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Water-use efficiency of winter wheat under heat and drought stress
Hlaváčová, Marcela ; Klem, Karel ; Novotná, Kateřina ; Rapantová, Barbora ; Urban, Otmar ; Hlavinka, Petr ; Smutná, P. ; Horáková, V. ; Škarpa, P. ; Trnka, Miroslav
Because such extreme weather events as dry spells and heat waves are expected to occur more frequently\ndue to climate change, the issue of appropriate water management for sustainable agricultural production\nis increasingly important. This study focuses on wheat, the second most widely grown cereal in the world\nand the most common cereal in European countries. The study assesses the effects of short periods (3 and\n7 days) of high temperatures (26°C as a control, 32°C, 35°C, and 38°C as daily temperature maxima from\n12:00 to 14:00) and drought stress at different developmental stages (DC 31 – beginning of stem elongation,\nDC 61 – flowering, and DC 75 – early grain filling) on water-use efficiency (WUE) in winter wheat\ncultivar Tobak. This cultivar is one of the most widespread winter wheat cultivars in Czech Republic fields.\nThe analysis of WUE showed that the cv. Tobak plants were able to withstand drought stress conditions\nthrough increased WUE. In contrast, wheat plants were stressed more markedly if exposed to higher temperatures\nand drought in combination. Generally, the wheat plants were most sensitive to drought at DC\n31.
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Anatomická analýza mezofylu stinného a slunného listu buku lesního pod vlivem zvýšené koncentrace CO2.
Horská, Jana ; Lhotáková, Zuzana (vedoucí práce) ; Urban, Otmar (oponent)
Práce se zabývá vyhodnocením vlivu koncentrace CO2 a ozářenosti na vybrané anatomické parametry listu buku lesního, Fagus sylvatica L. Proces fotosyntézy je zásadně ovlivňován řadou vnějších faktorů, mezi nimi atmosférickou koncentrací CO2 a ozářeností a úzce souvisí s anatomickými parametry listu. Jedním z těchto důležitých anatomických parametrů ovlivňujících rychlost asimilace je vnitřní povrch listu, který představuje plochu mezofylu, na které dochází k výměně plynů. Experimentální materiál využitý v této práci byly listy z juvenilních stromů buku lesního zasazených v r. 2005 a rostoucích v aktuální koncentraci CO2 (390ppm, AC) a ve zvýšené koncentraci CO2 (700 ppm, EC) na experimentálním stanovišti Bílý Kříž v Beskydech Centra výzkumu globální změny AV ČR. Vyhodnoceny byly anatomické parametry slunných a stinných listů z obou ošetření CO2 odebrané ve dvou sezónách s odstupem tří let (2009 a 2012). Ke stanovení anatomických parametrů listu byly využity stereologické metody, které poskytují nevychýlený odhad měřených parametrů, především metoda fakír pro stanovení vnitřního povrchu listu. Na listech odebraných v roce 2009 byl účinek EC zaznamenán pouze ve snížení zastoupení mezibuněčných prostor v mezofylu. V roce 2012 způsobila EC u listů navýšení mocnosti palisádového parenchymu a trend...
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Sekvestrace uhlíku lesními ekosystémy v měnícím se klimatu.
Hlaváčková, Lucie ; Lhotáková, Zuzana (vedoucí práce) ; Urban, Otmar (oponent)
Studium globálního cyklu uhlíku je v popředí zájmu vědců, protože pochopení jednotlivých sinků uhlíku a vazeb mezi nimi může nastínit řešení problémů spojených se zvyšující se koncentrací CO2 v ovzduší v budoucnosti. Práce je zaměřena na roli lesních ekosystémů v tomto cyklu. Lesy pokrývají skoro třetinu povrchu pevniny a prostřednictvím fotosyntézy váží velkou část uhlíku do své biomasy. Síla sinku lesního porostu se však může lišit v závislosti na typu biomu, stáří porostu a na aktuálních klimatických podmínkách. Lesní biomy můžeme obecně rozdělit podle zeměpisné šířky na biom tropického, temperátního a boreálního lesa. V tomto pořadí klesá i jejich velikost zásob uhlíku. Ostatní parametry, jako čistá primární produkce a respirace, se liší v závislosti na konkrétním ekosystému. Tropické deštné lesy jsou velkou zásobárnou uhlíku, ovšem jejich značné kácení způsobuje také obrovské uvolňování emisí C zpět do atmosféry. Boreální lesy nejsou tak významným sinkem uhlíku, ale mají velký vliv na tamní klima. Jisté spekulace také vyvstávají v případě starých lesů. Je možné najít autory, kteří tvrdí, že starý les již není sinkem uhlíku a jejich celková uhlíková bilance je tedy neutrální. Mnoho prací však toto vyvrací a dokazuje sice nižší poutání uhlíku v porovnání s dospělými či mladými lesy, ale celkovou...
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Effects of vegetation season and needles’ position in spruce canopy on emissions of volatile organic compounds
Večeřová, Kristýna ; Holišová, Petra ; Pallozi, E. ; Guidolotti, G. ; Calfapietra, Carlo ; Urban, Otmar
The main objective of this study was to investigate seasonal changes and vertical distribution in emissions of biogenic volatile organic compounds (BVOCs) within a Norway spruce canopy profile. Emissions were measured on current-year needles from the upper and lower canopy in early July and late August. Our results show that total BVOC emissions under standardized conditions (light intensity 1,000 µmol m–2 s–1, temperature 30°C) are higher in July than they are in August. BVOC emissions from upper canopy needles were approximately 3 times higher than were those from lower canopy needles. This difference was observed in July but not in August. The monoterpenes α-pinene, camphene, and terpinolene showed the most significant differences between emissions from upper and lower canopy needles.
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Comparison of emissions of biogenic volatile organic compounds from leaves of three tree species
Holišová, Petra ; Večeřová, Kristýna ; Pallozi, E. ; Guidolotti, G. ; Esposito, R. ; Calfapietra, Carlo ; Urban, Otmar
Biogenic volatile organic compounds (BVOCs) play many roles in plants’ ecophysiology and have the potential to affect atmospheric quality due to their chemical reactivity. Rates of BVOC emissions are highly variable depending on plant species and growing condition. Our study evaluated the amounts and spectra of BVOCs emitted from three tree species. We investigated BVOC emissions from the leaves of mature Norway spruce and sessile oak saplings grown in the field and from 1-year-old cuttings of hybrid poplar grown under laboratory conditions. Emitted BVOCs were sampled on desorption Tenax tubes in parallel with gas-exchange measurements. After subsequent thermal desorption of Tenax tubes, BVOC profiles were estimated by gas chromatography coupled with mass spectrometry. The tree species showed substantial differences in BVOC emission rates per unit leaf area ranging between 2.33 and 25.67 nmol m–2 s–1. Spruce trees had the lowest BVOC emissions and oak had slightly higher BVOC emissions on average than did poplar. Isoprene composed more than 97% of total BVOC emissions from oak and poplar, while no isoprene emissions from spruce needles were detected. Spruce BVOC emissions were mainly composed of such monoterpenes as α-pinene, β-pinene, and limonene.
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Diurnal changes of monoterpene fluxes in Norway spruce forest
Juráň, Stanislav ; Fares, S. ; Křůmal, Kamil ; Večeřa, Zbyněk ; Urban, Otmar
Biogenic volatile organic compounds (BVOCs) are important components of biosphere–atmosphere exchange. Their emissions depend on various meteorological parameters and stresses. Diurnal fluxes of different monoterpenes were studied within a Norway spruce (Picea abies) mountain forest to investigate their dependence on temperature and global radiation. Fluxes of monoterpenes, the most abundant BVOCs in spruce, were modelled using an inverse Lagrangian transport model, and representative diurnal variation trigged by both temperature and light was observed. This research enables future parametrization and quantification of various factors driving bidirectional fluxes.
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Interactive effects of UV radiation and drought on the accumulation of flavonols in selected herbs and grass in a mountain grassland ecosystem
Veselá, Barbora ; Surá, Kateřina ; Rajsnerová, Petra ; Klem, Karel ; Holub, Petr ; Urban, Otmar
The main objective of this 4-year experiment conducted in a mountain grassland ecosystem was to investigate the interactive effects of ultraviolet (UV) treatment and drought on changes in accumulation of UV-screening compounds (flavonols) in selected herbs (Hypericum maculatum Crantz, Rumex obtusifolius L.) and grass (Agrostis tenuis Sibth.). Inasmuch as drought and UV radiation induce similar protective mechanisms, we tested the hypothesis that UV radiation and drought elicit synergistic effects on flavonol accumulation. The experimental plots were manipulated using rainout shelters enabling the exclusion and transmission of incident precipitation and UV radiation. Generally, UV and drought treatments had similar effects on flavonol accumulation. For R. obtusifolius, UV exclusion resulted in a substantial reduction of UV-screening compounds, particularly under ambient precipitation conditions, while for H. maculatum and A. tenuis UV exclusion caused only a slight reduction of flavonol content. Similarly, the drought treatment caused an increase in flavonol accumulation.
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Convergence of morphological, biochemical, and physiological traits of upper and lower canopy of European beech leaves and Norway spruce needles within altitudinal gradients
Rajsnerová, Petra ; Klem, Karel ; Večeřová, Kristýna ; Veselá, Barbora ; Surá, Kateřina ; Rajsner, Lukáš ; Holub, Petr ; Urban, Otmar
Climatic variation along altitudinal gradients provides an excellent natural experimental set-up for investigating the possible impacts of climate change on terrestrial organisms and ecosystems. The present work has explored for the first time the acclimation of upper versus lower canopy leaves or needles in European beech (Fagus sylvatica) and Norway spruce (Picea abies) forests along an altitudinal gradient. We tested the hypothesis that restrictive climatic conditions associated with high altitudes reduce within-canopy variations of leaf traits. The investigated beech and spruce forests were located on the southern slope of the Hrubý Jeseník Mountains (Czech Republic). All measurements were taken on leaves from the upper and lower parts of the canopy of mature trees (>60 years old) growing at low (400 m a.s.l.), middle (720 m a.s.l.), and high (1,100 m a.s.l.) altitudes. Generally, we observed that with increasing altitude, which is associated with adverse microclimatic conditions, a convergence of CO2 assimilation rate and other physiological, morphological, and biochemical characteristics between the upper and lower canopy occurred. However, differences in altitudinal response among individual traits and species were found. Such plasticity in acclimation of leaves and needles has the potential to cause substantial change in the photosynthesis of individual parts of forest canopies within the vertical profile and their contribution to the overall carbon balance of vegetation.
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Summer fluxes of nitrous oxide from boreal forest
Macháčová, Kateřina ; Pihlatie, M. ; Halmeenmäki, E. ; Pavelka, Marian ; Dušek, Jiří ; Bäck, J. ; Urban, Otmar
Boreal forests cover almost one-third of the global forest area, and results of soil measurements show them to be a natural source of the important greenhouse gas nitrous oxide (N2O). Nevertheless, N2O fluxes from boreal tree species have been excluded from calculations of N2O exchanges from forest ecosystems. Therefore, our objective was to quantify and scale up the N2O fluxes from stems of mature silver birch (Betula pendula), Scots pine (Pinus sylvestris), and Norway spruce (Picea abies), as well as from the forest floor of a boreal forest in Finland during June and July 2014. This study shows that boreal tree species emit N2O from their stems under natural field conditions and significantly contribute up to 8% of forest floor fluxes of N2O. Spruce trees seem to be the strongest N2O emitter among the studied tree species. Moreover, the N2O flux rates from both coniferous tree species increased with decreasing soil water content. This study highlights the necessity to include N2O fluxes from trees within the total greenhouse gas budget of forest ecosystems.
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