Les polyesters insaturés sont des résines thermodurcissables particulièrement appréciées pour leur facilité de mise en œuvre et leur coût modéré. Cependant, comme tous les polymères organiques ils ont une réaction au feu médiocre, ce qui est critique dans un certains nombres de d'applications. L'objectif de cette thèse était d'élaborer de nouvelles formulations de résines ayant un comportement au feu amélioré. La première stratégie développée a été le greffage de monomères phosponés dans la matrice polyester. Des monomères méthacryliques et styrénique ont été synthétisés et utilisés pour remplacer une partie du styrène dans la résine. La stabilité thermique des résines modifiées est diminuée, mais leur comportement au feu est globalement meilleur. Des effets du phosphore en phase gazeuse et en phase condensée ont pu être mis en évidence.Dans une seconde partie, une sélection de particules se distinguant par leur nature, leur taille et leur facteur de forme a été testée. Si l'impact des ces charges est assez limité lorsqu'elles sont utilisées individuellement, des tests calorimétriques ont révélé que certaines combinaisons de particules pouvaient améliorer significativement la réaction au feu des résines. Enfin, des associations d'additifs phosphorés et de particules submicroniques ont été investiguées. Le polyphosphate d'ammonium se distingue des autres additifs par un impact très important sur le comportement au feu et particulièrement par le charbonnement important qu'il engendre, cependant sa combinaison avec des charges inorganiques ne s'est pas révélée probante. / Unsaturated polyesters are thermoset resins particularly appreciated for their low cost and easy processing. Nevertheless one of their main drawbacks is their poor fire resistance. The aim of this PhD thesis was to prepare new resin formulations with an improved fire behaviour. The first part of this work was dedicated to the grafting of phosphorous monomers in the polyester matrix. Methacrylic and styrenic monomers were synthesized and used to replace of part of the styrene in the resin. Resin thermal stability was decreased, but on the whole their fire behaviour was improved. Condensed phase and gas phase effects of phosphorus were highlighted.In a second part, a screening of various kinds of particles with different sizes was performed. Calorimetric tests revealed that, while the effect of these particles used alone is limited, a decrease of resin flammability could be achieved with specific combinations. Finally, commercial phosphorous additives were associated with submicronic fillers. From all the additives tested, ammonium polyphosphate stands out, with a powerful impact on the resin fire reaction and especially a much increased charring. However, its combination with inorganic particles was not conclusive.

Wildfires are a natural process critical to the health of forests around the world. However, recent decades have witnessed unprecedented wildfire seasons in many forested regions, leading to a range of unprecedented socio-economic, environmental, and human health impacts. Mitigating these impacts relies in part on fire behaviour prediction systems, which provide information to assist operational wildfire managers with addressing wildfire risk and prioritizing wildfire fighting efforts. A key aspect of fire behaviour prediction systems are rate of spread models that rely on observational and experimental fire behaviour data from naturally occurring wildfires and prescribed burns, respectively. Given the challenge with observing and measuring wildfires in situ, rate of spread models typically rely on a small set of data inputs that are not always representative of the range of wildfires occurring in certain forest types. Furthermore, existing fire behaviour models often lack empirical data on forests that have more recently experienced significant compositional shifts due to climate change or various ecological or anthropogenic disturbances. To address these shortcomings, the objective of this thesis is to establish a method of acquiring empirical fire behaviour data to enhance fire behaviour prediction science through two distinct studies. The first evaluates the utility of monophotogrammetry to extract fire behaviour data from oblique aerial wildfire photographs. The results demonstrate how this approach can provide new and accurate fire spread observations to inform fire behaviour prediction or other aspects of wildland fire science where databases of such wildfire photos exist. The second study is an empirical wildfire spread analysis in forest stands affected by mountain pine beetle (MPB), and utilizes the method of monoplotting to acquire spread rate data from wildfire photographs of grey-attack MPB-affected forest stands. Results from this study further demonstrate the efficacy of the previously established monoplotting technique while providing novel empirical evidence of fire behaviour in grey attack MPB-affected forest stands. Overall, the research results presented in this thesis demonstrate the potential of monophotogrammetry for the acquisition of fire behaviour data and evaluating the results derived from fire behaviour prediction systems in different ecological contexts. This thesis exhibits the potential for this method to expand into other areas of fire behaviour, such as flame or smoke plume dimensions, spotting, and the relationship between fire behaviour and disturbance events such as pest insect outbreaks. / Graduate / 2023-04-14

Fuels management in eucalyptus plantations is essential to minimise the impact of wildfire. Prescribed burning has the potential to reduce the fuel hazard in plantations, but is not routinely conducted due to concerns relating to tree damage. Through a series of experimental burns, the issues of tree damage are addressed and minimum tree sizes are recommended that are capable of withstanding the effects of low to moderate intensity fires. Data was collected between 2005 and 2007 over six sites, two species, and three age classes. Tree response results came from multiple measurements of over 1700 individual trees. The fuel characteristics commonly found in sub-tropical eucalypt plantations from age four to eleven are described and quantified. These fuel characteristics are related to fire behaviour and new fire behaviour models, specific to young eucalypt plantations, are presented. The fuel characteristics that most influence fire behaviour in young eucalypt plantations are fuel load, fuel height, and fuel moisture content. These characteristics can be used to predict the rate of spread of a plantation fire under benign wind conditions. A novel technique for assessing the extent of stem damage in eucalypts is developed and described. This technique enables immediate assessment of stem damage following fire; previous assessment techniques recommend waiting a considerable period of time (up to 2 years) until dead bark dropped off and fire scars were evident. This new assessment technique is likely to be suitable for post-fire assessment of any eucalypt species and will provide forest managers with the capability of deciding whether to leave a stand to ???grow-on??? or commence recovery operations. Minimum stem sizes recommended to ensure no long-term damage are between 5 ??? 8 cm DBH (diameter at breast height, i.e. 1.3m above ground level) for Eucalyptus dunnii (Dunn???s white gum) and 5 ??? 13 cm DBH for Corymbia spp. (spotted gum) depending on the quantity of fuel around the stem. Stem sizes vary between species because of the variation in bark thickness between species. This thesis provides all the necessary information to conduct prescribed burning operations in young eucalypt plantations.

Heathlands typically experience regimes consisting of frequent and intense fires. These fire regimes play important roles in the lifecycles and population dynamics of all species in these communities. Prescribed fire is commonly applied to heathlands to minimise the risk of wildfires as well as to promote biodiversity. Ignitions in heathlands tend to either be unsustainable, or quickly develop into rapidly spreading intense fires. This presents a major problem for the application of prescribed fire and is the primary focus of this thesis. Heathland ignition has been investigated in three sections; litter ignition; vertical development of fire into the shrub layer; and horizontal spread through the shrub layer. These were studied in laboratory experiments using miniature versions of field fuels. Ignition success in litter layers was related to the dead fuel moisture content. Litter type, ignition source, and presence of wind were found to affect the range of ignitable fuel moisture contents of a litter bed. The effect of litter type was best explained by density. Dense litter beds required drier conditions for ignition than low density litter beds. The vertical development of fire into shrubs was mostly dependent on live fuel moisture content, but crown base height, presence of wind, ignition source, shrub height and the percentage of dead elevated fuel were also important. Horizontal spread of fires through shrub layers was most affected by the presence of a litter layer, with nearly all ignitions successful when there was an underlying litter fire. Fire spread would only occur in shrubs without a litter layer when the shrub layer was dense and dry, or had a substantial dead fuel component. Spread was more likely to be sustained when there was wind. Models predicting the moisture content of dead fuels were tested in heathlands, and as would be expected those that can be calibrated for different fuel types were found to have the best performance. Fuel moisture content and fuel load models were reviewed for heathlands, and a number of recommendations for future research were made.

Les forêts sont une ressource naturelle importante sur le plan écologique, culturel et économique, et sont confrontées à des défis croissants en raison des changements climatiques. Ces défis sont difficiles à prédire en raison de la nature complexe des interactions entre le climat et la végétation, dont une le feu. Compte tenu de l’importance des écosystèmes forestiers, des dangers potentiels des feux de forêt et de la complexité de leurs interactions, il est primordial d'acquérir une compréhension de ces systèmes à travers le prisme de la science des systèmes complexes. La science des systèmes complexes et ses techniques de modélisation associées peuvent fournir des informations sur de tels systèmes que les techniques de modélisation traditionnelles ne peuvent pas. Là où les techniques statistiques et basées sur équations cherchent à contourner la dynamique non-linéaire, auto-organisée et émergente des systèmes complexes, les approches de modélisation telles que les automates cellulaires et les modèles à base d'agents (MBA) embrassent cette complexité en cherchant à reproduire les interactions clés de ces systèmes. Bien qu'il existe de nombreux modèles de comportement du feu qui tiennent compte de la complexité, les MBA offrent un terrain d'entente entre les modèles de simulation empiriques et physiques qui peut fournir de nouvelles informations sur le comportement et la simulation du feu. Cette étude vise à améliorer notre compréhension du feu dans le contexte de la science des systèmes complexes en développant un tel MBA de propagation du feu. Le modèle utilise des données de type de carburant, de terrain et de météo pour créer l'environnement des agents. Le modèle est évalué à l'aide d’une étude de cas d'un incendie naturel qui s'est produit en 2001 dans le sud-ouest de l'Alberta, au Canada. Les résultats de cette étude confirment la valeur de la prise en compte de la complexité lors de la simulation d'incendies de forêt et démontrent l'utilité de la modélisation à base d'agents pour une telle tâche. / Forests are an ecologically, culturally, and economically important natural resource that face growing challenges due to climate change. These challenges are difficult to predict due to the complex nature of the interactions between climate and vegetation. Furthermore, fire is intrinsically linked to both climate and vegetation and is, itself, complex. Given the importance of forest ecosystems, the potential dangers of forest fires, and the complexity of their interactions, it is paramount to gain an understanding of these systems through the lens of complex systems science. Complex systems science and its attendant modeling techniques can provide insights on such systems that traditional modelling techniques cannot. Where statistical and equation-based techniques seek to work around the non-linear, self-organized, and emergent dynamics of complex systems, modelling approaches such as Cellular Automata and Agent-Based Models (ABM) embrace this complexity by seeking to reproduce the key interactions of these systems. While there exist numerous models of fire behaviour that account for complexity, ABM offers a middle ground between empirical and physical simulation models that may provide new insights into fire behaviour and simulation. This study seeks to add to our understanding of fire within the context of complex systems science by developing such an ABM of fire spread. The model uses fuel-type, terrain, and weather data to create the agent environment. The model is evaluated with a case study of a natural fire that occurred in 2001 in southwestern Alberta, Canada. Results of this study support the value of considering complexity when simulating forest fires and demonstrate the utility of ABM for such a task.

Fires occur in most forest reserves in Ghana. However, there is a limited understanding of the fires and their behaviour in the different ecological zones. Therefore, this research was to analyze the spatial and temporal distribution of fires, examine the driving factors, direct and underlying causes and impacts of the fires, determine and compare the fuel dynamics to predict fire behaviour and estimate the effects of fire on carbon stocks in different ecological zones of Ghana. The research used different methodologies including questionnaires, fire records, satellite fire data from MODIS (2001 to 2015) (first approach) and field experiment (second approach). A total of 304 respondents was sampled for eight communities, two communities each around the moist and dry semi-deciduous forest, upland evergreen forest and savanna. The spatial distribution of fire showed a trend along the forest boundaries, open vegetation, degraded areas, human settlements, shrubs, farms, rivers and roads. The temporal trend was significant in the dry forest (435 hotspots), followed by the savanna (229 hotspots), moist forest (76 hotspots) and the least in the evergreen forest (5 hotspots). The fires were observed from August, October to May with the dry forest having the longest seasonality. Sunday, Tuesday and Thursday were the peak days of the detected fire hotspots in the dry, moist and savanna respectively. Most of the fires in the different ecological zones peaked from 13 to 14 pm. The results of the research also revealed that the fires were driven primarily by socioeconomic factors which were supported by environmental, type of vegetation and cultural factors. In all the ecological zones, fires were originating from humans. The study pointed out three categories of human-caused fires through activity (farming), non-activity (carelessness or negligence) and others (unknown causes). The major underlying causes of fire mentioned were the inadequate management of the forest and weak compliance and enforcement of forest laws. All these fires have resulted in several impacts in the various ecological zones. Concerning the fuel dynamics, the total downed woody fuel load in the evergreen forest was found to be higher (228 and 208.4 tonnes per hectare). The litter and duff density (112.2 kilogram per cubic meter) in unburned area and loading (6.3 and 13.5 tonnes per hectare) for both burned and unburned area respectively were significantly greater in the moist forest. Also, the dry forest showed 2.4 tonnes per hectare of herbaceous loading in the burned area. However, fires were predicted to be severe in the savanna regarding the surface rate of spread, flame length and fireline intensity, but with low reaction intensity and heat per unit area. The total amount of aboveground tree carbon, aboveground non-tree and belowground root for both burned and the unburned area varied under the different ecological zones. The highest was seen in the moist forest with the emission of 294 tonnes of carbon per hectare accounting for 82% losses. This research has brought out the current situation of fire in the various ecological zones for the implementation of necessary actions for the future.