• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 94
  • 13
  • 4
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 141
  • 141
  • 39
  • 32
  • 25
  • 24
  • 24
  • 21
  • 18
  • 17
  • 16
  • 16
  • 15
  • 14
  • 13
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Aplicação de lama de cal em solo de floresta de Pinus taeda e seus efeitos sobre a microbiota do solo e biodegradabilidade da serrapilheira / Lime sludge effects on soil microorganisms and on litter biodegradability of Pinus taeda forests

Platte, Eduardo Barcelos January 2002 (has links)
A serrapilheira da floresta de Pinus possui baixa biodegradabilidade, o que acarreta em acúmulo de nutrientes nesta camada superficial, diminuindo a sua disponibilidade no solo. Além disto é observada acidificação do solo destas florestas. Estes fatores diminuem a atividade dos microrganismos no solo e selecionam, por limitação fisiológica, o estabelecimento de alguns grupos microbianos. A indústria de papel e celulose produz um resíduo conhecido como lama de cal, que apresenta potencial para utilização como corretivo da acidez do solo. A proposta deste trabalho é avaliar a aplicação da lama de cal em solo de floresta de Pinus taeda e avaliar os seus efeitos sobre a degradação da serrapilheira e na microbiota do solo. Com este objetivo, foi montado um experimento de bancada, mantido em laboratório, onde foram testadas as aplicações de duas doses de lama de cal, 19t/ha e 26t/ha, associadas à aplicações de nitrogênio, nas doses de 40 e 80 kgN/ha, com a incorporação ou não da serrapilheira no solo. Foram realizadas análises químicas e microbiológicas do solo e ecotoxicológicas da lama de cal e do solo utilizando a bactéria luminescente Vibrio fischeri (Sistema Microtox®). Os resultados indicaram que após a aplicação da lama de cal houve elevação do pH do solo. Os testes de toxicidade do solo após aplicação da lama de cal não indicaram efeitos tóxicos para a bactéria Vibrio fischeri. Os tratamentos que receberam lama de cal apresentaram taxas de respiração maiores (atividade microbiana), o que promoveu não só um aumento da mineralização da matéria orgânica do solo como também da biodegradação da serrapilheira. A incorporação das acículas e da lama de cal ao solo também promoveu o aumento das taxas de respiração. A aplicação de lama de cal promoveu um incremento no número de bactérias e actinomicetos do solo, especialmente nos tratamentos que receberam a dose de 26t/ha deste resíduo. A adição de nitrogênio aos tratamentos não acarretou incrementos à atividade microbiana no solo ou na biodegradação da serrapilheira. / The Pinus litter shows low biodegradability rates, decreasing the soil nutrient content and increasing the soil acidification. Soils under Pinus forests show limitations to microbial activity and exclusion of some microbial groups by soil acidity and litter quality. The pulp and paper industry produces a solid waste with high concentration of CaCO3 (lime sludge) that can be used for soil acidity correction. In order to evaluate the effects of the lime sludge application on soil microorganisms and litter biodegradability of Pinus taeda forest, a laboratory study was conducted. Two doses of lime sludge (19t/ha and 26t/ha) were tested associated to two nitrogen doses (40 and 80kgN/ha), with and without litter incorporation to the soil. The evaluations included soil chemical and microbiological analyses and ecotoxicity tests with Vibrio fischeri (Microtox® Sistem). The results show that application of lime sludge on soil increased the soil pH, microbial activity and number of bacteria and actinomycetes, contributing to acceleration of organic matter mineralization and litter degradation. The incorporation of lime and litter to the soil increased the microbial activity. No toxic effects were observed to Vibrio fischeri on soil with application of lime sludge. The nitrogen application showed no significant effects on soil microorganisms activity and litter degradation.
52

Equações de viabilidade para sementes de Eucalyptus grandis W.Hill ex Maiden e Pinus taeda L.

Fantinatti, Jussara Bertho 17 March 2004 (has links)
Orientador: Roberto Usberti / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola / Made available in DSpace on 2018-08-03T20:04:08Z (GMT). No. of bitstreams: 1 Fantinatti_JussaraBertho_D.pdf: 2348536 bytes, checksum: dbfcb64dd706d0f1658b43bd0dd0fb7d (MD5) Previous issue date: 2004 / Resumo: o conhecimento do comportamentodas sementes em relação às condições de armazenamento a que são submetidas, é de extrema importância para a avaliação de sua armazenabilidade. Para a definição de metodologia para assegurar a sobrevivência e a preservação de espécies florestais, este experimento analisou o armazenamento de sementes de Eucalyptus grandis W.Hill ex Maiden e Pinus taeda L. visando a obtenção das constantes da equação de viabilidade para as espécies, para a sua conservação bem como para garantir a sua disponibilidade. As sementes de E. grandis e P. taeda (saftas 1999 e 2000, respectivamente) foram reumidificadas sobre água e/ou secas em sílica gel, ambos à 25°C, até a obtenção dos valores de umidade desejados, a partir dos seus valores iniciais. Subamostras de sementes com oito graus de umidade para E. grandis (1,2 a 18,1%, valor inicial de 11,3%) e oito graus de umidade para P. taeda (1,4 a 19,4%, valor inicial de 12,3%) foram acondicionadas em embalagens de alumínio hermeticamente fechadas e armazenadas à 40, 50 e 65°C até a obtenção de curvas completas de deterioração. As análises estatísticas foram realizadas pelo programa "Glim". As duas espécies apresentaram comportamento ortodoxo em relação ao armazenamento, mas as sementes de E. grandis mostraram melhor armazenabilidade do que as de P. taeda. Dois grupos de constantes foram obtidos para prever a longevidade de sementes de Eucalyptus grandis e Pinus taeda, a saber: Kr 9,661 e 8,838; CuF 6,467 e 5,981; CIF 0,03498 e 0,10340; Cg= 0,0002330 e 0,0005476, respectivamente. Para as duas espécies foi observada uma relação inversa entre o teor de água e a longevidade das sementes. Os limites inferiores calculados para aplicação da equação para E. grandis e P. taeda situam-se ao redor de 4,85 e 4,06, respectivamente, em equilíbrio com valores de UR ao redor de 20% / Abstract: The knowledge of seed performance under storage conditions is extremely important to determine its storability potential. The main aim of this work was determine the best methodology to achieve the survival and preservation of Eucalyptus grandis W.Hill ex Maiden and Pinus taeda L. seeds, under controlled storage conditions, through the detection of the viability equation constants for the species. The seeds used in this experiment were harvested in 1999 (E. grandis) and 2000 (P. taeda). Before the storage period, the seeds were rehydrated over water and or dried over silica gel, both at 25°C, ITominitial moisture contents, until achieving the desired values. Seed subsamples with 8 moisture contents for E. grandis (1.2 to 18.1%, initial value of 11.3%) and 8 moisture contents for P. taeda (1.4 to 19.4%, initial value of 12.3%) were then sealed in laminate aluminium-foil packets and stored in incubators maintained at 40, 50 and 65°C. Those storage temperatures were chosen in order to get complete survival curves in relatively short periods of time. Statistical analysis was performed through Glim software. The two species showed orthodox behaviour in relation to the storage, however E. grandis seeds presented higher storability than P. taeda ones. Two different viability eonstant sets were aehieved to predict the longevity of Eucalyptus grandis and Pinus taeda seeds, as follows:KE= 9.661 and 8.838; Cw= 6.467 and 5.981; CH= 0.03498 and 0.10340; CQ = 0.0002330 and 0.0005476, respectively. An inverse relationship was observed between the water content and seed longevity for both species. The lowest limits estimated for applieation ofthe viability equation for E. grandis and P. taeda were 4.85 and 4.06 me, respectively, in equilibrium with 20% RH / Doutorado / Tecnologia Pós-Colheita / Doutor em Engenharia Agrícola
53

Parametros de corte na usinagem de madeiras de reflorestamento / Parameters of cutting in the wood machining of reforestation

Neri, Antonio Carlos 28 February 2003 (has links)
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
54

Forest Harvesting Disturbance and Site Preparation Effects on Soil Processes and Vegetation in a Young Pine Plantation

Lister, Tonya Whitcomb 10 April 1999 (has links)
The favorable growth of young loblolly pines (Pinus taeda L.) in response to controlling non-crop vegetation is well documented. However, the beneficial effects of non-crop vegetation on soil quality, nutrient cycling, and biodiversity have not been thoroughly explored. A study was conducted to determine the effects of harvesting-induced soil disturbance, bedding and chemical vegetation control on soil processes and productivity, and to characterize the effects of silvicultural treatments on non-crop vegetation dynamics. Study plots were established on a wet pine flat on South Carolina's lower Coastal Plain. Treatments included a range of 5 disturbance classes (undisturbed, compression tracked, shallowly rutted, deeply rutted and churned), two site preparation treatments (flat planted and bedded) and a gradient of vegetation control (no vegetation control, operational-level weed control and complete weed control). Soil disturbances had relatively small effects on soil quality. Soil compaction reduced soil aeration, but this condition was fully ameliorated by bedding. Churning did not degrade the soil physical environment in any measureable way, largely because slash and litter were incorporated into the surface soil. Bedding and churning increase soil biological activity, which increased nitrogen mineralization in excess of pine demand. When non-crop vegetation was chemically controlled, mineralization rates increased due to increases in surface soil temperatures. With less vegetation on the site, the amount of nitrogen sequestered was less, furthering the potential for nitrogen loss by leaching or denitrification. Soil quality improved somewhat with increasing levels of non-crop vegetation biomass; however, these beneficial effects were marginal during two years of operational vegetation control. The majority of dominant species on undisturbed treatment areas were woody, and soil disturbance, including bedding, reduced the proportions of these species. Silvicultural treatments had little effect on the prevalence of hydrophytic species on these wetland study sites. From a forest management point of view, for this site type, it appears that much is gained by reducing competition from non-crop vegetation; the benefits of controlling the density of non-crop vegetation for encouraging early pine growth are clear. While non-crop vegetation slightly improved system function by sequestering available nitrogen, increasing diversity and increasing soil quality, these improvements do not appear to be critical to forest function on these inherently high-quality sites. / Master of Science
55

Genomic Selection and Genome-Wide Association Study in  Populus trichocarpa and Pinus taeda

Kaplan, Abdullah 20 September 2016 (has links)
Forest tree breeding methods rank among the most efficient ways to increase productivity and quality of forests. With the advent of high-throughput genotyping technology, genome-enabled breeding has started to gain importance and may overcome some weaknesses of traditional tree breeding. Genomic Selection (GS), which involves using genome-wide markers to predict breeding values of individuals in a population, has been proposed for animal and plant breeding programs. GS enables very accurate selection decisions through estimation of genomic estimated breeding values (GEBVs). While the goal of GS is to predict phenotype from genotype, it does not identify the underlying genes that have important roles in a trait. Genome-Wide Association Studies (GWAS) approaches are therefore complementary to GS, enabling identification of these genes, which may be useful for marker-assisted selection in some traits. In this study, we first estimated heritability for several adaptive traits (cold hardiness, dbh, bud flush, height, and bud set) in a population of Populus trichocarpa and for height, diameter, and stem straightness in Pinus taeda. GEBVs accuracies were estimated using a ridge regression–best linear unbiased prediction (rrBLUP) model, and these accuracies were compared with estimated heritabilities. GWAS was also performed for the both imputed and non–imputed data of P. taeda population using TASSEL (Trait Analysis by aSSociation Evolution and Linkage) software, as well as rrBLUP and FFBSKAT (Fast Family-Based Sequence Kernel Association Test) packages in R. Heritabilities ranged from 0.34 to 0.56 for P. trichocarpa and 0.14 to 0.37 for P.taeda. GWAS identified 3244 associations for dbh, 4077 associations for stem straightness, and 5280 SNPs for height (p≤0.05) in TASSEL using the reduced model (marker data only), whereas 2729, 3272 and 3531 associations were found with the full model where we also included population structure as a covariate. FFBSKAT showed a similar number of SNP associations (2989, 3046 and 3058). There was an inflation of SNP associations (~20k) found in rrBLUP, which suggests population structure was not effectively controlled. The GEBVs accuracies ranged from 0.09 and 0.22 for P.trichocarpa and 0.09 to 0.23 for P.taeda using rrBLUP method. Testing the effect of repetation on the accuracy of GEBV for poplar showed that there was no significant difference between the number of cycles. Also, there was no significant difference the accuracy of GEBVs in pine between two different imputation methods, the marker mean value and Beagle software. / Master of Science
56

Environmental And Stand Variables Influencing Soil CO2 Efflux Across The Managed Range Of Loblolly Pine

Templeton, Benjamin Sean 10 April 2009 (has links)
Managed loblolly pine forests comprise an important pool in the global carbon cycle. Understanding the influences upon inputs and outputs of this pool, including the effects of management activities, will allow landowners to understand how carbon can be sequestered in their stands. Specific to this study, we sought to create multivariate models of the output of carbon from the soil in the form of soil CO2 efflux (Rs) and a component of that total efflux, heterotrophic respiration index (Rh), from data collected across the managed range of loblolly pine in the Southeastern U.S. We also performed tests of significance on controlled subsets of these data for the effects of fertilization and of thinning. Finally, we sought a connection between stand leaf area index (LAI) and total soil CO2 efflux or heterotrophic respiration. Our models indicated variability in both Rs and Rh across latitude and physiographic province, respectively, within this range. The Rs (R2 = 0.56) model included temperature, latitude, a soil moisture by temperature effect, soil nitrogen, and bulk density variables. The Rh (R2 = 0.50) model included soil moisture, a temperature by moisture interaction, and physiographic province. Rs was not significantly affected by either fertilization or thinning, yet Rh was influenced by both (negatively and positively, respectively). This indicates a shift in relative contributions of heterotrophic respiration and root respiration components to Rs in response to these treatments. Heterotrophic respiration was shown to have a weak negative response (R2 = 0.04) to increasing stand LAI. / Master of Science
57

Projecting Carbon Pools in Aboveground Woody Accumulations and Harvested Wood in Loblolly Pine Plantations of the Southern United States: From Stand-level to Regional Scales

Wang, Huei-Jin 24 January 2011 (has links)
Accounting for in-woods carbon storage in carbon accounting systems may be insufficient when substantial amounts of sequestered carbon are harvested and converted to long-lived wood products and landfills. The potential for offsetting greenhouse gas (GHG) emissions by storing carbon in managed loblolly pine forests in the southern United States was projected over the next half-century, both in terms of in-woods aboveground carbon pools and harvested products, including wood used for energy production. A region-wide data set from the Forest Inventory Analysis (FIA) program of USDA Forest Service was used to set initial conditions and estimate model parameters for projecting management activities including plantation area, age distributions of thinning, and clearcut harvest on an annual timestep. The stand-level growth and yield model FASTLOB was linked to the FIA data to project growth rates and annual harvest volumes of sawtimber and pulpwood for the projection period, accounting for annual timber harvests and the life cycles of wood products. In addition to baseline management practices, projections were made for scenarios that assumed increasing management intensities including the use of chemical fertilizers and herbicides and genetically-improved growing stock. Present-day carbon storage in well-managed southern pine plantations averaged 30.54 Mgâ ha⁻¹ (± 2.54%) for aboveground carbon. Over a 50-year projection, annual wood production was 62.1 and 45.9 million green metric tons from pulpwood and sawtimber yield, with roughly one-fourth of the green weight being carbon. Baseline projections showed aboveground carbon pools of up to 341 million metric tons being maintained over the next 50 years, with 93% in aboveground live trees and 7% in coarse woody debris (CWD). The carbon storage in wood products increased steadily over the half-century projection and showed no sign of leveling off, while the storage in plantations was found to remain constant or increase slightly over time. An additional 11 million metric tons of harvested carbon was used for energy per year on average, equivalent to 25% of annual forest-products-industry renewable energy use in U.S.A. Intensified forest management practices showed the potential to increase as much as 30% total carbon stored in in-woods and harvested-wood-products pools, with potential increases up to 40% in energy offsets above the baseline scenario. Reducing management intensity greatly increased in-woods carbon storage potential, but eliminated the wood-products carbon sink. / Ph. D.
58

Coarse Woody Debris in Industrially Managed Pinus taeda Plantations of the Southeastern United States

Pittman, Judd R. 25 August 2005 (has links)
Coarse woody debris (CWD) plays an influential role in forested ecosystems by adding organic matter to soils, stabilizing the soil environment, providing wildlife habitat, preventing soil erosion, providing seedling establishment habitat, and involvement in the nutrient cycle. Most CWD research has been conducted in old-growth and unmanaged, second-growth forests. However, less is understood about CWD in intensively managed ecosystems, such as industrialized southern pine plantations. The objectives of this study were to determine the climatic and ecological factors that affect the decomposition rate of CWD, to predict the decomposition rate, specific gravity, and time since death (TSD) using multiple linear regression in industrial loblolly pine (Pinus taeda L.) plantations in the southeastern United States. The study sites for this project were part of a long-term, loblolly pine thinning study maintained by the Loblolly Pine Growth and Yield Research Cooperative at Virginia Tech. Measurements included piece size, position, and decay class. Samples of CWD were collected and analyzed to determine their mass and density. Decomposition rate of CWD was significantly different across position classes and decay classes: disk decomposition rates were significantly negatively correlated with disk diameter, large and small end piece diameter, estimated disk height, and disk dry weight. Average annual precipitation and average annual temperature were not significantly correlated with CWD disk decomposition rate. / Master of Science
59

Ação de cupins de madeira seca (Cryptotermes brevis) e de solo (Nasutitermes corniger) nas madeiras termorretificadas de Pinus taeda e de Corymbia citriodora / Action of dry wood termite (Cryptotermes brevis) and subterranean termite (Nasutitermes corniger) on the thermorectified wood of Pinus taeda and Corymbia citriodora

Brito, Juliana Pires 27 May 2015 (has links)
A termorretificação ou retificação térmica é uma técnica auxiliar na preservação da madeira, sendo um processo controlado de pirólise, em temperaturas que variam entre 140°C a 220°C. No presente trabalho, foi testada a hipótese de que a termorretificação na temperatura de 200ºC aumenta a resistência da madeira em relação ao ataque de cupins, buscando identificar se tal efeito é resultante da menor disponibilidade de água ou da deposição de substâncias tóxicas ou repelentes formadas durante a degradação térmica. Foi constatado que as alterações provocadas pela termorretificação reduzem a capacidade de adsorção de água pela madeira e, consequentemente, o seu teor de umidade de equilíbrio. As substâncias geradas durante o processo de termorretificação, extraídas em água quente, tem efeito preservativo quando aplicadas à madeira natural, com diferentes resultados entre as espécies florestais. A termorretificação reduziu a capacidade de ação do Cryptotermes brevis, com efeito mais acentuado no Pinus taeda. A remoção dos extrativos da madeira termorretificada, por si só, não implicou no aumento da intensidade da ação dos cupins, o que somente se tornou mais evidente quando aumentou o teor de umidade do material. Em relação ao Nasutitermes corniger, ocorreram diferenças na ação dos cupins em relação ao tipo de oferta de alimento, bem como em relação às espécies de madeira. Para a alimentação forçada, houve acentuado efeito da termorretificação, em ambas as espécies de madeira, tendo ocorrido uma acentuada redução na perda de massa das madeiras quando comparada à madeira original. Constatou-se haver efeito dos extrativos na redução da ação dos cupins de solo, com maior ênfase para a madeira de Pinus taeda. No ensaio de preferência alimentar, nenhum dos tratamentos avaliados foi eficiente para prevenir a degradação pelos cupins, com o Pinus taeda apresentando maior suscetibilidade em comparação com o Corymbia citriodora. Considerando o conjunto dos resultados, conclui-se que a madeira termorretificada é resistente ao ataque de cupins de madeira e essa resistência é decorrente da interação entre a menor higroscopicidade provocada pela modificação química do material e a presença dos extrativos gerados durante o processo de termorretificação; e que o efeito preservativo da termorretificação não é suficiente para indicar o uso da madeira termotratada em contato direto com o solo, devido à suscetibilidade aos cupins subterrâneos. / The thermorectification, a controlled pyrolysis at temperatures ranging between 140°C to 220°C, is considered a technique that could preserve the wood against biological degradation. In this study it was tested the hypothesis that the thermorectification at 200ºC increase the lumber resistance against termite attack, looking to identify if this effect is a result of the reduced available moisture or due the deposition of toxic substances formed during the thermal treatment. It was evidenced that the chemical modifications caused by thermorectification reduced wood sorption capacity and, by consequence, its equilibrium moisture content. The substances formed during the thermal treatment, extracted with hot water, have a preservative effect when applied to natural lumber, with different results between the two wood species. The thermorectification reduced the attack of Cryptotermes brevis and this influence was more effective on Pinus taeda. The removal of extractives from thermotreated wood did not cause an increase in the intensity of termite action, which only became more evident when the lumber moisture content increased. In relation to Nasutitermes corniger, there were differences in the action of termites, depending of the feeding conditions and wood species. In the food choice test, there was an important effect of thermorectifiction in both wood species, reducing the loss of mass due to termite attack when compared to original wood. The extractives also reduced the action of soil termites, with greater emphasis on Pinus taeda lumber. In the no food choice test, no one of the treatments evaluated was enough to prevent the termite action, and it was showed that Pinus taeda wood was more susceptible compared to Corymbia citriodora. Considering all the results, it is possible to conclude that thermorectified lumber is resistant against dry wood termite attack and this resistance is due to interaction between the reduced wood hygroscopicity promoted by the wood chemical changes and the presence of substances generated during the thermal treatment; and the preserving effect of thermorectification is not enough to suggest the use of thermorectified lumber in direct ground contact due its susceptibility to subterranean termite action.
60

Idade da madeira na qualidade da polpa e do papel / Wood age in quality of pulp and paper

Ampessan, Camilla Gabriela Melo 31 July 2015 (has links)
Submitted by Claudia Rocha (claudia.rocha@udesc.br) on 2017-12-07T15:23:08Z No. of bitstreams: 1 PGEF15MA049.pdf: 1458610 bytes, checksum: d39de60e31342944508856b042c477f4 (MD5) / Made available in DSpace on 2017-12-07T15:23:08Z (GMT). No. of bitstreams: 1 PGEF15MA049.pdf: 1458610 bytes, checksum: d39de60e31342944508856b042c477f4 (MD5) Previous issue date: 2015-07-31 / Capes / The objective of this study was to investigate the influence of age on quality of Pinus taeda wood in different cooking conditions, including the Kappa numbers 40, 50 and 60 of the cellulosic pulp, seeking the reduction of forest cutting age and increasing the quality of pulp to produce tougher Kraft paper. The sampled trees in this study were from reforestation areas located at the city of Otacílio Costa belonging to the company Klabin S.A., state of Santa Catarina. The sampled trees were 14, 16 and 19 years old where was determined the basic density of the discs, chemical characteristics (holocellulose, lignin, extractives, sodium hydroxide and ash content) and anatomical characteristics (length, width, lumen diameter, wall thickness, felting index, coefficient of flexibility, wall fraction and Runkel ratio) of the timber. The Kraft process of obtaining cellulose was also rated (rough and debugged yields, waste content, Kappa number, viscosity), the anatomical characteristics of the fibers (length, Coarseness, width, Curl and Kink) and the paper properties (weight, thickness, density, tensile index, burst index, stretching, TEA, tear index and air resistance). The values were submitted to the factor variance analysis (ANOVA). The results showed a significant difference among all ages, to the wood density and all the anatomical characteristics analyzed. For the chemical characteristics the extractives results showed significant differences between ages, with the higher value for 19 years old. The ash content of 14 years old showed significant difference over the other ages. The cooking variables, rough and debugged yields did not vary between ages, only the Kappa factor influenced. The viscosity and the waste content were influenced by the different applied Kappa and also by the wood ages. In relation to the morphology of the fibers, all the characteristics analyzed suffered influence of the age and Kappa, except the width that showed significant differences only for Kappa. Changes in the paper characteristics due to the variation of age and Kappa were observed, which may conclude that the applied variables had an influence on the properties of pulp and paper / Este trabalho teve como objetivo verificar a influência da idade na qualidade da madeira de Pinus taeda em diferentes condições de cozimento, compreendendo aos números Kappa de 40, 50 e 60 da polpa celulósica, buscando a redução da idade de corte da floresta e aumentando a qualidade da celulose para papéis mais resistentes. As árvores amostradas neste estudo foram provenientes de áreas de reflorestamento localizadas no Município de Otacílio Costa pertencentes à empresa Klabin S.A., Estado de Santa Catarina. A amostragem foi realizada em árvores com 14, 16 e 19 anos de idade, onde foi determinada a densidade básica dos discos, características químicas (holocelulose, lignina, extrativos totais, hidróxido de sódio e teor de cinzas) e características anatômicas (comprimento, largura, diâmetro do lume, espessura da parede, índice de enfeltramento, coeficiente de flexibilidade, fração parede e índice de Runkel) da madeira. Foi avaliado também o processo Kraft de obtenção de celulose nos diferentes números Kappa (rendimentos bruto e depurado, teor de rejeitos, número Kappa, viscosidade), as características anatômicas das polpas (comprimento, Coarseness, largura, Curl e Kink) e as propriedades do papel (gramatura, espessura, densidade, índice de tração, índice de arrebentamento, alongamento, TEA, índice de rasgo e resistência ao ar). Os valores observados foram submetidos a análise de variância fatorial (ANOVA). Os resultados demonstraram que houve diferença significativa entre todas as idades, para a densidade da madeira e as características anatômicas analisadas. Já para as análises químicas os resultados de extrativos totais apresentaram diferenças significativas entre as idades, com maior valor para 19 anos. Para o teor de cinza a idade 14 apresentou diferença significativa sobre as demais idades. As variáveis de cozimento: rendimentos bruto e depurado não apresentaram variações entre idades, apenas entre os Kappa. A viscosidade e o teor de rejeitos variaram pelos diferentes Kappa aplicados e também idades da madeira. Quanto a morfologia das fibras, todas as características analisadas sofreram influência da idade e Kappa, exceto, a largura que apresentou diferenças significativas apenas para o Kappa. Variações nas características do papel em função das diferentes idades e Kappa foram observadas, podendo concluir que as variáveis aplicadas nos cozimentos exerceram influência sobre as propriedades da celulose e do papel

Page generated in 0.0647 seconds