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  • 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.
1

Fragmentos de cerrado : espécies arbóreas de usos múltiplos para conservação do cerrado /

Silva, Alexandre Marques da. January 2019 (has links)
Orientador: Mario Luiz Teixeira de Moraes / Resumo: O conhecimento da ecologia e da genética das espécies arbóreas que ocorrem nos fragmentos do Bioma Cerrado é uma etapa importante para a criação de programas conservacionistas. Os objetivos deste trabalho foram: i) identificar e selecionar fragmentos de Cerrado, na região de Três Lagoas – MS, que apresentam diversidade em relação à ocorrência de espécies arbórea; ii) localizar, nos fragmentos selecionados, os indivíduos das espécies arbóreas, que se destacam quanto as possibilidades de utilização de produtos não madeireiro; iii) marcar árvores matrizes, nas espécies arbóreas selecionadas, com base em caracteres de crescimento e na sua localização, para que os fragmentos possam ser denominados de “áreas de coleta de sementes – ACS”. O estudo foi realizado em quatorze fragmentos do Bioma Cerrado distribuídos em sete fazendas no município de Três Lagoas, (MS). A distância em quilômetros entre os fragmentos, variou de 3,0 a 64,8 km. O levantamento das espécies arbóreas ocorreu mensalmente entre os meses de julho a dezembro de 2012 e 2013. Todos os fragmentos foram visitados, e, nestes, foi realizado levantamento de diversidade das espécies arbóreas com potencial para produtos não madeireiros e madeireiros. A identificação das espécies arbóreas dos fragmentos foi feita a partir de caminhamento dentro da área e nas bordas, a considerar indivíduos reprodutivos. Para conhecer as estratégias ecológicas das espécies arbóreas de interesse, pesquisou-se sobre as características ecológica... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Knowledge of the ecology and genetics of tree species occurring in the Cerrado Biome fragments is an important step towards the creation of conservation programs. The objectives of this work were: i) to identify and select Cerrado fragments, in the Três Lagoas - MS region, which present diversity in relation to the occurrence of arboreal species; ii) to locate, in the selected fragments, the individuals of the tree species, which stand out as the possibilities of use of non-timber products; and (iii) marking selected tree species, based on growth characters and their location, so that the fragments can be referred to as "ACS - seed collection areas". The study was carried out in fourteen fragments of the Cerrado Biome distributed in seven farms in Três Lagoas, (MS). The distance in kilometers between the fragments ranged from 3.0 to 64.8 km. The survey of tree species occurred monthly between July and December of 2012 and 2013. All the fragments were visited, and, in these, a survey was carried out on the diversity of tree species with potential for non-timber and timber products. The identification of the tree species of the fragments was made from walking within the area and at the edges, to consider reproductive individuals. In order to know the ecological strategies of the arboreal species of interest, we investigated the ecological characteristics: uses, pollination syndrome, dispersion syndrome and successional group. It was proposed classification model for the species... (Complete abstract click electronic access below) / Doutor
2

Mechanical processing for improved products made from Swedish hardwood

Johansson, Jimmy January 2008 (has links)
Swedish hardwood is today used in the energy, pulp and mechanical hardwood industries. Only very small volumes of Swedish hardwood are, however, consumed by the mechanical industry that normally pays the highest timber price. The smallness of the volumes used for mechanical refinement is a result both of forestry not focusing on the production of hardwood for these uses, and of the fact that the mechanical hardwood industry, particularly the sawing industry, is not designed to process the existing raw material in an optimal manner. This thesis discusses the possibilities of improving the conditions for the mechanical refinement of hardwood. The aim of the work has been to investigate the possibilities of developing products and methods for processing of Swedish hardwood. The thesis proposes a new manufacturing system for Swedish hardwood to better utilize the inherent properties of the wood material. The system is based on the so-called PrimWood Method and the star-sawing concept. Compared to normally sawn wood, the sawing concept utilizes the raw material more efficiently with regard to volume yield, and increases the distance between knots in the sawn wood. The material produced has vertical annual rings which give the wood smaller movements as a result of moisture variations and a different textural appearance. Using the PrimWood Method for hardwood would make it possible to more closely match customer requirements regarding hardwood products. Since Swedish hardwood is nowadays mainly used indoors, a possible way of expanding the market would be to increase the outdoor use of the material. Here the durability is of great importance, and one important factor is then the capillary characteristics of the material. The thesis therefore focuses on the characterisation of the capillarity in wood for the future improvement of its durability. It is shown that with the material produced by the proposed manufacturing system, i.e. wood with vertical annual rings, the possibility of using hardwood outdoors increases, because the susceptibility to cracking decreases.
3

A transition towards higher value uses of natural-resource based products

La Thi, Tham 01 June 2021 (has links)
Forestry and the wood-based sector provide increasing contributions to the national and rural economy development. Tree plantations serve as a business opportunity to secure the livelihood of thousands of small-scale timber producer households in several tropical countries. Given that forest land and the timber production it supports is limited, sustainable management of forest-based resources including timber is required. By integrating the value chain and livelihood analysis framework, this study investigates the value chains and impacts on rural livelihoods of commercial Acacia hybrid timber in central Vietnam. Besides that, scenario analysis is applied with a view to proposing the development pathways of the timber value chains and to providing improved information for developing the plantation policy in Vietnam at large. The empirical analysis employs a case study research design to examine the transition towards higher value uses of timber resources, thereby exploring the performance of woodchip, non-FSC furniture and FSC-certified furniture value chains in Thua Thien Hue province. Furthermore, two production areas named Nam Dong and Phu Loc districts are selected as embedded cases to examine the rural development potentials of Acacia hybrid timber production and commercialization. A mix-method approach, including both qualitative such as review and analysis of secondary data and key informant interviews, and quantitative data collection methods such as producer household surveys are applied to gather primary and secondary data. Diverse qualitative and quantitative analyses including content analysis, value chain analysis, livelihood analysis, and scenario analysis are also utilized corresponding to the specific research objectives. The macro-level analysis reveals the strategic responses of Asian wood-based firms to the global economy, particularly in terms of geographical scope, governance, cooperation, and overall performance. In addition, a literature review points out the potential impacts of Asian timber VCs on the environment and livelihoods. While timber product commercialization generates benefits to the value chain actors, unsustainable forest management leads to diverse negative environmental effects. The findings demonstrate considerable knowledge gaps and call for broader geographic coverage, as well as more transparent and quantitative assessments. To deepen the understanding on timber VCs, further research efforts should scrutinize the origins, functions, operations, and interactions of firms in these chains, and incorporate environmental and social aspects. The meso- and micro-level analysis exposes the structure of Acacia hybrid timber value chains which are shaped by various socio-economic, political, and environmental conditions. All three analyzed timber value chains are buyer-driven, led by processing and exporting companies in the downstream node of chains. At the upstream node, small-scale timber producers are normally less organized and lack market access. Timber production and commercialization provide profitable business activities to timber producers, traders, and processing and exporting companies. From a chain perspective, the woodchip value chain is financially profitable. However, its contribution to the national economy is the least. In contrast, the FSC-certified furniture value chain contributes fundamentally to economic development. The micro-level analysis indicates the difference regarding the socio-economic features, resource access, and management of producer households between the two analyzed districts. Relevant findings also indicate the importance of Acacia hybrid woodlots in the current livelihood system. However, more wealthy households benefit more from the Acacia hybrid timber income, especially in a well-developed market. Timber production and commercialization contribute to rural poverty reduction. Nevertheless, it is the main driver of the overall income inequality in both districts. Results from the literature review and empirical study support to conceptualize and evaluate the three development scenarios, displaying different levels of forest transition interventions and reactions of key actors in the chains. Under the current situation, a fast transition model with strict plantation control is not advisable for timber value chains’ stakeholders, especially those who operate on the ground. A slow transition scenario with a co-management model, instead, serves as a suitable development pathway. To improve the current management system, this study implies five management strategies, including (i) adaptive management; (ii) multi-stakeholder cooperation; (iii) target interventions; (iv) collaborative management and (v) integrated planning. The study can be of interest for further policy interventions focusing on sustainable reforestation and livelihood development in Vietnam. The approach of transition towards high added value products can further be applied in other comparable contextual cases searching for sustainable utilization of timber and forest-based products at large. Theoretically, the thesis highlights that sustainable management of forest-based products will not be obtained unless the related economic, social, and environmental aspects are considered in conjunction. These conditions are driven by several factors, such as national policy frame and market condition. Therefore, it is crucial to understand the interrelations within the economic-socio-ecological system to achieve long-term development targets. / Die Forstwirtschaft und der holzverarbeitende Sektor leisten einen wachsenden Beitrag zur nationalen und ländlichen Wirtschaftsentwicklung. Baumplantagen dienen Tausenden von kleinen Holzproduzentenhaushalten in vielen tropischen Ländern als Geschäftsmöglichkeit, um ihren Lebensunterhalt zu sichern. Da die Waldflächen und die darauf gestützte Holzproduktion begrenzt sind, ist eine nachhaltige Bewirtschaftung der waldbasierten Ressourcen, einschließlich Holz, erforderlich. Diese Studie untersucht die Wertschöpfungsketten und die Auswirkungen von kommerziellem Akazien-Hybridholz auf den Lebensunterhalt der ländlichen Bevölkerung in Zentralvietnam durch Integration von Wertschöpfungsketten- und Lebensunterhaltsanalysen. Außerdem wird eine Szenarioanalyse durchgeführt, um Entwicklungswege für die Holzwertschöpfungsketten vorzuschlagen und bessere Informationen für die Entwicklung der Plantagenpolitik in Vietnam insgesamt bereitzustellen. Die empirische Analyse verwendet ein Fallstudien-Forschungsdesign, um den Übergang zu höherwertigen Nutzungen von Holzressourcen zu untersuchen und dabei die Leistung von Wertschöpfungsketten für Hackschnitzel, nicht FSC-zertifizierte Möbel und FSC-zertifizierte Möbel in der Provinz Thua Thien Hue zu analysieren. Darüber hinaus werden zwei Produktionsgebiete, die Distrikte Nam Dong und Phu Loc, als Fallbeispiele ausgewählt, um die ländlichen Entwicklungspotenziale der Akazien-Hybridholzproduktion und -vermarktung zu untersuchen. Um Primär- und Sekundärdaten zu sammeln wird ein Methodenmix aus qualitativen Methoden, wie der Sichtung und Analyse von Sekundärdaten und der Befragung von Schlüsselinformanten, sowie quantitativen Datenerhebungsmethoden, wie der Befragung von Produzentenhaushalten, verwendet. Außerdem werden diverse qualitative und quantitative Analysen wie Inhaltsanalyse, Wertschöpfungskettenanalyse, Lebensunterhaltsanalyse und Szenarioanalyse entsprechend den spezifischen Forschungszielen eingesetzt. Die Analyse auf der Makroebene zeigt die strategischen Reaktionen der asiatischen Holzfirmen auf die globale Wirtschaft, insbesondere in Bezug auf geografische Reichweite, Governance, Kooperation und Gesamtleistung. Darüber hinaus zeigt eine Literaturübersicht die potenziellen Auswirkungen asiatischer Holzwertschöpfungsketten auf die Umwelt und die Lebensgrundlagen der lokalen Bevölkerung auf. Während die Kommerzialisierung von Holzprodukten Vorteile für die Akteure der Wertschöpfungskette mit sich bringt, führt eine nicht nachhaltige Waldbewirtschaftung zu diversen negativen Umwelteffekten. Die Ergebnisse zeigen erhebliche Wissenslücken auf und fordern eine breitere geografische Abdeckung sowie transparentere und quantitativere Bewertungen. Um das Verständnis von Holz-Wertschöpfungsketten zu vertiefen, sollten weitere Forschungsarbeiten die Ursprünge, Funktionen, Abläufe und Interaktionen von Unternehmen in diesen Ketten untersuchen und dabei ökologische und soziale Aspekte mit einbeziehen. Die Analyse auf der Meso- und Mikroebene legt die Struktur der Akazien-Hybridholz-Wertschöpfungsketten offen, welche von verschiedenen sozioökonomischen, politischen und ökologischen Bedingungen geprägt sind. Alle drei analysierten Holzwertschöpfungsketten sind käufergesteuert, angeführt von Verarbeitungs- und Exportunternehmen im nachgelagerten Knotenpunkt der Ketten. Am vorgelagerten Knotenpunkt sind die kleinen Holzproduzenten in der Regel weniger organisiert und haben keinen Marktzugang. Die Holzproduktion und -vermarktung bieten profitable Geschäftsaktivitäten für Holzproduzenten, Händler sowie Verarbeitungs- und Exportunternehmen. Aus der Kettenperspektive ist die Wertschöpfungskette Hackschnitzel finanziell profitabel. Ihr Beitrag zur Volkswirtschaft ist jedoch der geringste. Im Gegensatz dazu trägt die FSC-zertifizierte Möbel-Wertschöpfungskette grundlegend zur wirtschaftlichen Entwicklung bei. Die Analyse auf der Mikroebene zeigt die Unterschiede zwischen den beiden analysierten Distrikten in Bezug auf die sozioökonomischen Merkmale, den Ressourcenzugang und das Management der Produzentenhaushalte. Relevante Ergebnisse weisen auch auf die Bedeutung von Akazien-Hybridholzplantagen im derzeitigen Lebensunterhaltssystem hin. Allerdings profitieren wohlhabendere Haushalte mehr von den Einnahmen durch Akazien-Hybridholz, insbesondere bei einem gut entwickelten Markt. Holzproduktion und Kommerzialisierung tragen zur ländlichen Armutsbekämpfung bei, dennoch ist sie der ausschlaggebende Kraft für die allgemeine Einkommensungleichheit in beiden Distrikten. Die Ergebnisse der Literaturrecherche und der empirischen Studie helfen dabei, die drei Entwicklungsszenarien zu konzipieren und zu bewerten, die unterschiedliche Ebenen der Waldumwandlungsmaßnahmen und Reaktionen der Hauptakteure in den Ketten darstellen. In der aktuellen Situation ist ein schnelles Übergangsmodell mit strikter Kontrolle der Plantagen für die Akteure der Holzwertschöpfungsketten nicht ratsam, insbesondere für diejenigen, die vor Ort tätig sind. Ein langsames Übergangsszenario mit einem Co-Management-Modell dient stattdessen als geeigneter Entwicklungspfad. Um das derzeitige Managementsystem zu verbessern, schlägt diese Studie fünf Managementstrategien vor, darunter (i) adaptives Management, (ii) Zusammenarbeit mehrerer Interessengruppen, (iii) gezielte Interventionen, (iv) kooperatives Management und (v) integrierte Planung. Die Studie kann für weitere politische Interventionen von Interesse sein, welche sich auf eine nachhaltige Wiederaufforstung und die Entwicklung der Lebensgrundlagen in Vietnam konzentrieren. Der Ansatz des Übergangs zu Produkten mit hoher Wertschöpfung kann auch in anderen vergleichbaren Fällen angewandt werden, in denen eine nachhaltige Nutzung von Holz- und Forstprodukten im Allgemeinen angestrebt wird. Theoretisch unterstreicht die Arbeit, dass eine nachhaltige Bewirtschaftung von Forstprodukten nur dann erreicht werden kann, wenn die damit verbundenen wirtschaftlichen, sozialen und ökologischen Aspekte in Verbindung betrachtet werden. Diese Bedingungen werden von verschiedenen Faktoren beeinflusst, wie z.B. dem nationalen politischen Rahmen und den Marktbedingungen. Daher ist es entscheidend, die Zusammenhänge innerhalb des ökonomisch-sozio-ökologischen Systems zu verstehen, um langfristige Entwicklungsziele zu erreichen.
4

Einsatz von Mediatoren bei der enzymatischen Aktivierung der fasereigenen Bindekräfte zur Herstellung von enzymgebundenen, bindemittelfreien Holzwerkstoffen / Application of mediators in enzymatical activation of fiberself cohesions for the production of enzyme-bonded, binder-free derived timber products

Euring, Markus 20 June 2008 (has links)
No description available.

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