Thesis (M.S.)--University of Nevada, Reno, 2008. / "August, 2008." Includes bibliographical references (leaves 23-26). Online version available on the World Wide Web.

The phenomenon of a fire occurring in nature comes with a very high level of complexity. One central obstacle is the range of scales in such fires. In order to understand wildfires, research has to be conducted across these scales in order to study the mechanisms which drive wildfire behavior. The hazard related to such fires is ever more increasing as the living space of communities continues to increase and infringe with the wildland at the wildland-urban interface. In order to do so, a strong understanding on the possible wildfire behavior that may occur is critical. An array of factors impact wildfire behavior, which are generally categorized into three groups: (1) fuel (type, moisture content, loading, structure, continuity); (2) environmental (wind, temperature, relative humidity, precipitation); and (3) topography (slope, aspect). The complexity and coupling of factors impacting various scales of wildfire behavior has been the focus of much experimental and numerical work over the past decades. More recently, the need to quantify wildland fuel flammability and use the knowledge in mitigating risks, for example by categorizing vegetation according to their flammability has been recognized. Fuel flammability is an integral part of understanding wildfire behavior, since it can provide a quantification of the ignition and burning behavior of wildland fuel beds. Determining flammability parameters for vegetative fuels is however not a straight forward task and a rigorous standardized methodology has yet to be established. It is the intent of this work to aid in the path of finding a most suitable methodology to test vegetative fuel flammability. This is achieved by elucidating the fundamental heat and mass transfer mechanisms that drive ignition and burning behavior of porous wildland fuel beds. The work presented herein is a continuation of vegetative fuel flammability research using bench-scale calorimetry (the FM Global Fire Propagation Apparatus). This apparatus allows a high level of control of critical parameters. Experimental studies investigate how varying external heat flux (radiative), ventilation conditions (forced airflow rate, oxygen concentration, and temperature), and moisture content affect the ignition and burning behavior of wildland fuel. Two distinct ignition regimes were observed for radiative heating with forced convection cooling: (1) convection/radiation for low heating rates; and (2) radiation only for high heating rates. The threshold for the given convection conditions was near 45 kW.m-2. For forced convection, ignition behavior is dominated by convection cooling in comparison to dilution; ignition times were constant when the oxygen flow rate was varied (constant flow magnitude). Analysis of a radiative Biot number including heat losses (convection and radiation) indicated that the pine needles tested behaved thermally thin for the given heating rates (up to 60 kW.m-2). A simplified onedimensional, multi-phase heat transfer model for porous media is validated with experimental results (in-depth temperature measurements, critical heat flux and ignition time). The model performance was adequate for two species only, when the convective Froude number is less than 1.0 (only one packing ratio was tested). Increasing air flow rates resulted in higher heat of combustion due to increased pyrolysis rates. In the given experiments (ventilation controlled environment) combustion efficiency decreased with increasing O2 flow rates. Flaming combustion of pine needles in such environments resulted in four times greater CO generation rates compared to post flaming smoldering combustion. A link was made to live fuel flammability that is important for understanding the occurrence of extreme fire conditions such as crowning and to test if live fuel flammability contributes to the occurrence of a typical fire season. Significant seasonal variations were observed for the ignition and burning behavior of conditioned live pine needles. Variation and peak flammability due to ignition time and heat release rate can be associated to the growing season (physical properties and chemical composition of the needles). Seasonal trends were masked when unconditioned needles were tested as the release of water dominated effects. For wet fuel, ignition time increases linearly with fuel moisture content (FMC, R2 = 0.93). The peak heat release rate decreased non-linearly with FMC (R2 = 0.77). It was determined that above a threshold of 60% FMC (d.w.), seasonal variation in the heat release rate can be neglected. A novel live fuel flammability assessment to evaluate the seasonality of ignition and burning behavior is proposed. For the given case (NJ Pine Barrens, USA), the flammability assessment indicated that the live fuel is most flammable in August. Such assessment can provide a framework for a live fuel flammability classification system that is based on rigorous experimentation in well controlled fire environments.

No description available.

Sea-level rise and stronger hurricanes associated with global climate change will likely result in farther reaching storm surges that will greatly affect coastal ecosystems. These surges can transport nutrients, salt water, and sediment to nutrient poor, fresh (i.e. low salinity) pine savannas. Purple pitcher plants (Sarracenia purpurea ) are pine savanna inhabitants that could potentially be at a disadvantage because their pitcher morphology and stout structure may leave them prone to collecting saline water and sediment after a surge. In this study, separate field and greenhouse experiments were conducted to test the effects of storm surge water salinity and sediment type on pine savanna soil characteristics, plant community structure, and pitcher plant vitality. In the field, plots (containing &ge genet of S. purpurea ) were experimentally storm surged with fresh or saline water crossed with one of four sediment types (local, foreign, fertilized foreign, or no sediment). Saline water inundation resulted in significantly higher pitcher plant mortality than the fresh water treatment combinations. However, a subsequent prescribed fire and regional drought affected the study area during the next growing season, resulting in the decline of all the pitcher plants to zero or near zero percent cover. Soil data revealed that the combination of salt water and fertilized sediment resulted in short-term increases in soil-water conductivity and nitrogen availability. Interestingly, there were no significant differences in plant community structure between treatments, suggesting that the community as a whole is not as vulnerable as the pitcher plants to the cumulative effects of multiple stressors (i.e. storm surge, fire, and drought) operating in this system. Indicator species analysis revealed that some species were significant indicators of certain treatments; thus suggesting that pitcher plants are not the only species affected by storm surge. In the greenhouse, pitcher plants received various forms of sediment (i.e. no sediment, sterile sediment, or one of two levels of fertilized sediment) within their pitchers to determine if nutrient uptake is either inhibited or enhanced. Plants that received sterile sediment had higher carbon:nitrogen ratios and higher leaf mass per unit area. Eutrophic sediment deposition resulted in a temporary decrease in relative growth rate as well as changes in pitcher morphology. There were no differences in chlorophyll content and photosynthetic rates between treatments. Both the field and greenhouse experiments indicate that global climate change may indirectly contribute to the further decline of southeastern purple pitcher plant populations in the future.

Wet pine savannas are among the most diverse ecosystems in North America and provide critical habitat for many species but have seen a dramatic decline in size over the past century due to urbanization, logging, and fire suppression. Coastal pine savannas are also vulnerable to anticipated effects of global climate change. Models of climate change predict rapid sea-level rise along the northern Gulf of Mexico and more intense hurricanes. Restoration of these fragile wetland ecosystems is needed, but the effects of climate change on restored, as well as remnant communities, are unknown. This research aimed to compare resiliency of remnant and restored plant communities to simulated hurricane disturbance. I hypothesized that species composition within both site types will be altered following experimental storm surge, and restored plots will follow a different compositional trajectory due to site conditions including invasion by non-target species and disturbed soils. I compared community composition and soil properties between remnant and restored sites experiencing experimental storm surge. Non-metric multidimensional scaling (NMDS) ordinations and a cluster analysis was used to visualize dissimilarities in composition and permutational analysis of similarity (PERMANOVA) was used to compare composition among treatment, site, and time. Repeated measure analysis of variance (ANOVA) was used to compare soil water conductivity and available ammonium over the course of the study. Results from compositional surveys suggested no significant effect of treatment on community composition, but there were significant vectors for soil moisture and ammonium resulting in different compositional trends and an apparent degree of divergence over time between the two site types. Soil characteristics (texture and bulk density) and pressure from neighboring plants within the restored site are also likely contributing to differences between the two site types. As climate change continues to alter disturbance regimes that shape coastal ecosystems, it will be necessary to assess structure and function of remnant and potentially novel plant communities and their capacity for adaptation.

Understanding the burning behaviour of litter fuels is essential before developing a complete understanding of wildfire spread. The challenge of predicting the fire behaviour of such fuels arises from their porous nature and from the strong coupling of the physico-chemical complexities of the fuel with the surrounding environment, which controls the burning dynamics. In this work, a method is presented to accurately understand the processes which control the burning behaviour of a wildland fuel layer using numerical simulations coupled with laboratory experiments. Simulations are undertaken with ForestFireFOAM, a modification of FireFOAM that uses a Large Eddy Simulation solver to represent porous fuel by implementing a multiphase formulation to conservation equations (mass, momentum, and energy). This approach allows the fire- induced behaviour of a porous, reactive and radiative medium to be simulated. Conservation equations are solved in an averaged control volume at a scale su cient to contain both coexisting gas and solid phases, considering strong coupling between the phases. Processes such as drying, pyrolysis, and char combustion are described through temperature-dependent interaction between the solid and gas phases. Di↵erent sub-models for heat transfer, pyrolysis, gas combustion, and smouldering have been implemented and tested to allow better representation of these combustion processes. Numerical simulations are compared with experiments undertaken in a controlled environment using the FM Global Fire Propagation Apparatus. Pine needle beds of varying densities and surface to volume ratios were subject to radiative heat fluxes and flows to interrogate the ignition and combustion behaviour. After including modified descriptions of the heat transfer, degradation, and combustion models, it is shown that key flammability parameters of mass loss rates, heat release rates, gas emissions and temperature fields agree well with experimental observations. Using this approach, we are able to provide the appropriate modifications to represent the burning behaviour of complex wildland fuels in a range of conditions representative of real fires. It is anticipated that this framework will support larger-scale model development and optimisation of fire simulations of wildland fuels.

Drought-induced tree mortality is a phenomenon affecting many forest ecosystems and is predicted to increase under ongoing climate change. Forest stability partly depends on regeneration: the process of renewing mature forest with subsequent generations. As seedlings are more susceptible to drought effects than mature trees, mortality of the seedling bank can represent a major bottleneck controlling forest structure and species composition. Scots Pine (Pinus sylvestris L.) is the most widely distributed of the Pinus species, covering a broad latitudinal gradient of ecological conditions. The thesis aims to deepen understanding of drought-induced mortality, while analysing intra-specific variation in the phenotypic and metabolic profile of Pinus sylvestris seedlings subjected to drought stress. I also consider the relevance of the results to the broader conceptual framework of drought-induced mortality. The experiments utilise seeds from different populations of origin (provenances) across the north-south axis of the European range of Pinus sylvestris, in order to determine the extent of regeneration capacity in this species under drought. Seeds were collected from different populations (provenances) that, along with other climatic and edaphic differences, span a gradient of water availability: from wet (Scotland) to intermediate (Austria, Poland) to dry (Spain). In Chapter 2, the effects of osmotic stress on the initial seedling establishment stage were studied by comparing phenotypic responses across provenances. Seedling germination, early growth, osmotic stress tolerance and survival were investigated using a polyethylene glycol irrigation treatment as a proxy for rapid and severe drought. Treatment, provenance and interaction effects were found for rate of germination, final proportion of seeds germinated, seedling size, and superoxide dismutase activity (an antioxidant enzyme). Root investment was affected by both provenance and time to germination. Although there was no significant effect of provenance on survival, a trend towards increased probability of survival under osmotic stress was indicated for the southernmost (driest) as compared with the northernmost (wettest) provenance. Chapter 3 investigates the responses of older seedlings (at 10 months) to a drying down of soil moisture for 40 days. Morphological and physiological data were collected to assess intra-specific and intra-population variation in the seedling stress response under drought. A metabolomics analysis using Ultra performance Liquid chromatography followed by mass spectrometry (UPLC/MS) was carried out to investigate whether metabolic markers could be identified that are suggestive of heightened oxidative stress and whether populations in different climatic and edaphic environments show variation in metabolic activity under drought. Preliminary results suggest large intra-population variability yet clear differentiation in metabolic responses to drought over the time course of the experiment. Univariate and multivariate analyses indicated that among the most significant increases in response to drought were those involved in osmoprotective and antioxidant capabilities, including the free amino acid proline and a quercetin derivative (a flavonoid). Interestingly, provenances, either under experimental drought or not, did not show significantly different metabolite profiles, even though provenance and its interaction with drought treatment did significantly affect seedling biomass and photochemical efficiency. In Chapter 4 the effects of provenance, maternal parentage and seed weight on germination rate, final germination percentage, as well as seedling drought responses in biomass allocation and the expression of selected antioxidant genes were analysed. Seed weights were measured individually and seed weight was found to have a strong positive effect on: germination rate, seedling dry weights, and number of needles. Expression of two antioxidant enzymes increased under drought. Seed weight was strongly determined by provenance and maternal parentage as well as their interaction. However, root to shoot biomass allocation depended on provenance and maternal effects that were not mediated by seed weight effects. Principal component analysis indicated that the Spanish provenances could be characterised by a higher root to shoot ratio and stem weight. Specific leaf area was also found to be lowest for the Spanish provenances.

Orientador: Raquel Gonçalves / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola / Made available in DSpace on 2018-08-04T02:41:40Z (GMT). No. of bitstreams: 1 Neri_AntonioCarlos_D.pdf: 2011024 bytes, checksum: f186a3983118cb93726e980979e74b80 (MD5) Previous issue date: 2003 / Resumo: As madeiras de reflorestamento têm grande importância na economia nacional, movimentando importantes setores, tais como os de papel e celulose, de recursos energéticos, moveleiros e de construção civil. Embora o Brasil apresente um grande potencial florestal, sendo detentor das maiores reservas florestais tropicais do mundo e possuindo condições de clima e solo favoráveis à implantação de florestas de rápido crescimento, sua participação no comércio internacional de madeiras (2,1%) é, ainda, muito pequena. Em geral, grande parte das indústrias que processam madeiras apresenta baixo rendimento de madeira serrada e qualidade insuficiente do produto final, principalmente devido ao emprego de técnicas de processamento (conhecimento de parâmetros de corte) além de fatores de planejamento da serraria (implantação e Layout) inadequadas. Esse fato revela, portanto, que o setor madeireiro necessita incorporação de inovações tecnológicas. A caracterização de espécies de reflorestamento, no que diz respeito aos parâmetros de usinagem, tais como forças de corte, geometria adequada da ferramenta, espessura de corte, densidade, etc., é imprescindível no processamento da madeira. O objetivo principal deste trabalho foi a determinação dos principais parâmetros de corte (forças de corte, pressão específica de corte e ângulo ideal de saída da ferramenta) para a espécie Pinus taeda, mediante o estudo do comportamento das forças de corte em diferentes posições e regiões de madeira juvenil e adulta do tronco. Além desse objetivo, o trabalho pretendeu, também, avaliar a metodologia de determinação de forças de corte para as espécies de eucalipto (Citriodora, Saligna e Grandis), proposta pelo autor em trabalho anterior. Para alcançar esses objetivos, foram ensaiados 96 corpos-de-prova da espécie Pinus taeda, obtidos de seis árvores provenientes do horto florestal de Manduri, S.P, com um total de 5760 ensaios. Como resultado, para o Pinus taeda foram determinadas as forças em função dos parâmetros espessura de corte e ângulo de saída, bem como foi calculado o ângulo de saída x ideal, que resultou da ordem de 40° para pequenas espessuras de corte e da ordem de 30° para maiores espessuras. Para as espécies de eucalipto (Citriodora, Saligna e Grandis), cujos resultados experimentais foram obtidos pelo autor em trabalho anterior, bem como para o Pinus taeda, foi calculada a pressão específica de corte. Os resultados permitiram, ainda, comprovar que a metodologia avaliada é adequada para utilização na espécie estudada / Abstract: The reforestation wood has great importance in the national economy, running important sectors, such as paper and the cellulose, energy resources, furniture and civil construction. Although Brazil presents a great forest potential, holding the biggest forest reserves of the world and possessing soil and climate conditions favorable to the implantation of forests of fast growth, its participation in the wood international trade (2.1%) is, still, very small. The techniques currently used in processing the wood, usually do not provide good income, neither propitiate good quality in the final product as well. Mainly due to the usage of inadequate parameters of the cutting process, along with inappropriate sawmill planning (implantation and Layout). This fact discloses, therefore, that the lumber sector needs the incorporation of technological innovations. The characterization of kinds of reforestation that respect the cutting parameters, such as, cutting force, adequate geometry of the tool, cutting thickness, density, etc., is essential in the processing of the wood. The main objective of this work was the determination of the main parameters of cutting (cutting force, specific cutting force and ideal exit angle of the tool), for the species of loblolly pine (Pinus taeda L.) by the study of the behavior of the cutting force in different positions of the trunk and in different regions of juvenile and adult of wood. Beyond this objective, the work is intended, also, to evaluate the methodology of determination of cutting force for the wood of eucalyptus, proposed by the author in previously work. To reach these objectives, 96 specimens of the specie Pinus taeda were assayed, taken from 6 trees proceeding from a research forest of Manduri, S.P, resulting in 5760 tests. As a result, the force as function of the evaluated parameters had been determined for Pinus taeda, as well, the ideal cutting angle for specimens thickness environ 0.2 mm was near 40° and for thickness between 0.4 mm and 1.0 mm was near 30°. The specific cutting force was calculated for Pinus taeda, as well as for the Eucaliptus. The former with experimental results obtained in this work and the latter using experimental results obtained in previous work from the author. Finally, the results had proved also that the methodology adopted in this research is appropriated to use in the studied species / Doutorado / Construções Rurais / Doutor em Engenharia Agrícola

Abstract The genetic basis of large adaptive differences in timing of bud set and frost hardiness between natural populations of Scots pine (Pinus sylvestris L.) was studied with the aid of RAPD markers and quantitative genetic tools. Steep clinal variation was found for both traits among Finnish Scots pine populations, and the differences between populations were found to be largely genetic. QTL mapping with Bayesian analysis revealed four potential QTLs for timing of bud set, and seven for frost hardiness. The QTLs were mostly different between the two traits. The potential QTLs included loci with large effects, and additionally smaller QTLs. The largest QTLs for bud set date accounted for about a fourth of the mean difference between populations. Thus, natural selection during adaptation has resulted in fixation of genes of large effect. This result is in conflict with the classical infinitesimal model, but agrees with the results of Orr (1998), suggesting fixation of large effects during adaptation. The applicability of RAPD and SSCP markers in quantitative genetic studies was also studied. The SSCP technique was found to be efficient in finding polymorphic markers. SSCP polymorphism in coding genes may provide candidate genes for QTL mapping studies. RAPDs were found to be useful for many descriptive analyses, but specific analyses would require more caution.

A method of linking SORTIE-ND and PrognosisBC was developed for the purpose of predicting natural regeneration and forecasting future stand conditions in mountain pine beetle (Dendroctonus ponderosae Hopkins - MPB) attacked stands in the Interior Douglas-fir (IDF) and Sub-Boreal Spruce (SBS) biogeoclimatic ecosystem zones of central and southeastern British Columbia. PrognosisBC, a spatially-implicit growth model, lacked a submodel suitable for predicting natural regeneration in unsalvaged MPB-disturbed stands. To fill this gap, estimates of regeneration (trees <7.5 cm diameter at breast height - DBH) were supplied to PrognosisBC using the light-mediated forest dynamics model SORTIE-ND and the linked model was used to forecast future stand conditions. In order to improve results, a density-dependent system of crown allometry equations to predict crown depth and crown radius was developed and then added to SORTIE-ND. The equations used stand-level measures of stems ha-¹, basal area (m² ha-¹), and the basal area of trees taller than the target tree to explicitly account of the effects of crowding on the crown axes. Additionally, crown radius and crown depth were used as dependent regressors. The equations were fit using a nonlinear three-stage least squares estimator and generally provided good estimates of crown depth and crown radius for lodgepole pine (Pinus contorta var. latifolia), hybrid spruce (Picea engelmannii x glauca (Moench) Voss), Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) and trembling aspen (Populus tremuloides Michx.). Tests of the hybrid model with the improved system of crown allometry equations were performed using reconstructed plot data collected from natural stands disturbed by MPB 25-years ago. The hybrid model provided good estimates (small mean bias and low root mean square error) for the basal area of advance regeneration (2 < DBH < 7.5 cm) for lodgepole pine (Pinus contorta var. latifolia). The best estimates were achieved when trees <7.5 cm DBH were transferred from SORTIE-ND to PrognosisBC 15-years after MPB-disturbance. For trees <2 m in height, poor estimates of stems ha-¹ where obtained. Despite the shortcomings with respect to trees <2 m tall, the results suggest that linking SORTIE-ND and PrognosisBC is an effective method of building a hybrid model capable of being used in MPB-disturbed forests. However, full parameterization of the SORTIE-ND model is likely needed to obtain accurate estimates for all sizes of natural regeneration. / Forestry, Faculty of / Graduate