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.     

Reservoir rainfall‐runoff geomorphological model. II: analysis,calibration and validation

The model presented in the complementary document entitled, Reservoir rainfall‐runoff geomorphological model I: parameter application and analysis is analysed, calibrated and validated in this paper. The accuracy of simulated hydrographs is analysed by means of the efficiency defined by Nash and Sutcliffe. The sensitivity of the influence of five parameters on the behaviour of the model developed is analysed. Two different calibration and validation processes of Reservoir rainfall‐runoff geomorphological model are performed in Aixola watershed. Twelve events have been selected for calibrations and 25 for validations. With the first calibration and validation process, the model parameters are set by assigning the medians' values of the distributions obtained by means of the optimum results. The second process is performed by calibrating the most determinant parameter in the adjustment, which is the one that indicates the proportion of infiltrated water that is retained and does not flow; this is done with an empirical formulation depending on the event characteristics. Subsequently, the obtained results are validated. This last process has achieved very good adjustments in both calibrated and validated events. Copyright © 2012 John Wiley & Sons, Ltd.     

Linking past flood frequencies in Norway to regional atmospheric circulation anomalies

Analysis of two continuous, high‐resolution palaeo‐flood records from southern Norway reveals that the frequency of extreme flood events has changed significantly during the Holocene. During the early and middle Holocene, flood frequency was low; by contrast, it was high over the last 2300 years when the mean flood frequency was about 2.5–3.0 per century. The present regional discharge regime is dominated by spring/summer snowmelt, and our results indicate that the changing flood frequency cannot be explained by local conditions associated with the respective catchments of the two lakes, but rather long‐term variations of solid winter precipitation and related snowmelt. Applying available instrumental winter precipitation data and associated sea‐level pressure re‐analysis data as a modern analogue, we document that atmospheric circulation anomalies, significantly different from the North Atlantic Oscillation (NAO), have some potential in explaining the variability of the two different palaeo‐flood records. Centennial‐scale patterns in shifting flood frequency might be indicative of shifts in atmospheric circulation and shed light on palaeo‐pressure variations in the North Atlantic region, in areas not influenced by the NAO. Major shifts are found at about 2300, 1200 and 200 years ago (cal. a BP). Copyright © 2011 John Wiley & Sons, Ltd.     

Trends,drivers and impacts of changes in swidden cultivation in tropical forest-agriculture frontiers: A global assessment

This meta-analysis of land-cover transformations of the past 10–15 years in tropical forest-agriculture frontiers world-wide shows that swidden agriculture decreases in landscapes with access to local, national and international markets that encourage cattle production and cash cropping, including biofuels. Conservation policies and practices also accelerate changes in swidden by restricting forest clearing and encouraging commercial agriculture. However, swidden remains important in many frontier areas where farmers have unequal or insecure access to investment and market opportunities, or where multi-functionality of land uses has been preserved as a strategy to adapt to current ecological, economic and political circumstances. In some areas swidden remains important simply because intensification is not a viable choice, for example when population densities and/or food market demands are low. The transformation of swidden landscapes into more intensive land uses has generally increased household incomes, but has also led to negative effects on the social and human capital of local communities to varying degrees. From an environmental perspective, the transition from swidden to other land uses often contributes to permanent deforestation, loss of biodiversity, increased weed pressure, declines in soil fertility, and accelerated soil erosion. Our prognosis is that, despite the global trend towards land use intensification, in many areas swidden will remain part of rural landscapes as the safety component of diversified systems, particularly in response to risks and uncertainties associated with more intensive land use systems.     

The photoelectron spectra of some Tl-Sb sulphosalts

The results of X-ray induced photoelectron spectroscopy (XPS) experiments on several phases of the ternary system Tl-Sb-S are reported. The binding energies of the inner S, Sb and Tl electrons increase with increasing quantities of Sb and decreasing amounts of Tl in these compounds. This is explained by the influences of the proportions of the bonded metals on the effective electron affinity of S. The higher proportions of the more electronegative element bonded to S cause the increase of its effective electron affinity. The results for Tl₂S (carlinite), Tl₃SbS₃, TlSbS₂ (weissbergite), TlAsS₂ (lorandite) and Sb₂S₃ (antimonite) can be interpreted in this way. The results for Tl₄S₃ suggest a predominantly covalent character of bonding for both Tl(III) and Tl(I), which are present in this sulfide. From comparison with Tl₃SbS₄ it could be supposed that Tl(III)-S bond has a more covalent character than Sb(V)-S bond. The results for Tl₃SbS₄ are in agreement with crystal structure data and the results of Moessbauer spectroscopy. For AsS (realgar) the binding energies of the inner electrons of As and S significantly increase, showing that the electrons in molecular orbitals are less strongly bonded to individual atoms, as compared to pure elements. The results for the amorphous TlSb₅S₈ (corresponding in composition to parapierrotite) suggest that in amorphous compound the Tl-S bonding is stronger and the coordination of Tl more regular than in a crystalline one.     

Olivine phenocrysts of Hawaiian olivine tholeiite and oceanite

Olivine phenocrysts of Hawaiian tholeiites display a variety of textures and a variation in composition which is due to supercooled crystallization. The highest forsterite content measured is 91%, and the highest magnesia content estimated for a tholeiitic liquid is 17%, using the olivine geothermometer. The liquid of this composition may be either a primary magma or a primitive magma. It is not yet possible to specify any particular composition range for the primary Hawaiian tholeiites.     

Are C1 chondrites chemically fractionated? a trace element study

Six C1 chondrite samples and a C2 xenolith from the Plainview H5 chondrite were analyzed by radiochemical neutron activation for the elements Ag, Au, Bi, Br, Cd, Ce, Cs, Eu, Ge, In, Ir, Lu, Nd, Ni, Os, Pd, Pt, Rb, Re, Sb, Se, Sn, Tb, Te, Tl, Yb, and Zn. The data were combined with 9 earlier analyses from this laboratory and examined for evidence of chemical fractionation in C1 chondrites.A number of elements (Br, Rb, Cs, Au, Re, Os, Ni, Pd, Sb, Bi, In, Te) show small but correlated variations. Those of the first 8 probably reflect hydrothermal alteration in the meteorite parent body, whereas those of Sb, Bi, In, and Te may at least in part involve nebular processes. Br and Au show systematic abundance differences from meteorite to meteorite, which suggests hydrothermal transport on a kilometer scale. The remaining elements vary from sample to sample, suggesting transport on a centimeter scale.There is no conclusive evidence for nebular fractionation affecting C1 's. Though C1 chondrites have lower $\text{Zr}\text{Hf}$ and $\text{Ir}\text{Re}$ ratios than do other chondrite classes, these ratios vary in other classes, suggesting that those classes rather than C1's are fractionated. Three fractionation-prone REE—Ce, Eu, and Yb have essentially the same relative abundances in C1's and all other chondrite classes, and hence apparently are not fractionated in C1's. We did not confirm the large Tb and Yb variations in C1's reported by other workers.We present revised mean C1 abundances for 35 elements, based on the new data and a critical selection of literature data. Changes are generally less than 10%, except for Br, Rb, Ag, Sb, Te, Au, and the REE.The Plainview C2 xenolith has normal trace element abundances, except for 3 elements falling appreciably above the C2 range: Rb, Cs, and Bi. Hydrothermal alteration may be the reason for all 3, though nebular fractionation remains a possibility for Bi.     

Numerical Modeling of the Ston-Slano (Croatia) Aftershock Sequence

The rate of aftershock occurrence after the M6 Ston-Slano (Croatia) earthquake is modeled as the Epidemic Type Aftershock Sequence (ETAS). Increase of the modeled cumulative number of aftershocks with time was fitted to observations by the least-squares criterion using the combined grid-search and Monte-Carlo approach. This enabled not only the estimation of the most probable ETAS parameters, but also the determination of their confidence limits, as well as the estimation of the bias between them. It has been found that the bias is significant for some of the parameter pairs, regardless of the threshold magnitude assumed. Residual analyses revealed that all strong aftershocks (M _L 4.5) occurred during the periods of normal to high aftershock activity. There were two periods of quiescence in the sequence, both of which were followed by a strong aftershock.