SEARCH

SEARCH BY CITATION

A reply to H.H. Birks, E. Larsen & H.J.B. Birks (2006) On the presence of late-glacial trees in western Norway and the Scandes. A further comment. Journal of Biogeography, 33, 376.

Birks et al. (2006) remain sceptical of my hypothesis concerning late-glacial tree immigration to northern Scandinavia from glacial refugia closer to Scandinavia than previously believed, possibly to the west. Here, I provide a new finding that clarifies the background for my conviction that this hypothesis best accounts for the available evidence.

Their central argument against my hypothesis concerns the purported absence of late-glacial trees on the Norwegian coast. During a holiday trip to Andøya (Nordland Fylke in north-western Norway) in 1998, the surroundings of a small pool were scrutinized for the presence of megafossil wood (Fig. 1). The site (69°14′ N, 15°55′ E and 60 m a.s.l.) is located in the valley of Stavedalen, 5 km SSW of the coastal village of Bleik and about 25 m west of the road from there to Nordmela. The pool has a diameter of 15 m and exists in a landscape dominated by young birch copses and valley floor mires. Close to its northern edge, wood remnants protruded 5–10 cm above the surface of a Sphagnum hummock. One piece of wood, a root from Betula pubescens, 40 cm in length and 8 cm in diameter, was retrieved (Fig. 2). Wood anatomical analysis by Dr Thomas Bartholin, Copenhagen, confirmed this species identification. Radiocarbon dating was not undertaken until 2003. The dating result was 16,900 ± 170 14C years bp (Beta-172304). This is consistent with pollen and macrofossil records from this area, indicating ice-free conditions at this time (Alm, 1993). Given this remarkable old age, close to the last glacial maximum, more detailed investigations of this site would have been desirable. Unfortunately, lack of funding has precluded this. Because of the present debate, and the increasing focus on the Norwegian coast, I have decided to publish the preliminary finding from the site.

image

Figure 1. The investigated site in Andøya. The sampling point is indicated by an arrow.

Download figure to PowerPoint

image

Figure 2. The dated root of Betula pubescens (arrow).

Download figure to PowerPoint

In conclusion, I contend that the purported absence of late-glacial trees on ice-free coastal strips of northern Norway (Birks et al., 2005, 2006) cannot be a conclusive argument against my basic hypothesis. I suggest that the focus should instead be on the megafossil data from the high-elevations sites along the southern Swedish Scandes (cf. Kullman, 2005).

References

  1. Top of page
  2. References