Mid-Holocene warming in the northwest Kola Peninsula,Russia: northern pine-limit movement and stable isotope evidence

A set of 40 subfossil Scots pines (Pinus sylvestris L.) was sampled in small lakes beyond the modernpine limit in the northwest Kola Peninsula, Russia. Radiocarbon dating suggests that the pine expanded north of its present-day limit between 7000 and 3500yr BP. The most extensive occurrence of pine forests was reconstructed between 6250 and 5750 yr BP. Numerous samples collected from trunks and stubs in situ clearly indicate lower lake levels between 6200 and 4400 yr BP. Living and ¹⁴C dated subfossil pine samples were analysed for the mean carbon, oxygen and hydrogen stable isotope composition of their wood cellulose. The mean δ¹³C, δ¹⁸O and δ²H values of the wood samples from the mid-Holocene time are C. 1.1%, 0.⁹% and lock, respectively - more positive than those of living trees in this region. These results suggest that the mid-Holocene climate in the region was warmer and drier than nowadays. The data agree with previous palynological, macrofossil and limnological studies from northernmost Fennoscandia. During the late-Holocene climatic deterioration after c. 3500 yr BP, the decline of the northern pine limit was synchronous with other parts of northern Eurasia. Comparison with dated pine series from the north-central Kola Peninsula and Finnish Lapland suggests that the decline of the northernmost pine limit in the eastern part of the area may have occurred somewhat earlier than in the western part.