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Stem CO2 efflux on Norway Spruce trees: uncertainty in sap flow effect
Bužková, Romana ; Dařenová, Eva ; Acosta, Manuel
Uhlíková bilance lesa je dána dynamickou rovnováhou mezi procesy zabudovávání uhlíku (fotosyntéza atd.) a procesy uvolňujícími uhlík jako např. respirace. Právě respirace je důležitou složkou uhlíkové bilance lesa, protože uvolňuje až 80% uhlíku fixovaného v autotorofních a heterotrofních potravních řetězcích. S rostoucí teplotou prostředí respirace exponenciálně roste. Ovšem vlivy dalších faktorů na respiraci, jako např. transpirační proud, nejsou jednoznačně známé. Nárůst toku CO2 z kmene může být spojen s poklesem transpiračního toku (Levy et al. 1999), jeho nárůstem (Bowman et al. 2005) a nebo se vzájemně neovlivňují (Cerasoli et al. 2009). Cílem této případové studie bylo (i) zlepšení poznatků o potenciálním vztahu mezi traspiračním proudem a respirací kmene a (ii) průzkum faktorů prostředí potenciálně ovlivňujících tento vztah.
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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.
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Forest floor respiration of tuczno scots pine stands
Urbaniak, M. ; Pavelka, Marian ; Heronim Chojnicky, B. ; Juszczak, R. ; Dařenová, Eva ; Baran, M. ; Danielewska, A. ; Ziemblinska, K. ; Olejnik, Janusz
Tuczno forest is a 60-year-old Scots pine stand that is located in the North-West part of Poland. During the period between 20th and 25th August 2012 an experiment consisting of the measurement of forest fl oor CO2 effl ux was carried out. For this purpose, manual chamber systems were used. Measurements were taken at 60 collars located on a rectangular plot 25m x 45m. Th is research area was located in the range of footprint of the Eddy-covariance (EC) tower. Th e preliminary results indicate that the average CO2 effl ux from the forest fl oor, as measured during the experiment (5.09 μmol m-2 s-1), is lower than the total ecosystem respiration, estimated from EC data (6.25 μmol m-2 s-1). Spatial variability of soil CO2 effl ux (Rs) can be explained by humus thickness (Ht) variability; however, the tree root respiration can be considered a valuable part of CO2 emission from the forest bottom.
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Treeline shift under global change - ectomycorrhizas as a limiting factor?
Vašutová, Martina ; Holub, Filip ; Čermák, Martin ; Cudlín, Pavel
It is assumed that global change will cause a treeline shift . Because competitive abilities and natural regeneration of trees are infl uenced by ectomycorrhizal (ECM) symbiosis and fi ne roots and ECM mycelia play a key role in belowground carbon turnover, we have studied the ECM associations of treeline ecosystems. We aim to fi nd out how resistant and resilient current ECM associations of these ecosystems are and whether the absence of appropriate ECM symbionts could be a limiting factor of an ecosystem shift . We have focused on natural mountain spruce forests and spruce forests on the treeline; dwarf pine stands with scattered spruce trees above the treeline will be studied in years to come. Ectomycorrhizas were described by morphological features and sequenced to identify fungal species. In the case of taxonomically complicated ECM fungal groups, sequences from microscopically identifi ed sporocarps were used for the identifi cation of ectomycorrhizas. A disproportion between ECM fungi diversity in spruce stands and dwarf pine stands revealed based on a literature review can indicate diff erent ectomycorrhiza patterns at the treeline. According to preliminary results from the Giant Mts. there is an adequate ECM fungal species diversity in mountain spruce forest and spruce forests on the treeline.
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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.
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Quality control and homogeneity testing of daily time series of eca ECA&D
Zahradníček, Pavel ; Štěpánek, Petr ; Farda, Aleš ; Skalák, Petr
For any meaningful climate analysis, it is necessary for analysed time series to be homogeneous, which means that their variations are caused solely by variations in weather and climate (Conrad and Pollak 1950). Th us, prior to any analysis, the need to homogenize data and check their quality arises. Unfortunately, most of the climatological series that span over decades, to centuries, contain inhomogeneities caused by station relocations, exchange of observers, changes in the vicinity of the stations (e.g. urbanization), changes in instruments, observing practices (e.g. diff erent formulas for calculating daily means, diff erent observation times), etc. In this work we focused on testing the quality and homogeneity of daily data produced by ECA&D. Th is is a free available dataset of daily meteorological elements from the European Climate Assessment & Dataset (http://eca.knmi.nl/). Th is database was used to create a regular grid of EOBS points, which are oft en used to validate climate models.
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Remotely sensed NDVI as a support tool for agricultural drouhgt assessment
Hlavinka, Petr ; Semerádová, Daniela ; Trnka, Miroslav ; Lukas, V. ; Bohovic, R. ; Balek, J. ; Wardlow, B. ; Hayes, M. ; Tseagaye, T. ; Žalud, Zdeněk
Th e main aim of the submitted study was to introduce how the remotely sensed NDVI (Normalized Diff erence Vegetation Index) could be used for agricultural drought assessment within the Czech Republic. Th e relationship between NDVI values and observed yields of spring barley and winter wheat was analyzed for selected districts. Moreover the ability of NDVI (at district level in the form of seasonal greenness – SG) to explain the water balance or drought occurrence and severity was tested. For this purpose a data mining technique was used. A relative form of the Palmer Drought Severity Index (rPDSI) was used as a dependent variable to indicate drought occurrence. A Standardized Precipitation Index (SPI), percentage of average SG (PASG), Start of Season Anomaly (SOSA) and district identifi cation were used as independent variables. MODIS (Moderate Resolution Imaging Spectroradiometer) observations from the Terra satellite were used as a source of NDVI. Th e situation within 6 selected districts (Olomouc, Přerov, Znojmo, Břeclav, Žďár nad Sázavou and Havlíčkův Brod) during the period from 2000 to 2012 was analyzed. Promising results were achieved, so practical use of this approach (e.g. for spatial and temporal assessment of drought stress within the vegetation) could be expected.
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Climate Change in the Area of the Czech Republic according to Various Model Simulations
Štěpánek, Petr ; Skalák, Petr ; Farda, Aleš ; Zahradníček, Pavel
In recent years, simulations from various regional climate models became available for the area of the Czech Republic, thank to several national or international projects (e.g. the EC FP6 projects CECILIA, ENSEMBLES or VaV). The simulations of the all models were performed according to the IPCC A1B emission scenario with various spatial resolutions. Since models suffer from biases, the model outputs were statistically corrected using the quantile approach of M. Déqué. After correction, RCM outputs were statistically processed and analyzed. In this paper, the differences between models outputs, as well as corrected and uncorrected results, are presented.
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The dynamics of temperature in birdboxes
Slavíková, Z. ; Žalud, Z. ; Bartošová, Lenka ; Fischer, Milan ; Trnka, Miroslav
The aim of the study was to detect the changing temperature in bird boxes of two bird species-collared flycatcher (Ficedula albicollis, T.) and great tit (Parus major, L.). The work is the result of the monitoring of nesting bird species for two years (2009 and 2010) by temperature sensors. Data was continuously recorded for several different breeding pairs with the micro-datalogers MINIKIN. Temperature sensors were fixed directly into the nest with eggs and also in the upper part of bird boxes or outside the boxes. Temperature data was then processed and analyzed. Experimental work was carried out in a floodplain forest in nature reserve Plačkův les a říčka Šatava near Vranovice, altitude: 170; latitude: 48°56´54´´; longitude: 16°35´50´´. The forest is dominated by full-grown, multi-aged canopy with no forestry management. Experimental site belongs to the same natural biogeocenoses group (i.e. Ulmi-fraxineta carpini) and to the same geobotanical group (i.e. suballiance Ulmenion of the Alnion incanae alliance). Our initial hypothesis assumed that the temperature of eggs in the nest and also the time spent in the bird boxes by both bird species (collared flycatcher and great tit) do not differ significantly. The results showed that during the period when the eggs were layed (by both bird species) the temperature were significantly however the temperature of eggs of collared flycatcher and great tit during the period of incubation were very.
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Calibration of the selected crop growth models for spring barely
Pohanková, E. ; Trnka, Miroslav ; Hlavinka, Petr ; Takáč, J. ; Kersebaum, Ch. ; Orság, Matěj ; Fischer, Milan ; Pokorný, E. ; Žalud, Zdeněk
The climate change is one of the most discussed global problems. One option how to estimate the effects of expected future climate conditions on plant production is the use of the crop growth models. Our aim was the calibration of two models (Daisy and Hermes) based on observed and measured data that were collected for spring barley (represented by cultivars Tolar and Blaník) at experimental site Bystřice nad Pernštejnem during 2011 and 2012. The onset of flowering was underestimated by an average of 1.1 and 1.6 days and maturity by 5.8 and 9.0 days using Daisy and Hermes respectively. On average Daisy systematically underestimated yields by 0.3 t/ha-1 and Hermes overestimated yields by 1.24 t/ha-1. We expect further improvement of these models estimates using the available result from the following years
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