"This thesis evaluates the effectiveness of BEHAVE: Fire Behavior Prediction and Fuel Modeling System in predicting fire behavior in the Northeastern pine-oak forest. This fuel complex is composed primarily of a litter and huckleberry shrub understory with a pitch pine and oak overstory. Measurements of fuel bed physical characteristics, weather and fire behavior are taken from a series of prescribed burn studies in Cape Cod National Seashore in Massachusetts. Site-specific fuel models are constructed which provide the necessary inputs for fire predictions. Observed spread rates and flame lengths are over-predicted by BEHAVE for burns conducted during the winter (dormant season) and under-predicted for burns conducted during the summer (growing season). Attempts to improve winter predictions are successful when the litter moisture is adjusted in order to account for the live wintergreen which increases the overall moisture content of the surface fuels. A sensitivity study is performed where each input parameter is varied over a reasonable interval in order to view its impact on predictions. The model’s high sensitivity to fuel bed depth and 1-hr surface-area-to-volume ratio appear to be the cause for fire prediction deviations during the winter, while the high live fuel moisture contents appear to overwhelm and suppress fire behavior predictions during the summer. It is concluded to overwhelm and suppress fire behavior predictions during the summer. It is concluded that BEHAVE’s representation of fuel complexes as a homogeneous fuel bed with constant properties does not take into account the unique features of the litter and shrub components. An alternative, simple model of fire spread is developed which treats each component as a separate fuel bed. The model is based on a measurement of the heat release rate which can be determined directly through the principle of oxygen consumption calorimetry. Future work using small- and large- scale testing apparatus will help determine the ignition process of the live shrubs and the effect of parameters such as moisture content on the burning characteristics of the fuels. "

First order fire effects in mixed grass and tallgrass prairies may differ between current and historic fire regimes. To determine potential differences, the thermal dynamics of nine prescribed grassland fires and six experimental fires were evaluated. Fires were instrumented with dataloggers and arrays of up to twelve thermocouples set at heights ranging from -5 cm to 300 cm. Soil moisture and texture were documented, along with fuel characteristics. A series of experimental fires allowed soil moisture to be manipulated while minimizing other variables. Maximum temperature for the prescribed fires was 875°C at 75cm, and for the experimental fires 920°C at 10 cm. In experimental fires, the greatest temperature difference was at the surface with the dry substrate averaging 130°C higher than saturated. Average temperatures at -1 cm differed by 33°C. At 60°C, residence times in dry substrate averaged almost four minutes, while the average for saturated treatment was only 1 second. Surface residence times on dry substrate averaged over 7 minutes, almost 3 times longer than saturated. Soil moisture was shown to influence relative humidity and fine fuel moisture near the ground surface. An increased evaporation of soil water at the surface is suggested by a slight drop in subsurface temperatures as the flaming front moves over the surface. These data suggest that soil moisture affects fire intensity, decreasing temperatures at all levels of a fire. Temperatures and residence times were compared with data from studies documenting temperatures significantly affecting seed germination and edaphic effects at and below the surface. Temperatures increasing the germination of some seeds were found at all heights. Temperatures documented can be expected to decrease organic matter content and aggregate stability at the surface, slightly increasing erodibility. Thermal dynamics from the fires in this study represent a broad range of grassland fires under conditions common for prescribed fire. Soil moisture appears to significantly affect temperatures and residence times below, at, and above the soil surface. Data were compared with output from FOFEM 5.2 to access the applicability of FOFEM for use in mixed grass and tallgrass prairie. FOFEM consistently underestimated soil heating by up to 419°C.

ABSTRACT EFFECTS OF WILDLAND-URBAN INTERFACE FUEL TREATMENTS ON POTENTIAL FIRE BEHAVIOR AND ECOSYSTEM SERVICES IN THE CENTRAL SIERRA NEVADA MOUNTAINS OF CALIFORNIA Christopher C. Hamma For the past several decades, the wildland-urban interface (WUI) has been expanding in the low- to mid-elevation mixed-conifer belt of California’s Sierra Nevada mountain range. Concurrently, the effects of fire exclusion and shifting climatic patterns in this region have led to increases in wildfire size and severity, posing an ever-greater risk to life and property. As a result, the need for implementation of fuel treatments to reduce fire hazard is generally recognized to be urgent. However, by removing vegetation, these treatments may also diminish the ability of forest ecosystems to provide valuable ecosystem services to society. Forest managers, landowners, and other WUI stakeholders would therefore benefit from a better understanding of the effects of various fuel treatment types on both fire hazard reduction and ecosystem benefits. The present study examined the effects of four commonly-used fuel treatment types on stand-level forest structural characteristics, surface and canopy fuel loading, potential fire behavior, air pollution removal, and carbon sequestration and storage. Fuel treatments involving thinning and/or prescribed burning were largely successful at reducing live and dead fuel loading, with corresponding reductions in predicted fire behavior. The little-studied but increasingly popular practice of mastication (chipping or shredding small trees and brush and leaving the debris on the ground) was associated with significantly increased surface fuel loading, although deleterious effects on potential fire behavior were not found. Overall, the findings from the fire and fuels portion of the present research largely match those reported in other, similar studies in Sierra Nevada mixed-conifer forest. However, the current analysis found little in the way of significant treatment effects on stand-level air pollution removal or carbon dynamics. This study was affected by challenges including small sample size and high variability in the data; nonetheless, the results underscore the general validity of fuel treatment implementation in central Sierra Nevada WUI areas for moderating wildfire severity and effects, with the recognition that the efficacy of such treatments may be limited under extreme weather conditions.

Master of Science / Department of Biology / John M. Briggs / Woody encroachment has altered the vegetative structure of grasslands worldwide and represents a potentially irreversible shift in grassland dynamics and biodiversity. Clonal woody species appear to be one of the greatest contributors to the shift from graminoid to woody dominance in the tallgrass prairie. Part of the high success rate of clonal species may be attributed to an ability to circumvent recruitment filters through the integration of environmental heterogeneity and acropetal translocation of resources from mother to daughter ramets. The clonal shrub Cornus drummondii persists in a tension zone of the graminoid-dominated tallgrass prairie, where the dominance structure is primarily maintained through the direct and indirect effects of fire. The competitive displacement of native herbaceous vegetation associated with the establishment and expansion of C. drummondii causes a major alteration in the fuel dynamics responsible for the propagation and sustainment of fire, potentially contributing to biofeedback mechanisms that facilitate shrub expansion. The goal of this research was to quantify fire behavior parameters (temperature, intensity, rate of spread, and heat flux) in relation to C. drummondii invasions and to test physiological integration as a mechanism driving encroachment, using manipulation experiments at the Konza Prairie Biological Station. We observed a significant decrease in fireline intensity associated with the encroachment of C. drummondii, which was amplified by the effects of stem density and shrub island area. This alteration in fire behavior also led to reduced heat flux at stems within shrub islands, reducing the likelihood of tissue necrosis and top-kill. With additional fuel, temperatures and fire intensities were higher, similar to open grasslands. In severing rhizomes, and effectively severing the integration of clonal ramets, we observed a higher risk of mortality of daughter ramets. These rhizome severed ramets were more water stressed, had lower photosynthetic rates, and lower woody and foliar biomass production. These results indicate that C. drummondii significantly alters fire behavior, releasing ramets from the fire trap of successive top-killing, while the integration of intraclonal ramets allows daughter ramets to survive mid-summer drought and increases the likelihood of successful establishment and further clonal reproduction.

La kaolinite est une des matières les plus utilisées depuis la plus haute antiquité. En effet, du fait de leurs propriétés, les argiles sont utilisées comme charges dans beaucoup d'applications industrielles notamment dans le domaine de la papeterie, de la céramique, de l'industrie cimentaire, dans le verre etc. Leur utilisation est liée à leurs bonnes propriétés optiques, minéralogiques et chimiques. L'ajout de kaolinites submicroniques pose cependant de multiples difficultés liées en particulier à leur incompatibilité avec la plupart des polymères et à la difficulté de les exfolier. Dans ce contexte, il est proposé, dans ce travail, une nouvelle voie de valorisation de la kaolinite à la fois comme charge renforçante et/ou compatibilisante et comme retardateur de flamme dans des matrices thermoplastiques.La surface de la kaolinite est tout d'abord traitée avec différents agents de type silane. Ces charges traitées ont été incorporées (entre 4 et 12% en volume dans le polypropylène et le polyamide et jusqu'à 35 % en volume dans le EVA) ce qui a permis à la fois de modifier les propriétés élastiques, les contraintes seuil ainsi que les performances au choc par rapport aux matrices contenant les charges non traitées et d'établir un lien entre ces différentes performances et la dispersion de la charge (estimée par analyse d'images).Due à l'hétérogénéité de la surface de la kaolinite, une nouvelle méthode pour modifier sa surface est proposée. Cette méthode est basée sur la modification sélective des alumines de surface avec des acides phosphoniques. Les silices de surface étant libres pour réagir avec un autre agent de modification, soit un silane porteur d'une fonction époxy, soit une amine. Il a été mis en évidence, dans un mélange PP/PA, que la kaolinite modifiée avec l'acide phosphonique à une tendance à se placer à l'interface des polymères et pourrait alors jouer un rôle de comptabilisation.Finalement, des études sur le comportement au feu des différentes formulations ont permis de montrer que la kaolinite a un grand potentiel en tant que retardateur de flamme. La réduction du pic de débit calorifique (pHRR) semble être en lien étroit avec le comportement rhéologique des polymères chargés et donc très sensible au traitement de surface. / Kaolinite is one of the most used mineral fillers since ancient times. Indeed, because of their properties, this clay is used as filler in many industrial applications, particularly in the industry of paper, cement, ceramics, glass etc... This use is related to their good optical, mineralogical and chemical properties. However the addition of kaolinite in polymer matrices leads to some difficulties especially related to their incompatibility with most polymers. In this context, this work proposes a new path of development of kaolinite as functional filler for the mechanical reinforcement and/or compatibilization of thermoplastic matrices, as well as a flame retardant.The surface of kaolinite was first modified with different silane agents. These fillers were then incorpored between 4 and 12% by volume in polypropylene and polyamide and 35% by volume in EVA copolymer. The surface treatment of kaolinite allowed the modification of the elastic and impact performances of composites compared to untreated fillers. These changes were related to the filler dispersion in the polymer matrix (dispersion was estimated by image analysis). Due to the surface heterogeneity of kaolinite (silica and alumina faces), a new method for a regiolelective surface modification was developed. This method was based on a first step of selective modification of the alumina faces with a product bearing a phosphonic acid group. In a second step, the silica facesare treated with a silane compound. It has been highlighted in a PP/PA blend that the regioselective surface modified kaolinite tend to be placed at the interface between the two polymer matrices.Finally, the study of the fire behavior of different formulations showed a great potential as flame retardant for kaolinite. Reduction of peak heat release rate (pHRR) values seems to be closely related to the rheological behavior of filled polymers and therefore very sensitive to surface treatment.

En dépit de moyens importants consacrés à la lutte, certains feux de forêt, en Europe méditerranéenne, en Australie ou en Amérique du Nord, parcourent de grandes surfaces et développent des comportements violents qui piègent les pompiers. L’étude de rapports internes aux services d’incendie révèle ici les conditions météorologiques et topographiques dans lesquelles se produisent ces feux dangereux. En France, alors que le vent violent est le principal contributeur des feux les plus grands et les plus dangereux, les températures élevées mènent à un autre type d’incendies violents qui se propagent rapidement. En Australie, les pompiers sont souvent piégés par une bascule brutale de la direction du vent mais aussi par des vents forts en terrain accidenté. Au-delà des disparités intercontinentales, la recherche des comportements dynamiques de feu impliqués dans plus de 100 accidents de pompiers à travers le monde amène à distinguer trois types d’incendie. Lors des feux topographiques, en zone de montagne, les accidents sont généralement causés par l’attachement de la flamme sur des pentes supérieures à 20°. Lors des feux guidés par le vent, les zones les plus propices aux accidents sont les pentes déventées où des effets de vortex peuvent se produire. Enfin, lors des feux convectifs, les plus violents, les accidents peuvent se produire loin de toute configuration dangereuse. Pour tenir compte de ces résultats et améliorer leur sécurité, les pompiers doivent adapter leur formation et de développer des compétences d’analyste du feu. Ces experts intègreront les retours d’expérience des incendies passés pour proposer les stratégies de lutte les plus efficaces et sécurisées. / Despite the large expenditure that is dedicated to forest fire suppression in Euro-Mediterranean countries, Australia and North-America, firefighters still face large and severe fire events which eventually entrap them. Investigation of Fire Services’ internal reports addresses here the weather and terrain leading to these dangerous fires. In France, strong wind is the main driver of the largest fires and of the fires that entrap firefighters. However, high temperature is also a key contributor as it influences violent fires with high rates of surface spread. In Australia, a lot of firefighters’ entrapments are due to shifts in wind direction, but others are associated to strong winds in rugged terrain. Whatever the regional specificities, more than 100 firefighters’ entrapments across the world were investigated to find the contribution of dynamic fire behaviors in these entrapments. The results return three different types of fires. During topography-influenced fires, in mountainous area, almost all the entrapments happen on slopes steeper than 20°, prone to flame attachment. During wind-driven fires, leeward slopes prone to vorticity-driven lateral fire spread are the most prominent configurations associated with entrapments. Finally, during convective fires, which are the most violent, entrapments can happen far away from any dangerous configuration. Firefighters should adjust their training courses and promote fire behavior analysts (FBAN) capabilities to benefit from the results of this work and improve their safety. FBAN may consider feedbacks from previous fires to suggest the most efficient and secure firefighting strategies and locations.

Carbon nanotubes (CNTs) have been a major interest of study since 1991. A panel of properties and phenomena associated with carbon nanotubes due to their special combination of dimension, structure and topology have been investigated in the last years. Recently, it appears interesting to use carbon nanotubes at low loading content to obtain materials with enhanced mechanical and thermal properties. One of the major challenges is actually to disperse easily and individually these nanotubes in polymer matrices to obtain materials with increased properties for different application uses. Ethylene-vinyl acetate (EVA) copolymer is commonly used in cable industry. It is required to introduce high contents of alumina trihydrate (ATH) or magnesium dihydroxide (MDH) as fire retardant, to avoid fire hazards and reduce flammability. But this high mineral loading results in a decrease of the mechanical performances of the materials. This work aims at studying the influence of the incorporation of multiwall carbon nanotubes (MWNTs) on the tensile properties and the fire behavior of EVA nanocomposites. This work demonstrates, on one side, the significant effect of the previous nanotube coating by a thin layer of high density polyethylene (HDPE-coating) on the mechanical behavior of the so-obtained nanocomposites and explain, on the other side, the flame retardant efficiency of MWNTs in EVA nanocomposites. An original mechanism related to the action of the MWNTs during the combustion process is proposed and the effect of the HDE-coating on the cohesion of the residues is discussed.

Conceptual and theoretical advancements have been developed in recent years to break down the assumptions and traditional boundaries that establish seemingly independent disciplines, and the research outlined in this dissertation aspires to build on these advancements to provide innovative solutions to a broad array of modern problems in social-ecological. I used a variety of techniques to address challenges ranging from disconnections between theory and application, perceived versus realized roles of prescribed fire in resprouting shrublands, and the need for broader participation in research as part of undergraduate education. The chapters in this dissertation serve as a case-study approach across multiple scientific disciplines that overcome the traditions and assumptions that conflict with our ability to develop innovative solutions to modern social-ecological problems. First, I bridge theoretical and applied concepts by showing how recent theoretical advancements in resilience can be integrated into a predictive framework for environmental managers. Second, experimental data from multiple experiments were collected in two ecological regions of Texas to assess the potential for using extreme fire, in isolation and in combination with herbicide, as a novel intervention approach in resprouting shrublands of the southern Great Plains. The findings from these experiments demonstrate the importance of moving past traditional assumptions of when prescribed fire should be applied to demonstrate new patterns of woody plant responses to the applications of “more extreme” prescribed fires while not causing undesirable invasions by exotic grasses and exotic insects. Finally, I initiated a PhD instructed course on undergraduate research that sought to increase undergraduate participation while lowering the costs of conducting research. This chapter shows how traditional approaches of supporting undergraduate research are incapable of meeting the broader goals established by society and reveal a novel approach that can provide an additional pathway for supporting undergraduate student participation at large, research-based universities. Ultimately, this research suggests that our capacity to enhance services in social-ecological systems ultimately hinges upon the integration of theoretical and applied concepts that drive policy and governance and overcoming the assumptions and traditions that limit their integration.

Studies were conducted to determine the effectiveness of using targeted grazing and prescribed burning as tools to reduce fire hazards and cheatgrass (Bromus tectorum) dominance on rangelands in the northern Great Basin. A field study, with four grazing-burning treatments (graze and no-burn, graze and burn, no-graze and burn, and no-graze and no-burn), was conducted on a B. tectorum-dominated site near McDermitt, Nevada from 2005-2007. Cattle removed 80-90% of standing biomass in grazed plots in May 2005 and 2006 when B. tectorum was in the boot (phenological) stage. Grazed and ungrazed plots were burned in October 2005 and 2006. Targeted grazing in May 2005 reduced B. tectorum biomass and cover, which resulted in reductions in flame length and rate of spread when plots were burned in October 2005. When grazing treatments were repeated on the same plots in May 2006, B. tectorum biomass and cover were reduced to the point that fires did not carry in grazed plots in October 2006. Fuel characteristics of the October 2005 burns were used to parameterize dry climate grass models in BehavePlus 3.0, and simulation modeling indicated that grazing in spring (May) would reduce the potential for catastrophic fires during the peak fire season (July-August). The graze-and-burn treatment was more effective than grazing alone (graze and no-burn treatment) and burning alone (no-graze and burn treatment) in reducing B. tectorum cover, biomass, plant density, and seed density, and in shifting species composition from a community dominated by B. tectorum to one composed of a suite of species [including tumble mustard (Sisymbrium altissimum), clasping pepperweed (Lepidium perfoliatum), and Sandberg bluegrass (Poa secunda)], with B. tectorum as a component rather than a dominant. A simulation study was designed to compare the cost-effectiveness of using cattle grazing and herbicide to create fuel breaks on B. tectorum-dominated landscapes in the northern Great Basin. Fuel characteristics from this targeted grazing study and from a Plateau® (Imazapic) herbicide study near Kuna, Idaho were used to parameterize fire behavior models and simulate flame lengths and rates of spread for the two fuel reduction treatments under peak fire conditions using BEHAVE Plus. Targeted grazing and Plateau® had similar reductions in flame length and rate of spread. Cattle grazing had high fixed costs (primarily fencing), and was more cost-effective than applications of Plateau® under five fuel loading scenarios except for three consecutive years of low fuel loads.

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