A 7500-YEAR UNBROKEN SCOTS PINE TREE-RING CHRONOLOGY FOR FINNISH LAPLAND

Tree rings are of great importance as high-resolution proxies of past climate. A long well-established dendrochronological record from a climatologically sensitive area can provide valuable indications of the Holocene climatic variability. Here we report a c. 7500 years long continuous Scots pine tree-ring record from the treeline area of northern Fennoscandia. This record can be used for reconstructions of the interannual variability of past summer temperatures and potentially for studies of many past climatic and environmental variables. Scots pine (Pinus sylvestris, L.) immigrated to northern Finnish Lapland by 9.5 - 9 ka calBP and spread in favourable climatic conditions to a larger area than that occupied by pine forests today. The time of the maximum extent was between 7 and 4.5 ka calBP. A large number of subfossil pine trunks and stumps have been preserved in small lakes in Lapland in the present treeline area and also beyond it. An earlier work in Lapland resulted in several dozens of radiocarbon dates for subfossil pine wood. The dated sample discs could be used to tie the initial floating chronologies to the radiocarbon timescale. Cores from living trees and beams of old wooden buildings were also used. The intensive phase of the data collection and chronology building lasted about 10 years until the master curve was completed in 1999. The present pine tree-ring chronology extends from the present time to c. 5520 B.C. Several studies have shown that the tree rings of forest-limit pines in northern Fennoscandia are good indicators of past summer temperatures, the July ones being the predominant decisive factor for the radial growth of pine. The long pine tree-ring curve should therefore indicate interannual variations of summer temperatures in northern Fennoscandia. The annual resolution makes it possible to reconstruct a high-frequency record of temperature variability over thousands of years. However, it is much more difficult to extract information about low-frequency climatic variations from this data. This high-resolution proxy record covering a major part of the Holocene can be used now for many kinds of analyses, measurements and correlations with other proxies.