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1.
Analyses of fossil mollusc successions have rarely been used to study the development of floodplain forests during the Holocene. The Oh?e River, located in a prehistorically settled chernozem area in the Czech Republic, is partly situated in Cretaceous marlstones, yielding sediments suitable for fossilization directly in floodplain deposits. We analysed five fossil mollusc successions situated in the lower stretch of the Oh?e River and compared the results with recent mollusc assemblages studied along the entire 256 km of the river. Fossil samples were composed mostly of open‐country species throughout the Holocene or the whole preserved succession. Only some samples also contained woodland assemblages, but these were always greatly impoverished, with a very low frequency of strictly woodland species. Although the natural‐looking appearance of the present‐day floodplain forests of the lower river stretch has resulted in its being declared a nature reserve, modern floodplain forest mollusc assemblages there are also impoverished. This reduction in the distribution of strictly woodland species compared with modern assemblages in the upper stretch of the river seems to be the result of an ancient human settlement and continuous disturbances of the floodplain forest development since the Neolithic. Thus, fully developed floodplain forest assemblages occur recently only in the upper non‐impacted stretch of the river. Based on the studied fossil successions we can conclude that the lower Oh?e River floodplain was probably a mosaic of open and disturbed forest habitats throughout the Holocene. This area is part of a central European landscape island, where forests probably never fully developed and open patches from the early Holocene continually developed into an agricultural landscape.  相似文献   
2.
Prehistoric settlements are usually perceived as being in opposition to the natural development of the landscape. Indeed, for woodland snail assemblages in anthropogenic landscapes in central Europe, considerable impoverishment is typical. However, it remains unclear whether this has been caused by humans only or also by climate effects. From an archaeological point of view, the Moravian Karst is one of the classic prehistorical locations in central Europe, but with a more humid climate than the previously studied anthropogenic areas. To learn more about coexistence of humans and natural forests during the Lateglacial and Holocene, we analysed 11 mollusc successions covering this entire area, a unique data set for such a relatively small area. These mollusc successions show several specific features compared to the standard development known from other mid‐European areas. One is that although the Moravian Karst is not far from the Western Carpathians, Carpathian species appeared relatively late, only during the second half of the Holocene climatic optimum. Similarly, some western European and Alpine elements appeared later than expected. In contrast to this, however, a number of forest species with central European range appeared relatively early during the Lateglacial or Early Holocene. Two even survived the Last Glacial Maximum in the Moravian Karst. This would suggest an early occurrence of forest patches in a mosaic landscape. Humans have apparently inhabited this area since the Lateglacial amongst islands of forests, which later changed during the Boreal and then the climatic optimum into humid canopy forests. Thus, a mosaic of anthropogenic and natural habitats persisting in close vicinity was possible in rugged and humid landscapes practically until the Industrial Revolution.  相似文献   
3.
Annual growth rings of a common hardwood species, Picea abies L., were investigated as a potential archive of past atmospheric Pb pollution. Wide distribution of trees in terrestrial settings and straightforward chronology are two advantages of this potential geochemical archive, but several processes described in the literature may obscure the trends in past Pb deposition. These confounding factors include, e.g., radial post-depositional mobility of Pb in xylem, and ecosystem acidification leading to higher bioavailability of Pb. One- to five-year annual wood increments were analyzed for Pb concentrations and 206Pb/207Pb ratios at Jezeri (JEZ), Uhlirska (UHL) and Na Lizu (LIZ), three sites in the Czech Republic, differing in atmospheric Pb loads. Three to four trees per site were included in the study. Distinct Pb concentration maxima between 1960 and 1990 at the two heavily polluted sites (JEZ and UHL) coincided with historical Pb emissions known from inventories of industrial production. No Pb concentration maxima were found at one site, LIZ, situated in a national park 150 km from major pollution sources. Spruce tree rings from JEZ, located just 5 km from coal-burning power stations, contained a large proportion of coal-derived Pb (a high-206Pb/207Pb ratio of 1.19). A coal-related maximum in 206Pb/207Pb in JEZ tree rings was found using two different analytical techniques, laser-ablation multi-collector ICP MS, and single-collector sector-field ICP MS. In a three-isotope graph (206Pb/207Pb vs. 208Pb/207Pb), tree-ring data plotted into the field of ombrotrophic (i.e., rain-fed) peat bogs, suggesting negligible contribution of bedrock-derived Pb in the xylem. We concluded that none of the potential confounding factors played a major role at our sites. Annual growth rings of P. abies in Central Europe faithfully recorded historical changes in atmospheric Pb depositions.  相似文献   
4.
In the Czech Republic, river bottom sediments have been systematically monitored since 1999. In the paper, their radioactive contamination due to uranium mining and milling is assessed. The sediments samples were analyzed by gamma spectrometry. Especially the radium-226 and radium-228 activities were further evaluated.The highest values of the radium-226 activities were found at river profiles where the uranium industry impact was obvious. It turned out that the radium-226 and radium-228 activities ratio is more convenient to assess the level of radium-226 contamination than only the radium-226 activity itself. Based on this hypothesis, the sediment classification scheme for uranium industry contamination was suggested. The natural background activities of radium-226 and radium-228 in the Czech Republic were also evaluated. The case of radium-226 contamination due to the uranium industry was studied in details at the Ploučnice River.  相似文献   
5.
Glyphs are small geometric shapes that in geovisualization are often used to represent multidimensional spatial data. The aim of this study is to investigate the effectiveness of their two types – star and polyline glyphs, as they can encode the same message and can provide similar functionality. Thus, if the two glyph types are similar and can be used for the same data, the question arises as to which of them better facilitates various user tasks. To address this question, an empirical study of 26 individual users is conducted to investigate differences in user performance for polyline and star glyphs shown either in a grid plot or on a map display. In this study, a task-based approach with eye-tracking is applied, as well as a subjective questionnaire and a psychological test of cognitive style. The finding is that polyline glyphs better facilitate tasks when datapoint values in glyphs are to be read, whereas star glyphs are better when a visual search among glyphs is to be done. Moreover, the results reveal that the map display works better than the grid plot. If star glyphs are to be used, the key (legend) needs to be better incorporated into a visual interface.  相似文献   
6.
Although there is evidence from molecular studies for the existence of central European last glacial refugia for temperate species, there is still a great lack of direct fossil records to confirm this theory. Here we bring such evidence in the form of fossil shells from twenty strictly forest land snail species, which were recorded in radiocarbon-dated late glacial or older mollusc assemblages of nine non-interrupted mollusc successions situated in the Western Carpathians, and one in the Bohemian Massif. We proposed that molluscs survived the last glacial period in central Europe in isolated small patches of broadleaf forest, which we unequivocally demonstrate for two sites of last glacial maximum age.  相似文献   
7.
Selenium has been determined in sixty five geological reference materials of different origins by graphite furnace atomic absorption spectrometry. Samples were decomposed with a mixture of nitric and hydrofluoric acids. Selenium was reduced to SeIV with hydrochloric acid, and then fixed and separated from the matrix on thiol cotton. After digestion of the thiol cotton in hot nitric acid, the Se concentration was measured using palladium and magnesium nitrates as a matrix modifier. The limit of determination was 0.02 μg g−1, the precision of the results (relative standard deviation of 3 to 8 replicates) varied from 2.6 to 17.7% with an average of 7.9% in the range 0.02-42.7 μg g−1 and was similar to the value obtained for synthetic samples. Our results are in good agreement with available literature values.  相似文献   
8.
A mathematical model used for determination of a local geoid model by combining airborne gravity disturbances and the Earth Gravitational Model 2008 (EGM08) is shortly reviewed. The precision of the estimated local geoid model of Taiwan is tested by its comparison with the “real” geoid at Global Satellite Navigation Systems (GNSS)/levelling points. The same comparison at GNSS/levelling points is done for the geoid evaluated only by using EGM08. Conclusions concerning a rate of improvement of the “global” geoid from EGM08 using the “local” geoid from airborne gravity data are presented.  相似文献   
9.
Atmospheric precipitation samples were collected in the Bohemian Karst (30 km SW from Prague, Czech Republic) at six localities in the vicinity of the limestone-quarry Čertovy schody during years 1996–2003. Samples were analyzed for major components (Na+, K+, Mg2+, Ca2+, F−, Cl−, NO3−, HCO3−, SO42−) and trace metals (Cu, Mn, Fe, Zn, Pb, Be, As, Sr, Cd, Al, Cr). Deposition fluxes were calculated from more than 10 000 elemental analyses of samples collected monthly. The fluxes of monitored substances show temporal and spatial variability. The most marked attribute is the strong affection by local emission sources confirmed by the investigation of seasonal variability, temporal trend and correlation analysis.  相似文献   
10.
We present ephemerides and solutions of one Algol-type (KZ Dra) and two overcontact systems (LR Cam and IM Vul) based on V(RI)C CCD observations obtained in the project Prosper (network of amateur observers).  相似文献   
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