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  • 1
    Language: English
    In: Trees (Berlin, West), 2019-12, Vol.33 (6), p.1657-1665
    Description: The axial structure of the hydraulic system in trees is relatively invariant and insensitive to temperature, while trees plastically adjust the number of cells within the tree ring.At higher elevations and latitudes in the treeline ecotone, reduction in the heat accrued during the growing season is reflected in gradually decreasing tree size. Due to low temperatures, treeline trees might produce smaller xylem cells and, as a consequence, tree growth could be limited. However, some xylem traits (i.e., cell lumen area) are considered relatively insensitive to climatic factors but highly dependent on tree size because of the natural widening of xylem conduits towards the stem base. We tested the hypothesis that earlywood cell lumen area is essentially invariant and depends largely on tree size. Tracheid traits in four conifer species from the lower (“timberline”) and upper (“treeline”) parts of the treeline ecotone (Picea engelmannii, Picea abies, Pinus cembra and Larix decidua) were measured in the Colorado Front Range (U.S.A.), Krkonoše Mts. (Czech Republic) and Dolomites (Italy). On transversal sections sampled at 1 m of stem height, we measured cell lumen areas, transversal cell size, cell wall thickness, tree-ring width and number of cells per radial file. Cell lumen areas were always greater at the timberline than treeline. When tree height is accounted for, the earlywood cell area did not differ between the two sites, thus showing that difference in temperature did not affect earlywood cell area in any of the four measured species. The number of cells within tree rings exhibited high inter-annual variability according to environmental factors. The fundamental hydraulic structure in trees is relatively rigid and insensitive to temperature, while trees plastically adjust the number of cells within the tree ring as a result of inter-annual climate variability and leaf production.
    Subject(s): Agriculture ; Alpine treeline ; Cell widening ; Conduit diameter ; Forestry ; Larix decidua ; Life Sciences ; Life Sciences & Biomedicine ; Picea abies ; Picea engelmannii ; Pinus cembra ; Plant Anatomy/Development ; Plant Pathology ; Plant Physiology ; Plant Sciences ; Science & Technology ; Stem allometry ; Wood anatomy
    ISSN: 0931-1890
    E-ISSN: 1432-2285
    Source: Web of Science - Science Citation Index Expanded - 2019〈img src="http://exlibris-pub.s3.amazonaws.com/fromwos-v2.jpg" /〉
    Source: Alma/SFX Local Collection
    Source: ProQuest Central
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  • 2
    Language: English
    In: Journal of vegetation science, 2018-11, Vol.29 (6), p.1007-1016
    Description: Questions Globally, mean growing season temperature at the climatic treeline was found to converge to a common isotherm, presumably related to similar growth limitations by low temperature. However, temperatures for high‐elevation tree limits are often higher than the corresponding thermal limit for tree growth, suggesting that trees are regionally absent from the potential treeline. We explore whether the regional uppermost tree stands in Central Europe are limited by low growing season temperature, reflect the action of a “summit syndrome” (harsh climatic conditions near summits of insufficiently high mountains), or have resulted from historical land use or other disturbances. Location Mountains of Central Europe, north and east of the Alps (48–51°N, 10–20°E). Methods In each region, the highest elevation, 3‐m tall individuals of Picea abies were sampled to measure radial and height growth and to record symptoms of wind‐induced damage (abrasion, bending, breakage). Trees were grouped based on their growth performance and growing season temperature. Differences in variables indicative of a summit syndrome (wind‐induced damage, elevation distance to nearest summit, height increment above 2 m stem height) were tested among groups. Results We identified four particular groups of trees. The first contains trees characterized by low growth rates at cold tree limits located distant from summit areas. These trees are considered to represent the climatic treeline. The second group consists of trees growing well at relatively “warm” tree limits located near summits. These upper tree limits are probably a consequence of disturbances, human interventions or tree establishment lagging behind the warming over the past century. Trees from the remaining two groups are characterized by intermediate temperatures and growth rates. They are usually located near summits and exhibit various ranges of symptoms of mechanical impact due to summit conditions. Their current range limits reflect a combination of the repeated loss of biomass, thermally‐limited growth and restricted space for further upslope advance. Conclusions Our study shows that comparing tree growth, growing season temperature and symptoms of biomass loss is helpful for explaining the formation of regional upper tree limits. For ten temperate European mountain regions, we identified three major types of conditions under which trees reach an upper range limit, each characterized by similar stem‐growth performance, temperature and degree of impact by the summit syndrome. We exemplify that comparing stem‐growth variables with growing season temperature is a suitable approach for identifying the origin of the regional uppermost tree limits.
    Subject(s): Carpathians ; Picea abies ; species‐specific upper limit ; Sudetes ; tree growth ; treeline
    ISSN: 1100-9233
    E-ISSN: 1654-1103
    Source: Academic Search Ultimate
    Source: Alma/SFX Local Collection
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  • 3
    Language: English
    In: Climate research, 2016-03-23, Vol.68 (1), p.1-12
    Description: Alpine treeline ecotones north of the Alps in Central Europe occur in 11 mountain ranges, including the Harz Mountains (Germany), mountain chains of the High Sudetes (Czech Republic and Poland) and the Western Carpathians (Czech Republic, Poland and Slovakia). These mountains are characterized by pronounced maritime−continental gradients, large differences in the mass elevation effect, and varying distance between the treeline and summits. We evaluated how these factors influence treeline temperatures and thus treeline elevation. We compared various treeline temperature metrics for all mountain ranges in the study region both among the mountain ranges and with treeline temperatures in the Alps. Our results show that treelines along the 50th parallel increase their elevation by approximately 94 m per 100 km to wards the east, a reflection of a rise in elevation of isotherms of growing season temperatures along the maritime−continental gradient and with increasing mass elevation effect. Among the majority of evaluated mountain ranges, growing season treeline temperatures did not differ significantly, suggesting identical thermal limitation of tree growth in these ranges. However, we identified 4 regions (the Harz, Králický Sněžník, Hrubý Jeseník and Velká Fatra Mountains) where the uppermost tree stands are situated below the common treeline isotherm, an indication that trees are limited by other factors (e.g. biomass loss). Based on a comparison of various treeline temperature metrics, we suggest that to reliably describe treeline climates in regions with pronounced maritime−continental gradients, it is necessary to use metrics capturing the entire growing season. Such metrics show that treeline temperatures in the study region are similar to those in the Alps.
    ISSN: 0936-577X
    E-ISSN: 1616-1572
    Source: Alma/SFX Local Collection
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  • 4
    Language: English
    In: Earth surface processes and landforms, 2020-09-30, Vol.45 (12), p.2761-2772
    Description: Tree radial growth is influenced by individual tree abilities, climate, competition, disturbance regimes, as well as biogeomorphic processes – including biomechanical interactions between trees and soil. Trees are actively involved in hillslope dynamics, both responding to and affecting many (bio)geomorphic processes. Using dendrochronology, we studied feedbacks associated with tree–soil–landscape formation, specifically relationships between hillslope processes, biomechanical effects of trees in soils, tree microhabitat conditions and their morphological adaptations, in the flysch zone of the Carpathians. We visually evaluated stem shape, microhabitat conditions and the biomechanical effects of 1663 trees. Cores were taken in four growing directions from 224 individuals of European beech (Fagus sylvatica L.). In a set of 193 cross‐dated beeches, average tree‐ring widths and tree eccentricities in all directions were calculated and analysed in relation to the biogeomorphic impacts of trees. Some significant drivers of tree radial growth and sources of stem eccentricity were detected. The radial growth of trees on which deadwood was leaning was markedly limited. In contrast, trees with exposed roots expressed the highest growth rates. This clearly suggests that root exposure may not be an effect of ‘exogenous’ soil creep, but may rather result from individually intensifying tree growth due to fine‐scale disturbance dynamics. The response of biomechanical tree–soil interactions in tree radial growth weakened with increasing stem diameter, reflecting the stabilizing role of larger trees. The significance of calendar year on radial growth suggests seasonality in the dynamic component of soil creep. Tree eccentricity was observed mainly in the downslope direction, which suggests a relatively complex effect of biomechanics on stem tilting. © 2020 John Wiley & Sons, Ltd. This study evaluates the impact of common (bio)mechanical interactions between trees and soil on radial growth and stem eccentricity. The importance of (bio)mechanical interaction generally decreases with increasing stem diameter, however, our results revealed complex effects of (bio)mechanical interaction on stem eccentricity. Therefore, (bio)mechanical interactions should be considered when evaluating the presence and intensity of hillslope processes using tree‐ring data.
    Subject(s): biomechanical interactions ; disturbance regime ; Fagus sylvatica ; hillslope processes ; stem eccentricity ; Western Carpathians
    ISSN: 0197-9337
    E-ISSN: 1096-9837
    Source: Alma/SFX Local Collection
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  • 5
    Language: English
    In: Environmental research letters, 2021-03-01, Vol.16 (3), p.34039
    Description: Increasing growing season temperatures and the seasonal redistribution of precipitation due to climate change have recently been recorded across the globe. Simultaneously, increases of severe droughts and windstorm frequency have also been documented. However, the impacts of climate change on tree growth performance and fitness might largely differ among coexisting species. Consequently, ongoing temperature increases could lead to extensive changes in tree species compositions in many forest biomes including temperate mountain forests. In this study we used an extensive dataset of 2824 cored trees of three species from two sites, and parameterized a purely climate driven process-based model (Vaganov–Shaskin) to simulate the growth dynamics and climatic limitations of coexisting Picea abies, Fagus sylvatica and Abies alba in two of the oldest mountain forest reserves in Central Europe (the Boubín and Žofín Primeval Forests). We assumed that the species composition reflects climatic growth limitations, and considered between-site differences in mean temperature due to elevation as a model of future climate change effects on mountain forests. Our results show a complexity of site- and species-specific responses of Central European forests to climate change. Over the last 70 years, the proportion of F. sylvatica in Central European natural forests has increased at the expense of conifers. During the investigated period, we observed an increase in the growth rates of the studied species mainly at the higher elevation site, while for the lower elevation site there was increasing intensity of moisture limitation. Despite being the most moisture-limited species, P. abies showed the highest simulated growth rates. In contrast, A. alba was the least moisture limited of all considered species. Given its recent proportion in the forest species composition and intermediate drought resistance, we anticipate the future expansion of F. sylvatica in Central European mountain forests.
    Subject(s): Climate change ; Climate effects ; Composition ; Conifers ; Drought ; Drought resistance ; Elevation ; Environmental impact ; Forests ; Growth rate ; Moisture ; Mountain forests ; Mountains ; Nature reserves ; Plant species ; Species composition ; Temperature
    ISSN: 1748-9326
    E-ISSN: 1748-9326
    Source: IOPscience extra
    Source: Alma/SFX Local Collection
    Source: DOAJ Directory of Open Access Journals - Not for CDI Discovery
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  • 6
    Language: English
    In: Trees (Berlin, West), 2015-04, Vol.29 (2), p.515-526
    Description: Byline: Vaclav Treml (1), Jakub Kaspar (1), Hana Kuzelova (1), Vladimir Gryc (2) Keywords: Cambium; Xylogenesis; Giant Mountains; Norway spruce; Tree ring; Elevation gradient Key message Picea abies requires warming of both the above- and belowground parts of the tree for full resumption of cambial activity. Elevation-related decrease in growing season temperatures is a highly important factor in limiting tree growth in cold environments such as alpine treeline ecotones. In this study, we aimed to identify radial growth timing differences in Picea abies (L.) Karst. between the lower (timberline) and upper (treeline) parts of an alpine treeline ecotone. Over three growing seasons, soil and air temperatures were measured and phenology of wood formation was analyzed at two sites separated by 140 m of elevation in the Giant Mountains, Czech Republic. The results showed that there were two periods with significant differences in wood phenology between timberline and treeline. In the early part of the growing season, higher ambient temperatures at timberline led to higher number of cambial and enlarging cells here than at treeline. In the second part of the growing season, the bigger and/or more numerous tracheids at timberline than at treeline required more time for maturation. Significant delay in the beginning of wood formation at treeline in comparison to timberline was observed only in 2011, when soil was frozen markedly longer at treeline. We found that cambial activity significantly increased when soil temperature increased from near zero to a threshold temperature of 4--5 [degrees]C. We therefore suggest that for P. abies both the above- and belowground parts of the tree must be sufficiently warm for full resumption of cambial activity. Author Affiliation: (1) Department of Physical Geography and Geoecology, Faculty of Science, Charles University in Prague, Albertov 6, 128 43, Prague, Czech Republic (2) Department of Wood Science, Faculty of Forestry and Wood Technology, Mendel University in Brno, ZemAdAlska 3, 613 00, Brno, Czech Republic Article History: Registration Date: 12/11/2014 Received Date: 02/07/2014 Accepted Date: 11/11/2014 Online Date: 21/11/2014 Article note: Communicated by A. Nardini.
    ISSN: 0931-1890
    E-ISSN: 1432-2285
    Source: Alma/SFX Local Collection
    Source: ProQuest Central
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  • 7
    Language: English
    In: Frontiers in plant science, 2021, Vol.12, p.613643
    Description: Significant alterations of cambial activity might be expected due to climate warming, leading to growing season extension and higher growth rates especially in cold-limited forests. However, assessment of climate-change-driven trends in intra-annual wood formation suffers from the lack of direct observations with a timespan exceeding a few years. We used the Vaganov-Shashkin process-based model to: (i) simulate daily resolved numbers of cambial and differentiating cells; and (ii) develop chronologies of the onset and termination of specific phases of cambial phenology during 1961-2017. We also determined the dominant climatic factor limiting cambial activity for each day. To asses intra-annual model validity, we used 8 years of direct xylogenesis monitoring from the treeline region of the Krkonoše Mts. (Czechia). The model exhibits high validity in case of spring phenological phases and a seasonal dynamics of tracheid production, but its precision declines for estimates of autumn phenological phases and growing season duration. The simulations reveal an increasing trend in the number of tracheids produced by cambium each year by 0.42 cells/year. Spring phenological phases (onset of cambial cell growth and tracheid enlargement) show significant shifts toward earlier occurrence in the year (for 0.28-0.34 days/year). In addition, there is a significant increase in simulated growth rates during entire growing season associated with the intra-annual redistribution of the dominant climatic controls over cambial activity. Results suggest that higher growth rates at treeline are driven by (i) temperature-stimulated intensification of spring cambial kinetics, and (ii) decoupling of summer growth rates from the limiting effect of low summer temperature due to higher frequency of climatically optimal days. Our results highlight that the cambial kinetics stimulation by increasing spring and summer temperatures and shifting spring phenology determine the recent growth trends of treeline ecosystems. Redistribution of individual climatic factors controlling cambial activity during the growing season questions the temporal stability of climatic signal of cold forest chronologies under ongoing climate change.
    Subject(s): Analysis ; cambial phenology ; Climatic changes ; dendrochronology ; growing season ; Models ; Plant Science ; process-based modeling ; treeline ; VS-model ; xylogenesis
    ISSN: 1664-462X
    E-ISSN: 1664-462X
    Source: PubMed Central
    Source: DOAJ Directory of Open Access Journals - Not for CDI Discovery
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  • 8
    Language: English
    In: Alpine botany, 2017-10, Vol.127 (2), p.109-120
    Description: Globally, treeline position is driven by temperatures during the growing season. Nevertheless, at regional scales, the position of uppermost tree stands also reflects other climatic factors, including wind action. It remains uncertain, however, how much do intense winds depress the treeline below its potential position. Our objective was to quantify the effect of wind speed on the possible depression of upper forest margins below the potential treeline in a windy mountain range with the treeline located close to summit areas. In the Giant Mountains, Czech Republic, growth parameters and symptoms of wind-induced loss of biomass were determined for Norway spruce (Picea abies [L] Karst.) in 70 plots distributed along a gradient of wind speed within the treeline ecotone. Wind speed was modelled for each plot. General linear models were applied to discern the effect of wind on tree growth. Our results show that high wind speeds are reflected in the presence of clonal tree islands and irregular tree crowns. Despite evident wind-induced biomass loss, radial growth was not significantly affected, and the effect of wind on height increment was limited only to parts of the stem from 2 m above ground. Considering that the height growth was substantially reduced by wind in about half of the treeline area, and wind was able to limit only growth of trees taller than 2 m, the overall wind-induced depression of highest treeline positions is probably low, even in windy mountain regions.
    Subject(s): Analysis ; Atmospheric physics ; Biomass ; Dendrochronology ; Dendroclimatology ; Ecology ; Forestry ; Height increment ; Life Sciences ; Life Sciences, general ; Mountains ; Picea abies ; Pine trees ; Plant Ecology ; Plant Sciences ; Radial growth ; Thigmomorphogenesis ; Tree rings ; Treeline ; Wind effects ; Wind speed
    ISSN: 1664-2201
    E-ISSN: 1664-221X
    Source: Alma/SFX Local Collection
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  • 9
    Language: English
    In: European journal of forest research, 2020-02, Vol.139 (1), p.97-109
    Description: Keywords: Picea abies; Fagus sylvatica; Growth plasticity; Disturbance history; Forestry management plans The disturbance regime of mountain spruce--beech temperate forests has not yet been sufficiently elucidated. We hypothesized that spruce and beech express completely different disturbance histories and behavioural strategies, potentially causing exceptionally complex disturbance regimes. We further hypothesized that the spontaneous development of mountain forests can temporarily result in a simplification of the forest's spatial structure. We wanted to discover how the disturbance history and growth plasticity of the main tree species differ, and whether some old managed forests arose from primeval forest remnants. We compared dendrochronological records of the unmanaged Boubin Primeval Forest and 30 sites with current forestry records. Using this comparison, we categorized all sites into three categories. In the disturbance history of all evaluated forest sites, there was clear evidence of the presence of severe disturbances in the nineteenth century. However, the regeneration of beech was more continuous and less dependent on the presence of severe disturbances than the regeneration of spruce, which depended on the presence of severe disturbances of low frequency. Human-induced changes at some sites were manifested in changes in the initial growth of both species and disrupted their mutual competition and also led to a higher growth plasticity of beech. Despite human impacts in the region since the end of the nineteenth century, about 30% of analysed trees were older than the severe disturbances in the nineteenth century therefore, some studies sites preserved the characteristics of primeval forest. Our results revealed three main forest development trajectories since the end of the nineteenth century. Author Affiliation: (1) Department of Forest Ecology, Silva Tarouca Research Institute, Lidicka 25-27, 602 00, Brno, Czech Republic (2) Faculty of Forestry and Wood Technology, Mendel University in Brno, ZemAdAlska 1, 613 00, Brno, Czech Republic (3) Department of Botany and Zoology, Faculty Science, Masaryk University, KotlaAska 267/2, 611 37, Brno, Czech Republic (a) jakub.kaspar@vukoz.cz Article History: Registration Date: 12/14/2019 Received Date: 03/28/2019 Accepted Date: 12/14/2019 Online Date: 12/20/2019 Byline: Jakub Kaspar (corresponding author) (1, a), Pavel Samonil (1, 2), Ivana Vasickova (1), Dusan Adam (1), Pavel DanAk (1, 3)
    Subject(s): Analysis ; Forest ecology ; Forest management ; Old growth forests
    ISSN: 1612-4669
    E-ISSN: 1612-4677
    Source: Academic Search Ultimate
    Source: Alma/SFX Local Collection
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  • 10
    Language: Czech
    In: Annales Scientia Politica, 2016, Vol.5 (1), p.17-31
    Description: The article analyses political transformations in Ukraine and Georgia after Orange and Rose Revolutions. Both countries are treated as hybrid regimes and the concept of competitive authoritarianism is used as the main framework for the comparison. Afterwards, diverging political paths of Ukraine and Georgia are interpreted by means of the theory of patronal politics. In the conclusion we argue that whereas Ukraine’s political liberalisation lead to political chaos, economic stagnation and, finally, to the autocratic backsliding, Georgia’s focus on reforms under relatively autocratic Saakashvili’s administration resulted in relatively stable and efficient institutional framework, which enabled political liberalisation of the country after 2012. The article analyses political transformations in Ukraine and Georgia after Orange and Rose Revolutions. Both countries are treated as hybrid regimes and the concept of competitive authoritarianism is used as the main framework for the comparison. Afterwards, diverging political paths of Ukraine and Georgia are interpreted by means of the theory of patronal politics. In the conclusion we argue that whereas Ukraine’s political liberalisation lead to political chaos, economic stagnation and, finally, to the autocratic backsliding, Georgia’s focus on reforms under relatively autocratic Saakashvili’s administration resulted in relatively stable and efficient institutional framework, which enabled political liberalisation of the country after 2012.
    Subject(s): Comparative politics ; Government/Political systems
    E-ISSN: 1339-0732
    Source: Alma/SFX Local Collection
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