Holocene dynamics of the southern boreal forest in Sweden

Holocene vegetation dynamics in the ecotone between the boreo-memoral and boreal forest were reconstructed from sediment cores of two small lakes using pollen and macrofossil analyses. Competition, migration and changing climate parameters determine species dynamics in the ecotone. The spread of Picea abies was the most important event in the vegetation history of the region, probably shaping the present distribution limits of Corylus avellana, Tilia cordata and Quercus robur through competitive exclusion. The expansion of Picea abies is well documented by abundant macrofossil finds at one of the lakes, mirroring the rise in pollen percentage and confirming the presence of the tree before Picea abies pollen frequencies reached 1%. No Picea abies macrofossils were encountered before pollen was regularly found. Changing vegetation composition through migration affects both sites at different times, while a shift in atmospheric circulation pattern may be responsible for a concordant change in vegetation composition at both sites around 5700 cal. BP.