Birch pollen measurements and the history of birch at Bruvatnet, Norwegian Lapland

Abstract

Birch pollen measurements were carried out on a Holocene sediment sequence from lake Bruvatnet, in the birch‐forest region of Norwegian Lapland. Betula pollen diameters were measured systematically from samples that were taken at 5 cm intervals. The resulting size‐frequency distributions were analysed statistically to infer their species composition and to reconstruct the local history of birch. Birch catkin scales and fruits were used as an independent supplementary evidence. According to the vegetation reconstruction based on these results shows that Betula tortuosa has grown in the area throughout the Holocene. In the beginning of the Holocene B. pubescens was also present and its occurrence reached a peak in the birch‐pine woodland phase prior to the onset of pine decline. While pine receeded southwards, 5000–3000 BP, B. pubescens also gradually ceased to grow around the lake and the vegetation became more open.