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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.

Abstract

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Eastern Denmark was an important region for the early immigration of humans into southern Scandinavia throughout the Late Glacial period. One possible explanation for this is that the landscape provided an especially favourable environment for Palaeolithic hunters. To examine this, the local and regional environment is reconstructed through the analysis of pollen and plant macrofossils from a small kettle hole and is discussed in relation to human presence in the region. The kettle hole is situated close to a Palaeolithic occupation site with artefacts belonging to the Federmesser and Bromme Cultures. The lake sediments encompass the Bølling, Allerød, Younger Dryas and the early Preboreal biostratigraphic periods. An increase in charcoal dust between c. 14,000 and 13,900 cal. BP may be related to the occupation site. This study shows that an ecotone was positioned between present-day Denmark and northern Germany during a large part of the Late Glacial period. This was especially the case during the Older Dryas and early Allerød periods, when woodland was expanding in northern Germany while the Danish area remained open. Later in the Allerød period, northern Germany seems to have been the northern limit for pine woodland. The low-lying region separating Denmark and Germany was periodically covered by the Baltic Ice Lake and this may have delayed the dispersal of plants from south to north. Areas lying between different habitats are known to have a high biodiversity and this may be why a high frequency of Palaeolithic finds is seen here. It has long been thought that tree birch grew in the Danish region from the beginning of the Late Glacial, but this study of both local and regional proxies clearly shows that the immigration of tree birch was delayed by more than 1000 years. A delay of c. 250 years between the climatic transition from GI-1a to GS-1 and the biostratigraphic transition from the Allerød to the Younger Dryas periods is also shown. The three 14 C ages available from the Danish Bromme Culture are from this transition phase when the birch woodland was becoming more open. Pollen analysis also shows the classical Younger Dryas cold separated into an early dry phase (until c. 12,100 cal. BP) and a later wetter phase. This was most likely due to a change in atmospheric circulation and variation in the extent of sea ice in the North Atlantic. The combined analysis of both pollen and plant macrofossils has led to a detailed and accurate reconstruction of the local environment and, in turn, the preconditions for human presence.