Living on the good soil: relationships between soils, vegetation and human settlement during the late Allerød period in Denmark

Abstract

The immigration of woody plants, especially Betula (tree birch), is examined in relation to geomorphological regions in a compilation of Late-glacial plant macrofossil records from Denmark. The immigration of trees led to a large ecological transformation of the landscape and had a major effect on the flora and fauna available to Palaeolithic people. We show that soil type was a controlling factor in the development of vegetation during the Allerød and Younger Dryas periods. Following the first immigration of trees during the Allerød period, woods became established in the eastern part of Denmark, where ice advances from the Baltic had deposited calcareous and clayey sediments. The western and northern parts of Denmark that are characterised by more sandy and noncalcareous sediments remained treeless throughout the whole Late-glacial period. Finds from the Bromme Culture are concentrated in the region which was wooded, suggesting that the regional variable environment allowed local adaptations using the diverse resources available.

To what extent did changes in July temperature influence Lateglacial vegetation patterns in NW Europe?

“…The increases to 40e80% in the Netherlands and England suggest that tree birches were forming woodlands in this area. This is supported by macrofossil evidence of tree birch from Whitrig Bog (Mayle et al, 1997), Hawes Water ('birch fruits', Marshall et al, 2007a,b), and nearby Windermere (Pennington, 1947), and from the Netherlands at Usselo (Van Geel et al, 1989), Denmark (Mortensen et al, 2011(Mortensen et al, , 2014, and S Sweden (Liedberg J€ onsson, 1988). The northernmost record is one tree-birch fruit at Abernethy Forest in central Scotland where pollen values reached 25%.…”

“…Birks, 2003;Mortensen et al, 2014). The evidence so far available suggests that tree birch spread during the AL into treeless vegetation containing B. nana across NW Europe, Denmark, Ireland, England, and S Scotland, (Fig.…”

“…Vetaas, 1994). However, the development of birch woodland in the AL on the calcareous clay-rich soils of eastern Denmark and its absence in the west and north on acid sandy morainic soils suggests that soil-moisture was an important factor in tree-birch establishment under similar temperature conditions (Mortensen et al, 2014).…”

“…Late-AL megafossils of Pinus have been recorded in NE Germany (e.g. Mortensen et al, 2014). A buried Allerød pine forest with birch was described by Polak (1963) from the coversand region in S Netherlands.…”

“…This was not an effect of cooling temperatures, as these remained at or above the thermal limits of these trees. It is more likely to have been due to increased aridity and continentality with strong winds associated with increased fire frequency which resulted in the replacement of woodland by grassland or dwarf-shrub heath (Mortensen et al, 2014).…”