Implications of recent long-distance pollen transport events for the interpretation of fossil pollen records in Fennoscandia

Abstract

Under favourable conditions, a considerable amount of long-distance transported pollen can be deposited far from its place of origin. In Fennoscandia, in most cases, such situations occur when there is a strong southerly air circulation from South-Europe and/or North-Africa. Soil particles and pollen grains associated with the top soil or the present vegetation, can be lifted up by strong surface winds and brought up to higher levels, where further transportation takes place. During the last few years several of these events have been reported.The pollen analysis of three events with coloured precipitation from different parts of Fennoscandia provides information about such exotic pollen rain and its extent. The quantity of exotic pollen in the snow samples analysed is high, generally in the range of 500–2000 pollen grains cm−2 per episode. However, the amount of transported pollen can even be as great as that deposited during local anthesis in the same year, and influx values can exceed 30, 000 pollen grains cm−2 per few hours of snowfall. The results are analysed in relation to trajectory calculations, the actual phenological data, and pollen concentrations monitored by volumetric sampling from the air. Since the long-distance transport of pollen grains depends mainly on climatological factors, the hypothesis that exotic pollen deposition was common throughout the whole of the Holocene in Fennoscandia is presented. Long-distance transport of pollen grains can, therefore, be regarded as a potential source of error in the interpretation of Holocene pollen diagrams from Fennoscandia.