National Repository of Grey Literature 88 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Ecological trends in xylem production of woody plants
Tichý, Jan ; Treml, Václav (advisor) ; Schnablová, Renata (referee)
Xylogenesis (wood formation) is one of the most important biological processes on Earth. Woody plants store atmospheric carbon during this process and are thus an essential player in the carbon cycle, and therefore in the interactions of the biosphere and the Earth's climate system. The course of xylogenesis is affected by many factors, the main factors include photoperiod, temperature and water availability. The significance and impact of individual factors on xylogenesis changes with time and place on Earth. The cambium, which by its division forms wood, enters the dormant and active phase during the year. As part of the changes in the activity of the cambium, rings are formed from which it is possible to read the conditions in which the tree was located during the formation of the given tree ring. This characteristic feature of wood is the subject of many studies and can be used to investigate the effects of climate change on xylogenesis.
Geographical characteristics of extreme growth depressions of Scots pine in Central Europe
Mík, Milan ; Treml, Václav (advisor) ; Rybníček, Michal (referee)
The presented diploma thesis studies extreme growth depressions of Scots pine (Pinus sylvestris L.) in Central Europe. Examination of significant growth anomalies (pointer year analysis) is one of the methods, which investigates the reactions of forest stands to the ongoing climate change. Dendrochronological data was obtained from Czechia (23 sites) and Slovakia (4 sites). The main hypotheses of the thesis states that the extreme growth depressions relate to climatic anomalies, hence they can be explained geographically. The objectives were to 1) create a Cropper values chronology for each site which describes growth extreme depressions; 2) explain climatic causes of negative Cropper values for each site; 3) define geographical predispositions of a spatial distribution of extreme growth depressions; 4) spatially interpolate extreme growth depressions. The calculation of Cropper values was based on a normalisation in a moving window method with a 13-year window size and the input data detrended by a 50-year cubic smoothing spline. Created chronologies were correlated with monthly climate data (temperatures, precipitation, SPEI). Geographical predispositions of the spatial distribution of growth depressions were calculated using a hierarchical cluster analysis. The cluster analysis was also applied...
The observed and projected temperature changes in the Alpine region and their consequences
Pinc, Martin ; Pokorná, Lucie (advisor) ; Treml, Václav (referee)
The observed and projected temperature changes in the Alpine region and their consequences Abstract This paper studies findings from researches that describe development of a climate change in the Alps. This text shows geography of the Alps, models that define future temperature changes and natural and human factors which affect climate change in the Alpine region. One of the main topics in this paper are possible consequences of the climate change. This paper studies climate change in the Swiss Alps and in Wallis Alps on Swiss-Italian border. The next section of this paper studies scenarios of climate change and divides them according to emission development. Paper also shows the projected temperature changes in the Alps. The main goal of this work is to accurately describe climate change models used in the Alpine region, to discuss their reliability and to determine in which cases the model temperatures differ from temperature data measured at meteorogical stations. Another goal of this work is to determine physical and human factors that contribute to surface temperature warming in the Alps. This paper also shows predictions of temperature development in the Alps and its possible consequences. In the Alps, The projected temperatures are compared with measured temperatures. Predicted temperatures are then...
The observed and projected temperature changes in the Alpine region and their consequences
Pinc, Martin ; Pokorná, Lucie (advisor) ; Treml, Václav (referee)
The observed and projected temperature changes in the Alpine region and their consequences Abstract This paper studies findings from researches that describe development of a climate change in the Alps. This text shows geography of the Alps, and also models that define future temperature changes and natural and human factors which affect climate change in the Alpine region. One of the main topics in this paper are possible consequences of the climate change. This paper studies climate change in the Swiss Alps and in Wallis Alps on Swiss-Italian border. The next section of this paper studies scenarios of climate change and divides them according to emission development. Paper also shows the projected temperature changes in the Alps. The last chapter of this paper describes modelling of climate change using tree-ring based temperature reconstructions. The main goal of this work is to accurately describe climate change models used in the Alpine region, to discuss their reliability and to determine in which cases the model temperatures differ from temperature data measured at meteorogical stations. Another goal of this work is to determine physical and human factors that contribute to surface temperature warming in the Alps. This paper also shows predictions of temperature development in the Alps and its...
MICROCLIMATIC INFLUENCES ON WOOD PHENOLOGY OF TREES AND SHRUBS IN TREELINE ECOTONE
Hejda, Tomáš ; Treml, Václav (advisor) ; Chuman, Tomáš (referee)
This thesis deals with the influence of microclimatic conditions (air temperature near tree/shrub top, temperature of the stem and root zone) on the wood phenology of trees (Picea abies) and shrubs (Pinus mugo) growing on the same site in the alpine tree line (ATL) ecotone. Phenological and microclimatic research was carried out in the Giant Mountains at 1,370 m a. s. l. in the 2017 vegetation period, with the aim to compare the course of wood formation depending on the microclimate, to determine the temperature thresholds of wood growth and differences in the morphology of trees and shrubs. Based on the microclimate analysis of trees and shrubs, individual variables were determined (average, average minimum, average maximum, daily amplitude of air, stem and root zone temperatures) characterizing the growing season. The collection of micro-drills of trees and shrubs took place from April to October in an interval of 6 - 11 days, which were subsequently processed and examined in the laboratory. The following phenophases of wood development were distinguished: cambial, enlarging, wall-thickening, mature cells and cells of the previous ring. Subsequently, differences in the number of cells of individual phenophases were identified between trees and shrubs. Furthermore, the temperature thresholds for...
Factors affecting growth trends and climate signal stability in central European conifers
Mašek, Jiří ; Treml, Václav (advisor) ; Rydval, Miloš (referee)
This thesis deals with the study of tree growth divergences, both in terms of climatic signal instability and the formation of subpopulations with different growth trends at one site (so-called individual growth variability, IGV). The aim of this work was to detect IGV and climatic instability and determine possible effects of geographical factors on divergence in forests of Scotch pine (Pinus sylvestris) from low altitudes and Norway spruce (Picea abies) from the high-elevation forest, that is typical habitats of two important Central European conifers. For this purpose, the dendrometric parameters of all trees were measured at two sites in Kokořínsko and two in the Krkonoše Mts. Climatic instability was detected by moving correlations of site chronologies with climate. A paired t-test of climate-growth responses of all trees was used to determine the change in response between two time windows. Principal Component Analysis (PCA) was used to reveal divergent growth trends within stand to develop responder chronologies. Variability was explained by correlations of z-scores of trees with individual conditions (topography, tree size, competition index). The results show that the reaction of trees to climate changes over time. In spruce, the limiting effect of summer temperatures has been recently...
Quantitative vessel parameters of broadleaves as a tool for reconstruction of physical geographical processes
Tumajer, Jan ; Treml, Václav (advisor) ; Kolář, Tomáš (referee) ; van der Maaten, Ernst (referee)
Trees adjust wood anatomical structure to environmental conditions, predisposing time series of quantitative wood anatomical parameters to be valuable source of palaeoenvironmental information. In this doctoral project we analysed the response of vessel parameters of i) floodplain Quercus robur to groundwater level fluctuation, hydroclimate variability and extreme events (droughts and floods), and of ii) Betula pendula to mechanical damage caused by various disturbances. Although climatic signal as well as pointer years stored in tree-ring width chronologies of Quercus robur largely differ between sites, quantitative vessel parameters contain spatially- homogenous positive signal of previous year summer temperature and current year winter/early spring temperature. The only between-site difference in wood anatomical chronologies is negative effect of moisture on vessel size in floodplain, which does not occur in not-flooded lowland sites. We suggest that while tree productivity benefits from high water availability, the wood anatomical structure of Quercus robur is constrained by high soil water saturation in floodplain zone. In addition, the response of tree-ring widths to moisture availability is not uniform inside single stand, but subgroups of trees with completely opposite response coexist...
Response of forest succession to agricultural land-abandonment in the Giant Mountains
Dobíhal, Michal ; Treml, Václav (advisor) ; Chuman, Tomáš (referee)
Response of forest succession to agricultural land-abandonment in the Giant Mountains ABSTRACT: Since the end of the 19th century, there is undergoing process of land-abandonment of mountain meadows and pastures in most of the European mountains, including the Giant Mountains. Mountain agriculture in the Giant Mountains was terminated no later than before World War II. Abandoned meadows were then subjected to secondary forest succession. The question is, how fast was this succession and how was its dynamics. My research was focused on 4 areas of interest, located in the vicinity of former mountain huts. Methods applied included the analysis of historical maps and aerial photographs and dendrochronological research of age structure of Norway spruce (Picea abies) stands. The aim of this thesis was to find out the extent of mountain agriculture near the huts and the dynamics of forest succession following land abandonment. Main peaks of seedlings establishment were observed in a very short time (10 - 20 years) following termination of mountain agriculture and in most cases these peaks were further followed by one or two more weaker peaks in the later periods. These peaks became evident in the change maps of forest development with approximately 20 years delay. Forest succession was moving gradually from the...
Renewable Energy Sources as a Part of Energy Transition and a Factor of Landscape Changes
Kronát, Jaromír ; Kučera, Zdeněk (advisor) ; Treml, Václav (referee)
The thesis deals with the process of development of renewable energy resources in Czechia as an important driving force of landscape changes at the beginning of the 21st century. It focuses on the influence of the political power holders on this development which they exercise through power relations and decision-making. The thesis examines the process of renewable energy development in terms of its political anchoring and in terms of spatial distribution of renewable energy facilities in Czechia, and defines its impact on landscape and societal transformations. Using the analysis of public strategic and legislative documents, it is demonstrated what attitudes towards the development of renewable energy sources were adopted by the political power in Czechia and what supportive or restrictive measures were applied to renewable energy sector. The development of renewable energy policy is divided into several phases and its crucial turning points are defined. The extent to which the spatial distribution of renewable energy sources corresponds with the distribution of favourable natural conditions and to which the spatial distribution of renewable energy sources is affected by other especially political and power factors is also clarified. For this purpose, the spatial database of solar powerplants,...
Comparison of expected and observed impacts of wind turbines on landscape character
Kočárková, Tereza ; Treml, Václav (advisor) ; Kupka, Jiří (referee)
The dissertation compares expected and observed impacts of wind turbines on landscape character. Wind turbines are large-scale constructions with a significant interference on landscape which can cause visual pollution. It is a new and unique element of landscape. Its number has increased significantly over the last fifteen years. The aim of this thesis is to compare whether the landscape assessments of selected wind turbines were done correctly or whether expected impacts on landscape character were underestimated or overestimated. Three areas of interest including wind turbines were selected for the comparison of observed and expected impacts of wind turbines on the landscape character: Dětřichov u Frýdlantu, Petrovice and Zlatá Olešnice. The partial objective of the thesis was to compare the photographic documentation of wind turbines with their computer visualizations. This research is complemented with interviews with local government representatives, which describe their attitude towards wind turbines in the municipality and its surroundings. Results of the comparison of expected and observed impacts of wind turbines on landscape character have shown that in Dětřichov u Frýdlantu and in Petrovice expected impacts of wind turbines were overestimated. In Zlatá Olešnice, expected impacts of wind...

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