Evaluation of Walnut Tree Flowering and Frost Occurrence Probability During 1961-2012

Strength and direction of the potential effect of climate change on walnuts is regionally specific (Gauthier and Jacobs, 2011) as climate change will probably affect the spatial distribution of the walnut. This paper evaluated the long-term phenological series (1961-2012) of the beginning of flowering, end of flowering and duration of flowering in walnut tree (Juglans regia) at two phenological stations located in different geographical locations of the Czech Republic but in the same climatic conditions (warm region). Phenological stages were analyzed in relation to growing degree days and to spring frosts occurrence. Onset of the beginning and end of flowering occurred earlier at Velké Pavlovice station (-2.1 and -1.3 days), and conversely occurred later at Doksany station (+1.8 and +1.0). Period of flowering shortened at Doksany station (-0.8 day) and prolonged at Velké Pavlovice station (+1.2 day). The occurrence of days with minimum air temperature < 0 oC during walnut tree flowering was more frequent at Doksany station (in total, 29 days) with absolute minimum value -5.5 oC. At Velké Pavlovice station 5 days with minimum air temperature below 0 oC were found during examined period with absolute minimum value -3.8 oC. The negative trend in number of frost days occurrence during flowering period was found at both stations. Pearson correlation coefficient between phenophase onset (and flowering period) and sums of growing degree days was stronger at Velké Pavlovice station, and the highest value was between period of flowering and temperature sums (0.782). The results confirmed our hypothesis of changes in phenophase onsets and duration of flowering including spring frosts occurrence according to west-east gradient (maritime climate-continental climate).O

Validity and reliability of drought reporters in estimating soil water content and drought impacts in central Europe

Increasing drought is considered one of the major threats associated with climate change in central Europe. To provide an objective, quantitative tool that represents current drought conditions, the Czech Drought Monitor System (CzechDM) was established in 2012. Like other drought monitoring systems worldwide, the CzechDM uses several approaches to provide drought data. However, the CzechDM is unique internationally due to its utilization of a network of voluntary reporters (farmers) who complete a weekly online questionnaire to provide information about soil water content and the impacts of drought on crop yield. In this study, the results from the questionnaires from individual farms were aggregated by district. Reporters’ data were compared and validated with the outputs of the SoilClim model (a core tool of the CzechDM) and with other drought monitoring tools, such as the water balance model, the soil water index and the evaporative stress index. The soil water content estimated by the reporters was significantly correlated (on average r = 0.8) with the outputs of the SoilClim model. Conversely, the correlation between the drought impacts on yield estimated by the reporters and the SoilClim outputs was lower (on average r = 0.4), suggesting that in situ observations by farmers provide additional insights into the occurrence of drought impacts. Importantly, it was found that farmers reported significant drought impacts on yield earlier in the season than any other methods (models or remote sensing). The main findings of this study are that the drought monitoring provided by reporters is a useful and reliable component of the CzechDM. We conclude that weekly reports by farmers represent a significant enhancement to drought monitoring and have potential for use in developing automated approaches that combine in situ, modeling and remote sensing data within a data fusion or machine learning framework

Automatizace měření výparu z volné vodní hladiny

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Monitoring zásoby využitelné vody v povrchové vrstvě půdy pod travním porostem

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Dlouhodobé kolísání počátku vegetační sezony v Polabí v letech 1876-2005

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Drought at various timescales for secular lowland climatological stations in the Czech Republic =Hodnocení sucha na vybraných sekulárních klimatologických stanicích v různém časovém měřítku

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