Subaerially preserved remains of pine stemwood as indicators of late Holocene timberline fluctuations in Fennoscandia, with comparisons of tree-ring and 14C dated depositional histories of subfossil trees from dry and wet sites

Abstract

Collections of subfossil wood provide useful evidence of past vegetation and climatic variability. Here, 172 samples of Pinus sylvestris stemwood found either as standing (snags) or fallen tree trunks (coarse woody debris) from forested and treeline (ecotone) sites in northwest Finnish Lapland was compared with living tree data representing 1071 P. sylvestris trees growing in the region. The number of subfossil samples was found to increase in both the ecotone and forested sites since AD 1000. Divergent courses of de positional histories were evident with the reversal of the trend in subfossil number circa AD 1600 in the ecotone sites and circa AD 1800 in the forested sites. Comparisons with subfossil P. sylvestris trees from lacustrine archives in the same region showed synchronous accumulation pulses around AD 1100, AD 1300, AD 1500 and AD 1700. Moreover, the percentage of ecotone samples showed a long-term decline since AD 1000, in agreement with previously published records of pine pollen influx and subfossil P. sylvestris trees from lacustrine archives. Two major phases of increased pine recruitment across the dryland sites in Finnish Lapland, Scandes Mountains and Kola Peninsula were evident for AD 1000–1200 and AD 1400–1600 periods. This suggests that the pine recruitment was generally increased during the Medieval Climate Anomaly (MCA) and during the fifteenth and sixteenth centuries AD, and impaired during the cold phases of the two-stage Little Ice Age. Living tree data demonstrated latitudinal and altitudinal advances and intensified regeneration of treeline P. sylvestris since AD 1930s.