Medúzka sladkovodní (Craspedacusta sowerbii) je jediným zástupcem rosolovitého zooplanktonu v našich vodách. Článek popisuje historii zkoumání, životní cyklus a ekologii tohoto u nás nepůvodního druhu, který byl do celého světa zavlečen z Číny., The Freshwater Jellyfish (Craspedacusta sowerbii) is the only representative of gelatinous zooplankton in Czech waters. This article describes the body of research on the invasive species, which has spread from China all over the world. The article also includes a description of the species´ life cycle and ecology., and Adam Petrusek.
Detailed knowledge of the circumstances behind the extermination of particular animal species is a key premise for their eventual return, reintroduction and ongoing preservation. Data on the presence of the Brown Bear (Ursus arctos) in the Czech landscape are usually limited to simple entries about the day and place where the last specimens in particular (usually mountainous) regions were slain. Demand for more precise data, especially regarding the last documented presence of bear cubs, has emerged in respect of the recently discovered ability of bears to migrate over long distances. The newly collected data allowed the author to present amuch more complete historical view of the process of extermination of the Brown Bear in the Czech territory. and Jan Andreska.
The prolonged survival of the Brown Bear (Ursus arctos) population in the Bohemian Forest was largely possible due to the protec tion of this animal, which was considered a rare and desirable trophy. Consequently the bear was able to survive in the Bohemian Forest for a hundred years longer than in the Ore Mountains. Isolated populations in the Sudetes survived in Moravia, and the last specimens were hunted down in the 1740s. Bears hunted down during the 19th century in the Beskydy Mts. can almost certainly be considered casual migrants from the Slovak part of this mountain range. The return of bears to the territory of Moravia and Silesia corresponds with the consolidation of the Slovak population due to the protection introduced in 1932. and Jan Andreska.
Large amounts of abandoned limestone quarries in the Bohemian Karst provide a great opportunity to study different stages of spontaneous succession simulta - neously. Molluscs are a suitable model group for this study –many land snail species including the rare ones occur in these quarries. Because of the large variability of habitats, quarries abandoned for around 60 years have higher species diversity. and Alena Kocurková, Lucie Juřičková.
Mesophyll conductance (gm) is essential to determine accurate physiological parameters used to model photosynthesis in forest ecosystems. This study aimed to determine the effects of time of day on photosynthetic parameters, and to assess the effect of using either intercellular CO2 concentration (Ci) or chloroplast CO2 concentration (Cc), on maximum carboxylation velocity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), Vcmax. We used Amazonian saplings of Myrcia paivae and Minquartia guianensis. Photosynthetic parameters were measured using an infrared gas analyzer (IRGA); gm was determined using both gas exchange and chlorophyll (Chl) a fluorescence and gas-exchange data alone. Leaf thickness (LT) and specific leaf area (SLA) were also measured. Air temperature, relative humidity or understory light did not correlate with gm and on average daily IRGA-fluorometer-determined gm was 0.04 mol(CO2) m-2 s-1 for M. paivae and 0.05 mol(CO2) m-2 s-1 for M. guianensis. Stomatal conductance (gs), gm, electron transport rate (JF), and light-saturated net photosynthetic rate (PNmax) were lower in the afternoon than in the morning. However, no effect of time of day was observed on Vcmax. LT and SLA did not affect any of the examined parameters.
IRGA-determined g m was almost the double of the value obtained using the IRGA-fluorescence method. Vcmax values determined using Cc were about 25% higher than those obtained using Ci, which highlighted the importance of using Cc in Vcmax calculation. Decline in PNmax at the end of the afternoon reflected variations in gs and gm rather than changes in Vcmax. Diurnal variation in gm appeared to be associated more with endogenous than with atmospheric factors. and H. C. S. Nascimento, R. A. Marenco.