National Repository of Grey Literature 45 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Dissolved and gaseous nitrogen losses in forests controlled by soil nutrient stoichiometry
Oulehle, Filip ; Chuman, T. ; Hruška, Jakub ; Krám, Pavel ; Navrátil, Tomáš ; Tesař, Miroslav ; Ač, Alexander ; Urban, Otmar
This study investigates the consequences of chronic nitrogen deposition in forests, including its effects on soil and surface water quality, and greenhouse gas emissions. To predict these effects, the authors explore the controls over dissolved and gaseous nitrogen fluxes in temperate forests. Their findings indicate that stream leaching losses of dissolved nitrogen correspond with the nutrient stoichiometry\nof the forest floor, with stream N losses increasing as ecosystems progress towards phosphorus limitation. Soil nitrogen storage increases with oxalate extractable iron and aluminium content. The authors estimate soil gaseous losses based on 15 N stocks, which averaged 2.5±2.2 kg N ha-1 year-1 , comprising 20±14% of total nitrogen deposition. They also extrapolate the current gaseous nitrogen loss flux from forests globally to be 8.9 Tg N year-1 , which represents 39% of current nitrogen deposition to forests worldwide.
Short-term application of elevated temperature and drought influences the isotopic composition of winter wheat grains
Pernicová, Natálie ; Urban, Otmar ; Čáslavský, Josef ; Klem, Karel ; Trnka, Miroslav
The study aimed to determine the differences in carbon (δ13C) and nitrogen (δ15N) stable isotope ratios in grains of three winter wheat varieties grown under optimal and stress conditions. We found that the wheat variety has a significant effect on both δ13C and δ15N isotope ratios. Short-term (nine days) exposure to drought and high temperature during the heading or stem extension development phase significantly enhanced δ13C values, but only high temperature affected δ15N values. Enhanced δ15N values support the assumption that global warming causes a higher representation of the 15N isotope in plants. Moreover, significant interactive effects of temperature and water availability on the values of both isotopes were found implying that C and N metabolisms have been altered under the investigated stress conditions. We conclude that δ13C and δ15N isotope ratios of cereal grains are sensitive indicators of stress conditions, even short-term ones
Comparison of gradient measurement and modelling of deposition rate of ozone to spruce forest in locality Bílý Kříž.
Zapletal, M. ; Chroust, P. ; Večeřa, Zbyněk ; Mikuška, Pavel ; Cudlín, Pavel ; Urban, Otmar ; Pokorný, Radek ; Czerný, Radek ; Janouš, Dalibor ; Taufarová, Klára ; Marek, Michal V. ; Hůnová, I. ; Černikovský, L. ; Medlen, A.
Comparison of measured and modelled deposition rate of ozone to spruce forest in locality Bílý Kříž. Estimation of daily changes in deposition and stomatal flux of ozone into spruce forest.
Anthocyanins in plant leaves: protective function and spectroscopic detection
Nikodymová, Michaela ; Albrechtová, Jana (advisor) ; Urban, Otmar (referee)
Plants have to cope with the change in the various environmental factors, the change of these factors means stress for plants. Stress factors can cause damage that lead to inhibition of growth and photosynthesis, resulting in the extreme cases in the death of the whole organism and negatively affect farm yields. Plants have to develop defensive mechanisms, including the accumulation of anthocyanins in leaves. The aim of the present review is to summarize the knowledge about the influence of stress factors on the accumulation of anthocyanins in leaves and about the function of anthocyanins in the protection. Anthocyanins most often act as antioxidants that react with ROS and inactivate them, they can also act as filters against UV radiation and as a protection against herbivores. Further, there are summarized the knowledge about spectral methods of detection of anthocyanins in leaves with emphasis on non-destructive detection methods. Spectral methods allow the analysis of anthocyanins based on the interaction of the leaf and its chemical components with the incident radiation. The most commonly used method is UV-VIS spectrophotometry. In order to study pigment change in leaves during ontogenetic development, non-destructive methods of pigment detection should be used. Suitable method can allow us...
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...
Study of quantitative parameters of Norway spruce needle structure under the effect of elevated CO₂ concentration and different irradiance
Kubínová, Zuzana ; Lhotáková, Zuzana (advisor) ; Urban, Otmar (referee) ; Gebauer, Roman (referee)
Zuzana Kubínová: Study of Quantitative Parameters of Norway Spruce Needle Structure under the Effect of Elevated CO2 Concentration and Different Irradiance, Doctoral Thesis, Prague 2019 Abstract Atmospheric concentration of CO2 is increasing, while its influence on plants is still not fully elucidated. Norway spruce (Picea abies L. Karst.) is an abundant conifer tree in European temperate and boreal forests, which behave as carbon sink in the global carbon cycle. The physiological response to elevated CO2 concentration may be interconnected with changes in leaf anatomy and morphology. Needle structure is also determined by other factors in addition to CO2 concentration, irradiance being the most important one. Thus, effect of irradiance was also included in our studies. The effects of elevated CO2 concentration and irradiance on Norway spruce needle structure were studied using new applications of well-established quantitative methods and novel methods enabling effective and unbiased analysis of needle structural traits. The General Procrustes analysis showed to be effective for needle shape on cross section comparison and the disector method proved to be suitable for chloroplast number estimates. The influence of elevated CO2 concentration and different irradiance on needle structure was studied at two...
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...
Study of quantitative parameters of Norway spruce needle structure under the effect of elevated CO₂ concentration and different irradiance
Kubínová, Zuzana ; Lhotáková, Zuzana (advisor) ; Urban, Otmar (referee) ; Gebauer, Roman (referee)
Zuzana Kubínová: Study of Quantitative Parameters of Norway Spruce Needle Structure under the Effect of Elevated CO2 Concentration and Different Irradiance, Doctoral Thesis, Prague 2019 Abstract Atmospheric concentration of CO2 is increasing, while its influence on plants is still not fully elucidated. Norway spruce (Picea abies L. Karst.) is an abundant conifer tree in European temperate and boreal forests, which behave as carbon sink in the global carbon cycle. The physiological response to elevated CO2 concentration may be interconnected with changes in leaf anatomy and morphology. Needle structure is also determined by other factors in addition to CO2 concentration, irradiance being the most important one. Thus, effect of irradiance was also included in our studies. The effects of elevated CO2 concentration and irradiance on Norway spruce needle structure were studied using new applications of well-established quantitative methods and novel methods enabling effective and unbiased analysis of needle structural traits. The General Procrustes analysis showed to be effective for needle shape on cross section comparison and the disector method proved to be suitable for chloroplast number estimates. The influence of elevated CO2 concentration and different irradiance on needle structure was studied at two...
Measured and modelled fluxes of tropospheric ozone in mountainous Norway spruce forest
Juráň, Stanislav ; Zapletal, Miloš ; Večeřa, Zbyněk ; Cudlín, Pavel ; Urban, Otmar
Tropospheric ozone fluxes (O3) were measured in Norway spruce forest at Bily Kriz, Czech Republic by eddy covariance technique. Within-canopy concentration gradient was measured by APOA-370 analysers (Horiba, Japan) in 7m, 25m and 30m above ground. Fluxes of O3 were modelled from the concentration gradient by applying Inverse Lagrangian Transport Model (Raupach, 1989). Next, O3 fluxes were modelled on the basis of resistent analogy. Ozone flux measured by eddy covariance technique amounted up to 1.19 nmol m-2 s-1 on daily average and the lowest -0.75 nmol m-2 s-1. Studied forest stand was net sink for ozone in 7.14 mmol m-2 per day (=0.343 g m-2 per day). The highest ozone emission peaked during noon hours, suggesting closure of stomata due to low air temperature and ozone production due to sufficient radiation. Both models proved to be imprecise when compared to measured data in autumn-winter transition period.
Methods of detection of fungal diseases applicable in plant phenotyping and remote sensing
Klem, Karel ; Veselá, Barbora ; Holub, Petr ; Urban, Otmar ; Mezera, J.
This methodology summarises findings from a comparison of three perspective methods of fungal disease detection applicable for remote sensing and plant phenotyping of fungal disease resistance. These methods are spectral reflectance, infrared thermal imaging, and blue-green fluorescence imaging. On the example of winter wheat infection with powdery mildew, stripe rust and brown rust the strengths and weaknesses of individual methods were demonstrated. From these results it is evident that all three methods are potentially applicable for non-destructive fungal disease detection, but their practical use may vary. Testing of spectral reflectance indices for the detection of fungal diseases showed particularly the high detection reliability of the red-edge and green band based spectral vegetation indices. Infrared thermal imaging has shown high detection accuracy for powdery mildew and brown rust, but lower for stripe rust. Blue-green fluorescence and thermal imaging seems to be also a very promising tools for evaluating the intensity and spatial distribution of infection on a leaf level.

National Repository of Grey Literature : 45 records found   1 - 10nextend  jump to record:
See also: similar author names
19 URBAN, Ondřej
19 Urban, Ondřej
2 Urban, Oto
1 Urban, Otto
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