Impoverishment of recent floodplain forest mollusc fauna in the lower Ohře River (Czech Republic) as a result of prehistoric human impact

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.     

Motion of particles in turbulent flow: Hyperbolicity,strange attractors and dynamic stochasticity of a system

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Deep structure of the bohemian massif from phase velocities of Rayleigh and Love waves

Summary Phase velocities of Rayleigh and Love waves have been measured between the broadband seismic stations KHC (Kaperské Hory, South Bohemia) and KSP (Ksi, Lower Silesia), a profile that nearly coincides with the Interactional DSS Profile VII. The data for both wave types were separately inverted into models of shear-wave velocity versus depth. Novotný's model KHKS 82[1] for the DSS Profile VII was used as a start model. While the crustal section of Novotný's model is compatible with both of our data sets, our Rayleigh-wave data require smaller shear-wave velocities, on the average by 0.24 km/s, in the top 180 km of the mantle. The average difference between Novotný's model and our Love-wave model in that depth range is only 0.06 km/s. If our identification of the observed Love waves as the fundamental mode is correct, this result indicates the presence of polarization anisotropy in the uppermost mantle.

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Earthquakes in the Czech Republic and Surrounding Regions in 1995–1999

In the time span from January 1995 to December 1999 the Czech National Seismological Network (CNSN), consisting of ten permanent digital broadband stations, several local networks and two data centers, detected and recorded 9530 regional natural seismic events, 27 greater than magnitude 2. Most of these events were located by the Czech Seismological Service (CSS), and the most prominent of them were analyzed in detail. A large number of quarry blasts were recorded as well but were not included in the analysis. We provide basic information on the configuration of the CNSN and on the way of routine data processing employed by the CSS in this paper. The over-all regional seismicity monitored by the CNSN in 1995–1999 is briefly reviewed. The main results of observations and evaluation of the local (NW-Bohemia/Vogtland, South Bohemia, Sudeten) and induced (Kladno, Píbram, Upper Silesia, Lubin/Poland) seismic activity within this period are presented in a condensed form. Finally, a summary on macroseismic observations on the territory of the Czech Republic in 1995–1999 is also presented.     

Comments on the definition of turbulence

Zusammenfassung Es werden Gründe erläutert, die zur Äusserung einer auf dem Begriff der Ergodizität beruhenden Definition der Turbulenz führen. Wir gehen von der Theorie der Unstabilität der Strömung bei Wirkung einer Störung der endlichen Amplitude aus. Es wird das Ergodenproblem im Landauschen Modell der entwickelten Turbulenz behandelt und einige mit der Ergodenhypothese zusammenhängende Folgen erörtert. Als ein Anfangselement gilt für uns der Begriff der Transitivität. Wir beachten auch die Beziehung zwischen der metrischen Transitivität und der Eigenschaft des Durchmischens der Bewegungen sowie die Relation zwischen dem energetischen Storungsspektrum und der Ergodenhypothese.     

Dynamic manifestations of the geomagnetic field in the Quaternary continental sediments of Czechoslovakia

Summary The paper brings a brief geological asessment of the sedimentational cycles, analyses the methods of collection and investigation of samples and the representativeness of the results obtained. Problems of magnetic cleaning and the types of demagnetization curves investigated are discussed. The continuous nature of the variations of the magnetic declination, inclination and remanent magnetization, determined by palaeomagnetic investigation of Quaternary sediments, is also discussed. The conclusion contains the principal facts about the dynamics of the geomagnetic field in the Quaternary and points out the possibility of applying them to the theory of the geomagnetic field, as well as to geological correlations.     

Foreword

Foreword

Foreword     

Dust Plasma Interactions at Jupiter

This is a review of recent in situ and remote sensing observations, and theoretical advances of our understanding dust plasma interactions in Jupiter's magnetosphere. Dust grains exposed to plasmas and UV radiation collect electrostatic charges and their dynamics can be altered due to electric and magnetic fields. Hence, magnetospheric effects can shape the size and spatial distributions of micron sized and smaller dust grains. The ring/halo region, the dust streams and the captured ring at Jupiter are recent examples where dust plasma interaction effects can best explain the observations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Magnitude scale structure from filtered broadbandP-wave records

A series of Hokkaido events, recorded by the FBV Broadband Seismograph System at the KHC Seismic Station, is used to study the structure of the earthquake magnitude scale on the basis of maximum velocity amplitudesA _vmax of teleseismicPwaves in different period bands. Amplitude-periodband (APB) diagrams are constructed for each event. According to the shape of the APB diagrams the events investigated can be divided into three types: (a) events with largestA _vmax values in the intermediate period range (periods ofA _vmax from 2.2 to 23 sec), (b) events with largestA _vmax values in the short-period range (periods ofA _vmax from 1 to 2 sec), (c) events exhibiting anomalous APB diagrams. Type (a) events seem to represent the process of wave generation that prevails for shallow earthquakes. Type (b) events approach to explosive-like generation of seismic waves. The nature of the exceptionally occurring type (c) events must be clarified in further investigations. The influence of the type of earthquake on the magnitude values estimated on the basis of standard class A and B (short-period and intermediate-band) seismograms is demonstrated. It appears that for estimating correct values of earthquake magnitudes complementary information on the process of seismic wave generation in the focus is necessary. At teleseismic distances this information can be obtained from either APB diagrams or amplitude spectra ofP waves recorded, e.g., by broadband velocity sensing instruments.     

On the universal character of particle transfer in a field of turbulence

Summary With the aid of elementary methods of the theory of dimensionality we approach the problem of existence of invariants in the process of mixing particles of a passive admixture in a field of turbulence.