Pollen analysis and radiocarbon dating of a peatbog (Pian di Nel, 2256 m) in Orco Valley, Western Alps, Italy

Abstract

The study was carried out as part of an ongoing research on the relationship between vegetation and pollen deposition in the Western Alps (2256 m, 45° 25' N, 07° 09' E). Information on climate, dominant lithotype and present vegetation types is reported; radiometric dating indicate a conventional 14C age of 1990 ± 50 years BP. In mountainous areas, winds rising from the valley floor alter the quality and quantity of the highland pollen flora, and analysis cannot be expected to provide a realistic picture of local vegetation and of its changes over the course of time. Even so, it can be suggested that the relatively large number of entities common to the 17 layers of the studied profile (Gramineae, Cyperaceae, Alnus, Pinus and Larix) is indicative of vegetational uniformity during the last 2000 years. A cold spell between AD 500÷600 and 1000÷1100 can also be deduced from variations in the quantity of Pinus, Picea and Larix pollen. The deeper layers are rich in mesophile pollen species, such as Abies, Fagus sylvatica and Corylus, indicative of a damper climate. The samples of the sub-Atlantic period (800-500 BC) show a good uniformity of pollen composition. Comparison between the present vegetation and pollen grains in superficial layers, along with the constant predominance of tree and shrub pollens, demonstrates that most of the grains of these entities are associated with average distance transport.