Klimat- och miljöförändringar under holocen i Sylarnaområdet, södra svenska Skanderna, baserat på analys av makrofossil och klyvöppningar

Sammanfattning: A sediment sequence from Lake Spåime, situated at 887 m a.s.l. in the Sylarna area, southern Scandes, mid-central Sweden, was investigated with respect to plant macrofossil, stomata and total organic carbon analysis. Age control for the sequence was obtained by calibrated AMS 14C-measurements. To compare fossil stomata, a reference collection with modern material was made. The analysis of fossil stomata allowed differentiating between coniferous and deciduous trees, but proved difficult at an identification to species level. Furthermore, snow was collected close to the lake, analysed in respect to its content of organic material and compared to the present vegetation. While the snow sample reflected the surrounding vegetation well, the correlation between the plant macrofossil content of the uppermost sediment sample in the lake and the vegetation showed some divergence. The results indicate warm and dry climatic conditions during the early Holocene. These were, however, shortly interrupted by a possibly cold phase at around 8000 cal years BP, as evidenced in a distinct decrease in organic content. Although speculative, this cold phase could correspond to the cooling which is reflected in other investigations at around 8200 cal years BP. Plant macrofossil and stomata finds show the presence of Pinus sylvestris at c. 6700-5500 cal years BP, which is later than inferred from other investigations in the area. However, the absence of plant macrofossils in a sedimentsequence is no prove for the absence of trees in an area, and it can, therefore, not be ruled out that Pinus sylvestris had already been present earlier. A marked change in vegetation and climate started at around 3600 cal years BP. The oceanic influence seems to have increased and the vegetation became dominated by Betula nana and Empetrum nigrum assemblages.