Water provision is an important tool in the management of savanna ecosystems. Artificial water sources are a potential focus for degradation (biodiversity and loss of ecosystem resilience at a range of spatio-temporal scales), because they alter plant-animal interactions and soil function and stability, through the creation of piospheres. This study was undertaken as part of a drive by the Kruger National Park (KNP) to enable managers to integrate artificial waterhole management (e.g. waterhole closure or rotation) when setting goals for heterogeneity and biodiversity conservation in the park. The over-arching goal was to quantify the relationship between water provision and different attributes of heterogeneity, as part of a broader initiative to place water provision and piospheres within an ecosystem threshold framework. Herbivore utilisation gradients (piospheres) around artificial waterholes in the KNP, described in 1990, were resurveyed in 2006-2007, against a backdrop of waterhole closure in the KNP, to contribute to an understanding of the factors governing recovery and resilience in grazing systems. The responses of the plant community and soil parameters to a relaxation of herbivore utilisation pressure around closed waterholes (recovering piospheres) were examined, as were changes in the same parameters at sites that have remained open (active piospheres). These ecosystem properties were considered in relation to structural and functional ecosystem thresholds, and the piospheres surveyed incorporated a range of rainfall and edaphic gradients in the KNP. Herbaceous basal cover and soil infiltration capacity both increased significantly between 1990 and 2006/7, regardless of waterhole status. This was linked to higher rainfall in 2006/7, compared to 1990. The only vegetation variables to respond consistently to distance from water were the remote-sensed Normalized Difference Vegetation Index (NDVI) and herbaceous species composition. NDVI increased with distance from water, and annual grasses and forbs were most abundant close to water. Perennial, disturbance-sensitive climax species increased in abundance further from water. Soil analyses (N, P, pH, organic matter, and texture) and field measurements (infiltration, compaction) revealed no systematic piosphere patterns. Waterhole closure did not result in soil or vegetation recovery, but piosphere intermittency and the increases of basal cover and infiltration rate indicated that ecosystem resilience has not been compromised vii by long-term artificial water provision in the KNP. This study has shown that the traditional piosphere model is of limited use in sub-humid savanna ecosystems like the KNP during above-average rainfall periods. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

This project predominantly investigated the implications of spatial heterogeneity in the ecological processes of competition and infection. Empirical analysis of spatial heterogeneity was carried out using the lepidopteran species Plodia interpunctella. Using differently viscous food media, it was possible to alter the movement rate of larvae. Soft Foods allow the movement rate of larvae to be high, so that individuals can disperse through the environment and avoid physical encounters with conspecifics. Harder foods lower the movement rate of larvae, restricting the ability of individuals to disperse away from birth sites and avoid conspecifics encounters. Increasing food viscosity and lowering movement rate therefore has the effect of making uniform distributed larval populations more aggregated and patchy. Different spatial structures changed the nature of intraspecific competition, with patchy populations characterised by individuals experiencing lower growth rates and greater mortality because of the reduced food and space available within densely packed aggregations. At the population scale, the increased competition for food individuals experience in aggregations emerges as longer generational cycles and reduced population densities. Aggregating individuals also altered the outcome of interspecific competition between Plodia and Ephestia cautella. In food media that allowed high movement rates, Plodia had a greater survival rate than Ephestia because the larger movement rate of Plodia allowed it to more effectively avoid intraspecific competition. Also the faster growth rate, and so larger size, of Plodia allowed it to dominate interspecific encounters by either predating or interfering with the feeding of Ephestia. In food that restricts movement, the resulting aggregations cause Plodia to experience more intraspecific encounters relative to interspecific, reducing its competitive advantage and levelling the survival of the two species. Spatial structure also affected the dynamics of a Plodia-granulosis virus interaction and the evolution of virus infectivity. Larval aggregation forced transmission to become limited to within host patches, making the overall prevalence of the virus low. However potentially high rates of cannibalism and multiple infections within overcrowded host aggregations caused virus-induced mortality to be high, as indicated by the low host population density when virus is presented. Also aggregated host populations cause the evolution of lower virus infectivity, where less infective virus strains maintain more susceptible hosts within the aggregation and so possess a greater transmission rate. The pattern of variation in resistance of Plodia interpunctella towards its granulosis virus was found using two forms of graphical analysis. There was a bimodal pattern of variation, with most individuals exhibiting either low or high levels of resistance. This pattern was related to a resistance mechanism that is decreasingly costly to host fitness.

Les tortues marines, espèces emblématiques des écosystèmes marins, sont de plus en plus menacées par les effets directs et indirects des activités humaines. Leur cycle de vie est complexe, partagé entre divers habitats, souvent très éloignés les uns des autres. Leur conservation nécessite donc d'identifier les habitats occupés à chaque stade de vie et les routes migratoires empruntées entre ces différents habitats. Si l'écologie spatiale des tortues adultes est relativement bien connue, notamment grâce au suivi par satellite, il n'en va pas de même pour les juvéniles qui se développent plusieurs années en milieu pélagique sans pouvoir être suivis. Dans ce contexte, les simulations numériques constituent un outil adapté pour explorer la dispersion des tortues juvéniles à partir de leurs plages de naissance. Jusqu'à présent il a le plus souvent été supposé dans ces simulations que les juvéniles dérivaient passivement avec les courants marins. Dans ce travail de thèse nous présentons STAMM (Sea Turtle Active Movement Model), un nouveau modèle de dispersion active des tortues juvéniles qui s'attache à dépasser l'hypothèse initiale d'une dérive purement passive. Dans STAMM, les juvéniles simulés se déplacent sous l'influence de la circulation océanique et d'une nage motivée par la recherche d'habitats favorables. Ce modèle est appliqué ici à l'étude de la dispersion des juvéniles de trois populations de tortues marines : les tortues luths (Dermochelys coriacea) du Pacifique Ouest et de l'Atlantique Nord-Ouest puis les tortues caouannes (Caretta caretta) de l'ouest de l'océan Indien. Nos résultats montrent que, même si la circulation océanique détermine, à grande échelle, les zones de dispersion, la prise en compte des mouvements motivés par l'habitat augmente considérablement le réalisme des simulations et impacte profondément la distribution spatiale et temporelle des individus simulés à l'intérieur de leur zone de dispersion. Les mouvements motivés par l'habitat induisent notamment des migrations saisonnières en latitude qui réduisent la mortalité par hypothermie. Ces mouvements induisent également une concentration des individus simulés dans des zones productives (comme les upwellings de bord Est) inaccessibles en dérive passive. Ces résultats questionnent la vision classique des juvéniles circulant passivement autour des gyres océaniques et devraient rapidement être pris en compte pour la mise en place de mesures de conservation ciblées visant les tortues marines juvéniles. / Sea turtles are increasingly threatened by the direct and indirect effects of human activities. Their life cycle is complex, shared between various, and often very distant, habitats. Their conservation therefore requires identifying the habitats occupied at each stage of life and the migration routes between these different habitats. While the spatial ecology of adult turtles is relatively well known, particularly through satellite monitoring, the situation is not the same for juveniles which pelagic development phase remains largely unobserved. In that context, numerical simulation constitutes an appropriate tool to explore the dispersal of juvenile sea turtles from their natal beaches. Until now, simulations were mostly performed under the assumption that juveniles disperse passively with oceanic currents. In this PhD thesis we present STAMM (Sea Turtle Active Movement Model), a new model of active dispersal that aims to go beyond the initial hypothesis of passive drift. In STAMM, juvenile sea turtles move under the influence of ocean currents and swimming movements motivated by the search for favorable habitats. This model is applied here to the study of the dispersal of juveniles from three sea turtle populations: leatherback turtles (Dermochelys coriacea) of the Western Pacific and the Northwest Atlantic Oceans, and loggerhead turtles (Caretta caretta) of the Western Indian Ocean. Our results show that, although ocean currents broadly shape juvenile dispersal areas, simulations including habitat-driven movements provide more realistic results than passive drift simulations. Habitat-driven movements prove to deeply structure the spatial and temporal distribution of juveniles. In particular, they induce seasonal latitudinal migrations that reduce cold induce mortality. They also push simulated individuals to concentrate in productive areas that cannot be accessed through pure passive drift. These results challenge the classical view of juveniles circulating passively around oceanic gyres. They should rapidly be taken into account for the implementation of targeted conservation measures concerning juvenile sea turtles.

Very little is known about the spatio-temporal ecology of the rusty-spotted genet, Genetta maculata. With this study I aimed to describe the activity patterns, resting site use and spatial ecology of G. maculata in Telperion Nature Reserve. I particularly looked at the activity profile and the activity period. I wanted to determine the spatial distribution of resting sites, the number of sites used per individual as well as the index of resting site reuse. I also calculated the distance between resting sites on consecutive days and tested for differences between sexes and seasons. I determined the size of home ranges, as well as that of core areas and compared space use between sexes and seasons as well as vegetation types. A total of six males and nine females were trapped, radio-collared and tracked during continuous night and daytime sessions between September 2015 and August 2016. Rusty-spotted genets were primarily nocturnal (nocturnality index: 0.84) and therefore made use of the darkness for cover when hunting. Overall, male effective activity duration (586 ± 172 min) was greater than for females (564 ± 175 min) possibly because they search for females to mate with as well as due to their larger body size. Seasonal changes in activity were evident – specifically in winter – and were probably a function of both food availability and temperature. Areas with a denser vegetation structure seemed to be more suitable for rusty-spotted genet resting sites. Neither the number of resting sites nor the reuse rate of these resting sites differed between sexes or seasons. The inter-resting site distance on consecutive days was higher for males (938 ± 848 m) than females (707 ± 661 m). This was possibly caused by males travelling larger distances when searching for females to mate with. The inter-resting site distance was higher during autumn, likely due to the decrease in food availability, which made it necessary for genets to increase their hunting efforts. However, a similar increase in hunting effort was not evident during winter as genets decreased their overall activity, possibly in order to avoid colder temperatures. No sexual or seasonal differences in home range size were found. This was attributed to a well-spread and consistent availability of food sources. Core areas only covered on average 7% of the total individual home range which further supports the hypothesis that food was readily available. Both intra- and intersexual home range overlaps were recorded. This was not unusual for carnivores and due to a combination of reproductive and social actions. Home ranges mainly included bushveld vegetation (78%) rather than grassland as these areas provided better cover and likely more abundant food sources. As this was the first exhaustive study of its kind on this species over a full annual cycle, the information gathered is important for the development of conservation strategies for this species, but also for other Genetta species in the rest of Africa. / College of Agriculture and Environmental Sciences / M. Sc. (Environmental Science)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / A área de vida pode ser definida como o espaço físico necessário para um animal desempenhar as atividades essenciais para sua sobrevivência, desenvolvimento e reprodução. O conhecimento sobre área de vida é essencial para a compreensão dos processos que regem o uso do espaço e a organização social em populações animais. Neste estudo, investigamos aspectos das áreas de vida do lagarto saxícola, endêmico da Caatinga, Tropidurus semitaeniatus, avaliando possíveis variações intersexuais, ontogenéticas e sazonais nos tamanhos das áreas de vida, bem como elementos da organização social da espécie. A área de estudo consistiu em uma área típica de Caatinga stricto sensu, localizada no município de Pentecoste - Ceará. Realizamos coletas em dois afloramentos rochosos, nos quais demarcamos pontos de referência a cada cinco metros. Coletamos os lagartos residentes nestes afloramentos, registrando, para cada indivíduo, o sexo e o tamanho rostro-cloacal (mm), e posteriormente, identificando-o com marcação única. Vistoriamos cada afloramento durante 20 dias em cada estação (chuvosa e seca), respectivamente em junho e dezembro de 2011, realizando recapturas visuais e coletando registros de posições espaciais de cada indivíduo. Estimamos as áreas de vida pelo método do Polígono Convexo Mínimo, para os indivíduos recapturados pelo menos seis vezes. Obtivemos 56 áreas de vida, das quais 10 foram de machos, 20 de fêmeas e 26 de jovens. Não existiu relação entre os tamanhos das áreas de vida e os comprimentos rostro-cloacais dos indivíduos. Não houve diferenças sexuais, ontogenéticas ou sazonais nos tamanhos das áreas de vida. Contudo, o espaçamento entre as áreas de vida foi menor durante a estação chuvosa e a maioria das sobreposições entre áreas de vida também ocorreu neste período. Ao todo, registramos 81 sobreposições de áreas de vida, sendo estas mais frequentes entre fêmeas e jovens e menos frequentes entre pares de machos. A proporção da área de vida total sobreposta com outro indivíduo foi maior entre pares de fêmeas e menor entre pares de machos. Os machos estiveram associados em média com 1,5 fêmeas, possuindo de zero a sete áreas de vida de fêmeas sobrepostas com suas áreas de vida. O número de áreas de vida de fêmeas sobrepostas às áreas de vida de machos esteve positivamente associado ao tamanho dos machos. Por outro lado, não houve associação entre o número de áreas de vida de fêmeas sobrepostas às áreas de vida de machos e os tamanhos das áreas de vida dos machos correspondentes. Em suma, à luz do conhecimento acumulado sobre a história natural do organismo de estudo, acreditamos que sua extrema especificidade por ambientes rochosos e a disponibilidade limitada de habitats adequados à ocupação constituem fatores preponderantes na determinação dos padrões singulares de uso do espaço e organização social em T. semitaeniatus. / The home range may be defined as the physical space required for an animal to perform the essential activities for its survival, development and reproduction. The knowledge on home range is essential to understanding the processes that govern the use of space and the social organization in animal populations. Herein, we investigated home range aspects of the saxicolous lizard, endemic from Caatinga, Tropidurus semitaeniatus, evaluating possible intersexual, ontogenetic and seasonal variations in home range size, as well as elements of the social organization of the species. The study area was a typical Caatinga stricto sensu area, located in Pentecoste municipality - Ceará. We performed sampling at two rocky outcrops, where we defined reference marks each five meters. We collect the lizards living in these outcrops, recording for each individual, the sex and snout-vent length (mm), and subsequently, identifying it with unique marking code. We scanned each outcrop for 20 days in each season (rainy and dry), respectively on June and December 2011, performing visual recaptures and collecting records of spatial positions of each individual. We estimated the home range size by Minimum Polygon Convex method, for individuals recaptured at least six times. We obtained 56 home range areas, of which 10 males, 20 females and 26 juveniles. There was no relationship between home range size and snout-vent length of individuals. There were no sexual, ontogenetic or seasonal differences in home range size. However, the spacing between home range areas was lowest during the rainy season and the most of the home range overlaps also occurred in this period. Overall, we recorded 81 home range overlaps, which were more frequent between females and juveniles and less frequent among pairs of males. The proportion of the total home range overlapped with another individual was highest among pairs of females and lowest among pairs of males. Males were associated on average with 1.5 females, having from zero to seven females home range overlapped with their own home ranges. The number of female home ranges overlapped with male ones was positively associated with the body size of males. Moreover, there was no association between the number of female home ranges overlapped with male ones and the home range size of the corresponding males. In conclusion, in the light of accumulated knowledge about the natural history of the studied organism, we believe that their extreme specificity to the rocky environments and restricted availability of suitable habitats for its occupation are important factors in determining patterns of use of space and social organization in T. semitaeniatus

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / A área de vida pode ser definida como o espaço físico necessário para um animal desempenhar as atividades essenciais para sua sobrevivência, desenvolvimento e reprodução. O conhecimento sobre área de vida é essencial para a compreensão dos processos que regem o uso do espaço e a organização social em populações animais. Neste estudo, investigamos aspectos das áreas de vida do lagarto saxícola, endêmico da Caatinga, Tropidurus semitaeniatus, avaliando possíveis variações intersexuais, ontogenéticas e sazonais nos tamanhos das áreas de vida, bem como elementos da organização social da espécie. A área de estudo consistiu em uma área típica de Caatinga stricto sensu, localizada no município de Pentecoste - Ceará. Realizamos coletas em dois afloramentos rochosos, nos quais demarcamos pontos de referência a cada cinco metros. Coletamos os lagartos residentes nestes afloramentos, registrando, para cada indivíduo, o sexo e o tamanho rostro-cloacal (mm), e posteriormente, identificando-o com marcação única. Vistoriamos cada afloramento durante 20 dias em cada estação (chuvosa e seca), respectivamente em junho e dezembro de 2011, realizando recapturas visuais e coletando registros de posições espaciais de cada indivíduo. Estimamos as áreas de vida pelo método do Polígono Convexo Mínimo, para os indivíduos recapturados pelo menos seis vezes. Obtivemos 56 áreas de vida, das quais 10 foram de machos, 20 de fêmeas e 26 de jovens. Não existiu relação entre os tamanhos das áreas de vida e os comprimentos rostro-cloacais dos indivíduos. Não houve diferenças sexuais, ontogenéticas ou sazonais nos tamanhos das áreas de vida. Contudo, o espaçamento entre as áreas de vida foi menor durante a estação chuvosa e a maioria das sobreposições entre áreas de vida também ocorreu neste período. Ao todo, registramos 81 sobreposições de áreas de vida, sendo estas mais frequentes entre fêmeas e jovens e menos frequentes entre pares de machos. A proporção da área de vida total sobreposta com outro indivíduo foi maior entre pares de fêmeas e menor entre pares de machos. Os machos estiveram associados em média com 1,5 fêmeas, possuindo de zero a sete áreas de vida de fêmeas sobrepostas com suas áreas de vida. O número de áreas de vida de fêmeas sobrepostas às áreas de vida de machos esteve positivamente associado ao tamanho dos machos. Por outro lado, não houve associação entre o número de áreas de vida de fêmeas sobrepostas às áreas de vida de machos e os tamanhos das áreas de vida dos machos correspondentes. Em suma, à luz do conhecimento acumulado sobre a história natural do organismo de estudo, acreditamos que sua extrema especificidade por ambientes rochosos e a disponibilidade limitada de habitats adequados à ocupação constituem fatores preponderantes na determinação dos padrões singulares de uso do espaço e organização social em T. semitaeniatus. / The home range may be defined as the physical space required for an animal to perform the essential activities for its survival, development and reproduction. The knowledge on home range is essential to understanding the processes that govern the use of space and the social organization in animal populations. Herein, we investigated home range aspects of the saxicolous lizard, endemic from Caatinga, Tropidurus semitaeniatus, evaluating possible intersexual, ontogenetic and seasonal variations in home range size, as well as elements of the social organization of the species. The study area was a typical Caatinga stricto sensu area, located in Pentecoste municipality - Ceará. We performed sampling at two rocky outcrops, where we defined reference marks each five meters. We collect the lizards living in these outcrops, recording for each individual, the sex and snout-vent length (mm), and subsequently, identifying it with unique marking code. We scanned each outcrop for 20 days in each season (rainy and dry), respectively on June and December 2011, performing visual recaptures and collecting records of spatial positions of each individual. We estimated the home range size by Minimum Polygon Convex method, for individuals recaptured at least six times. We obtained 56 home range areas, of which 10 males, 20 females and 26 juveniles. There was no relationship between home range size and snout-vent length of individuals. There were no sexual, ontogenetic or seasonal differences in home range size. However, the spacing between home range areas was lowest during the rainy season and the most of the home range overlaps also occurred in this period. Overall, we recorded 81 home range overlaps, which were more frequent between females and juveniles and less frequent among pairs of males. The proportion of the total home range overlapped with another individual was highest among pairs of females and lowest among pairs of males. Males were associated on average with 1.5 females, having from zero to seven females home range overlapped with their own home ranges. The number of female home ranges overlapped with male ones was positively associated with the body size of males. Moreover, there was no association between the number of female home ranges overlapped with male ones and the home range size of the corresponding males. In conclusion, in the light of accumulated knowledge about the natural history of the studied organism, we believe that their extreme specificity to the rocky environments and restricted availability of suitable habitats for its occupation are important factors in determining patterns of use of space and social organization in T. semitaeniatus

No description available.

No description available.

L'équilibre arbre-herbe dans la savane tropicale est reconnu comme l'une des principales<p>énigmes de l'écologie des plantes. Les origines du difficile équilibre entre ces formes de vie<p>sur des dizaines de millions de kilomètres carrés à l'échelle mondiale sont en partie attribuées<p>aux perturbations fréquentes induites par les feux de végétation dont les effets varient dans<p>l'espace et dans le temps selon les conditions environnementales. Les résultats de recherche<p>dépendent de l’échelle et les conclusions tirées d’études locales sont rarement transposables à<p>d’autres échelles. La question du transfert d'échelle s’avère donc cruciale dans l'étude des<p>effets du feu, et nécessite une approche transdisciplinaire.<p>En raison de la variété des échelles couvertes, cette étude constitue une première dans la<p>confrontation de données sur l’historique des feux dérivé de l'imagerie satellitaire à des<p>données de terrain incluant des mesures détaillées sur la structure et la composition de<p>végétation, ainsi que des propriétés édaphiques et topographiques. Elle s’est focalisée sur la<p>composante ligneuse de par son caractère pérenne et son influence sur les processus<p>écologiques majeurs. Sur une zone de plus de 2000 km², le Parc National du W du Niger<p>(PNWN), où le feu est utilisé comme outil pour la gestion et la conservation des écosystèmes<p>semi-arides, une carte de l'historique des feux a été élaborée à partir d'images MODIS de 250<p>m de résolution spatiale et de résolution temporelle journalière couvrant une période de sept<p>années (2002-2009). Pour comprendre la variabilité, à la fois dans l'espace et le temps, de la<p>propagation du feu dans la végétation, nous avons étudié les caractéristiques de distribution<p>des feux en termes de régime du feu (i.e. période d'occurrence et fréquence) et de structure<p>spatiale (métriques paysagères). Les relations causales plausibles entre les régimes du feu, les<p>conditions édaphiques et topographiques à l'échelle régionale comme locale, et les<p>caractéristiques de la végétation ligneuse (composition et structure) ont été examinées à<p>travers des analyses multivariées et des modèles d'équations structurales. Nous avons aussi<p>examiné plus en détails les stratégies adaptatives mises en oeuvre par les ligneux, et les<p>interactions biologiques qui sous-tendent l'organisation spatiale des ligneux à travers une<p>approche des processus ponctuels.<p>Les résultats montrent que l'activité du feu dans le PNWN se caractérise par une hétérogénéité<p>spatio-temporelle induite principalement par les conditions édapho-topographiques via la<p>structure de la végétation ligneuse. Les feux précoces de gestion créent des pare-feux<p>efficaces, limitant une large extension des feux de saison tardifs. Cependant, ces feux tardifs<p>pourraient ne pas être aussi destructifs comme qu’on le suppose généralement. En effet,<p>l'adaptation des espèces aux différents régimes defeu correspond à des stratégies de croissance<p>contrastées. Dans le cas des feux tardifs, les surfaces terrières et hauteurs moyennes les plus<p>fortes sont rencontrées, permettant aux arbres de résister au feu. Quant aux zones non<p>affectées par les feux l'analyse "patron-processus" désigne clairement la facilitation entre<p>ligneux comme un processus fondamental de l'organisation spatiale périodique du couvert, une<p>structure émergente qui empêche le passage du feu. Bien qu’ils ne se substituent pas aux<p>études expérimentales, ces résultats basés sur une expérimentation naturelle à large échelle<p>apportent des informations nouvelles précieuses tant au niveau fondamental que pour la mise<p>en place d'une gestion raisonnée du PNWN.<p><p><p>The tree-grass equilibrium in tropical savanna is recognized as one of plant ecology's main<p>conundrums. The origins of the difficult balance between these life forms over tens of millions<p>of square kilometers worldwide are in part attributed to the frequent disturbances caused by<p>vegetation fires effects of which vary in space and time depending on local environmental<p>factors. Research results are scale-dependent and findings from local studies are rarely<p>transposable to higher levels of ecosystem organization. The question of scaling (scale<p>transfer) is therefore crucial in the study of fire effects, and requires a multidisciplinary<p>approach.<p>Because of the variety of scales covered, this study is a premiere in the confrontation of<p>satellite-imagery derived fire history data with detailed field data including measurements of<p>vegetation parameters (structure and composition), as well as soil and topographic properties.<p>The study focuses on the woody component, because of its perennial character and its<p>influence on major ecological processes. On an area of more than 2000 km², the W National<p>Park of Niger (WNPN) where fire is used as a tool for the management and conservation of<p>semi-arid ecosystems, a fire history map was elaborated from MODIS images with a 250 m<p>spatial resolution and a daily temporal resolution over a period of seven years (2002-2009). To<p>understand the variability, both in space and time, of fire propagation in vegetation, we studied<p>the fire distribution characteristics in terms of fire regime (i.e. timing and frequency) and<p>spatial structure (landscape metrics). Plausible causal relationships at regional and local scales<p>between fire regimes, edaphic and topographic conditions, and the woody vegetation<p>(composition and structure) characteristics were examined through multivariate analyses and<p>structural equations models. We also examined in detail the woody species adaptive strategies<p>as well biological interactions, which underlie their spatial organization, using point statistics.<p>Results show that the WNPN fire's activity is characterized by spatial and temporal<p>heterogeneity induced mainly by edaphic and topographic conditions via the structure of the<p>ligneous component. Prescribed early season fires create effective firewalls, limiting wide late<p>season fires. However, these late fires might not be as destructive as is commonly assumed.<p>Indeed, species adaptation to different fire regimes corresponds to contrasting growth<p>strategies. In the case of late fires, increased basal areas and mean tree heights were<p>encountered, enabling trees to resist fire and escape flames. As for the unburned areas, the<p>"pattern-process" analysis clearly indicates that facilitation between shrubs is a fundamental<p>process determining the woody cover periodic spatial organization, an emergent structure that<p>prevents fire spread.<p>Although they do not replace experimental studies, these results based on a large-scale natural<p>experiment provide valuable new information both on a fundamental level and for setting up<p>the rational management of the WNPN. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

<p>Effective conservation strategies for sea turtles require knowledge of animal movements and protection of biologically important habitats and life history stages. For breeding adult sea turtles, understanding both their inshore and pelagic spatial patterns is imperative to the successful protection of the species and the accurate identification of their vulnerabilities. This study provides insight into the inter-nesting, post-nesting, and foraging movements of green sea turtles (<i>Chelonia mydas</i>) that nest on Bioko Island, Equatorial Guinea, by using satellite telemetry to track green turtles (n=12) during two nesting seasons (2017-18, 2018-19), and as they migrated to foraging grounds after the nesting season. These tracks were fit with a switching state space model to characterize movements, and then analyzed in relation to environmental and anthropogenic factors. Dive depth data was also used to determine utilization patterns within the water column. The 12 tagged turtles migrated for an average of 1064 km to two distinct foraging grounds, with 10 migrating west for an average of 1115 km to the coastal waters of Ghana, and 2 migrating south for an average of 1563 km to the coastal waters of Angola. Migrating turtles used both direct, pelagic migration strategies, and biphasal, coastal strategies, which included intermittent foraging throughout migrations. Dive depths varied depending on behavior, with an average of 19.3 m during inter-nesting, 12.6 m during migration and 8.5 m during foraging. Knowledge of inter-nesting habitat use, migration patterns, and foraging ground locations will be critical for the development of marine conservation management plans in the Gulf of Guinea and aide in sea turtle conservation efforts throughout the area. Additionally, spatial and dive depth data can inform zonal fishing regulators and provide information needed for modifications to fishing practices and gear that is most likely to reduce sea turtle bycatch. These data will provide a more complete understanding of marine areas critical to sea turtle conservation and aide in sustainable economic development in the Gulf of Guinea.</p><br>