|
|
Modulation of ozone flux in a mountain spruce forest under different cloud cover
Juráň, Stanislav ; Fares, S. ; Urban, Otmar
Ozone (O3) fluxes were modelled from a concentration gradient in a Norway spruce forest at the Bílý Kříž experimental station for years 2012–2016. Daily and seasonal O3 depositions were calculated separately for days with cloudy, partly cloudy, and clear sky conditions. The hypothesis that overcast conditions modulate O3 flux in the forest ecosystem via controlled stomatal conductance is tested. Indeed, the highest stomatal conductance followed by the highest O3 deposition was found during partly cloudy and cloudy sky conditions in all seasons.
|
|
|
Effect of elevated CO2 on morphological and photosynthetic parameters in two understory grass species in Beskydy Mountains
Holub, Petr ; Klem, Karel ; Urban, Otmar
We transplanted two grass species, Calamagrostis arundinacea and Luzula sylvatica, to the understory of\na 10-year-old experimental mixed forest exposed to ambient (385 μmol CO2 mol–1, AC) and elevated (700\nμmol CO2 mol–1, EC) atmospheric CO2 concentration using a glass dome facility. Effects of EC on plant\nmorphology and photosynthesis were examined after three years of treatment. We tested the hypotheses\nthat shade-tolerant species can profit from EC even at low light conditions and that relatively low accumulation\nof assimilates at such light conditions will not cause CO2-induced down-regulation of photosynthesis.\nWe expected that EC can substitute insufficient light intensities under the tree canopy and lead to both\nhigher biomass production and survival of plants in deep forest understories. The typical shade-tolerant\nspecies L. sylvatica exhibited positive acclimation under EC allowing higher light use efficiency under subsaturating\nlight intensities as compared to plants grown under AC. In contrast, C. arundinacea showed\nhigher stimulation of growth and photosynthetic rates by EC mainly under saturating light intensities at\nthe beginning of the growing season, when the forest leaf area is not fully developed and the open canopy\nallows a greater proportion of incident light to reach the understory. Our data indicate that growth and\nphysiological responses of EC plants in forest understories are species specific, differ from responses of\nsun-exposed plants, and depend on degree of shading.
|
|
|
Interactive effect of UV radiation and CO2 treatment on extractable volatile organic compounds from European beech leaves
Večeřová, Kristýna ; Pernicová, N. ; Klem, Karel ; Urban, Otmar
The main objective of this experiment was to investigate the combined effect of different UV treatments\nand elevated CO2 concentration on monoterpene and methyl salicylate (MES) content in leaves of\nEuropean beech during the growing season. Plants were grown under ambient (AC, 400 μmol mol–1) and\nelevated (EC, 700 μmol mol–1) CO2 concentrations and three UV radiation treatments (ambient – UVamb,\nexcluded – UV-, and enhanced – UV+). Leaves collected from July to September were extracted in cold\nheptane to determine volatile organic compounds content using gas chromatography. Our results show\nthat AC plants had higher total content of extractable monoterpenes and MES than did EC plants over\nthe whole growing season and irrespective of UV treatment. Limonene, 2-bornene, and ester MES were\nthe most abundant volatile compounds in beech leaves. The highest contents of 2-bornene and MES were\nfound under the UV- treatment and AC. Contents of α-pinene, β-pinene, and carene decreased during the\ngrowing season while the content of limonene increased.
|
|
|
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.
|
|
|
Anatomical study of shade and sun European beech leaf under elevated CO2.
Horská, Jana ; Lhotáková, Zuzana (advisor) ; Urban, Otmar (referee)
The present Master thesis focuses on evalution of CO2 concentration and irradiance on selected leaf anatomical parameters of European Beech (Common Beech) Fagus sylvatica L.. The process of photosynthesis is remarkably determined by numerous extrenal factors, among them by atmoshperic CO2 concentration and irradiance and is closely correlated with leaf anatomical parameters. One of these most important anatomical parameters affecting the net assimilation rate is an internal leaf surface, which corresponds to mesophyll area avialable for gas exhcange. Experimental material of the study was sampled from the leaves of juvenile trees of F. sylvatica planted in 2005 and growing under ambient (390 ppm, AC) and elevated (700 ppm, EC) CO2 concentrations on the experimental site of the Global Change Research Center AS CR at Bílý Kříž in the Beskydy Mountains. Sun and shade leaves were sampled from trees of both CO2 treatments in two seasons 3 years apart (2009 and 2012). To determine leaf anatomical parameters, the stereological methods were applied, which yield unbiased estimation of measured parameters, particularly the Fakir method for internal leaf surface determination. The EC effect was observed on the leaves sampled in 2009 only in the decrease of proportion of intercellular spaces in mesophyll. In...
|
|
|
Carbon sequestration by forest ecosystems in canging climate.
Hlaváčková, Lucie ; Lhotáková, Zuzana (advisor) ; Urban, Otmar (referee)
The global carbon cycle is in the focus of the scientists' interest, because understanding carbon sinks and their relationships can show the solutions of problems related with increasing CO2 concentration in the atmosphere in the future. I focused on the role of forests ecosystems in this carbon cycle. All forests cover almost one third of the Earth's land area. By photosynthesis they bind big part of atmospheric carbon to their biomass. Sink strength of forest can differ according to the type of biome, forest stand age and actual climatic conditions. Forest biomes can be generally divided according to the latitude to three groups: tropical forest biomes, temperate forests and boreal forests. The size of carbon stock decreases in this order. Other parameters, such as net primary production and respiration differ in dependence on the particular ecosystem. Tropical rain forests represent great carbon stock, but their deforestation causes massive C emissions back to the atmosphere. Boreal forests aren't considered as important carbon sink, but they influence local climate. Some speculations can also appear about the old forests. It is possible to find authors, who claims, that old forests are no more carbon sinks, so that their carbon balance is neutral. Many surveys prove that they bind less carbon...
|
|
| |
|
|
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.
|
|
|
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.
|
|
|
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.
|
guest ::
RSS feed.