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Heavy metals and macroelements in the tundra of southern Spitsbergen: the effect of little auk Alle alle (L.) colonies 总被引：1，自引：1，他引：0
BARBARA GODZIK 《Polar research》1991,9(2):121-131
Samples of two species of widely distributed mosses (Sanionia uncinata and Hylocomium splendens) were collected in the Ariekammen-Fuglebergct catchment area (Hornsund. Spitsbergen) within and outside little auk Alle alle (L.) colonies. The concentrations of Cd. Pb, Ni, Zn, Cu, Mn. Fe. N, P, and S in the moss samples were found to be 1.5-2 times higher within than outside the colonics. Significant differences were found for Cd, Pb, Zn, Cu, and Fe, but not for Ni, Mn, N, P, and S. Sanionia uncinata accumulates up to 8 ug g−1 d. wt Cd, 14-Pb, 8-Ni, 47-Zn, 9-Cu, 90-Mn, and 1920 u, g g−1 d. wt Fe, while Hylocomium splendens accumulates up to 4 μg g−1 d. wt Cd, 12-Pb, 3-Ni, 31-Zn, 5-Cu, fiO-Mn, and 840 μg g−1 d. wt Fc. The colonics of seabirds contribute greatly to the supply of elements in the tundra ecosystems of southern Spitsbergen. The effect seems, however, to be limited to rather small areas. 相似文献
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BARBARA WOHLFARTH SVANTE BJÖRCK GÖRAN POSSNERT GEOFFREY LEMDAHL LARS BRUNNBERG JONAS ISING SIV OLSSON NILS-OLF SVENSSON 《Boreas: An International Journal of Quaternary Research》1993,22(2):113-128
The increasing focus on the chronology of environmental and climatic changes of the last glacial-interglacial transition has led to several independent attempts to try to calibrate the 14 C time-scale beyond the Holocene. The Late Weichselian Gotiglacial varved clays of the Swedish Time Scale could potentially be used for this purpose. The reliability of the Swedish Time Scale is discussed as well as different ways of using the Swedish varved clays for calibrating the 14 C chronology. The strategy and initial results from an ongoing calibration project are presented. They show clearly that, if the right strategy is adopted, varved clay may be dated by accelerator mass spectrometry (AMS) 14 C measurement of terrestrial macrofossils. A Late Weichselian 'event stratigraphy', including the Vedde Ash fall-out, is established for south Scandinavia using three dating categories: clay varve measurements, terrestrial macrofossil measurement, and lake sediment (including aquatic mosses) measurements. It suggests that a 14 C chronology based on terrestrial organic remains is not consistent with the traditional Late Weichselian chronostratigraphy based on lake-sediment samples, and that 'clay varve years' exceed 'terrestrial 14 C years' by c. 900 years at the end of, and by 1100–1200 years at the beginning of the Younger Dryas Chronozone. Further back in time, the time-scales appear to converge. These results are compared with other recently published calibration studies. 相似文献
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BARBARA SCHIPPERGES 《Polar research》1992,11(2):47-68
Two abundant and partly dominating lichen species, Celraria nivalis and Cetraria delisei , were compared with respect to their thallus water content and their gas-exchange response to light, temperature and moisture in the field and in the laboratory. C. nivalis had higher net photosynthetic rates than C. delisei . The differences between the species were more pronounced when photosynthesis was related to dry weight than to chlorophyll content. Light compensation and light saturation of photosynthesis increased with increasing temperature. Higher light compensation and saturation values were found in C. delisei than in C. nivalis . The chionophobous C. nivalis showed moisture compensation and optimum water content for net photosynthesis at higher thallus water contents than the chionophilous C. delisei . Depression of net photosynthesis at thallus saturation, found in both species, is thought to be due to the increased internal CO2 diffusive resistance at high thallus water content. The maximum thallus water contents of C. nivalis were higher than those of C. delisei . The lower drying rate, found in C. delisei in comparison with that of C. nivalis , is attributed to the more sheltered position of its habitat and to morphological characteristics. 相似文献
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ROBERT WEIBEL BARBARA P. BUTTENFIELD 《International journal of geographical information science》2013,27(3):223-245
Abstract Current geographical information systems (GIS) include functions to create cartographic output interactively or automatically. However, none of the systems presently incorporates mechanisms to ensure correct application of graphic functions. Many of today's users of GIS are not trained in the design and production of graphics and may create maps that confuse or mislead map users. Poorly-designed maps may obliterate the patterns in displayed information. This article investigates ways to improve the quality of GIS graphical displays and increase their effectiveness for decision-making. Alternatives are presented for improving map design in GIS, ranging from non-technical efforts to enhancement of software functionality. Suggestions propose augmenting users' abilities to create maps in an automated environment, using an approach termed amplified intelligence: key decisions default explicitly to users, whose knowledge is amplified by a range of high-level tools to carry out map design operations automatically. 相似文献
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DANIEL VERES BARBARA WOHLFARTH VALÉRIE ANDRIEU-PONEL SVANTE BJÖRCK JACQUES-LOUIS DE BEAULIEU GUNNAR DIGERFELDT PHILIPPE PONEL LINDA AMPEL SIWAN DAVIES EMMANUEL GANDOUIN SOUMAYA BELMECHERI 《Boreas: An International Journal of Quaternary Research》2007,36(3):326-340
Two new long sediment cores (EC1 and EC3), recovered from different locations within the infilled basin at Les Echets, France, provide a new high-resolution record of terrestrial and lacustrine responses to climatic changes during Marine Isotope Stages (MIS) 3 and 2. The lithologies of the cores are described in detail and correlated with each other by stratigraphic marker horizons, fluctuations in organic matter and AMS radiocarbon ages. The tentative correlation of the new cores to those described and analysed by de Beaulieu et al. (1980) and de Beaulieu & Reille (1984a) provides a preliminary chronostratigraphic framework. Sedimentation during MIS3 started with accumulation of sands and silts and was followed by alternating gyttja and clayey gyttja silts. Exceptionally high sedimentation rates during MIS2 led to the infilling of the basin. Alternating organic-rich and minerogenic-rich sediments appear to coincide with changes in pollen assemblages (de Beaulieu & Reille 1984a) and suggest that millennial-scale climatic changes controlled lake productivity and catchment stability during most of MIS3. 相似文献
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BARBARA WOHLFARTH SVANTE BJÖRCK GÖRAN POSSNERT BJÖRN HOLMQUIST 《Boreas: An International Journal of Quaternary Research》1998,27(4):243-257
More than 50 varve-thickness diagrams, which were established from glacial varved clays in south-eastern Sweden were correlated with each other to form an 800-year long floating varve chronology. AMS |214|0C measurements on terrestrial macrofossils from the varved clays enabled synchronization of the record with other high-resolution archives. The synchronization indicates that the chronology spans between c. 13 150 and c. 12 350 calendar years BP and covers the later part of the Allerørd and the early part of the Younger Dryas. Calibrated radiocarbon dates, which were obtained on varved clays south of the floating chronology, indicate that the ice recession in south-eastern Sweden may have started during late Bølling. Our results indicate a longer time-span in varve years for the deglaciation than has been previously estimated 相似文献
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BARBARA WOHLFARTH JENS‐OVE NÄSLUND 《Boreas: An International Journal of Quaternary Research》2010,39(2):325-327
Wohlfarth, B. & Näslund, J.‐O. 2010 (April): Fennoscandian Ice Sheet in MIS 3 – Introduction. Boreas, Vol. 39, pp. 325–327. 10.1111/j.1502‐3885.2010.00151.x. ISSN 0300‐9483. 相似文献
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The 12·7–10·5 Ma Cougar Point Tuff in southernIdaho, USA, consists of 10 large-volume (>102–103 km3each), high-temperature (800–1000°C), rhyolitic ash-flowtuffs erupted from the Bruneau–Jarbidge volcanic centerof the Yellowstone hotspot. These tuffs provide evidence forcompositional and thermal zonation in pre-eruptive rhyolitemagma, and suggest the presence of a long-lived reservoir thatwas tapped by numerous large explosive eruptions. Pyroxene compositionsexhibit discrete compositional modes with respect to Fe andMg that define a linear spectrum punctuated by conspicuous gaps.Airfall glass compositions also cluster into modes, and thepresence of multiple modes indicates tapping of different magmavolumes during early phases of eruption. Equilibrium assemblagesof pigeonite and augite are used to reconstruct compositionaland thermal gradients in the pre-eruptive reservoir. The recurrenceof identical compositional modes and of mineral pairs equilibratedat high temperatures in successive eruptive units is consistentwith the persistence of their respective liquids in the magmareservoir. Recurrence intervals of identical modes range from0·3 to 0·9 Myr and suggest possible magma residencetimes of similar duration. Eruption ages, magma temperatures,Nd isotopes, and pyroxene and glass compositions are consistentwith a long-lived, dynamically evolving magma reservoir thatwas chemically and thermally zoned and composed of multiplediscrete magma volumes. KEY WORDS: ash-flow tuff; Bruneau–Jarbidge; rhyolite; Yellowstone hotspot; residence time 相似文献