Doctoral theses

Doctoral theses 14,911 records found  previous11 - 20nextend  jump to record: Search took 0.00 seconds. 
Pařezová výmladnost jako základ obnovy a produkce nízkého lesa =: Stump sprouting as a basis for the regeneration and production of coppice /
Uherková, Barbora
In 2008, a young coppice was established and studied in the south-eastern part of the Czech Republic. The main studied species Quercus petraea (Matt.) Liebl agg. and Carpinus betulus L. are typical species of Central European coppices. The aim of the dissertation thesis was to study the topic of re-sprouting, the process when the new regeneration of sprouts is created. Re-sprouting occurred after thinning carried out at the turn of the years 2014/2015. The number of live and dead new sprouts was recorded, and their heights were measured. Subsequently, the effects of the stump basal area before and after thinning, the thinning intensity, leaf area index and light conditions (gap fraction, openness, direct, indirect and total site factor) were studied on the newly established generation of sprouts. Another aim of the dissertation thesis was to find out the effect of thinning on the growth of the coppice in the current changing climate conditions. For three growing seasons (2015 –2017) after the thinning, the growth (diameter and height increments) and soil water content were observed. To study the effect of climatic conditions, a throughfall reduction was simulated by using drainage channels. Similar system of drainage channels was used in Spain, France and other countries. To address the topic of soil degradation, the impact of throughfall reduction and thinning on soil CO2 efflux was investigated. Comparison between subplots with and without thinning, subplots with and without throughfall reduction and coppice with false high forest (control area to the research area of coppice forest) were carried out. As far as the re-sprouting is concerned, the stump basal area before thinning and the thinning intensity statistically significantly influenced the number and height of the new sprouts. Among all factors of light condition, only the indirect site factor was statistically significant. Therefore, the thinning affected soil moisture and the amount of light in the coppice. In the first year after the thinning, the diameter increments of sessile oak and European hornbeam were positively influenced by thinning. In the following two growing seasons, thinning did not significantly influence the diameter increment. However, the height increment of both trees during the whole study period has not been positively affected by thinning. On the other hand, thinning significantly affected the soil moisture. During the three-year study period, soil moisture was higher on thinned plots. This finding is in coincidence with research experiments carried out in southern Europe. The second studied factor, which was the throughfall reduction, did not influence neither the diameter increment, nor the height increment and nor the soil moisture in both species for the entire period. Thinning did not affect soil CO2 efflux rates, whereas the throughfall reduction did. Coppice reached almost the same soil CO2 efflux rates as the false high forest. In conclusion, thinning in coppice leads to an increase of available soil water. The water availability will be very actual issue at lower altitudes – here the tree species are sensitive to high air temperatures and drought stress. It should be noted that the younger developmental stages of the forest stands show increased sensitivity to water deficit due to drought. Thanks to sprouting ability, coppicing can therefore be appropriate management in some deciduous stands at lower altitudes under changing climate conditions.
Aplikace nových materiálů pro tvorbu nábytku budoucnosti s ohledem na uživatelský komfort =: Aplication of new materials for furniture development with respect to user comfort /
Šprdlík, Václav
This thesis was focused on solid wood surface treatments. The goal of the thesis was to achieve superhydrophobic behavior of solid wood surface and its application on furniture design – bathroom furniture. In the first part of experiment the thesis dealt with plasma discharge surface treatment of 3 different wood species – larch (Larix decidua), oak (Quercus robur) and pine (Pinus sylvestris). These treatments were performed in atmospheric and inert (nitrogen) environment with different time of treatment. Effect of plasma discharge was evaluated by contact angle measurement. The second part of the experiment was focused on wax deposition on wooden samples with different roughness. The wax n-hexatriacontane is naturally found as a component of wax blends on the surface of plant leaves. The deposition was performed by physical evaporation in vacuum. This wax has a self-assembly ability, e.g. it creates 3D objects on the surfaces after deposition. The dependence of roughness on self-assembly and wettability in time were examined. Self-assembly ability was observed with scanning electron microscopy and confocal microscopy. Plasmatic treatment hasn´t led to increased hydrophobicity, nevertheless, a significant increase of hydrophilicity was observed during contact angle measurement which could be used as a preparation for surface coating. Surface treatment with wax has led to significant increase of hydrophobicity. Samples of larch and oak achieved superhydrophobic surface behavior (CA > 150°) and pine samples achieved highly hydrophobic behavior (CA > 140°).
Wood Extractive Compounds - Extraction, Chemical composition, Biological activity, Native durability =: Extraktivní látky dřeva: Extrakce, Chemické složení, Biotická aktivita, Přirozená trvanlivost /
Sablík, Pavel
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.
Analýza parametrov trakčného ústrojenstva ťažobno-dopravných strojov a ich vplyvu na pôdne prostredie =: Analysis of the parameters of the traction system of the harvesting and transport machines and their influence on the soil environment. /
Marušiak, Milan
This PhD thesis deals with analysis of the forest machines traction device and the ma-chine operation to the soil environment. Within the thesis are solved problems covering transmission of drive force in the traction device, where the traction characteristic for most used types of transmission is developed. Within the scope of machine action on the soil there is elaborated problem of the soil contact pressure determination and the rut depth determination by the first and multiple passage of the machine. Particular attention is paid to dynamic load calculation where the vehicle speed is used as input para-meter. An important part of this work is the verification of the calculation relationships for determination of several parameters (tire contact area, soil contact pressure, rolling resistance, rut depth) with the measured data. The last part of this thesis compares ma-chine mobility calculations according to the WES and MMP method, together with the mobility estimation according to the rolling resistance coefficient and the pulling force. The result of traction analysis is the creation of a computing application in MS Excel which provides basic data on machine mobility in the field.
Loranthus europaeus Jacq. verzus druhy r. Quercus L. resp. Carpinus L. =: Loranthus europaeus Jacq. vs. Quercus L. resp. Carpinus L. genera. /
Kubíček, Jan
A better understanding of host – hemiparasite association can lead to deepening and improving strategies, which would result in a long-term sustainability of their mutual balance or prosperity of urban and forest vegetation growth. The aim of the thesis is to describe and explore periodicity and dynamics of hemiparasite (Loranthus europaeus Jacq.) on various host woody species (Quercus petraea (Matt) Liebl., Carpinus betulus L., Prunus spinosa L.), options of the host support and means of a careful removal of parasite. However, to determine the progress of the infestation in time was the primary aim of the thesis. The research has been carried out in Brno – Kohoutovice and National Park Podyjí. The emergence of both hemiparasite´s and host´s phenophases were mutually compared in the critical conditions. The variation of the growth modules of mistletoe was compared in relation to the host species. The growth and fruit yield of the host and hemiparasite were analysed after the application of fertilizer based on the variations of the mineral content of leaves and soil. Between the years 2011-2015, 1599 stems were monitored for the degree of infestation by mistletoe. The results indicate that the vitality of the hemiparasite depends on the type of host. Fertilizer application improved the growth of the host. Arboricide application on the leaves of the hemiparasite was proven to be efficient. The abundance of hemiparasite increases with the increasing diameter at breast height (DBH), time and mutual interaction. The amount of hemiparasite slightly increases with the lower DBH. However, with the increasing DBH the mentioned phenomenon decreases. The trees with high DBH even show the decrease in the mistletoe infestation in time. Nevertheless, the decrease was accompanied by negative effect – gradual reduction of the crown and loss of the host tree branches. Hemiparasite is able to eradicate the whole stand. Hence, the necessity of paying attention to this issue since the young age of the individual trees. It is necessary to protect trees against stress aspects which can accelerate the negative effect of hemiparasite on the host.
Zhutňování vyklizovacích linek vlivem kolových těžebně dopravních systémů =: Strip road compaction caused by wheeled logging machinery /
Kleibl, Miroslav
The aim of the study is an assessment of forest soil compaction caused by wheeled logging technology and the soil ability to regenerate into the original conditions. The method is based on assumption that multiple passage significantly affects the rate of compaction and that the compaction occurs not only on striproads, but reaches deeper into the stand. After the operation the soil has an ability to return into the original condition thanks to natural processes. The return level assessment is done using a range of laboratory tests and a number of devices, respectively. Each of the device works on different principle which sets the limitation of usage and the study ambition is also an evaluation, which kind of device is applicable for soil compaction assessment. The results of the study displays that the soil compaction reaches more than 1 m deep into the stand side of the striproad. The regeneration ability of the soil into the original condition is visible after 5 years after the operation and on sandy soils can reach about 50%. For assessment of the soil compaction and soil recovery could be used in limited applicability deflectometer, penetrometer, laboratory tests of Kopecky metal rings and CO2 gauge, respectively. Since the limitation of each method or device, the assumption of the study is different devices combination during evaluation process.
Fyziologické, anatomické a morfologické reakce sazenic buku lesního a smrku ztepilého na stres suchem a následnou závlahu =: Physiological, anatomical and morphological response of European beech and Norway spruce seedlings on drought stress and subsequent irrigation /
Hájíčková, Martina
European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst) are the most abundant deciduous and coniferous tree species in the Czech Republic. Both beech and spruce are due to their sensitivity to drought threatened by ongoing climate change that can cause deterioration of their vitality in current habitats. Drought periods are already becoming longer and stronger and previously rare spring droughts become more frequent. The dissertation thesis is based on experiments with Norway spruce and European beech seedling exposed to different levels of drought (well-watered, moderate drought and severe drought). After three to six weeks of drought, the seedlings were well-watered for another two weeks and their response of physiology, anatomy and morphology was evaluated. Experiments were conducted with seedlings at early stage of leaf development and with fully developer leaves to compare response to spring and summer drought. Overall drought response was stronger in spring. Both spring and summer drought reduced gas exchange parameters (in both beech and spruce seedlings up to 100 %), hydraulic conductivity and less strongly also fluorometric parameters. Efficiency of water use in stressed seedlings decreased in spring, while it increased in summer. Shoot and leaves biomass was more reduced by drought than root biomass. Tree-ring width decreased about two times more in beech seedlings than in spruce seedlings. Vessel and tracheids in stem and shoots reduced their number and size, on the contrary, vessel size increased in beech petioles. After rewatering the reduced parameters increased, however, hydraulic conductivity, anatomy and morphology did not reach values of well-watered seedlings. While most of physiological parameters restored in moderately stressed seedlings, in severely stressed seedlings mainly gas exchange parameters remained lower.
Chřadnutí rostlin v bioremediační krajině =: Failing Plants in Bioremediation Landscapes /
Funai, James
Current soil media recommendations for stormwater bioremediation landscapes contain large ratios of sand. These same landscapes suffer catastrophic plant loss within several years thus losing a majority of biological functionality. Filter and planting media used in stormwater management landscapes should improve floral and faunal health while maintaining engineered specifications and esthetic requirements. With improved ecosystem health and activity, these landscapes could last longer, perform better, and cost less to maintain. Through evaluation of experimental plots over 3 years, lessons shared in this dissertation include realized failures in a high sand soil and success in soils engineered with expanded shale to achieve a better functioning landscape.
Geobiocenologická diferenciace lesa a krajiny jako podklad lidské činnosti v krajině =: The geobiocoenological system of forests and landscape classification as a tool of human activity in landscape /
Friedl, Michal
The topic of the dissertation is a development of geobiocoenology and geobiocoenological system of classification and their possible application in landscape management. The thesis is structured into four thematic blocks or case studies and is composed of reviewed and published works. The first part introduces the application of biogeographical differentiation of the landscape by a geobiocoenological approach in the development of the concept of ancient coppice forests, estimation of their distribution in the Czech Republic and description of their state. The second study deals with the testing of empirically defined units of the Czech Forest Ecosystem Classification based on the evaluation of 11,885 geobiocoenological relevés stored in the Database of Czech Forest Ecosystem Classification and containing a series of accurately measured environmental data. The last two studies are operational applications of geobiocoenology. In the first one, geobiocoenology was used for the construction of a regional forest development plan in the Ukrainian Carpathians. In the second one was geobiocoenology used for the differentiation of the peak positions of Hrubý Jeseník, because of which, besides other things, was predicted the development of biotopes in case of removing allochthonous stands of mountain pine. This dissertation demonstrates the multifaceted use of geobiocoenology, contributes to its development and enriches it also at the level of operational applications.
LAI- kvantifikátor pěstebního zásahu =: LAI- quantifier of silvicultural treatment /
Černý, Jakub
The thesis divided into four research topics dealt with an issue of the relation between silvicultural treatments and an amount of the bearing photosynthetically active assimilation apparatus quantified by leaf area index (LAI) in forest stands of an economically important tree species in the Czech Republic. In pure Norway spruce pole stands at the middle altitudinal zone, an effect of silvicultural treatments on the LAI and an efficiency of the photosynthetically active radiation (PAR; 380-720 nm) by foliage within the photosynthetic uptake was evaluated through both canopy production index (CPI) and leaf area effectivity (LAE), and the highest value of the LAI was achieved in a plot with the highest stand density. However, the highest efficiency of the PAR utilisation (CPI, LAE) was noted in the stand, which was tended by thinning from above. Thus, it was proved that not only the total LAI value but especially an efficacy of the leaf area reflecting sun and shade foliage ratio is the more relevant parameter for an evaluation of the effectivity of the thinning treatment. In a forest regeneration, the LAI can also be used for quantification of the regeneration process stage related to a growth dynamic of the natural regeneration. Besides that the newly developed device LaiPen LP 100 (PSI, ČR) for indirect optical LAI estimation was tested within this study. LAI values measured by LaiPen LP 100 showed almost same accuracy of the measurement and identical trends as world standard (LAI-2200 PCA; LI-COR, NE, USA); both at the stand level and the particular measurement point level. Within the study of the efficacy of the PAR utilisation by foliage in photosynthetic uptake expressed by radiation use efficiency (RUE) in pure, fully-stocked and not defoliated Norway spruce mature stands, it was found that mean air temperature most significantly affect annual and monthly values of the RUE with the significant linear relationship (R2 = 0.19; p < 0.05). In the spruce stands, the significant linear relationship (R2 = 0.85; p < 0.001) between an amount of the sequestrated carbon in the form of atmospheric CO2 molecules and the RUE was also proved. The research topic dealt with a seasonal dynamic of the LAI in selected pure and even-aged European beech and sycamore maple stands revealed findings that a culmination of the LAI is achieved within summer months (DOY 120-140) in the investigated stands. The period is the most suitable for estimation and mutual comparison of the LAI due to the stability of its values in investigated (but also in another deciduous) stands. In studied beech and maple stands, maximum LAI values were noted in the second half of June (DOY 170). General findings of underestimation of LAI values estimated by indirect optical methods compared to direct methods were also confirmed. In the last research topic, an effect of the stand age on the leaf area development was studied in pure, even-aged, and fully-leaved (not defoliated) forest stands of an economically important tree species (Norway spruce, Scots pine, silver fir, Douglas fir, European beech, pedunculate oak, and black walnut). Except for black walnut stands, significant linear relationships proving a decrease of the leaf area with increasing age of the stand were found. The relation between the leaf area expressed by effective plant area index (PAIe) and the age of stands was studied for monitoring of the leaf area dynamic within forest stands with a different age.

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