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  • Switzerland  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Modern diatom, cladocera, chironomid, and chrysophyte cyst assemblages as quantitative indicators for the reconstruction of past environmental conditions in the Alps. I. Climate (1997)
    Springer
    Journal of paleolimnology 18 (1997), S. 395-420 
    Details
    ISSN: 1573-0417
    Keywords: transfer functions ; weighted-averagingpartial-least-squares ; summer temperatures ; surfacesediments ; modern training-sets ; Switzerland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Diatom, chrysophyte cyst, benthic cladocera, planktonic cladocera, and chironomid assemblages were studied in the surface sediments of 68 small lakes along an altitudinal gradient from 300 to 2350 m in Switzerland. In addition, 43 environmental variables relating to the physical limnology, geography, catchment characteristics, climate, and water chemistry were recorded or measured for each lake. The explanatory power of each of these predictor variables for the different biological data-sets was estimated by a series of canonical correspondence analyses (CCA) and the statistical significance of each model was assessed by Monte Carlo permutation tests. A minimal set of environmental variables was found for each biological data-set by a forward-selection procedure within CCA. The unique, independent explanatory power of each set of environmental variables was estimated by a series of CCAs and partial CCAs. Inference models or transfer functions for mean summer (June, July, August) air temperature were developed for each biological data-set using weighted-averaging partial least squares or partial least squares. The final transfer functions, after data screening, have root mean squared errors of prediction, as assessed by leave-one-out cross-validation, of 1.37 °C (chironomids), 1.60 °C (benthic cladocera), 1.62 °C (diatoms), 1.77 °C (planktonic cladocera), and 2.23 °C (chrysophyte cysts).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007982008956
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The relationship between air and water temperatures in lakes of the Swiss Plateau: a case study with pal\sgmaelig;olimnological implications (1998)
    Springer
    Journal of paleolimnology 19 (1998), S. 181-198 
    Details
    ISSN: 1573-0417
    Keywords: air temperature ; lake water temperature ; temperature inference models ; Switzerland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract In pal\sgmaelig;olimnological studies, inference models based on aquatic organisms are frequently used to estimate summer lake surface water temperatures. However, the calibration of such models is often unsatisfactory because of the sparseness of measured water temperature data. This study investigates the feasibility of using air temperature data, usually available at much higher resolution, to calibrate such models by comparing regional air temperatures with surface water temperatures in 17 lakes on the Swiss Plateau. Results show that altitude-corrected air temperatures are sufficiently uniform over the entire Swiss Plateau to allow local air temperatures at any particular lake site to be adequately estimated from standard composite air temperature series. In early summer, day-to-day variability in air temperature is reflected extremely well in the temperature of the uppermost metre of the water column, while monthly mean air temperatures correspond well, with respect to both absolute value and interannual variations, with water temperatures in most of the epilimnion. Standardised altitude-corrected air temperature series may therefore be a useful alternative to surface water temperatures for the purposes of calibrating lake temperature inference models. In Northern Hemisphere temperate regions, mean air and water temperatures are likely to correspond most closely in July, suggesting that calibration and reconstruction efforts be concentrated on this month.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007904817619
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  • 3
    Electronic Resource
    Electronic Resource
    Modern diatom, cladocera, chironomid, and chrysophyte cyst assemblages as quantitative indicators for the reconstruction of past environmental conditions in the Alps. II. Nutrients (1998)
    Springer
    Journal of paleolimnology 19 (1998), S. 443-463 
    Details
    ISSN: 1573-0417
    Keywords: transfer functions ; WA-PLS ; total phosphorus ; trophic state ; eutrophication ; surface sediments ; Switzerland ; diatoms ; cladocera ; chironomids ; chrysophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Surface sediments from 68 small lakes in the Alps and 9 well-dated sediment core samples that cover a gradient of total phosphorus (TP) concentrations of 6 to 520 μg TP l-1 were studied for diatom, chrysophyte cyst, cladocera, and chironomid assemblages. Inference models for mean circulation log10 TP were developed for diatoms, chironomids, and benthic cladocera using weighted-averaging partial least squares. After screening for outliers, the final transfer functions have coefficients of determination (r2, as assessed by cross-validation, of 0.79 (diatoms), 0.68 (chironomids), and 0.49 (benthic cladocera). Planktonic cladocera and chrysophytes show very weak relationships to TP and no TP inference models were developed for these biota. Diatoms showed the best relationship with TP, whereas the other biota all have large secondary gradients, suggesting that variables other than TP have a strong influence on their composition and abundance. Comparison with other diatom – TP inference models shows that our model has high predictive power and a low root mean squared error of prediction, as assessed by cross-validation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007994206432
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  • 4
    Electronic Resource
    Electronic Resource
    Late-glacial and Holocene vegetation history and dynamics as shown by pollen and plant macrofossil analyses in annually laminated sediments from Soppensee, central Switzerland (1999)
    Springer
    Vegetation history and archaeobotany 8 (1999), S. 165-184 
    Details
    ISSN: 1617-6278
    Keywords: Vegetation dynamics ; Palynology ; Macroremains ; Plant diversity ; Laminated sediments ; Climate change ; Switzerland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Archaeology , Biology
    Notes: Abstract The palynostratigraphy of two sediment cores from Soppensee, Central Switzerland (596 m asl) was correlated with nine regional pollen assemblage zones defined for the Swiss Plateau. This biostratigraphy shows that the sedimentary record of Soppensee includes the last 15 000 years, i.e. the entire Late-glacial and Holocene environmental history. The vegetation history of the Soppensee catchment was inferred by pollen and plant-macrofossil analyses on three different cores taken in the deepest part of the lake basin (27 m). On the basis of a high-resolution varve and calibrated radiocarbonchronology it was possible to estimate pollen accumulation rates, which together with the pollen percentage data, formed the basis for the interpretation of the past vegetation dynamics. The basal sediment dates back to the last glacial. After reforestation with juniper and birch at ca. 12 700 B.P., the vegetation changed at around 12 000 B.P. to a pine-birch woodland and at the onset of the Holocene to a mixed deciduous forest. At ca. 7000 B.P., fir expanded and dominated the vegetation with beech becoming predominant at ca. 50014C-years later until sometime during the Iron Age. Large-scale deforestation, especially during the Middle Ages, altered the vegetation cover drastically. During the Late-glacial period two distinct regressive phases in vegetation development are demonstrated, namely, the Aegelsee oscillation (equivalent to the Older Dryas biozone) and the Younger Dryas biozone. No unambiguous evidence for Holocene climatic change was detected at Soppensee. Human presence is indicated by early cereal pollen and distinct pulses of forest clearance as a result of human activity can be observed from the Neolithic period onwards.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02342718
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    Paper (German National Licenses)
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