National Repository of Grey Literature 7 records found  Search took 0.00 seconds. 
The influence of wind on treeline position - the question of summit syndrome
Kašpar, Jakub ; Treml, Václav (advisor) ; Kaczka, Ryszard (referee) ; Altman, Jan (referee)
Title: The influence of wind on treeline position - the question of summit syndrome Author: Jakub Kašpar Department: Department of Physical Geography and Geoecology, Faculty of Science, Charles University Supervisor: Václav Treml, Department of Physical Geography and Geoecology, Faculty of Science, Charles University Abstract: Growing season temperatures drive treeline position on a global scale. However, environmental factors including wind action may critically modify the position of treeline ecotone on a regional or a local scale. The intensity of wind action increases with shortening of treeline-summit distance. High intensity of wind action may cause the presence of a summit syndrome. This results into the lowering of treeline below its potential limit given by temperature conditions. Alpine treeline ecotones occurring in 11 mountain ranges including the Harz Mts., the High Sudetes and the Carpathians represented the model areas for my research. These mountains are located at the 50th parallel and reflect an increase in the gradient of continentality. Moreover, the distance of treeline from the summit is highly variable among these mountains. These mountains are moreover characterized by differences in mass elevation effect and in the summit syndrome intensity. Treeline position in Central Europe is...
Structure evolution of primary mixed temperate forests depending on disturbance regime
Dušátko, Martin ; Svoboda, Miroslav (advisor) ; Altman, Jan (referee)
Our thesis reconstructs disturbation history of primary forest remnant in Kornietová reservation in Slovakia. We extracted dendrochronological samples and collected data about the structure of a stand on sampling plots. 6 of total 14 plots were affected by an extreme disturbance around the year 1830. It removed almost complete upper canopy layer. This event was followed by a long period of minimal disturbance activity. The rest of plots was characterized by a regime of weak disturbances returning every 30 or 40 years. Between these two groups of plots, the shape of DBH distibution and the amount of large trees were significantly different. The plots which were affected by the extreme disturbance had distinctly more trees over 600 mm of DBH, because total extend of disturbances was markedly lower after 1830. The other parameters like amount of dead wood, species composition and quantity of saplings were not significantly different. The other studies suppose, that weak disturbances promote regeneration of beech, while large disturbances allow conifers to regenerate. The results of you study do not support such a relation. During data processing and evaluation, we discovered a high error rate the data suffered. It is more difficult to crossdate correctly a beech, then previously thought, but finally...
Tree-ring reconstruction of forest disturbances: evaluation of methods and past changes on forest dynamic
ALTMAN, Jan
Tree-ring data serves as a chronicle of the past environment and provides long-term records about climate variations, volcanic eruptions, glacial activity and many others processes. Over the past few decades, dendrochronology has become common in studying disturbances. This thesis is focused on release detection methods (i.e. abrupt growth after death of neighbouring tree(s)) and their application. The presented review showed that despite the some uncertainties in methodological approaches, release detection is a reliable tool for forest disturbance reconstruction. In this thesis, release detection was applied in various forest ecosystems for reconstruction of disturbances and their effects. The achieved results importantly contribute to the understanding of the ecological processes concerning forest management, long-term changes in natural forest ecosystems, forest diversity and the impact of global changes.
The analysis of forest vegetation on the Hallasan volcano: evaluation of impact of disturbances and competition on growth and survival of tree populations along altitudinal gradient
ALTMAN, Jan
The study was conducted on Mt. Hallasan (1950 a.s.l.) in South Korea. Forest plots were established along altitudinal gradient (950-1770 a.s.l.) from oak-hornbeam (Quercus serrata, C. laxiflora), to mixed-oak (Quercus mongolica, Taxus cuspidata), and fir (Abies koreana, Sorbus commixta) forests. Vascular plants were identified to species, and their total cover and covers of individual species in herb ({>} 1 m), shrub (1 - 5 m) and tree ({<} 5 m) layers estimated using Braun-Blanquet scale. Dentrended Correspondence Analyses was used to analyze relationship between environment and species composition, lifeforms spectra and plant diversity. The spatio-temporal variations in stem dispersion, radial growth, and mode of competition among trees were examined using the mapped location of trees and tree-rings. Changes in radial-growth were used to analyse stand disturbance history using 36647 measured tree-rings. Histories of radial-growth of individuals trees were further examined using visual classification to 5 different groups of growth trends. Ripley´s K-function was used to determine whether the spatial distribution pattern of trees was random, regular or clumped. Spatial size autocorrelations were used to determine the mode and extant of neighbor interactions. Spatial associations of different groups of trees and random mortality test were also computed for tree stands where Abies koreana was a dominant species.
Vegetation and tree growth analysis along altitudinal and latitudinal gradients in mixed-oak forests in mountain ecosystems of southern part of Korean penninsula
ALTMAN, Jan
This study deals with the altitudinal and latitudinal changes in mountain-temperate vegetation of mixed-oak (Quercus mongolica) forests in southern part of Korean Penninsula. 108 forest relevés containing 283 vascular plant species were described at elevations from cca 400-1500 m in four mountains from Seorak Mts. (38°N, 1708 m a.s.l.) to Mt. Halla (33°N, 1950 m a.s.l.). Vascular plants were identified to species, and their total cover and covers of individual species in herb (< 1 m), shrub (1 - 5 m) and tree (> 5 m) layers estimated using Braun-Blanquet scale. Both classification and ordination methods (TWINSPAN cluster analysis and Dentrended and Canonical Correspondence Analyses) were used to analyze the variability in plant species composition and species-environment relationships. Redundancy analysis was used to analyze the variability in Raunkiaer life-form spectra in forest vegetation along the main gradients. Linear regressions were used to relate the species richness and diversity values to environmental variables. Finally, tree growth pattern in stem diameter (radial growth) was analyzed based on tree-ring data in major woody species co-occurring in two contrasting forest communities.

See also: similar author names
4 Altman, Jakub
7 Altman, Jan
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