Pine trees in the north have lived for hundreds of years and experienced a variety of climate conditions.
Usually, pines live for 200–300 years, but a pine that is 800 years old has been found in Lapland. During their lives, pines collect valuable information about the prevailing conditions in their trunks.
By comparing the thicknesses of growth rings, you can create a database on the variation of summers that extends far beyond written weather observations.
In Finland, growth ring chronology is based on pines, because their growth rings are highly visible, pine is a common tree in Finland and plenty of pines grow in the whole of the country. Furthermore, the stemwood of a pine can survive for thousands of years if the sedimentation conditions are favourable.
The growth ring series of subfossil trunks – i.e. trunks that have been retained as such – covers the last 7,600 years. Luke has collected samples and stored them for research purposes since the 1990s.
“The environment has an impact on how well wood is retained. We have found trunks that are thousands of years old in the bottom sediment of small lakes in Northern and Eastern Lapland. They have survived surprisingly well,” Samuli Helama says.
The variation of carbon isotopes is analysed from chips carved from the growth rings of trees. In research projects funded by the Academy of Finland, such analyses have been created in cooperation with the University of Helsinki Laboratory of Chronology.
The carbon isotopes depict the photosynthesis of the trees, and the volume of photosynthesis depends mostly on the amount of solar radiation in the summertime. The growth rings can be used to collect not only growth data, but also a variety of data about the weather in summers past.
“We eat solar radiation, energy created by plants through photosynthesis. If the amount of solar radiation drops for some reason, the volume of photosynthesis by plants drops as well.”
Published in Finnish in Maaseudun Tulevaisuus newspaper on 12 of June 2019.