A Norway spruce Blue Intensity summer temperature reconstruction from the Central Scandinavian Mountains

Abstract

Fennoscandia is a favourable region for dendroclimatological research. Yet, most of the dendroclimatological research in Scandinavia has focused on Scots pine (Pinus sylvestris L.) while fewer studies have focused on Norway spruce (Picea abies L.), despite its wide distribution. In the present study we explore the potential of increasing the fidelity of the climate information from Norway spruce tree-ring data by investigating Late Wood Blue Intensity (LWBI) measurements from trees sampled at the elevational tree line in the Central Scandinavian Mountains. We present -to the knowledge of the authors- the first LWBI chronology and summer temperature (June through August) reconstruction based on LWBI measurements from the species, which covers the period 1750–2020. The LWBI chronology has a substantially stronger temperature signal than its corresponding tree-ring width (TRW) chronology, and displays a good spatial representation across the Nordic countries. The temperature reconstruction follows the general patterns of the temperature history previously reported for the central Scandinavian mountains. This suggests that Norway spruce and the LWBI technique are viable for studying past climate history and evaluating ongoing changes. The introduction of another species in dendroclimatic reconstructions in the area could yield more precise insights of regional climate variations, as different species exhibit varying sensitivities to climatic conditions. However, while Norway spruce can be preserved for a long time under favourable conditions, the use of Norway spruce subfossil wood in LWBI research is untested. Therefore, further research is required to develop longer Norway spruce LWBI chronologies and to fully evaluate the potential of using Norway spruce in dendroclimatic studies.