitions of landscape entropy follow the logic of thermodynamics or information<p>theory, that are not compatible. Only unpredictability could be properly interpreted in<p>thermodynamic terms if energy transfer measurements were performed at the appropriate<p>level. The anthropogenic effects on heterogeneity completely diverge depending on the<p>amount of already anthropised surface, on the land cover type (natural or anthropogenic),<p>and on the heterogeneity components.<p>The aforementioned findings could be adapted to include functional aspects and<p>better address the relationship between spatial pattern and ecological processes. Such<p>integration would help designing response actions that can recommend human activities<p>and spatial patterns that could optimise the use of land to ensure ecological functioning<p>while supporting human development. / <p>L’influence croissante de l’homme sur son environnement affecte désormais le monde<p>entier, ce qui induit des pressions sur la santé des écosystèmes et raréfie les ressources<p>en terres. L’Afrique présente un intérêt particulier à cet égard car elle contient de vastes<p>zones quasi vierges et fournit des services écosystémiques importants mais est soumise<p>à des pressions anthropiques croissantes. L’écologie du paysage étudie ces phénomènes<p>de façon intégrative au moyen de sa composante spatiale et de son échelle d’intérêt. Elle<p>étudie l’impact des transformations de la structure spatiale — en particulier l’hétérogénéité<p>et ses différentes composantes—sur les processus écologiques et fournit de puissants outils<p>analytiques de l’anthropisation.<p>L’objectif de cette thèse est d’organiser les concepts et méthodes de différentes disciplines<p>de façon à mettre en évidence leurs forces et faiblesses pour proposer une nouvelle<p>quantification de l’anthropisation, orientée vers la gestion, et de la tester sur des paysages<p>africains pour examiner la structure spatiale de l’anthropisation. Le DPSIR est utilisé pour<p>assembler les différents concepts. La nouvelle méthodologie est testée sur Lubumbashi<p>(RDC). Ensuite, le lien entre la thermodynamique et l’utilisation du terme entropie en<p>écologie du paysage est examiné. Vingt paysages servent alors à mettre en évidence la<p>complexité de l’impact de l’anthropisation sur l’hétérogénéité du paysage. Enfin, cette<p>modélisation sert à mettre en évidence l’origine anthropique de la structure spatiale d’une<p>classe d’occupation du sol à Lubumbashi.<p>Les résultats principaux de cette recherche sont que pléthore de termes sont utilisés<p>pour représenter différents aspects de l’anthropisation et que sa quantification dépend de<p>la définition d’états de référence. Cependant, la combinaison de différents formats de<p>données peut aboutir à une nouvelle méthodologie plus précise et adaptable, mais cela<p>nécessite une bonne connaissance de terrain. Les définitions de l’entropie dépendent soit de<p>la thermodynamique soit de la théorie de l’information, qui ne sont pas compatibles. Seule<p>l’imprévisibilité pourrait être interprétée thermodynamiquement, si les mesures de transfert<p>d’énergie étaient effectuées à l’échelle appropriée. L’impact humain sur l’hétérogénéité<p>diverge selon la quantité de surface déjà anthropisée, le type de couverture du sol pris en<p>compte ainsi que les composantes de l’hétérogénéité mesurées.<p>Ces découvertes peuvent être adaptées pour intégrer des aspects fonctionnels de la<p>structure spatiale et mieux cerner le lien entre celle-ci et le fonctionnement écologique, ce qui<p>permettrait de proposer des activités humaines et des structures spatiales qui optimiseraient<p>l’utilisation des ressources en sol pour assurer tant le fonctionnement écologique que le<p>développement humain. / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished
482

Influence des gradients anthropique et géomorphologique sur la variation de la biodiversité végétale dans la réserve de biosphère de la boucle du Baoulé au Mali: cas de la réserve de Fina

Diallo, Hady 25 February 2014 (has links)
Les travaux de recherche ont été menés dans la réserve de biosphère de la boucle du Baoulé (RBBB) au Mali. Cette réserve est constituée de 3 aires, Badinko, Kongosambougou et Fina. Cette étude a été faite dans l’aire de Fina, la plus importante pour sa richesse en faune. La péjoration des conditions climatiques et les impacts des pressions anthropiques croissantes ont entraîné une dégradation des écosystèmes en particulier la biodiversité végétale. L’objectif de notre recherche est d’étudier l’influence des gradients anthropique et géomorphologique sur la variation de la biodiversité végétale dans la RBBB. Elle contribuera à la caractérisation et à l’évaluation de l’état actuel de la végétation dans une perspective de conservation durable des ressources végétales en particulier la biodiversité. Nous sommes partis de l’idée que les aires protégées constituent des espaces témoins de conservation des milieux naturels qui, comparés aux milieux perturbés permettraient de caractériser l’état d’évolution de la biodiversité végétale. Deux approches ont été utilisées pour aborder cette étude :l’approche synchronique et l’approche diachronique. Un recensement et une classification des espèces ont été effectués en s’appuyant sur le dispositif de zonage d’une réserve de biosphère basée sur les degrés de pression (régimes de protection) et la situation géomorphologique. Puis une quantification des variations de pressions liées aux activités anthropiques a été faite. <p>Nos résultats ont montré que les facteurs structurants de la végétation varient suivant la géomorphologie et surtout le dispositif de zonage (gradient anthropique). C’est dans les milieux perturbés que la diversité est élevée, mais avec un niveau d’organisation peu homogène comparativement aux milieux non perturbés. L’intensification actuelle des pressions dans les milieux perturbés et la dégradation des formations végétales qui en résulte n’entraînent pas actuellement dans la réserve une baisse de diversité. Aussi, dans les conditions écologiques locales pratiquement semblables dans la réserve, le zonage caractérisant les niveaux d’anthropisation est autant important que les facteurs texture du sol qui sont liés aux conditions géomorphologiques dans la structuration floristique. Les résultats phytosociologiques ont montré l’individualisation de 10 groupements végétaux dont 6 en milieux perturbés avec une tendance à la dégradation de la végétation et sa transformation en savane arbustive et 4 en milieux non perturbés marqués par la disparition des formes de végétation originelles. La plus forte densité en espèces est observée dans les groupements végétaux des unités de plaine et de vallée pour l’ensemble des 3 zones. C’est dans ces unités également que la surface terrière pour les arbres de plus de 8 m et la valeur pastorale sont importantes. La diminution du recouvrement des espèces herbacées de bonne valeur fourragère en particulier les pérennes est corrélée aux perturbations liées aux intenses activités anthropiques (agricole et pastorale par exemple). Ces activités engendrent la dégradation du milieu, une baisse de la valeur pastorale qui est indépendante de la biodiversité. Les dynamiques temporelles de la composition du paysage forestier de la réserve ont montré une ouverture du paysage caractérisée par une extension des superficies cultivables de la zone de transition vers la zone protégée ainsi que la réduction de la superficie des savanes arborées et la transformation progressive du paysage en savane arbustive. L’étude a permis de comprendre que le dispositif législatif classique de protection ne correspond pas à la réalité de terrain. De façon générale, l’influence des gradients géomorphologique et surtout anthropique est perceptible sur la structure de la flore et de sa diversité. <p>Une extension de notre approche d’étude dans les réserves de Badinko et de Kongosambougou permettra d’asseoir un dispositif de suivi de l’évolution spatio-temporelle de la végétation et de poser les bases d’une politique rationnelle de conservation de la réserve de biosphère de la boucle du Baoulé.<p><p>Mots clés :Anthropisation, diversité floristique, dynamique spatiale, géomorphologie, réserve de Fina, Mali.<p><p>ABSTRACT<p>The research was conducted in the Fina, part of biosphere reserve of « boucle du Baoulé » (RBBB) in Mali. This reserve consists of 3 areas, Badinko, Kongosambougou and Fina. Fina area is the most important for its rich fauna, this study was done. The climatic conditions pejoration and the impacts of increasing human pressures have led to ecosystem degradation, particularly plant biodiversity of the Fina reserve. In this study we have updated data on plant diversity and its variation based on the device of biosphere reserve zoning based on the pressure degree (protects systems). The objective of this thesis was to test the main hypothesis that protected areas are witness spaces of natural settings conservation that, compared to the disturbed areas, would characterize plant biodiversity evolution. Two approaches were used to address this study: synchronic and diachronic approach. Our results showed that the vegetation structural factors vary with the environment (zones) and geomorphology. The correlations between vegetation and ecological factors showed that the disturbance gradient is a major factor in the floristic variability. Human pressure intensification in disturbed habitats and resulting vegetation degradation do not currently induce any decrease of diversity in the reserve. In local similar environmental conditions as is the Fina reserve case, zoning characterizing the human impact levels is as important as the soil texture factors that are related to geomorphological conditions in the floristic structure. The phytosociological results showed the individualization of 10 plant groups in disturbed habitats, including 6 with a tendency to shrubby savanna and 4 in undisturbed environments marked by the disappearance of the vegetation original forms. The highest density of species is observed in plant communities of the plain and valley units in all the three zones. It is also in these units that basal area for trees over 8 m and pastoral value are important. The herbaceous species of good fodder value recovery reduction in particular the perennial causes the environmental degradation, and the pastoral value reduction that is independent of biodiversity. Temporal dynamics of the forest landscape composition of the reserve showed an opening of the landscape characterized by an expansion of arable land in the transition zone to the protected area of the reserve, the decrease in savanna area and gradual transformation landscape in shrubby savanna.<p>An extension of our study approach in the Badinko and Kongosambougou reserves could help establishing a monitoring of the spatial and temporal vegetation evolution and putting the rational politics bases of Baoulé biosphere reserve conservation.<p><p>Key words: Anthropisation, geomorphology, floristic diversity, Fina reserve, spatial dynamics, Mali.<p><p> / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished
483

Anthropisation des paysages au Bénin: dynamique, fragmentation et développement agricole / Landscape anthropisation in Benin: dynamics, fragmentation and agricultural development

Mama, Adi 20 December 2013 (has links)
Résumé<p>Afin de mieux comprendre l’anthropisation des paysages au Bénin, la dynamique de l’occupation du<p>sol a été évaluée en zone soudanienne (Nord-Bénin), soudano-guinéenne (Centre-Bénin) et guinéenne (Sud-Bénin) à partir de trois images satellitaires de type Landsat MSS 1972, TM 1986 et ETM+ 2006.<p>Ces trois zones reflètent assez bien le contexte environnemental et humain de la zone intertropicale.<p>L’objectif principal de la présente thèse est de quantifier la dynamique paysagère due à l’anthropisation des paysages de forêts-savanes à partir de la télédétection, du système d’information géographique et de l’écologie du paysage.<p>Nos résultats ont montré que l’équilibre écologique des paysages de forêts-savanes a subi<p>d’importantes perturbations. L’agriculture itinérante sur brûlis, l’exploitation forestière, la carbonisation, l’urbanisation, les feux de végétation et les plantations ont été identifiés comme les principales forces motrices de ces dynamiques. Les matrices paysagères, qui étaient historiquement constituées de forêts-savanes ont été remplacées par une mosaïque de savanes, de champs-jachères, de sols nus-agglomérations, des plantations forestières et fruitières. L’exploitation des données de télédétection a permis de distinguer 4 grands processus de transformation spatiale des classes d’occupation du sol.<p>Ainsi, entre 1972 et 2006, les processus dominants dans le paysage ont été la déforestation, la savanisation, le développement agricole marqué par la création suivie de l’agrandissement des taches de champs-jachères.<p>La quantification des perturbations anthropiques, des indices de la structure spatiale calculés pour<p>chaque classe d’occupation du sol sur la base de la densité, de l’aire moyenne, de la dominance, de<p>l’indice de forme et la dimension fractale des taches des classes a permis de détecter un processus global de fragmentation et d’anthropisation des paysages.<p>Les dynamiques temporelles de la structure et de la composition des paysages de forêts-savanes dans<p>les 3 zones climatiques du Bénin ont montré une anthropisation illustrée surtout par la fragmentation des forêts-savanes. La simulation des dynamiques à l’horizon 2025 à partir de la chaine de Markov de premier degré a montré que pendant que les champs-jachères, plantations et les sols nus-agglomération s’étendront, les forêts-savanes connaîtrons une forte diminution. En définitive, notre étude a mis en évidence que toutes les trois zones étaient fortement dynamiques. Ces transformations anthropiques vont compromettre dangereusement l’avenir de ces paysages dont dépend la survie des populations locales. Notre approche permet de poser les bases d’une politique rationnelle de conservation et d’aménagement des paysages naturelles en établissant des seuils structuraux minimaux des fragments nécessaires à la préservation de la biodiversité.<p><p>Abstract<p>To understand better the landscape anthropization in Benin, the dynamics of the land use was<p>estimated in soudanian zone (North-Benin), soudano-Guinean (Centre-Benin) and guinean (south-<p>Benin) from 3 Landscape satellite images (MSS 1972, TM 1986, and ETM+ 2006), supported by field<p>visits. These 3 zones reflect well enough the environmental and human context of the intertropical zone. The main objective of the present dissertation was to quantify the landscape dynamics due to the landscapes anthropization of forests-savannahs from the Remote Sensing, Geographic Information System and from Landscape Ecology.<p>Our results showed that the ecological balance of the forests-savannahs underwent important<p>disturbances. Slash-and-burn agriculture, logging for timber, carbonization, urbanization, vegetation fire and tree plantations have been identified as the main driving strengths of these dynamics.<p>The landscape matrix’s, which were historically constituted by forests-savannah, has been substituted by a mosaic of savannah, fields-fallows, grounds nudes-urban area and plantations. The use of Remote Sensing data allowed distinguishing four big spatial transformation processes of the land cover classes.<p>So, between 1972 and 2006, the dominant processes in the landscape were the deforestation, the<p>savanization, the agricultural development marked by the creation followed by the enlargement of the<p>spots of field-fallows. The anthropogical disturbances quantification of the spatial structure indications calculated for every land cover classes on the basis of the density, average area, dominance, shape index and the fractal dimension index of the patches classes allowed detecting a global fragmentation<p>process and the anthropization of the landscapes.<p>The temporal dynamics of the structure and composition of the forests-savannahs landscape in the 3 climatic zones area of Benin showed an anthropization illustrated especially by the forest-savannahs fragmentation. The dynamics simulation by 2025 referring to Markov chains of the first degree tendency showed that while fields-fallows, tree plantations and nudes-urban area will extend, forestssavannahs shall know a strong decrease.<p>After all, our study highlighted that every 3 zones were highly disturbed. These anthropogenic<p>transformations are dangerously going to compromise the future of these landscapes on which depends the local populations survival.<p>Our approach allows putting the bases of a rational preservation policy and management natural landscapes by the thresholds establishment of fragments necessary for the biodiversity conservation.<p><p> / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished
484

Analyse de la composition, de la structure spatiale et des ressources végétales naturelles prélevées dans la forêt dense de Kigwena et dans la forêt claire de Rumonge au Burundi / Study of the taxonomic composition, the spatial pattern and the botanical resources taken away from the Kigwena dense forest and the Rumonge Miombo forest in Burundi

Hakizimana, Paul 30 March 2012 (has links)
Dans cette étude, la composition taxonomique, la structure spatiale et les ressources végétales naturelles prélevées dans les forêts de Kigwena et de Rumonge ont été analysées. Les deux forêts sont situées au Sud-Ouest du Burundi, dans une région de forte densité de population. L’objectif global de l’étude était d’élucider des éléments de l’écologie de la forêt dense de Kigwena et de la forêt claire de Rumonge en vue de leur conservation optimale. Les résultats montrent que les deux forêts sont floristiquement différentes malgré leur proximité géographique. Les types biologiques sont dominés par les phanérophytes, les chaméphytes et les thérophytes ;ce qui traduit des adaptations des espèces aux conditions du milieu de vie forestier caractérisé par un stress hydrique et par d’importantes perturbations d’origine anthropique. Le spectre phytogéographique est en concordance avec la localisation des forêts étudiées dans le territoire phytogéographique du District du Mosso/Malagarazi, caractérisé par la présence des espèces à distribution soudano-zambézienne et des espèces de liaison soudano-zambézienne et guinéo-congolaise. La forêt dense de Kigwena et la forêt claire de Rumonge sont soumises aux mêmes influences phytogéographiques et n’ont donc pas connu d’isolement géographique. Dans la forêt dense de Kigwena, l’hétérogénéité spatiale de la végétation, reflétée par l’existence de quatre groupements végétaux distincts, obéit aux gradients d’humidité et d’anthropisation. Par contre, dans la forêt claire de Rumonge, l’hétérogénéité spatiale de la végétation se traduit par des variations stationnelles dans un même fond floristique. L’analyse de la distribution spatiale a montré que les arbres sont répartis selon le modèle spatial agrégé. Les ressources végétales prélevées dans les deux forêts par les populations riveraines servent en grande partie à des fins médicinales, matérielles, alimentaires, énergétiques et/ou socio-culturelles. Les prélèvements de ces ressources, l’agriculture intensive, l’exploitation des carrières, l’aménagement des infrastructures, les feux de forêt et les chablis ont été identifiés comme étant des facteurs de perturbation qui amplifiaient la dégradation et le risque de disparition des forêts de Kigwena et de Rumonge. En définitive, cette étude a montré que les forêts étudiées ont une richesse taxonomique et une valeur conservatoire considérables. Mais ces forêts sont menacées sous l’action d’une anthropisation croissante. Pour remédier à cette situation, des mesures et des actions de conservation ont été proposées pour un court terme. /The taxonomic composition, the spatial pattern and the botanical resources used by Man around the Kigwena and Rumonge forests were studied. Both forests are located in the south-western part of Burundi, in a zone characterized by a high population density. The overall objective of this study was to understand the ecology of the Kigwena and Rumonge forests in order to support their conservation. Results show that the flora of the two forests are different although their geographical proximity. The life forms are dominated by phanerophytes, chamaephytes and therophytes; this observation corresponds to an adaptation of the floras to water stress and anthropogenic disturbances. The phytogeographical spectrum is directly related to the presence of the forests in the Mosso/Malagarazi District. It is characterized by the presence of species with a soudano-zambezian distribution and by species of the soudano-zambezian/guineo-congolese connexion. No geographical isolation was evidenced which could have altered the composition of the Kigwena and Rumonge forests. In the Kigwena forest, the spatial floristic heterogeneity is shown by four different plant communities which occur according to anthropogenic disturbance and soil moisture gradients. But, in the Rumonge forest, the spatial floristic heterogeneity occurs with more common species, in the same flora. The analysis of the spatial pattern of the trees revealed a general tendency towards a clumped distribution. Many natural plant resources are removed from the Kigwena and Rumonge forests by neighbouring populations for medicinal use, material use, food use, energy use and cultural use. Removal of natural plant resources, intensive agriculture, quarry exploitation, infrastructure development, forest fires and windfall of trees have been identified as disturbance factors which amplify the degradation and the risk of disappearance of the forests of Kigwena and Rumonge. Ultimately, this study shows that the Kigwena and Rumonge forests are characterized by a high taxonomic richness as well as by their importance for conservation. Nevertheless, these forests are threatened by increasing anthropogenic activities. Consequently, short-term measures and actions for conservation are proposed. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished
485

Anthropisation et dynamique spatio-tamporelle de paysages forestiers en République démocratique du Congo

Bamba, Issouf 13 October 2010 (has links)
A l’image du bassin du Congo, la République Démocratique du Congo (République Démocratique du Congo) fait face à une réduction de la qualité et de la superficie de son couvert forestier. La présente étude avait pour objectif d’étudier l’effet de l’anthropisation, à travers la présence et les activités humaines sur la dynamique des paysages forestiers en République Démocratique du Congo. L’écologie du paysage, en tant que science pluridisciplinaire offre une très bonne approche à travers les indices et une méthodologie alliant la structure et la composition du paysage pour mettre en évidence les causes et les conséquences des processus écologiques. Ces approches sont basées sur le fait que en analysant la structure du paysage, des déductions utiles au sujet des processus écologiques fondamentaux peuvent être faites et vice versa. Les résultats ont montré, en quantifiant la dynamique spatio-temporelle de l’occupation du sol et par l’analyse et la caractérisation de la structure spatiale, que l’anthropisation est le moteur de la dynamique dans ces milieux forestiers. L’impact humain se traduit par une déstabilisation ou un dysfonctionnement des écosystèmes forestiers entraînant la dégradation, la fragmentation et la déforestation. Ainsi il a été montré que la proximité des villes est fortement corrélée à la dégradation et la perte d’habitats forestiers. Cela est fonction de l’importance socio-économique de ces villes car plus la ville est importante, plus elle attire la population ;que la densité de la population influence la fragmentation et l’incursion dans la forêt se fait en suivant les pistes et les routes mises en place généralement par les sociétés d’exploitation forestière. Le tout amplifié par la situation socio-économique difficile des populations et le manque de politiques de gestion appropriées de la part des gestionnaires publiques. Cette dynamique régressive du paysage forestier en République Démocratique du Congo aura une incidence négative sur les cycles climatiques globaux vu que le bassin du Congo est le plus grand bloc forestier après le bloc de l’Amazonie. La présente étude est donc un argument supplémentaire qui milite en faveur de la nécessité de prendre en compte les caractéristiques des populations locales dans les programmes de gestion de la forêt du bassin du Congo pour un meilleur équilibre écologique de la planète. / Like Congo basin, Democratic Republic of Congo’s forest covers are facing their reduction in quality and size. This study aimed to investigate the effect of human impact on forest landscape dynamics in DR Congo, through the human presence and its activities. Landscape ecology as a multidisciplinary science offers a very good approach through the index and a methodology combining the structure and the composition of the landscape to highlight the causes and the consequences of ecological processes. These approaches are based on the fact that by analyzing the structure of landscape, useful deductions about the underlying ecological processes can be made and vice versa. By quantifying the spatio-temporal dynamics of land use and by analysis and characterization of spatial structure, our results showed that anthropization is the driver of the dynamics in these forest environments. Human impact results in a destabilization or a dysfunction of the forest ecosystems involving degradation, fragmentation and deforestation. Thus it was shown that proximity to cities is strongly correlated to the degradation and loss of forest habitats. This depends on the socioeconomic importance of these cities because more the city is important, more it attracts people. Population density influences the fragmentation and the incursion into the forest is done by following the tracks and roads generally implemented by the logging companies. All amplified by socio-economic problems of population and lack of appropriate management policies on the part of public managers.This regressive dynamic forest landscape in République Démocratique du Congo will have a negative impact on global climate cycles because the Congo Basin is the largest forest block after Amazonia block. This study is another argument which advocates the need to take into account the characteristics of local population in forest management programs in the Congo Basin for a better ecological balance of planet. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished
486

Population size, demography and spatial ecology of cheetahs in the Timbavati Private Nature Reserve, South Africa

Dyer, Siobhan Margaret January 2013 (has links)
The cheetah (Acinonyx jubatus) has experienced a drastic decline in numbers over the last 20 years globally and is currently listed as vulnerable by the International Union for the Conservation of Nature (IUCN). In South Africa, there are only an estimated 763 free-ranging cheetahs and conflict with humans is arguably the most significant reason for this low number. The aim of my study was to determine the population size and demographic characteristics of the cheetah population within the Timbavati Private Nature Reserve (TPNR), South Africa, and to contribute to a better understanding of cheetah space use and habitat selection. The research was conducted on TPNR between November 2009 and June 2011 and I used a photographic survey to assess cheetah population size and demographic characteristics. Location data was obtained by collaring two adult male cheetahs with GPS/GSM collars and ad hoc sightings data from across the reserve for an adult female with cubs and three adolescent females. A relatively high minimum population density of 4.46 cheetahs/100km² was estimated, signifying a relatively healthy cheetah population. The sex ratio data indicated a higher male to female ratio and an average litter size of three cubs. The relatively high cub survival rate and density is promising in terms of the status of species within the area, as the data denote the success and potential persistence of the species. Cheetah home ranges varied between 20.97km² for the female with cubs and 659.65km² for the younger collared male. Season did not appear to be a determining factor in terms of home range sizes for the three social groups within the TPNR. However, the males did show a slight increase in their home range sizes during the dry season when resources where presumably more widespread. My results indicate that the cheetah is an adaptable species, flexible in behaviour and able to tolerate a variety of habitat types. Such knowledge is fundamental for planning and implementing the effective management and conservation of cheetahs in South Africa.
487

Anthropogenic threats to resident and dispersing African wild dogs west and south of the Kruger National Park, South Africa / Antropogenic threats to resident and dispersing African wild dogs west and south of the Kruger National Park, South Africa

Watermeyer, Jessica Patricia January 2012 (has links)
African wild dog Lycaon pictus populations are declining and the species is listed as Endangered by the IUCN. The Kruger National Park (KNP) is home to the only viable population of wild dogs in South Africa, but census results reveal consistently low numbers since the late 1990s. Wild dogs display wide-ranging behaviour and it is possible that the species might frequently use unprotected lands adjacent to the KNP. However, very little is known about wild dog movements beyond the boundaries of the KNP, and whether or not adjacent land owners are tolerant of the species. Significantly, threats along the boundaries may have negative consequences for the KNP population. This research investigated the dispersal habits of wild dogs beyond the western and southern boundaries of the KNP, and gathered information on human tolerance, and anthropogenic threats in an area of mixed land use. The land west of the KNP presented the best prospect for wild dog range expansion. The wild dog packs operating outside the KNP had smaller home ranges and less home range overlap than the packs operating within the KNP. In addition, my data suggested that the development of conservancies and the formation of ecotourism-based land use practices would be beneficial for wild dog conservation. Failed wild dog dispersals due to snaring and human persecution could threaten the genetic stability and persistence of the KNP population. Therefore, raising awareness and an understanding of the plight of wild dogs is important for improving land owner perception and tolerance outside of protected areas. The rapidly increasing human population continues to infringe on protected lands and fragment landscapes, thus cooperation from individual land owners is vital for the conservation of free-ranging large carnivores.
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An assessment of caracal population density and human-predator conflict in the Winterberg, Eastern Cape, South Africa

Smith, Emma Ruth January 2012 (has links)
Human-wildlife conflict frequently involves carnivores, mainly because of their large home ranges and dietary requirements. As such, carnivores tend to be the first animals to be lost in human-dominated ecosystems. This is significant because the removal of carnivores can alter the functionality of ecosystems. However, the conservation of carnivores depends as much on the socio-political and socio-economic landscapes as it does on the ecological one. The consolidation of vast, un-fragmented conservation areas in Africa and the world is unlikely. Thus, unravelling the factors (both biological and sociological) responsible for and influencing human-predator conflict is critical for carnivore conservation. The Winterberg district in the Eastern Cape, South Africa has been a sheep (Ovis aries) farming stronghold for nearly 200 years. Consequently, conflict between farmers and predators is commonplace and depredation of livestock by caracals (Caracai caracal) remains a perennial problem. However, the extent of this human-predator conflict (including a reliable assessment of caracal density) has not been quantified. This study used camera trapping to estimate the density of caracals (a nonindividually recognisable species) in the Winterberg and a structured questionnaire to gauge the general attitudes of the farmers of the region. Caracal density was estimated to be 0.20 caracals/km². This estimate equates to a population of approximately 54 caracals across the entire district. Therefore, caracals do not appear to occur at high densities in the Winterberg. However, the survey of the residents of the Winterberg Conservancy revealed that predators were rated as the greatest problem faced by farmers in the area. Although not significant, it also showed that the size of a respondent's property and sheep mortality due to caracals had the greatest probability of affecting attitudes towards predators. The farmers lost less than 10% of their stock to caracal depredation on an annual basis. Therefore, the general perception that predators were the most important factor in stock loss in the area does not appear to be fully supported by my data. The Winterberg is a male-dominated, multigenerational society and it is likely this propagates certain perceptions towards predators which are a reflection of long-held family traditions and beliefs. Such situations can result in reactions which are disproportionate to the actual scale of the problem. However, my study was limited to a sub-set of the landowners in the Winterberg. Thus, more intensive assessments of caracal space use and community attitudes towards predators are recommended.
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Regeneration potential of selected medicinal plants used to treat human and livestock diseases in Limpopo Province of South Africa

Ojelade, Babatube Solomon 16 May 2018 (has links)
MSCAGR ( Plant Production) / Many high valued tree species of medicinal significance in the Limpopo Province, South Africa exhibit seed dormancy, and also contain aromatic oils which inhibit rooting of their stem cuttings. These plant species are under pressure due to human over-exploitation. The main objective of this study was to investigate effects of rooting hormones on the rooting ability that will help in domesticating some of the selected high valued medicinal plants, Elaeodendron transvaalense (bushveld saffron), Brackenridgea zanguebarica (yellow peeling plane), and Warburgia salutaris (pepper-bark tree). Stem cuttings of these plant species were prepared and treated with various concentrations (500, 1000 and 2000 ppm) of IBA, IAA and NAA in different growth media (Natural soil, farm soil and hygromix) at a nursery house. 180 experimental units were sown and arranged in Randomized Complete Block Design (RCBD), each treatment replicated five times and then monitored for a period of three months. Data were only obtained from Brackenridgea zanguebarica as other species dried up two weeks after sprouting. The two variables measured from the experiments were sprouted stems and number of leaves. The data obtained were subjected to analysis of variance and least significant difference (LSD) at 5% probability level was used to compare treatment using STATISTICA software analysis package. The hormone, hormone concentration, growth media and their interactions had effect on sprouted stems and number of leaves produced on Brackenridgea zanguebarica cuttings, with no record of rooting ability. IBA (500 ppm and 1000 ppm) and control (without rooting hormone) showed high significant results with natural soil and farm soil in terms of leaf production compared to the hygromix, which is significantly lower from others. IBA at the various concentrations (500, 1000 and 2000 ppm) and the control gave the highest percentage sprouted stem on both natural soil and farm soil as compared with other hormones at the same / NRF
490

Impacts of landscape restoration on the environment and farmers' livelihood in Hita-Borkena watershed, northeastern Ethiopia

Alemayehu Assefa Ayele 10 1900 (has links)
Land degradation has been a global agenda. It has been affecting both developed and developing nations (including Ethiopia). The overall objective of the study was to assess the impact of landscape restoration (including area closure) on the environment and farmers‘ livelihood in Hita-Borkena watershed, northeastern Ethiopia. Three Landsat images (1986, 2001 and 2015) were used to detect land cover dynamics. Laboratory analysis of selected soil physico-chemical properties were made to compare the soil properties of closed/restored and open grazing areas. Household questionnaire was administered to investigate environmental problems before and after landscape restoration, the role of area closure and different conservation measures, and the impact of the restoration on farmers‘ livelihood. A total of 255 household heads were selected randomly for the questionnaire survey. This survey was also substantiated by interviewing agricultural experts, observation and reviewing reports prepared by Kalu District Agriculture Office. Both descriptive and inferential statistics were employed to analyze quantitative data. Besides, qualitative approach was implemented in order to analyze qualitative data. The study found out that forestlands and shrublands shrunk through 1986 – 2015, grasslands expanded mainly due to the implementation of area closure under MERET project since 2001. The study revealed that better organic matter, total nitrogen, clay and silt contents, CEC and total porosity were recorded under area closure than under open grazing land. However, both available P and K were found minimum under the former land use type. This may be due to the reason that such nutrients exist more in unavailable form or it may be because of the fact that large amount of those nutrients are extracted by the restored vegetation. The study showed that rates of soil erosion, overgrazing and illegal cutting of trees were relatively higher before landscape restoration. The respondents also appreciated the positive role of land restoration in improving the fertility of the soils of the study watershed and then the positive impact to their livelihood. Based on the results of the study, it is recommended that similar restoration activities shall be implemented in similar environments in Ethiopia to improve both the environment and farmers‘ livelihood / Geography / Ph. D. (Geography)

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