A Dendrochronological Investigation of the Effects of Climate on Latewood Growth in Bohuslän, Sweden

Abstract

As climate change becomes a more important issue all over the world, information about past climate is of high relevance to better understand what is changing and different from the past. Tree rings can provide information about past climates and has been of value for paleoclimate research and the study of ongoing climate change. This study focuses on using the section of a tree ring that form at the end of the growing season, known as latewood. Rather than only using the whole ring width, the study of the different sections of a tree ring can provide further information. While dendrochronology has a long history in Fennoscandia and Sweden, southwestern Sweden has not been studied to a large extent. This study aims to be a beginning step to explore if tree rings from Bohuslän can be used as a climate proxy to reconstruct past climate in this region. The climate parameter affecting latewood and the differences between the climate parameter affecting latewood and the whole ring is investigated in this study. Whether a difference before and after 1950 can be found is also explored. Tree ring samples from Scots pine (Pinus sylvestris) was collected in the nature reserve of Halle-Vagnaren in Bohuslän (Sweden). A correlation analysis between latewood and normalised monthly precipitation as well as temperature data was conducted. The same correlation analysis was conducted for the whole ring width as well. A statistically significant correlation was found between the latewood and the same year’s precipitation in July before 1950 was found as well as for the same year’s precipitation in June after 1950. A statistically significant correlation for the whole ring was only found for the same year’s precipitation in May before 1950, but an indication can be seen for a shift toward the same year’s precipitation in June after 1950. The shift of the statistically significant correlation for the latewood could be due to an earlier start of the growing season or due to changed precipitation patterns. The results show a stable relationship between latewood and summer precipitation over time and latewood from the study area could therefore possibly be used as a climate proxy in the future.