|
|
Leaf area index development and radiation use efficiency of a poplar short rotation coppice culture
Tripathi, Abishek ; Fischer, Milan ; Trnka, Miroslav ; Orság, Matěj ; Vanbeveren, S. ; Marek, Michal V.
Leaf area index (LAI) is the most appropriate parameter for analyzing canopy structure and crop productivity. LAI and radiation use efficiency (RUE) were estimated to evaluate the productivity of a short rotation coppice culture of a poplar clone. RUE was calculated as the ratio between total aboveground woody biomass and available photosynthetic active radiation (PAR) accumulated during one growing season. Prior to coppicing, LAI reached a maximum value of 7.3 (in 2009), whereas the maximum LAI after coppicing was 6.8 (in 2012). The maximum RUE reached prior to coppicing was 0.25 g mol−1 (in 2009), while after coppicing it was 0.20 g mol−1 (in 2012), which did not represent a significant difference (p > 0.05).
|
|
|
Are there any changes in the beginning of flowering of important allergens in the Czech Republic?
Bartošová, Lenka ; Hájková, L. ; Kožnarová, V. ; Možný, M. ; Trnka, Miroslav ; Žalud, Z.
Phenological observations have a long tradition in the Czech Republic; the first phenological notes were taken in the 18th century. Within the entire phenological observation network of the Czech Hydrometeorological Institute, 45 plant species can be observed. These include perennial herbs, grass, and ground bushes growing wildly. Some observed species are among the group of so-called allergens, e.g. silver birch (Betula pendula Roth), cocksfoot (Dactylis glomerata L.), and meadow foxtail (Alopecurus pratensis L.). In this paper, we evaluated the phenological phase beginning of flowering for two of the aforementioned plants at the Mlýny, Chřibská research site (50°52’N, 14°29’E, 350 m a.s.l.). The aim was to assess which meteorological parameters influence phenological onsets as well as to analyze shifts in phenophase onset dates and temperature trends during 1959–2014. During this period, for B. pendula the average date of beginning of flowering was 28 April with a standard deviation of 10 days and for A. pratensis it was 20 May with a standard deviation of 8 days. The studied species are allergens and their timing and phenological shifting during the spring and their relationship with climate parameters may provide important information for forecasts as part of a pollen warning service.
|
|
|
LINCOLN – an algorithm for filtering daily NDVI MODIS data and deriving the start of the season
Bohovič, R. ; Hlavinka, Petr ; Semerádová, Daniela ; Bálek, L. ; Tadesse, T. ; Hayes, M. ; Wardlow, B. ; Trnka, Miroslav
Monitoring drought has become an important tool for farmers and agriculture decision makers. This has increased efforts to create a monitoring system using satellite data that could provide an independent and current source of real information on vegetation condition. The aim of this study was to develop an algorithm for processing Normalized Difference Vegetation Index (NDVI) data from the Moderate Resolution Imaging Spectroradiometer. A software utility called LINCOLN was developed for this purpose. Its filtering output was further processed to yield a start of the season (SOS) metric. Different settings of the utility were tested and correlated to such phenological ground observations as the emergence of spring barley and the beginning of leaf sheath elongation in winter wheat. There was higher correlation observed in the case of winter wheat, probably due to its weaker dependence on crop sowing date. The matrix of coefficients of determination was applied to determine the optimal settings for the LINCOLN filter. The optimal absolute threshold NDVI value for SOS was set to 4,500.
|
|
|
Aplikace růstových modelů pro lokální hodnocení dopadů změny klimatu na vybrané plodiny
Hlavinka, Petr ; Trnka, Miroslav ; Balek, Jan ; Dubrovský, Martin ; Pohanková, Eva ; Žalud, Zdeněk
Metodika je zaměřena na přehledný popis problematiky využití specializovaných softwarových nástrojů nazývaných růstové modely s důrazem na jejich aplikaci pro hodnocení dopadů změny klimatu na lokální úrovni. Ambicí této publikace je seznámit čtenáře se stručnou historií vývoje růstových modelů, jejich členěním, aktuálními trendy jejich vývoje a využití, ale v první řadě prezentovat metody přípravy vstupních databází, prvotního nastavení modelů, kalibraci jejich parametrů, přes ověření spolehlivosti prostřednictvím nezávislého vzorku dat (validace), propojení se scénáři očekávaného vývoje klimatu v budoucnu až po hodnocení dopadů změny podmínek na významné polní plodiny a vybrané reprezentativní lokality v České republice.
Plný tet: Metodika_rustove_modely_2015 -  PDF
Plný text: content.csg - PDF
|
|
|
Stagnace HDP v Československu na přelomu 70. a 80. let 20. století
Trnka, Miroslav ; Kolman, Ondřej (vedoucí práce) ; Dyba, Karel (oponent)
Tato práce se primárně zabývá problematikou hospodářské situace v Československu na konci 70. a počátku 80. let 20. století, vyznačující se poklesem tempa růstu HDP. Cílem práce je ukázat, že ani centrálně plánované ekonomiky se nedokáží vyhnout krizím. Práce se dále zabývá problematikou počítání HDP z tehdy používaného národního produktu, hospodářským vývojem poválečného Československa a srovnáním dopadů krize v socialistickém Československu s okolními zeměmi vyznávajícími jak centrálně plánovaný, tak tržní systém. Okrajově se také pokouší o propojení ekonomických jevů s jevy společenskými.
|
|
| |
|
|
Analysis of Spring Barley Actual Evapotranspiration
Pozníková, Gabriela ; Fischer, Milan ; Pohanková, Eva ; Žalud, Zdeněk ; Trnka, Miroslav
Evapotranspiration (ET) represents the main water-loss part of the water balance in agricultural landscape. The reliable quantification of the agricultural field ET is, however, still a challenge. To calculate ET, the Bowen ratio/energy balance (BREB) method was used in this study. It is based on measurements of the temperature and humidity gradients and radiation balance with the soil heat flux. Calculated ET was further used to quantify crop coefficient (Kc). Subsequently, we analysed the crop coefficient of spring barley during one growing season since 7th May 2013 to 30th July 2013. We used the data obtained above 1-ha spring barley field in Bystřice nad Pernštejnem, Czech Republic. In particular, we investigated how Kc correlates to climatic conditions as rainfall and soil humidity and how it reflects Plant Area Index (PAI) during the year during different parts of growing season. The cumulative ET of spring barley was 228.6 mm per investigated period. For reference evapotranspiration (ETo) two different approaches were used. Typically, a reference grass cover 0.12 m high standard for Europe. On the other hand, in the USA it is common to use also alfalfa (0.50 m high). ETo of grass was 296.3 mm and ETo of alfalfa was 351.4 mm. Maximum Plant Area Index occurred in June and its value was 4.1. Mean Kc in May was 1.17 for reference grass and 1.03 for alfalfa. Similarly in June, Kc was equal to 1.16 (grass) and 1.03 (alfalfa). Finally in July, for reference grass Kc was 0.55 and 0.48 for alfalfa. The decline at the end of the growing season was caused by dry weather and ripe stage of spring barley.
|
|
|
Poplar-based short rotation coppice under artificially induced drought stress
Orság, Matěj ; Fischer, Milan ; Trnka, Miroslav ; Žalud, Zdeněk
The main aim of this study was to evaluate the diff erences in chosen microclimatological and ecophysiological variables between two types of experimental plots with diff erent levels of available soil water within a poplar-based (Populus nigra × P. maximowiczii) short rotation coppice plantation (SRC) during summer 2012. Diversity of sap fl ow, stomatal conductance and biomass increment were monitored between two treatments during the growing season of 2012. Th ere are 3 pairs of experimental plots under research. Each pair comprises a control plot and a neighbouring plot, equipped with a roof system, draining 40 % of the incoming rain water away (the water reduced plot). Our results show that a 40 % reduction in through-fall resulted in a 26 % reduction in transpiration and a 27 % reduction in stomatal conductance over the four month study period, which led to a statistically signifi cant (p = 0.03) deceleration of above-ground biomass accumulation at the plots with water-reduced treatment.
|
|
|
Determination of errors in energy flux estimates using the bowen ratio energy balance method
Pozníková, G. ; Fischer, Milan ; Trnka, Miroslav ; Žalud, Zdeněk
The Bowen ratio energy balance method (BREB) is based on the measurement of air temperature and humidity gradients in at least two vertical levels above the surface of interest. So far, there have been a limited number of studies dealing with the footprint of the BREB. Staying conservative, many authors used the upper sensor of the BREB as a single point to determine the footprint of the BREB. In fact, the footprint of the fl uxes rather should be explained as a source area of the single point measurement carried out somewhere between the two BREB levels. It was suggested that this single point lies close to the geometrical mean of the two aero dynamical heights. However, there has still been no consensus regarding if this apparent height is fi xed or not, and if the second is true, whether it is a function of the Bowen ratio itself. Th e submitted study deals with the footprint of the BREB using several BREB experiments above various covers with diff erent fetches. Moreover, by simulating diff erent Bowen ratios between the area of interest and the contaminating area we attempt to investigate for which conditions (dry or wet) and type of transition (from drier to wetter or vice versa) the method is more sensitive to the limited fetch.
|
|
|
Comparison of eddy covariance and bowen ratio energy balance method. Energy balance cloruse versus bowen ratio similarity assumption
Fischer, Milan ; Trnka, Miroslav ; Pozníková, Gabriela ; Sedlák, Pavel ; Orság, Matěj ; Kučera, J. ; Žalud, Z.
The Bowen ratio and the Monin-Obukhov similarity principles are based on the assumption that the eddy diff usivities for temperature and humidity are equal to each other under all atmospheric stratifi cations within turbulent surface boundary layer. However, several authors reported that this equality was violated under advective inversion or during the non-stationary conditions due to clouds passing by and sudden change of wind speed and direction. Th e inequality of the eddy diff usivity can lead to errors in the energy partitioning estimates by gradient techniques like the Bowen ratio energy balance (BREB) and the aerodynamical method, or methods based on residual energy balance such as the Penman-Monteith or Priestley-Taylor models. Th is study investigates two seasons of simultaneous measurement by eddy covariance (EC) and BREB above a high density poplar plantation at the Domanínek locality. Th e direct measurement of eddy diff usivities by EC is reinvestigating the validity of the long term measurement (since 2008) by BREB. Results showed unequal exchange coeffi cients with their mean 0.31 to 0.35 m2 s-1 for 2011 and 2012, respectively, favouring the transport of latent heat. Th is might be explained by the diff erent footprints of the BREB and EC methods, an undeveloped internal boundary layer or instrumental errors.
|
host ::
RSS.