Construction of a 7500-Year Tree-Ring Record for Scots Pine (Pinus sylvestris, L.) in Northern Fennoscandia and its Application to Growth Variation and Palaeoclimatic Studies

1996

S. 7-18

zahlr. Lit. Ang.

Unselbständiges Werk

200103952

Precisely dated subfossil trees and long chronologies of tree growth provide a unique calendrical record for studies on growth variations in the past and climate history. A total of 1465 subfossil Scots pines (Pinus sylvestris L.) has been sampled from 42 sites in northern Fennoscandia. The sampling sites are mostly small lakes in the timberline zone located between 68°30' N and 70°00' N and at elevations ranging from 75 m a.s.l. to 515 m a.s.l. A total of 1023 subfossil trees have been dated by dendrochronology. From the dated trees we have constructed a chronology for each growing site and also a common chronology for the entire area. In this study, subfossil pines are used as "growth reference" of forest site productivity in the past. The abundance of subfossil pines makes it possible to explore the longterm stand history of pine at each site over thousands of years. The unbroken tree-ring record extends from the present back until 165 B.C. and after a 150-200-year gap until about 7500 years before the present time. The continuous part of the master curve is 664 years longer than earlier published pine chronology for northern Sweden. This 7500-year pine master chronology can be used for dating subfossil pines from a wide area in northern Fennoscandia. The subfossil pine material has been used for studies on the Holocene climatic history, growth variations, year-to-year variability in ring widths, periods of germination and mortality, population size and age structure at the sampling sites and tree-line changes. These combined data are valid indicators of diverse environmental changes in the past. A detailed register of the growth variations is available for two periods in mid- to late-Holocene times. The data for the period 4500-3000 B.C. suggest increased variability in tree growth after 3800 B.C. The mid-Holocene climatic change at this time was thus largely the result of a shift towards less stable growing conditions. For the late holocene period from 165 B.C. to the present, the dating accuracy of variations in tree growth and climate is 1 year. The mean annual growth has temporarily varied significantly, being hirghly dependent on growing conditions at each site, but when the entire material is considered, in the long term the mean ring width has remained rather constant, being approximately 0.6 mm. The available data from the Holocene climatic optimum and late Holocene do not differ from each other in this respect.