Late-Holocene climatic variability south of the Alps as recorded by lake-level fluctuations at Lake Ledro, Trentino, Italy

International audienceA lake-level record for the late Holocene at Lake Ledro (Trentino, northeastern Italy) is presented. It is based on the sediment and pollen analysis of a 1.75 m high stratigraphic section observed on the southern shore (site Ledro I) and a 3.2 m long sediment core taken from a littoral mire on the southeastern shore (site Ledro II). The chronology is derived from 15 radiocarbon dates and pollen stratigraphy. The late-Holocene composite record established from these two sediment sequences gives evidence of centennial-scale fluctuations with highstands at c. 3400, 2600, 1700, 1200 and 400 cal. BP, in agreement with various palaeohydro-logical records established in central and northern Italy, as well as north of the Alps. In addition, high lake-level conditions at c. 2000 cal. BP may be the equivalent of stronger river discharge observed at the same time in Central Italy's rivers. In agreement with the lake-level record of Accesa (Tuscany), the Ledro record also suggests a relatively complex palaeohydrological pattern for the period around 4000 cal. BP. On a millennial scale, sediment hiatuses observed in the lower part of the Ledro I sediment sequence indicate that, except for a high-stand occurring just after 7500 cal. BP, lower lake levels generally prevailed rather before c. 4000 cal. BP than afterwards. Finally, the lake-level data obtained at Lake Ledro indicate that the relative continuity of settlements in humid areas of northern Italy during the Bronze Age (in contrast to their general abandonment north of the Alps between c. 3450 and 3150 cal. BP), does not reflect different regional patterns of climatic and palaeohy-drological conditions. In contrast, the rise in lake level dated to c. 3400 cal. BP at Ledro appears to coincide with a worldwide climate reversal, observed in both the hemispheres, while palaeoenvironmental and archaeological data collected at Lake Ledro may suggest, as a working hypothesis, a relative emancipation of proto-historic societies from climatic conditions

Neolithic settlement at the woodland's edge: palynological data and timber architecture in Orkney, Scotland

It has often been assumed that the islands of Orkney were essentially treeless throughout much of the Holocene, with any ‘scrub’ woodland having been destroyed by Neolithic farming communities by around 3500 cal. BC. This apparently open, hyper-oceanic environment would presumably have provided quite marginal conditions for human settlement, yet Neolithic communities flourished and the islands contain some of the most spectacular remains of this period in north-west Europe. The study of new Orcadian pollen sequences, in conjunction with the synthesis of existing data, indicates that the timing of woodland decline was not synchronous across the archipelago, beginning in the Mesolithic, and that in some areas woodland persisted into the Bronze Age. There is also evidence to suggest that woodland communities in Orkney were more diverse, and therefore that a wider range of resources was available to Neolithic people, than has previously been assumed. Recent archaeological investigations have revealed evidence for timber buildings at early Neolithic settlement sites, suggesting that the predominance of stone architecture in Neolithic Orkney may not have been due to a lack of timber as has been supposed. Rather than simply reflecting adaptation to resource constraints, the reasons behind the shift from timber to stone construction are more complex and encompass social, cultural and environmental factors

Beitraege zur Moor- und Klimageschichte Niedersachsens fuer den Zeitraum 7000 v. Chr. bis 1000 n. Chr. durch dendroklimatologische Auswertung subfossiler Hoelzer

TIB Hannover: D.Dt.F. AC 1000 (37,36) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Hochaufloesende Zeitreihen der Klima- und Vegetationsgeschichte von NW- bis Aequatorialafrika. Palynologische Untersuchungen ueber die CO_2-Festlegung und -Freisetzung durch die Vegetation NW- und Aequatorialafrikas im Quartaer Schlussbericht

For tropical regions which are ecologically sensitive, the present day knowledge on the extent, result and speed of climatic changes is to be improved. Relevant data would give insight to changes of water and carbon dioxide balance. Information can be obtained by the study of climate changes in the past. By palynological studies on marine sediment cores off NW and W Africa, the changing position of vegetation belts which are defined by climate parameters has been reconstructed for the last 600,000 years. Calculations have been made for the speed of climatic changes within the glacial-interglacial-cycles and for the changes of the carbon content stored by the biomass of the vegetation which in turn can be used for calculations about the changing carbon dioxide content in the atmosphere during climatic cycles. At 21 N, the development of aridity, climatic cycles and trade winds was studied for the Pliocene-Pleistocene transition. By considering fossil pollen and spores as well as dinoflagellate cycles, terrestrial and marine climatic signals have been integrated. Data obtained can be used for climate modelling purposes. (orig.)Available from TIB Hannover: F95B566+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman