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Assessing the impact of drought stress on winter wheat canopy by hermes crop growth model
Wimmerová, Markéta ; Pohanková, Eva ; Kersebaum, K. C. ; Trnka, Miroslav ; Žalud, Zdeněk ; Hlavinka, Petr
The main aim of this study was evaluate a drought stress effect on winter wheat development, growth (leaf area index), soil moisture and yields. Simultaneously, the ability of Hermes crop growth model to simulate drought stress response was tested. The field trial was established at Domanínek station (Bystřice nad Pernštejnem district, Czech Republic) in 2014. Mobile rain-out shelters for precipitation reduction were installed on the plots of winter wheat in May 2015. Results of this study showed that model is able to reproduce well a soil moisture content and to certain extent the drought stress for grain yields of winter wheat. Using the rain-out shelters (from 19 May to harvest on 6 August 2015), real winter wheat yields were reduced by 1.7 t/ha. The model was able to estimate the average yield with a deviation of 0.15 t/ha (6%) for no stressed variant. Model underestimated the yields for sheltered variant with a difference 0.67 t/ha (71%) on average against observed yields.
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Odhad výnosů zemědělských plodin na základě družicového monitoringu
Lukas, V. ; Trnka, Miroslav ; Semerádová, Daniela ; Rajdl, Kamil ; Balek, Jan ; Štěpánek, Petr ; Zahradníček, Pavel ; Hlavinka, Petr ; Žalud, Zdeněk
Znalost výnosů plodin před dosažením sklizně je významná nejen pro plánování aktivit na úrovni zemědělských podniků, ale také z národohospodářského pohledu pro zabezpečení produkce potravin. Cílem studie bylo ověřit vývoj modelu odhadu výnosů významných plodin (pšenice ozimé, ječmene jarního a řepky ozimé) z výsledků vegetačních indexů NDVI (Normalized Difference Vegetation Index) a EVI2 (Enhanced Vegetation Index) ze senzoru MODIS v podobě 16 denních kompozitů za období 2000 – 2014. Za vybrané území 14 okresů České republiky, které představují regiony s vyšší intenzitou zemědělské produkce a rozdílnými pedo-klimatickými podmínkami. Přesnost predikčního modelu byl testována zejména v ročnících se silným výskytem sucha a nízkou úrovní výnosu (2000, 2003, 2006 a 2012). Stabilnější výsledky byly dosaženy ve výnosově nejproduktivnějších okresech, jako jsou Olomouc a Přerov, zatímco u výše položených území byl model značně ovlivněn nižším podílem sledovaných plodin na úkor pícnin. Ve většině případů byla vyšší přesnost stanovení výnosu dosažena pomocí vegetačního indexu EVI2 a postupným průměrováním hodnot kompozitů v průběhu vegetačního období plodin.
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Mapování sucha a odhad výnosů polních plodin pomocí indexu ESI
Jurečka, František ; Anderson, M. ; Hlavinka, Petr ; Hain, C. ; Wayne, D. ; Gao, F. ; Johnson, D. M. ; Otkin, J. ; Žalud, Zdeněk ; Trnka, Miroslav
Dálkový průzkum Země (DPZ) se již řadu let se používá k různým analýzám, které zjišťují limitující faktory pro zemědělskou produkci. V souvislosti s klimatickými podmínkami posledních let se do oblasti zájmu dostává zejména monitoring sucha, zjišťování stavu vegetace na zemědělských pozemcích a odhad výnosů polních plodin. Metody dálkového průzkumu využívají záření o různé vlnové délce, které při pozorování jednotlivých složek zemského povrchu a vegetace vykazuje různé chování. Dálkový průzkum využívá ke zjišťování stavu vegetace, zemědělské krajiny a odhadů výnosu celou řadu indexů. V této studii byl k monitoringu sucha a odhadu výnosů použit index ESI (Evaporative Stress Index) používaný modelem ALEXI (Atmosphere-Land Exchange Inverse).
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Drivers of soil moisture trends in the Czech Republic between 1961 and 2012
Trnka, Miroslav ; Brázdil, Rudolf ; Balek, J. ; Semerádová, Daniela ; Hlavinka, Petr ; Možný, M. ; Štěpánek, Petr ; Dobrovolný, Petr ; Zahradníček, Pavel ; Dubrovský, Martin ; Eitzinger, Josef ; Fuchs, B. ; Svoboda, M. ; Hayes, M. ; Žalud, Zdeněk
Soil moisture dynamics and their temporal trends in the Czech Republic are forced by various drivers. Our analysis of temporal trends indicates that shifts in drought severity between 1961 and 2012 and especially in the April, May, and June period, which displayed such results as a 50% increase in drought probability during 1961–1980 in comparison to 2001–2012. We found that increased global radiation and air temperature together with decreased relative humidity (all statistically significant at p < 0.05) led to increases in the reference evapotranspiration in all months of the growing season; this trend was particularly evident in April, May, and August, when more than 80% of the territory displayed an increased demand for soil water. These changes, in combination with the earlier end of snow cover and the earlier start of the growing season (up to 20 days in some regions), led to increased actual evapotranspiration at the start of the growing season that tended to deplete the soil moisture earlier, leaving the soil more exposed to the impacts of rainfall variability. These results support concerns related to the potentially increased severity of drought events in Central Europe. The reported trend patterns are of particular importance with respect to expected climate change, given the robustness and consistency of the trends shown and the fact that they can be aligned with the existing climate model projections. Introduction
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Reliability of regional crop yield predictions in the Czech Republic based on remotely sensed data
Hlavinka, Petr ; Semerádová, Daniela ; Balek, Jan ; Bohovič, Roman ; Žalud, Zdeněk ; Trnka, Miroslav
Vegetation indices sensed by satellite optical sensors are valuable tools for assessing vegetation conditions including field crops. The aim of this study was to assess the reliability of regional yield predictions based on the use of the Normalized Difference Vegetation Index and the Enhanced Vegetation Index derived from the Moderate Resolution Imaging Spectroradiometer aboard the Terra satellite. Data available from the year 2000 were analysed and tested for seasonal yield predictions within selected districts of the Czech Republic. In particular, yields of spring barley, winter wheat, and oilseed winter rape during 2000–2014 were assessed. Observed yields from 14 districts were collected and thus 210 examples (15 years within 14 districts) were included. Selected districts differ considerably in soil fertility and terrain configuration and represent a transect across various agroclimatic conditions (from warm/dry to relatively cool/wet regions). Two approaches were tested: 1) using 16-day temporal composites of remotely sensed data provided by the United States Geological Survey, and 2) using daily remotely sensed data in combination with an originally developed smoothing method. Yields were predicted based on established regression models using remotely sensed data as an independent parameter. In addition to other findings, the impact of severe drought episodes within vegetation was identified and yield reductions at a district level were predicted. As a result, those periods with the best relationship between remotely sensed data and yields were identified. The impact of drought conditions as well as normal or above-normal yields of the tested field crops were predicted using the proposed method within the study region up to 30 days prior to harvest.
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The Bowen Ratio/Energy Balance method and detailed temperature profile measurements to improve data quality control
Pozníková, Gabriela ; Fischer, Milan ; Orság, Matěj ; Trnka, Miroslav ; Žalud, Zdeněk
Water plays a key role in the functionality and sustainability of ecosystems. In light of predicted climate change, research should focus on the water cycle and its individual components. The main component of water balance driving water from ecosystems is evapotranspiration (ET). One standard method for measuring ET is the Bowen Ratio/Energy Balance (BREB) method. It is based on the assumption that water vapour and heat are transported by identical eddies with equal efficiency. When using the BREB method, we assume that the profiles of temperature and air humidity are ideally logarithmic or at least consistent. Since the BREB method is usually based on measurements of temperature and humidity at only two heights, it is difficult to verify whether this assumption has been fulfilled. Potential profile inconsistencies are more likely for temperature because the sensible heat flux changes its sign more often and negative latent heat flux is not physically possible during positive sensible heat flux. We therefore conducted a field experiment using a 4-mhigh measurement mast with 20 thermocouples for detailed measurement of air temperature profiles above different covers, e.g. grassland, spring barley, and poplar plantations. Our main objective was to investigate the basic assumptions of the BREB method, i.e. the temperature profile’s consistency under various weather conditions. To be more specific, we aimed to investigate whether inflexion points occurred within the temperature profile and if so when.
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Surface water temperature modelling to estimate Czech fishery productivity under climate change
Svobodová, Eva ; Trnka, Miroslav ; Kopp, R. ; Mareš, J. ; Spurný, P. ; Pechar, L. ; Beděrková, I. ; Dubrovský, M. ; Žalud, Zdeněk
Freshwater fish production is significantly correlated with water temperature, which is expected to increase under climate change and affect fish growth, productivity, and survival. This study deals with estimating the change in water temperature in productive ponds and its impact on fishery in the Czech Republic. The target fish species were common carp (Cyprinus carpio), maraena whitefish (Coregonus maraena), northern whitefish (Coregonus peled), and rainbow trout (Oncorhynchus mykiss). It was hypothesized that there would be an increasing risk of high water temperature stress for fish. Water temperature calculations based on 3-day means of air temperature were tested in several ponds in three major fish production areas. The verified model was applied to the climate change conditions determined by standardized scenarios derived from the five global circulation models MPEH5, CSMK3, IPCM4, GFCM21, and HADGEM. The results for changed climate indicated limitations for Czech fish farming in terms of prolonged periods with fish temperature stress as well as the increased number of stress periods and increased number of days within these periods. It is very likely that Czech fishery will have to change the fish species farmed in particular productive areas. In particular, higher altitudes are likely to become less suitable for the Salmonidae.
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Long-term productivity of short rotation coppice under decreased soil water availability
Orság, Matěj ; Fischer, Milan ; Tripathi, Abishek ; Žalud, Zdeněk ; Trnka, Miroslav
Wood, in fact, is the unsung hero of the technological revolution that has brought us from a stone and bone culture to our present age (Perlin 1991). Given its high-energy content and versatile use, biomass in the form of wood has been used for energy purposes for millennia. The production and use of woody biomass resources has been expanding around the world. The main drivers of its use as a source of energy are diversification and mitigation of energy related greenhouse gas emissions through partial substitution for fossil fuels. An alternative to sourcing wood biomass from natural forests is short rotation woody coppice. Its productivity is largely dependent on the environment in terms of climatic conditions. Especially drought is the main constraint on woody biomass production and involves serious economic consequences. For that reason, our field experiment was designed to evaluate the impact of decreased soil water availability on productivity of a poplar based short rotation coppice plantation over multiple growing seasons during 2011–2014. Aboveground biomass productivity of treatments with and without throughfall exclusion was assessed within this study. Our results show a systematic decline in the productivity of the plots subjected to decreased soil water availability by 30% in 2011, 20% in 2012, 49% in 2013, and 51% in 2014 compared to control plot. Aboveground biomass productivity ranged from 8.8 to 9.9 t dry matter ha−1 year−1 for the control treatment and 4.5 to 8.0 t dry matter ha−1 year−1 for the treatment with throughfall exclusion.On average, the throughfall exclusion treatment exhibited 47% less productivity than control treatment had over the entire study period.
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