Holocene vegetational history and climatic change in west Spitsbergen - plant macrofossils from Skardtjørna, an Arctic lake

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Abstract
Macrofossil analyses of a 335 cm-long core from Skardtjørna, a small lake on the west coast of Spitsbergen, Svalbard, are presented. The known processes of deposition of plant remains to arctic lake sediments are summarised, and used in the interpretation of the vegetation history at Skardtjørna. The basal sediment is AMS-dated to 8110 ± 110 BP. The rest of the profile is dated by palaeomagnetic correlation. The lowest sediments have the greatest macrofossil concentration and numbers of taxa per sample. The occurrences of Cassiope hypnoides and Salix cf. glauca before 4000 BP indicate a mean July temperature for the early Holocene about 2°C higher than today, comparable to the Cassiope tetragona vegetation zone of the mid-arctic region of the inner fjords. Increasing climatic severity resulted in the threshold from the Cassiope to the Dryas vegetation zone being passed at about 2500 BP. The inferred climatic history at Skardtjørna is compatible with other evidence from Svalbard and elsewhere in the arctic. The phytogeography of Salix herbacea, Cassiope hypnoides, and Saxifraga flagellaris is discussed in terms of their historical occurrences.