Os incêndios estão entre as principais causas da perda de diversidade em florestas tropicais e aparentemente seus impactos são ainda mais intensos em áreas de floresta sob efeito de borda. Com o objetivo de quantificar os danos causados pelo fogo sobre o ecossistema e verificar se a dimensão dos danos e a resiliência do ecossistema estão correlacionados com a distância da borda, foram analisados o banco de sementes e a comunidade vegetal em um trecho de floresta estacional semidecidual, na estação ecológica dos Caetetus, Gália, SP. A área experimental compreende dois setores: a floresta queimada, alvo de incêndio acidental e a floresta não queimada adjacente, utilizada como controle. Cada setor foi subdividido em duas faixas de distância da borda da floresta: 0-20 m e 20-50 m. Para o estudo do banco de sementes foram coletadas amostras nas quatro situações de amostragem, cinco dias após o fogo. Para avaliação dos impactos do incêndio sobre a comunidade vegetal e monitoramento da regeneração dos estratos arbóreo e regenerante na área queimada, foram amostrados cinco transectos de 10 x 50 m sentido borda - interior, avaliados aos seis, 15 e 24 meses após a passagem do fogo. O mesmo desenho amostral foi utilizado na área não queimada, em um único levantamento. Visando verificar se a eliminação de gramíneas invasoras e lianas facilitaria a regeneração da comunidade arbórea, foram instalados cinco transectos adicionais de 10 x 20 m, perpendiculares à borda, nos quais foram efetuadas quatro operações de retirada de lianas e capins, em um período de 24 meses. No banco de sementes, tanto a densidade quanto o número de espécies foram consideravelmente inferiores na área queimada (97 sementes.m-2, de 26 espécies) em comparação com a área não queimada (257 sementes.m2, de 40 espécies). A avaliação dos impactos na estrutura da floresta revelou que o fogo foi mais intenso na faixa mais externa da borda, em que houve perda de 100% da biomassa arbórea, enquanto na faixa mais interna a perda foi de 89%. Em comparação com a floresta não queimada, a comunidade vegetal na área atingida pelo fogo apresentou 43 espécies a menos aos seis meses, diferença que diminuiu para 14 espécies aos 24 meses. A resiliência, analisada com base na recuperação da biomassa arbórea, é maior na faixa mais interna, devido às espécies pioneiras oriundas de sementes que se desenvolvem rapidamente. A rebrota de árvores atingidas pelo fogo também é maior na faixa mais distante da borda e contribuiu significativamente na recuperação da riqueza. O controle de gramíneas e cipós apresentou efeito benéfico exclusivamente para o estrato arbóreo e apenas na faixa de 0-10 m de distância da borda da floresta, proporcionando aumento de área basal, densidade total de plantas e cobertura de copas. Os resultados das operações de manejo indicam que técnicas complementares devem ser aplicadas, visando à facilitação da restauração da floresta após o incêndio. O fogo mostrou-se como elemento de degradação, desde o banco de sementes até o estrato arbóreo. Ainda que a floresta tenha recuperado parte de sua riqueza em dois anos, este processo é lento, caracterizando baixa resiliência, especialmente na faixa mais externa da floresta onde o fogo é ameaça permanente. / Fire is one of the main factors causing biodiversity losses in tropical forests and such losses are reported to be still more intense in forest edges. With the aim of quantifying the damages by fire on the seasonal semideciduous forest, and verifying weather their extension and the ecosystem resilience are correlated to the border distance or not, we analyzed both the seed bank and the plant community after fire in the forest edge of Caetetus ecological station (Gália, São Paulo state, Brazil). The experimental area comprised two sectors: 1) burned area (after an incidental fire in October 2003), and 2) unburned neighboring area (control). Every sector was divided in two strips, according to the distance from the edge: 0-20 m and 20-50 m. The soil seed bank was surveyed in the four situations described, five days after fire. Plant community structure and regeneration were assessed in five permanent transections (10 x 50 m), instaled from the edge to the interior, where plant individuals were measured and identified, at six, 15, 18 and 24 months after fire. The same design was repeated once in the unburned area, for comparison. Additionally, with the aim of verifying the hypothesis that arboreal community regeneration after fire could be improved by controlling lianas and invasive grasses, five managed transections (10 x 20 m each) were installed, perpendicular to the edge, where grasses and lianas were eliminated four times within a 24 months period. Fire effects on the ecosystem were remarkable. Richness and density of the seed bank after fire (97 seeds.m-2, 26 species) were considerably lower than in the neighboring unburned forest (257 seeds.m-2, 40 species), the difference being still larger close to the edge (0-20 m). Forest structure was totally changed, 100% of the arboreal biomass lost in the external strip (0-20 m) and 89% lost in the internal strip (20-50 m). Six months after fire the burned area had 43 species, less than the unburned forest. Richness has been slowly recovered and, 24 months after fire, that difference had decreased to 14 species. Resilience, analyzed in terms of biomass recovery, is higher in the internal strip (20-50 m from the edge), where pioneer species quickly regenerate from seeds. Sprouting, which has also been more effective in the internal strip, has equally contributed to the richness recovery. Eliminating grasses and lianas favored only arboreal species in the external strip (0-10 m) where their density, basal area and crown cover were slightly higher than in the unmanaged plots. We consider that this technique, alone, can not be recommended to improve the forest restoration after fire. Fire was, though, a very strong degrading agent in the studied forest, almost completely destroying the arboreal biomass, besides the remarkable reduction in species richness in the seed bank and in the arboreal layer as well. Even though the forest richness and biodiversity have been recovered, that has been a very slow process (low resilience) specially close to the forest edge, where fire is a permanent threat.

Forest Park, a 5,000 acre heavily-forested park within the city limits of Portland, Oregon was selected as the study area for performing a fire simulation analysis. A well-documented fire swept over a large area of the park in 1951, and provides both direct inputs, including the ignition point, and context for the present day fire simulations. The goal of the research was two fold. First, determine the difference between small area simulations using standard and custom surface fuel models. Second, determine if fire simulation can be an effective tool in assessing fire danger and behavior in a wildland-urban interface environment like Forest Park.

A comparison of the soil fertility and relationships between soil fertility and early regenerating vegetation were examined following clearcut harvesting and wildfire in the black spruce-feathermoss zone of west-central Quebec. During the summer of 1997, sampling was conducted in wildfires burnt 2, 14, and 21 years ago, stands clearcut within +/-3 years of each fire, and undisturbed control stands. At each site an estimation of vegetative cover of each species present and a volumetric sample of the forest floor (FH), and mineral soil (0--10 cm) were collected from at least 8 fire and cut sites and at least 4 control sites in each study area. The comparison between the soil fertility of stands clearcut and burnt suggested that important differences exist following these two disturbance types in the boreal forest. The forest floor of clearcut sites had greater dry mass, mass of total nutrients and mineralized N than fire or control sites, whereas fire sites generally had higher pH and concentrations of total nutrients than clearcut or control sites. Partitioning of the variance of the vegetation data between soil fertility and general site characteristic variables was carried out to evaluate the direct influence of post-disturbance soil fertility on the composition of regenerating vegetation. All explanatory variables accounted for 53.6% of the variance, of which 23.2% was exclusively attributed to soil fertility variables. Disturbance severity is suggested as an important factor, directly affecting the initial composition of the regenerating vegetation, and indirectly affecting soil fertility and stand productivity in the later stages of regeneration.

This study was undertaken to determine the effect of vegetation structure (the ratio of re-seeding to re-sprouting plants) on post-fire catchment water yield. Plant communities are the only components of mountain catchments which can be manipulated to augment water supplies on any practical scale. Burning, which is one of the options available to catchment managers, reduces plant biomass and increases water yield by reducing transpiration and interception losses. Communities dominated by re-seeding species tend to recover more slowly after fires than when sprouters predominate. The rate of vegetation recovery will determine the rate at which streamflow returns to pre-fire levels. Sprouters may use more water than seeders in the early post-fire period by virtue of their greater leaf area, which both increases interception and transpiration losses. Leaf area development could be used as a simple determinant of post-fire water yield if transpiration losses per unit leaf area are similar in seedlings and sprouters. In this study, a comparison was made of the transpiration rates of seedlings and sprouters of Protea nitida after a fire in Swartboskloof (Cape Province) in 1987. Plant water potentials were determined (index of the degree of stress) and leaf stomatal conductances were measured. Results indicate that transpiration rates are similar throughout the year except during the short summer drought period when the seedlings have comparatively low transpiration rates (< 1 mmo1 m-2 s-1 compared to 2-3 mmo1 m-2 s-1 of the sprouter), and i immediately after the first winter rains where the seedlings have comparatively high rates (approxi.mately 4 mmol m-2 s-1 compared to 2 mmol m-2s-1.) The 1ow summer rates are thought to be the result of drought stress induced by limited water supply and the shallow root systems of the seedlings. The higher winter rates suggest that the shallow surface roots of the seedlings respond quickly to increased surface moisture. Differences in root structure (Le. shallow seedling roots and well-developed deep sprouter roots) rather than regeneration mode appear to be responsible for the marginal differences observed in transpiration rates. These differences are expected to disappear as seedling roots develop and occupy the profile. Leaf area could therefore, be used as a determinant of catchment water yield. / Thesis (M.Sc.)-University of Natal, 1990

Forest fires are an increasing concern under climate change. Substantially increased fire vulnerability could become a reality for many areas, including the Rocky Mountains. Forest fire hazard was examined in the upper North Saskatchewan and St. Mary watersheds for the period of 1960 to 2100. Ensemble climate scenarios were chosen to represent a wide range of possible future climates. The GENGRID meteorological model and the Canadian Forest Fire Weather index System were combined to assess possible changes in forest fire hazard in the Rocky Mountains. A wind model was developed to estimate daily wind speed variation with elevation. It was found that under most climate scenarios, fire hazard is predicted to increase. If future temperatures are warm, as expected, it could offset future precipitation increases, resulting in greater severity of fire weather and an in increase the number of days per year with high fire hazard. / xiii, 130 leaves ; 29 cm

Air pollution has changed from an urban environmental problem to a phenomenon spreading to state, country and even global scales. In response, a variety of regulations, standards, and policies have been enacted world-wide. Policy-making and development of efficient and effective control strategies requires understanding of air quality impacts from different sources, which are usually estimated using source-oriented air quality models and their corresponding uncertainties should be addressed. This thesis evaluates emission uncertainties and their impacts on air quality modeling (Models-3/Community Multiscale Air Quality Model (CMAQ)), with special attention to biomass burning. Impacts of uncertainties in ozone precursors (mainly NOX and VOC) emissions from different sources and regions on ozone formation and emission control efficiencies are evaluated using Monte Carlo methods. Instead of running CMAQ multiple of times, first and higher order ozone sensitivities calculated by Higher-order Decoupled Direct method in Three Dimensions (CMAQ-HDDM-3D) are employed to propagate emission uncertainties. Biomass burning is one of the major sources for PM2.5. Impacts of uncertainties in biomass burning emissions, including total amount, temporal and spatial characteristics, and speciation on air quality modeling are investigated to identify emission shortcomings. They are followed by estimation of seasonal PM2.5 source contributions over the southeastern US focusing on Georgia. Results show that prescribed forest fires are the largest individual biomass burning source. Forest fire emissions under different forest management practices and ensuing air quality impacts are further studied. Forest management practices considered here include different burning seasons, fire-return intervals (FRIs), and controlling emissions during smoldering. Finally, uncertainties in prescribed forest fire emissions are quantified by propagation of uncertainties in burned area, fuel consumption and emission factors, which are required inputs for emissions estimation and quantified by various fire behavior models and methods. In summary, this thesis has provided important insights regarding emission uncertainties and their impacts on air quality modeling.

Radio propagation in the presence of fire is known to be problematic to communications. In this thesis we use both experimental and theoretical approaches to examine and understand radio propagation in fire environments. Propagation is examined for three small scale fires with broadband equipment operating from 50MHz to 1GHz. Results for line of sight propagation show a strong interaction of fire with electromagnetic propagation. The next section develops electromagnetic modelling of the fire environment. A model of the combustion induced plasma is developed, as well as a refractive index model of the surrounding atmosphere of a fire. Simple propagation calculations are undertaken, using the developed fire models, to provide an intial understanding of propagation in fire environments. The next portion of the thesis considers propagation using a more rigorous electromagnetic simulation technique. A modified Finite Difference Time Domain method is presented and is utilised to examine three dimensional propagation in the small scale fire experiments. The outcome is a more solid understanding of propagation and the contributing factors. The last portion of the thesis is the application of the above electromagnetic modelling and simulation methods to bushfire scenarios. Various scenarios that are problematic to radio communication are examined. Discussion and recommendations are made concerning radio communication frequency selection and considerations for propagation in fire environments. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1457560 / Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2009

Radio propagation in the presence of fire is known to be problematic to communications. In this thesis we use both experimental and theoretical approaches to examine and understand radio propagation in fire environments. Propagation is examined for three small scale fires with broadband equipment operating from 50MHz to 1GHz. Results for line of sight propagation show a strong interaction of fire with electromagnetic propagation. The next section develops electromagnetic modelling of the fire environment. A model of the combustion induced plasma is developed, as well as a refractive index model of the surrounding atmosphere of a fire. Simple propagation calculations are undertaken, using the developed fire models, to provide an intial understanding of propagation in fire environments. The next portion of the thesis considers propagation using a more rigorous electromagnetic simulation technique. A modified Finite Difference Time Domain method is presented and is utilised to examine three dimensional propagation in the small scale fire experiments. The outcome is a more solid understanding of propagation and the contributing factors. The last portion of the thesis is the application of the above electromagnetic modelling and simulation methods to bushfire scenarios. Various scenarios that are problematic to radio communication are examined. Discussion and recommendations are made concerning radio communication frequency selection and considerations for propagation in fire environments. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1457560 / Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2009

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.

Thesis (M.S.)--Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.