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Subseasonal temperature trends in Europe (1961-2000) and their links to atmospheric circulation
Cahynová, Monika ; Pokorná, L.
We use daily maximum and minimum temperatures and the daily temperature range from 136 stations in Europe in the period 1961–2000 to precisely locate their seasonal and subseasonal trends within the year. Linear trends are calculated for moving “subseasons” of 10, 20, 30, 60, and 90 days, each shifted by one day. Over most of Europe, the observed warming is greatest in winter. In Iceland and the Mediterranean, a pronounced warming is only present in summer. Significant autumn cooling was found in Eastern and Southeastern Europe for both TX and TN. Other non-warming periods occur in Western and Central Europe in February, April, and late June. Trends of DTR are inconclusive. Changes in the frequency of atmospheric circulation types usually explain a substantial part of the observed climatic trends; however, the influence varies between regions, times of the year, subseason lengths, numbers of circulation types, and input variables for the classification of circulation types.
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Mathematical methods of modelling the morphology of spruce trees
Janoutová, Růžena ; Novotný, Jan ; Pivovarník, Marek ; Zemek, František
Radiative transfer (RT) models are simulation tools which can be used to quantify relationships between vegetation canopy properties and observed remotely sensed data. Th is study aims at creating a spruce tree growth model as a key input for use in RT models. Th e spruce tree model is built on data obtained from terrestrial laser scanning of spruce trees. Each tree model is unique. Th is uniqueness is achieved by using L-systems which are able to simulate natural randomness while complying with the given tree parameters. L-systems are established on a theory of grammar that enables rewriting a string of symbols according to specifi ed rewriting rules. In practice, our tree models are generated in Blender visualization soft ware, implementing an algorithm written in Python. Th e algorithm generates the basic parameters of the whole tree and then creates the parameters of the spruce trunk and initial branches. Th e parameters are generated randomly within a range that is calculated from measured data. Th en each branch is grown on the basis of annual increments defi ned by fi eld measurements. Tree needles are distributed with respect to the age of individual branches; therefore, the needles have diff erent colours according to their age. Cones and faces are graphical representations of the spruce model. Branches are represented by cones and needles are represented by faces around the branches. Th e faces are transparent, thus simulating light transmittance in-between the needles. The whole model is highly computationally demanding, especially with respect to computer memory.
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Is it possible to measure CO2 effluxes in an arable ecosystem using chambers without soil frames?
Juszczak, R. ; Acosta, Manuel ; Sakowska, K. ; Leśny, J. ; Uździcka, B. ; Chojnicki, B. H. ; Urbaniak, M. ; Olejnik, Janusz
The push-in chamber and chambers with alternative gaskets were tested under fi eld conditions in order to estimate the rates of under- or overestimation of the CO2 effl uxes measured with chambers placed directly on a soil surface (without collars). Th e experiment was conducted on a spring barley fi eld which was harvested just before the measuring campaign. Th e following were tested: 1) a pushed-in chamber with a sharp metal blade installed on the edge of the chamber walls which was inserted to a depth of 1–2 cm to the soil, 2) a chamber with a 10 cm wide and 3 cm high rubber gasket, and 3) a chamber with a 10 cm wide and 2 cm high neoprene gasket. Th e results indicated that the application of the pushed-in chamber led to overestimation of the fl uxes by 55%, while application of chambers with alternative gaskets led to underestimation of the fl uxes by 30–40% due to the leakage of the gas from the chamber headspace through holes beneath the gaskets. Our experiment confi rmed that soil frames should be applied in fi eld conditions to assure the tightness of the chambers. Other tested solutions increase the biases of the chamber measurements and increase the uncertainties of the estimated CO2 effl uxes.
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Zonation of NP as an important tool of nature conservation: consequences of fragmentation of zonatio in Šumava NP
Křenová, Zdeňka
The Šumava NP zonation has been debated since the very establishment of the National park and refl ects the views and opinions on nature conservation principles among various groups of experts. Th e fi rst zonation developed in 1991 fully respected the original intention of the goals of the National park, i.e. leaving space for spontaneous processes in nature. In 1995, the zonation was dramatically changed, because the NP’s senior managers supported the opinion that a European Spruce Bark Beetle (Ips typographus) outbreak can be reduced only by forest management measures, i.e. by extensive felling. Th us, only 13 % of the NP’s territory was within the Zone I and was fragmented into 135 patches, which was strongly criticized by experts. Th e necessity to adopt the new zonation graduated aft er the hurricane Kyrill in 2007, when large parts of fragmented forests were destroyed by wind. A new proposal for delineating the Zone I is based on botanical, forest management and zoological criteria, carefully assessing the NP’s values. Th e proposed Zone I covers 39.2 % of the NP territory and is distributed into 10 units. Th e proposal was delivered as a background for a working group draft ing a New Act on Šumava NP on behalf of the Ministry of the Environment of the Czech Republic. Good zonation of NPs is concluded to be an important tool of nature conservation but respect for legislation, international NP principles, and current scientifi c knowledge should be the main rule for responsible decision making in protected areas and biodiversity conservation.
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Projections of future water-energy-vegetation regimes at the Lysina catchment, Czech Republic
Lamačová, Anna ; Yu, X. ; Duffy, Ch. ; Krám, Pavel ; Hruška, Jakub ; Farda, Aleš
Hydrologic models represent useful tools for the understanding of forest hydrological functions. At the Lysina Critical Zone Observatory (50°03’ N, 12°40’ E; area 0.293 km2), a forest catchment in the western Czech Republic, a distributed physics-based hydrologic model, the Penn State Integrated Hydrologic Model (PIHM), was used to simulate long-term hydrological change under forest management practices, and to evaluate the comparative scenarios of the hydrological consequences under anticipated climate change. Stand age-adjusted LAI (leaf area index) curves were generated from an empirical relationship to represent changes in seasonal tree growth. By considering the age-adjusted LAI, the spatially distributed model was able to successfully simulate the integrated hydrologic response from snow melt, recharge, evapotranspiration, groundwater levels, soil moisture and streamfl ow, as well as spatial patterns of each hydrologic state and fl ux variables. Corrected climatic data from the ALADIN-Climate/CZ regional climate model with SRES A1B scenario and diff erent forest age categories (Norway spruce monoculture) were used for projection of hydrologic pattern shift at the study site in the future (2025–2050, 2071–2100). Th e model projections suggested that that the decrease in mean annual runoff would be from 422 mm (observed in 1990–2011) to 361 mm (2021–2100) and 345 mm (2071–2100) with notable changes in seasonal patterns represented by a runoff decrease in the spring and summer months.
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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.
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Hyperspectral image segmentation for estimation of biomass at reclaimed heaps
Pikl, Miroslav ; Zemek, František
This paper presents the preliminary results from a study that aims at estimation of above ground biomass and soil carbon content at reclaimed mining heaps in the Sokolov region. Two image segmentation methods are presented. We applied maximal likelihood (ML) and neural network (NN) classifi ers on airborne hyperspectral data. Th e objective of this part of the study was to prepare a land cover classifi cation of the region. Th e main focus was paid to discrimination of six classes with prevailing forest species cover. Th e classifi cation accuracy of the training sites was 93.75 % for NN and 79.12 % for ML respectively. But ML outperformed NN in overall classifi cation accuracy with 61.54 % compared to 40.9 % of NN. Th e more accurate results of the ML classifi er are probably infl uenced by properties of the training samples. Th e larger size of the training samples derived for ML enabled better representation of class histograms. Th e lower overall NN accuracy could result from high spatial resolution of HS data.
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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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