Les travaux de recherche présentés portent sur l'utilisation des produits de la liquéfaction des écorces d'épicéa dans le phénol pour la préservation du bois. Les produits de la liquéfaction permettent la synthèse d'une résine thermodurcissable de type phénolique. Les résines formulées sont imprégnées dans le bois suivi d'un durcissement in situ. Un prétraitement est mis au point dans le but d'enrichir la fraction phénolique des écorces. Ce prétraitement consiste à hydrolyser les polysaccharides principalement la cellulose et les hémicelluloses dans une solution acide. Ce prétraitement permet d'obtenir un taux de lignine dans les écorces de 60 %, et un taux de cellulose de 28 %. Un procédé de liquéfaction dans un système composé de phénol, d'eau et d'éthanol est optimisé dans le but d'obtenir des taux de liquéfaction supérieur à 85 %, et un taux d'écorces liquéfiées par rapport à la masse de phénol supérieur à 50 %. Les produits de la liquéfaction présentent l'avantage de polymériser sans ajout de formaldéhyde. La durabilité conférée au bois par les résines est bonne, surtout pour les résines phénol/formaldéhyde. Les résines sont peu lessivables. L'imprégnation du bois par les résines provoque un gonflement du bois ce qui améliore la stabilité dimensionnelle de ce dernier / This work focuses on the use of liquefaction products of spruce bark in phenol for the wood preservation. The liquefaction products allow the synthesis of phenolic thermosetting resins. The formulated resins were impregnated into the wood followed by in situ polymerization. A pretreatment was developed in order to increase the phenolic compounds in the spruce bark. This step is an acid hydrolysis of polysaccharides. This pretreatment allowed obtaining a Klason lignin content of 60 %, and a cellulose content of 28 %. A liquefaction process was developed in a mixture of solvent composed of phenol, ethanol, and water. The optimized experimental conditions allowed obtaining a liquefaction yield superior to 85 %, with liqui?ed bark/phenol ratio superior to 50 %. The lique?ed products had the advantage to polymerize without formaldehyde. The resins enhanced the wood durability especially for the phenol/formaldehyde resins. The leaching was low. The wood impregnation allowed a wood swelling, thereby the impregnated wood had a better dimensional stability

A dissertation submitted to the Faculty of Science University of the Witwatersrand, Johannesburg for the degree of Master of Science / The object of this dissertation is to develop a cost effective plasticiser/water-reducer from tannin extracts which does not retard initial strength development. Model compounds of tannins indicated the suitability of substiuued phenols for this purpose, Catechol with adjacent hydroxide groups gave a good combination of improved workability with compressive strengths equivalent to the control. Combinations with ammonia and torrnaldehyde resulted in some greatly improved performances, but also reduced stability of the additives. Urea and metabisulphite did provide some improvements ai!1ddid not adversely affect shelf life. Some of the tannin extracts tested on their own gave considerate improvements in workability and some strengths. To improve the stability of extract solutions, tannins were modified with urea, metabisulphite, small amounts of potassium hydroxide and a alcohol mixture used for pretreatment. Only the first two listed were consistently effective without producing any disadvantages. They even further improved the concrete performance of condensed tannins in particular. Small additions of TEA or its acetate salt resulted to better one day strengths of the modified tannins. Analytical techniques such as infrared and nuclear magnetic resonance were used to monitor some; modifications of the tannins and their result. A test representing early hydration conditions and X-ray diffraction provided clues to the additives mechanism in its interaction with cement. The additives performance was evaluated by comparison with a leading plasticiser/water-reducer, an independent concrete testing laboratory and conduction calorimetry by a research and testing council. A tannin based plasticiser made largely from local raw materials was quickly accepted during a recession by brick and precast manufactures . / Andrew Chakane 2018

Exploitation of botanical resources has resulted in significant decreases in the sizes of some plant populations, especially for species that have a high commercial value and are important to the lives and livelihoods of rural communities. Medicinal plant resources are used and traded commercially in both rural areas and urban centres, and over-exploitation has become a deterministic factor in the extinction risks to certain species. The main aim of the study was to design a risk assessment model to determine the impact of the medicinal plant trade on the Witwatersrand (centred around Johannesburg) on indigenous plant resources. The goal was to incorporate trade variables correlated with harvesting risks together with biological characteristics of the harvested species to predict which species are most threatened by the trade and are thus high on the list for conservation priority. The study required semi-quantitative surveys of the medicinal plants sold by traders in the Witwatersrand to be conducted. In 1994 and 2001, the plants sold in 50 muti shops and by 100 vendors in the Faraday Street market respectively were inventoried. Quantitative trade data were also captured, including volume, pricing structures and plant size (e.g. bark thickness and bulb diameter). A scientific sampling strategy was adhered to throughout the study to add statistical validity to the results. In a novel approach to analysing ethnobotanical data, the frequency of plant occurrences in the markets was analysed using measures (analysed by EstimateS) of species diversity traditionally used in ecology. The measures allowed for sampling strategies and sizes to be compared between data sets and for the number of species likely to be sold in the region to be estimated. Furthermore, data sets could be compared in terms of species richness, diversity, evenness and complimentarity. Another novel approach taken in the thesis was to estimate the number of individual plants harvested annually by gatherers, specifically the number of trees that are debarked and the number of whole bulbs that are removed. In order to estimate the number of trees debarked, a study was conducted to determine the relationship between bark thickness and stem diameter for six species. The results made it possible to estimate the condition of the resource in the wild from market records (i.e. bark thicknesses) and to see how the availability of larger trees has declined for species such as Warburgia salutaris between 1994 and 2001. Results for bulbs showed that there has been a significant decrease in the diameter of Eucomis autumnalis bulbs present in the markets in the same period, suggesting significant levels of resource depletion. The thesis explored the use of a multivariate methodology for assessing the extinction risks of species and assigning species harvested for the medicinal plant trade to various hierarchies of risk and conservation priority. Hierarchical and non-hierarchical cluster analysis (Ward’s and K-means respectively) methods were found to be effective in assigning species to clusters of similar risk and conservation priority. From a combined list of 392 ethnospecies recorded in the muti shops and Faraday market, a short-list of 119 higher risk species was identified using four to five trade variables. This list was further reduced to 87 species to ascertain conservation priorities based on the additional inclusion of seven biological variables in the assessment. From this list, approximately 31 species were identified as having higher conservation priority and would be candidates for further research, management and protection within the ambit of conservation and sustainable utilisation programmes. These species would further benefit from Orange Listing or having their IUCN Red List status re-evaluated. The methods developed in this study are recommended for other ethnobotanical studies. Furthermore, the risk assessment method could be applied to the assessment of species similarly traded in other medicinal plant markets or applied to the assessment of species under threat from other stressors at a regional, provincial and/or national level using the appropriate variables.

O Brasil destaca-se como o sétimo produtor mundial de fundidos, com mais de 30 empresas de microfusão localizadas nas regiões Sul e Sudeste do país eum dos grandes desafios é a gestão dos resíduos, entre eles, a casca cerâmica. Para a mitigação dos seus impactos é necessário o uso de técnicas de reciclagem que combinem desenvolvimento técnico com proteção ao meio ambiente e utilize a construção civil, mais especificamente o concreto, como fonte de incorporação do resíduo de casca cerâmica. Para isso, foi estudado o resíduo como agregado graúdo e miúdo em comparação com a areia e a brita 0. A massa específica do agregado seco e a massa unitária dos agregados foram avaliadas, sendo que o resíduo apresentou uma pequena redução para ambos os casos. A absorção de água foi maior para o agregado reciclado. O agregado miúdo reciclado apresentou resultados maiores para o módulo de finura e a massa específica. O índice de forma do agregado graúdo reciclado apresentou melhores resultados do agregado natural. Para avaliação do comportamento do resíduo no concreto foi utilizado o método de dosagem do IPT EPUSP. A relação água/cimento aumentou com a incorporação do resíduo Ainda, houve redução do consumo de cimento com o resíduo incorporado. As adições com até 75% de substituição do agregado graúdo apresentaram maior resistência à compressão axial comparado ao concreto convencional e, quanto maior a relação a/c menor a resistência à compressão obtida.Para o concreto em estado endurecido a absorção de água aumentou com a adição de resíduo. O índice de vazios do concreto aumenta com a incorporação de resíduo na mistura. A incorporação de resíduo aumenta a massa específica real e da amostra seca das dosagens até a substituição de 50% do agregado graúdo e após esta, tem-se uma pequena redução nestes parâmetros. A espessura carbonatada aumentou com a idade e as dosagens até 50% de adição do agregado graúdo apresentaram valores menores do que o concreto convencional. Palavras-chave: Casca cerâmica, concreto, resíduo, agregado reciclado. / Brazil stands out as the seventh world-wide producer of castings, with more than 30 microfusion companies located in the South and Southeast regions of the country and one of the great challenges is waste management, among them the ceramic shell. To mitigate its impacts, it is necessary to use recycling techniques that combine technical development with protection of the environment and use civil construction, specifically concrete, as a source of incorporation of the residue of ceramic shell. For this, the residue was studied as a large aggregate and small compared to sand and gravel 0. The specific mass of the dry aggregate and the unit mass of the aggregates were evaluated, and the residue presented a small reduction for both cases. The water absorption was higher for the recycled aggregate. The recycled kid aggregate presented higher results for the modulus of fineness and the specific mass. The shape index of the recycled aggregate presented better results from the natural aggregate. To evaluate the behavior of the residue in the concrete, the IPT EPUSP dosing method was used The water / cement ratio increased with the incorporation of the residue. Also, there was a reduction of the cement consumption with the incorporated residue. Additions with up to 75% of the large aggregate substitution showed greater resistance to axial compression compared to conventional concrete, and the higher the a / c ratio the lower the compressive strength obtained. For concrete in the hardened state the water absorption increased with the addition of residue. The void content of the concrete increases with the incorporation of residue into the mixture. Residue incorporation increases the actual specific mass and the dry sample of the dosages up to the replacement of 50% of the large aggregate and after this, a small reduction in these parameters is observed. The carbonate thickness increased with age and the dosages up to 50% addition of the coarse aggregate presented lower values than the conventional concrete.

Naturen inspirerar mig, i detta projekt jobbar jag med strukturen hos trädstammar och bark, och översätter det jag ser till vävda textiler. När jag befinner mig i naturen känner jag mig ofta lugn och kan koppla bort allt annat i min omgivning. Det lugnet vill jag återskapa och föra in i en rumslighet. I barkens olika strukturer såg jag intressanta varierande ytor som jag ville jobba med i textil. I mitt examensarbete har jag designat textilier med uppmätt akustiska egenskaper för offentlig miljö. Genom att testa materialen på SP Sveriges Tekniska Forskningsinstitut, har jag undersökt hur akustiskt dämpande de är. Resultatet har blivit en kollektion med tre vävda textilier med olika utseende och ljudpåverkande funktioner.Nature inspires me, in this project I am working with the structure of tree trunks and bark, and the translation of things I see into woven fabrics. When I am in the nature I often feel calm and relaxed. I can ignore everything else in my environment. I would like to re-create this calm feeling and bring it into a room. In the different bark structures can I see an interesting variety in the shapes witch I would like to work with in textile. In my bachelor degree work I have designed textiles with measured acoustical effects for public spaces. By making samples and test them at SP Technical Research Institute of Sweden, I have examined the acoustic damping of the materials. The result is a collection of three woven fabrics with different appearances and sound affecting functions. / Program: Textildesignutbildningen

Made available in DSpace on 2014-06-11T19:31:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-15Bitstream added on 2014-06-13T21:02:06Z : No. of bitstreams: 1 sonsinoliveira_j_dr_botfca.pdf: 3063371 bytes, checksum: 437298f5fa9c3a7b35ffe6d09d04b92a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O cerrado é o considerado a savana mais rica em biodiversidade do mundo, possui uma flora estimada em 7000 espécies, sendo 44% endêmicas, além de ser um dos 25 “hotspots” globais. Devido a grande importância desse bioma, esse trabalho apresenta as características anatômicas macro e microscópicas de 97 espécies arbóreas e arbustivas que ocorrem no cerrado sensu lato (s.l.), procurando identificar padrões estruturais comuns na madeira, e peculiares às espécies que ocorrem nas diferentes fitofisionomias, cerrado sensu stricto (s.s.), cerradão e zona ripária. Adicionalmente, foi caracterizada a morfologia externa da casca dessas espécies. As características anatômicas macroscópicas da madeira aliadas as da morfologia externa da casca que facilitaram a separação das espécies em uma mesma família, principalmente espécies que pertencem ao mesmo gênero foram: arranjo de vasos, padrão de parênquima axial, largura de raios (TR), estratificação de raios, presença de exsudatos e a cor interna da casca. Para as espécies de cerrado s.l. foram observadas características que podem contribuir tanto para segurança quanto para eficiência na condução hídrica, como: alta ocorrência de vasos múltiplos e frequência de vasos por mm², pontoações intervasculares alternas pequenas, pontoações guarnecidas; placas de perfuração simples. O índice de vulnerabilidade foi de 1,6 e de mesomorfia 600. Apesar da maioria das características anatômicas das espécies do cerrado s.l. se enquadram nas tendências ecológicas para espécies que ocorrem em terras baixas dos trópicos, as espécies que ocorrem nas diferentes fitofisionomias possuem características anatômicas que mostram estratégias particulares para sobrevivência das mesmas. Quando comparando as fitofisionomias, de uma maneira geral, os espécimes da zona ripária apresentaram vasos de maior diâmetro... / The cerrado is considered the richest savanna in biodiversity in the world, its flora has about 7000 species, being 44% endemic, besides being one of the 25 global hotspots. Due to the great importance of this biome, this paper shows macro and microscopic wood anatomical features of 97 arboreal and shrubby species which occur in cerrado sensu lato, aiming to verify the common structural patterns in the wood, and peculiars to the species that occur in three different physiognomies, cerrado sensu stricto (s.s.), cerradão and riparian zone. Additionally, the external bark morphology of these species was characterized. Macroscopic wood features allied to bark surface features which facilitate separation of species within a family and, mostly species from the same genus were: vessel arrangement, axial parenchyma pattern, ray width (TR), storied rays, presence of exudates and bark internal colour. For cerrado s.l. species we observed anatomic features that may contribute to both safety in water flow and efficiency, such as: high incidence of multiple vessels and high vessel frequency per mm², small intervessel pits alternate, vestured pits, simple perforation plates. The vulnerability and mesomorphy index were 1.6 and 600, respectively. Despite of the majority of cerrado s.l. species anatomical features were framed in the ecological trends for species which occur in tropical lowlands, the specimens which occur in the different physiognomies have anatomical features that show particular strategies for survival in each physiognomy. When comparing the physiognomies, in a general way, riparian zone specimens have larger vessels, low frequency per mm² and larger intervessel pits diameter, what indicates better efficiency in conduction, while cerrado s.s. specimens were the opposite and showed low vulnerability and mesomorphy index, demonstrating greater safety under conditions... (Complete abstract click electronic access below)

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The thesis describes several unknown aspects of the spruce bark beetle, Ips typographus (L.), and the double-spined bark beetle, Ips duplicatus (Sahlberg.), life-cycles and ecophysiology. The first study focuses on I. typographus and its dispersal under epidemic conditions in the National park Šumava and introduces a novel method of fluorescent marking and detection of captured specimens. The second study is focused on ability of I. typographus to establish so-called sister-broods, i.e. re-emergence of females that are capable to continue egg laying without a need to mate again. The importance of sister-broods becomes apparent mainly in recent hot and dry vegetation seasons, which is demonstrated by a comparison of recent and historical data. The third study focuses on temperature-dependent development of I. duplicatus under laboratory conditions by the means of sandwich method. Altogether, the studies underline practical importance of ecophysiological studies on bark beetles as one of the tools for their effective management.

In response to the furniture industry’s growing demand for raw material, large volumes of juvenile silver birch and downy birch stems available from pre-commercial thinning operations in Sweden’s forests could offer solutions. However, such stems are not currently used on an industrial scale, and most research conducted on birch stems in general has neither focussed on young trees nor the potential use of the central stem part around the tree pith. The resulting lack of knowledge about the juvenile part of birch wood thus requires additional information about the material properties of birch, which could encourage its use for various purposes in the furniture and other industries. The initial literature review performed for this thesis has highlighted some properties of juvenile birch required for its use as a furniture material, as well as identified topics concerning the physical characteristics of juvenile birch about which knowledge is currently limited. Consequently, the objectives of this thesis were to explore some characteristics of juvenile birch—bark thickness, wood-to-bark bonding ratio after drying, variations in the density and width of growth rings, and anatomical growth response to fertilisation—in order to increase the knowledge. The material studied came from mixed birch and Norway spruce stands at two sites in southern Sweden, namely Asa and Toftaholm. The birch stems were naturally regenerated silver birch and downy birch, with breast height diameters between 30 and 83 mm. Fertilised and unfertilised silver birch trees were sampled at Toftaholm, whereas unfertilised stems of silver birch and downy birch were sampled at Asa. The characteristics of stems from the pith to bark (radial direction) and along the stem (longitudinal direction) were measured. The wood-to-bark bonding ratio on downy birch after drying was calculated as the percentage of the stem circumference with full contact between the wood and bark, while oven-dry density and basic wood density for silver birch were determined by using the water displacement method. The impact of ring width on wood density was statistically analysed, and an image analysis of the wood anatomy was conducted to elucidate their relationship. Amongst the results, bark thickness along the stem had the highest deviation in the section closest to the stump. Moreover, the wood-to-bark bonding ratio after drying measured for juvenile downy birch seemed to depend more on the stem’s diameter than the sampling height along the stem. Such results are relevant for processors seeking to estimate the volume of wood under the bark. The wood-to-bark bonding ratio was highest for diameters between 30 and 39 mm, and neither did that relationship correlate with the sampling height along the stem. Variation in wood density in the radial and longitudinal directions in juvenile silver birch suggested that such density negatively correlated with growth rate (ring width). That relationship held true for stems at each site and between the sites, irrespective of management or growing conditions. As expected, mean wood density was lower in fertilised trees than in unfertilised ones, and towards the bark, radial density increased more in trees that grew more slowly. At the same time, variation in longitudinal density in young silver birch trees was low. Quantitative wood anatomy studies confirmed that the fertilised juvenile birch had younger cambia, thinner cell walls, and fewer vessels per mm2 than unfertilised trees in the same diameter class. Overall, the knowledge generated in the study may facilitate the industrial use of juvenile birch stems and wood in interior and furniture applications. The role of wood anatomy in determining the mechanical performance of juvenile birch stems should be further examined, however, to possibly reveal new opportunities for the use of juvenile birch. / Det finns ett växande behov av råvaror till möbelindustrin. Stammar av juvenil vårtbjörk och glasbjörk finns tillgängliga i stora volymer från röjning i svenska skogar. För närvarande finns det inget storskaligt industriellt nyttjande av det virket. Bättre kunskap om dess virkesegenskaper kan öppna upp möjligheterna till olika användningsområden. Dock har en majoritet av den befintliga björkforskningen ofta exkluderat studier av innersta veden närmast kärnan, vilket resulterat i en låg kunskapsnivå om det juvenila virket. I den inledande litteraturstudien i denna uppsats belyses vilka krav som ställs på materialegenskaperna i möbelvirke. Vidare identifieras befintliga kunskapsluckor i fysiska och mekaniska egenskaper för juvenil björk. Målet med denna uppsats är därför att utforska några egenskaper, såsom barktjocklek, barkvidhäftning efter torkning, densitet och årsringsbreddsvariation samt hur gödsling kan påverka vedanatomin. Materialet kom från blandskogsbestånd med gran och björk i Asa och Toftaholm i Götaland. Björkarna var självföryngrad vårtbjörk och glasbjörk och stammarna hade en brösthöjdsdiameter mellan 30 och 83 mm. I Toftaholm var en del av beståndet gödslad respektive ogödslad vårtbjörk. Från Asa togs stammar av både vårtbjörk och glasbjörk. Virkesegenskaper och dess variationer i stammens radiella och longitudinella riktning studerades. Vidhäftningen av barken till veden efter torkning bedömdes procentuellt på omkretsen av ändträet. Relativ torrdensitet och rådensitet mättes. Påverkan av årsringsbredd på veddensitet analyserades statistiskt och vedanatomin studerades med mikroskop och bildanalys för en vidare förståelse av dess samband med gödsling. Resultaten gällande barktjocklekens variation visade att den nedre delen av stammen hade störst medelavvikelse. Dessa resultat kan vara relevant information för vidareförädling efter avbarkning. Barkens vidhäftning till veden efter torkning mättes på juvenil glasbjörk. Det visade ett visst samband med stamdiameter där den högsta vidhäftningen fanns på stammarna med en diameter mellan 30 och 39 mm. Sambandet var däremot inte korrelerat till stamhöjden där provet togs. Densitetsvariation i radiell och longitudinell riktning studerades för juvenil vårtbjörk. Densiteten hade en svag negativt korrelation till årsringsbredd. Detta samband sågs både inom bestånd och mellan bestånd med olika tillväxtförhållande samt skötsel. Medeldensiteten för virket var, som förväntat, lägre i de gödslade träden jämfört med de ogödslade. I den radiella riktningen  hade det senvuxna virket en högre faktor på densitetsökningen. Den longitudinella densitetsvariationen i unga vårtbjörkar var låg. Kvantitativa vedanatomistudier bekräftade att ungdomsveden i gödslad vårtbjörk hade en lägre kambiumålder, tunnare cellväggstjocklek och färre kärl jämfört med ogödslade träd med samma diameter, resultat som tidigare påvisats för mogen björk. Sammanfattningsvis kan resultaten från den här uppsatsen förbättra kunskapen och därmed underlätta för en industriell användning av juvenila björkstammar inom inredning och möbler. Dock bör vedanatomins påverkan på de mekaniska egenskaperna för juvenila björkstammar studeras vidare. Det kan möjliggöra nya användningsområden för juvenil björk.

Les insectes coléoptères Scolytinae, ou scolytes, sont des agents biotiques majeurs de perturbation des écosystèmes forestiers à travers le monde. Ils peuvent être avoir des impacts écologiques et économiques sévères en milieu naturel et dans les plantations forestières. La dynamique et l’écologie des scolytes des forêts tempérées, boréales et méditerranéennes ont été abondamment documentées, définissant un cadre conceptuel approprié pour l’étude de ces insectes dans d’autres écosystèmes forestiers où les connaissances restent parcellaires. C’est le cas des forêts néo-tropicales équatoriales, au sein desquelles les communautés de scolytes restent à ce jour relativement méconnues, malgré leur implication croissante dans les dégâts et mortalités observés dans le cadre du changement global et du remplacement des forêts naturelles en plantations forestières. Dans cette thèse, je me suis intéressée aux facteurs climatiques et écologiques qui régissent la diversité et l’impact des scolytes dans des forêts naturelles et dans des plantations de balsa (Ochroma pyramidale) en Equateur, ainsi qu’aux associations scolytes-champignons mises en place chez certaines espèces dans ce milieu. Ce travail a permis d’enrichir les connaissances actuelles que les connaissances actuelles sur la diversité des scolytes en Equateur. J’ai pu montrer notamment que les différents types d’habitats forestiers (forêts naturelles et plantations de balsa) influencent davantage la composition en espèces que la richesse spécifique cumulée. Il existe par ailleurs des espèces indicatrices de ces habitats, dont l’une d’entre elles est un ravageur majeur du balsa dans les plantations (Coptoborus ochromactonus), et trois autres sont des espèces exotiques. L’étude spécifique de la biologie et de la dynamique des populations de C. ochromactonus dans les plantations de balsa a montré que des facteurs climatiques et d’âge des arbres influencent significativement les dégâts occasionnés par ce scolyte. Enfin, j’ai pu mettre en évidence l’association des champignons ambrosia Raffaelea sp. nr. arxii et Fusarium ambrosium avec des scolytes Xyleborus, l’un des genres les plus diversifiés et abondants en forêt naturelle et en plantation de balsa. Ma thèse de nouvelles perspectives en termes de biodiversité et de gestion des risques sanitaires liés aux scolytes dans les écosystèmes forestiers d’Equateur.Mots-clés: scolytes, richesse, abondance, composition des espèces, forêt primaire, balsa, dégâts, phénologie, interaction plante-insecte, champignon ambrosia, Xyleborus / Scolytinae insects, or bark beetles, are major biotic agents of forest ecosystem disturbance throughout the world. They can have severe ecological and economic impacts in both natural forests and commercial plantations. The dynamics and ecology of bark beetles in temperate, boreal and Mediterranean forests have been extensively documented, defining an appropriate conceptual framework for the study of these insects in other forest ecosystems where knowledge remains fragmented. This is the case of the equatorial neo-tropical forests, in which bark beetle communities remain to date relatively unknown, despite their increasing involvement in the damage and mortality observed in the context of global change and the replacement of natural forests by plantations. In this thesis, I focused on the climatic and the ecological factors driving the diversity and impact of bark beetles in natural forests and in balsa (Ochroma pyramidale) plantations in Ecuador, as well as in scolytines-fungi associations that can take place in a number of scolytine species. This work has enriched current knowledge on the diversity of bark beetles in Ecuador. In particular, I have shown that different types of forest habitats (natural forests and balsa plantations) have a greater influence on species composition than on cumulative species richness. I also identified indicator species of these habitats, one of which is a major pest of balsa in plantations (Coptoborus ochromactonus), and three others are exotic species. The specific study of the biology and population dynamics of C. ochromactonus in balsa plantations has shown that climatic and tree age factors significantly influence the damages caused by this bark beetle. Finally, I was able to highlight the association of ambrosia fungi Raffaelea sp. nr. arxii and Fusarium ambrosium with Xyleborus bark beetles, one of the most diverse and abundant genera in natural forest and balsa plantation. My thesis provides stimulating new perspectives in terms of biodiversity and management of health risks related to bark beetles in forest ecosystems of Ecuador.Key words: scolytine, richness, abundance, species composition, primary forest, damage, phenology, insect-plant interaction, ambrosia fungi, Xyleborus