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Cette thèse visait à étudier la variabilité génétique et plasticité phénotypique de la vulnérabilité à la cavitation chez le hêtre (Fagus sylvatica L.). A cette fin, nous avons tout d’abord testé les variations dues à la méthodologie de mesure de la vulnérabilité à la cavitation. Notre étude a montré que les variations de vulnérabilité à la cavitation au cours du temps sont faibles. Néanmoins, il est préférable d’éviter de récolter les échantillons durant le début de la période de formation du bois. Par ailleurs il est possible de conserver au frais les échantillons sans dégrader les mesures durant au moins un mois. Nos résultats montrent également que la vulnérabilité à la cavitation peut être variable aussi bien au sein d’un même arbre qu’entre populations in situ. Ensuite, nous avons voulu déterminer la part de plasticité phénotypique de la part de variabilité génétique dans la variabilité de la vulnérabilité à la cavitation. Pour cela nous avons étudié 17 populations de hêtre venant de toute l’Europe et poussant dans une plantation comparative. Parmi les 17 populations 6 d’entre elles ont été étudiées dans trois plantations comparatives différentes (France, Espagne et Slovaquie). Nos résultats indiquent que chez le hêtre la vulnérabilité à la cavitation varie considérablement au sein de chaque population. Ils indiquent également que l’on observe peu de différenciation génétique entre populations. Les résultats montrent également que la plasticité phénotypique de la vulnérabilité à la cavitation est importante entre les plantations, et que le degré de cette plasticité peut varier d’une population à l’autre. Pour finir, nous avons regardé s’il existait des relations entre la vulnérabilité à la cavitation et des paramètres d’efficience hydraulique ainsi qu’avec l’efficience d’utilisation de l’eau. Nos résultats ne permettent pas de mettre en évidence des preuves d’un trade-off entre l’efficience et la sureté du xylème. / This work aimed at studying the genetic variability and the phenotypic plasticity of vulnerability to cavitation in beech (Fagus sylvatica L.). We tested the variations due to the methodology of measuring vulnerability to cavitation. Our study showed that the variations in vulnerability to cavitation over time are low. However, it’s better to avoid collecting samples during the period of initial wood formation. Furthermore it’s possible to store samples without degrading measures for during one month. Our results also show that vulnerability to cavitation can be variable both within the same tree and between populations in situ. We determined the proportion of phenotypic plasticity and the proportion of genetic variability in the variability of vulnerability to cavitation. For this we studied 17 beech populations from all Europe and growing in a common garden. Among the 17 populations 6 of them have been studied in three different common gardens (France, Spain and Slovakia). Our results indicate that for beech, vulnerability to cavitation varies considerably within populations. They also indicate that there are few genetic differentiations between populations. The results show that the phenotypic plasticity of vulnerability to cavitation is important among common garden, and the degree of this plasticity can vary between populations. To complete our study, we looked at the relationships between vulnerability to cavitation and hydraulic efficiency parameters and with the water use efficiency. Our results do not reveal evidence of relationships vulnerability to cavitation and other physiological traits.

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The full-field optical techniques such as e.g. a digital image correlation are capable to fully reflect the natural wood heterogeneity. Therefore, this thesis aspires to contribute to the experimental mechanics of wood and wood-based composites by the implementation of the full-field optical technique based on the digital image correlation to the standard mechanical tests. A supplementation of the conventional displacement sensors should help to obtain more precise mechanical characteristics and to do more sophisticated analyses of the deformation behaviour of wood and wood-based composites. The experimental part of the thesis is divided into the five independent case studies listed as the original papers. The measurements were carried out on the most wide-spread wood species in central Europe such as European beech (Fagus sylvatica, L.) and Norway spruce (Picea abies, L. Karst). Beside the solid wood, the new wood-based sandwich structure, which consists of a core made from birch plywood and the particleboard facings, was investigated too. The loading of the samples was carried out using of the standard mechanical tests such as tension, compression, three-point bending and torsion test. In the first study, the full-field deformation data were used to indentify reasons for the non-standard deformation behaviour of spruce and beech wood during compression parallel to grain. Reason for this was recognized in the abrubt compression of damage zones located near the compression plates, which induced the expansion of the middle zone located between them. The second study aimed to find out neutral axis position in native and thermally modified beech wood during the conventional three-point bending test. The relative neutral axis position was obtained from mutual position of the neutral axis and centroidal axis, which was determined based on the appropriate image processing methods. It was found that the neutral axis and centroidal sample axis are almost coincident. Objective of the third study was to determine both longitudinal shear moduli of beech wood with help of the full-field shear strains, obtained from a single torsion test, together with use of the appropriate analytical solutions for the calculation of the stress distribution within the radial and tangential direction on the longitudinal-radial and longitudinal-tangential sample surfaces. Both longitudinal shear moduli increasingly mutually differed as the load increases. Within the fourth study, verification of the elastic material model used in finite-element analyses was carried out with help of full-field deformations induced around notches within dog-bone shaped sample during the uniaxial tension. Great correlation was found between numerically predicted and experimentally measured strain data sets for both longitudinal-radial and longitudinal-tangential shear planes. The fifth study dealed with the characterization of elastic deformation behaviour of newly developed wood-based composite with a sandwich structure. Based on the full-field strain analysis the local strain concentrations were identified. They took place within the core during flatwise compression, and within the facings, when the edgewise compression test was done. A variety of presented results confirmed widespread applicability of optical methods in the mechanics of materials. Therefore, the utilization of full-field optical method based on digital image correlation in experimental mechanics of wood and wood-based composites can be highly recommended.

Wood chemical composition research is of significant importance for various fields like wood-manufacturing, food and pharmaceutical industries. Much research work has been motivated by the fundamental knowledge that wood of some tree species demonstrate significantly higher native durability against biological degradation and therefore is much convenient to use in more demanding applications, e.g. in contact with soil or water. This important wood property was assign mainly to presence of extractive chemical compounds or secondary metabolites, produced by wood when heartwood is formed. The presented doctoral thesis aims to find the possibilities of how to utilize extractive chemical compounds found in Black locust (Robinia pseudoacacia L.) as treatment solutions. These can be used to increase the durability of low durable wood species. The experimental part of the presented thesis was carried out using the laboraties and equipment of the Mendel University in Brno, and their external laboratories of research centre in Útěchov. Paper 01 aims to establish methodology for extraction apparatus fexIKA. Describes mainly possibilities for quantitative gains of extractives when using various organic solvents. Within this papers research scope heartwood, sapwood and bark of Black locust were used as the source material. Black locust was choosen mainly due to its extremely high native durability, together with oak considered highest in Central Europe, and for longer term experimental plans and reason. The established methodology for primal solvents (acetone, benzene, cyclohexane, ethanol and distilled water) was the result of this paper. The influence of extraction inputs (particles size, solvent type and temperature) on quantitative and qualitative result of extraction process was the topic for research design presented in Paper 02. In the paper comparable results with literature and established fexIKA methodology were proven. Also the effect of the above mentioned inputs are described and extracted chemical content was identified using HPLC-HRMS technique. The possibility of utilizing chemical compounds obtained, based on Paper 01 extractive methodology, aimed for higher content of phenolic compounds according to Paper 02 results, were the topic of Paper 03. This research paper proves antifungal activity of Black locust (Robinia pseudoacacia L.) and African padauk (Pterocarpus soyauxii Taub.) extracts after impregnation into European beech (Fagus sylvatica L.) sapwood. This wood species is assessed as class 5 (not durable), with an average mass loss result after the durability test of untreated samples 43.6 %. Native durability of European beech wood was significantly improved after impregnation with extractives, mass loss resulted in average 12.7 %. This revalued treated beech sapwood into durability class 3. Paper 04 continues with a study of extractives retention in wood matrix after impregnation whilst introducing adjusted leaching tests. Despite standard EN 84, this research employed miniaturized Bravery wood blocks for impregnation and leaching tests, which were at the end shortened to 144 hours. In order to increase the biologicaly active chemical compounds retention in the specimens, heat treatment was used. The results of the experiment proved the significance between heat treatment and retention.

This study addressed the development of natural regeneration of tree species over the period 2009-2016 in a temperate fir-beech old-growth forest left to a spontaneous development since 1930s. The research site was located in the strictly protected National Nature Reserve Salajka, lying in the Western Carpathians mountain range. Ungulate game browsing, establishment and mortality of natural regeneration as the main drivers of species coexistence were studied, using two alternative sampling methods, permanent network of 98 inventory plots regularly positioned across the whole forest reserve and transect with 54 transect plots. Beech was found to secure gradually absolute dominance over other tree species in natural regeneration. The growth of fir, maple and spruce was hindered by browsing since the individuals rarely exceeded the height of 0.5 m. Further, the resource concentration effect was found in fir as browsing was more intense under high conspecific densities. Establishment and mortality of fir and beech differed, suggesting the species-specific life-history strategies. The results demonstrated the importance of regular and inextensive establishment of fir and huge but relatively less frequent establishment of beech. Mortality overweighed establishment in both species, though fir ratio tended to be almost balanced. The height of natural regeneration was revealed to be the only good predictor of mortality. Browsing, establishment and mortality of natural regeneration comprise an important part of forest regeneration processes and their role should be acknowledged by both forest and nature conservation management.

Regarding the vegetation, the most affected areas by high levels of surface ozone (O3) are the mountain ridges. Our study has been carried out in the Jizerske hory Mts. High O3 levels together with the convenient environmental conditions for stomatal conductance could be a threat for the health of recovering ecosystems in this area. The aims of this study was both to assess the influence of O3 on vegetation in the Czech mountains and to provide recommendations and outlooks for possible future using of relatively new methods (visible symptoms and stomatal O3 flux modelling) used for O3 impact assessment on native vegetation in the field; that means physiologically relevant methods for the determination of O3 influence. During 2006 and 2007, O3-like visible symptoms were assessed on the leaves of seven species at four sites. Symptoms on only two species (Fagus sylvatica L. and Rubus idaeus L.) have been determined as O3-induced. To our knowledge, it is the first study in the Czech Republic in which the O3-like symptoms on native plants have been verified by the Ozone Validation Centre for Central Europe. Our results based on O3-induced symptoms indicate that ambient O3 is likely to have a much lower impact than expected, considering the measured O3 concentrations (measured with passive samplers) and...

Cette thèse visait à étudier la variabilité génétique et plasticité phénotypique de la vulnérabilité à la cavitation chez le hêtre (Fagus sylvatica L.). A cette fin, nous avons tout d'abord testé les variations dues à la méthodologie de mesure de la vulnérabilité à la cavitation. Notre étude a montré que les variations de vulnérabilité à la cavitation au cours du temps sont faibles. Néanmoins, il est préférable d'éviter de récolter les échantillons durant le début de la période de formation du bois. Par ailleurs il est possible de conserver au frais les échantillons sans dégrader les mesures durant au moins un mois. Nos résultats montrent également que la vulnérabilité à la cavitation peut être variable aussi bien au sein d'un même arbre qu'entre populations in situ. Ensuite, nous avons voulu déterminer la part de plasticité phénotypique de la part de variabilité génétique dans la variabilité de la vulnérabilité à la cavitation. Pour cela nous avons étudié 17 populations de hêtre venant de toute l'Europe et poussant dans une plantation comparative. Parmi les 17 populations 6 d'entre elles ont été étudiées dans trois plantations comparatives différentes (France, Espagne et Slovaquie). Nos résultats indiquent que chez le hêtre la vulnérabilité à la cavitation varie considérablement au sein de chaque population. Ils indiquent également que l'on observe peu de différenciation génétique entre populations. Les résultats montrent également que la plasticité phénotypique de la vulnérabilité à la cavitation est importante entre les plantations, et que le degré de cette plasticité peut varier d'une population à l'autre. Pour finir, nous avons regardé s'il existait des relations entre la vulnérabilité à la cavitation et des paramètres d'efficience hydraulique ainsi qu'avec l'efficience d'utilisation de l'eau. Nos résultats ne permettent pas de mettre en évidence des preuves d'un trade-off entre l'efficience et la sureté du xylème.