Northern Fennoscandian fire activity exhibits strong links with proxies of solar activity

• Main Author: CORRÒ, FEDERICO
• Other Authors: CARRER, MARCO
• Language: unknown
• Published: 2022
• Subjects: Forest fires; Dendrochronology; Fennoscandia; Fennoscandian
• Online Access: https://hdl.handle.net/20.500.12608/37156

open Fire has been a major factor shaping the vegetation of the boreal zone over the Holocene. The Common Era, or the last 2000 years, is of particular interest as it represents an important period in the development of the boreal forest post-glaciation. Analysing past patterns and trends of forest fires activity in relation to their causes is crucial for understanding long-term dynamics within the forest and projecting future fire activity. While earlier studies have mostly focused on associations between fire activity and proxies of ocean-atmosphere conditions, solar irradiance, which has an important role as source of climate variability, has been understudied. In this study, I explored forest fire activity over the Common Era in northern Fennoscandia and its relationship with climate, specifically solar irradiance, through a synthesis of high fire activity periods from available charcoal and dendrochronological records over the last 2000 years. The charcoal and dendrochronological based fire activity syntheses resulted into differences in the occurrence of high fire activity periods which can be related to a number of limitations in the two methods. The differences in temporal resolution and methodology applied to assess the peaks in fire activity between the two syntheses suggest higher accuracy of the dendro record. However, both the dendrochronological and the charcoal record point to general decline in fire activity across Fennoscandia over the 20th century, in accordance with earlier studies. I analyzed the relationship between fire activity and total solar irradiance for the reconstructed period by conducting contingency analysis with non-parametric bootstrapping to test if there is a significant difference in the likelihood of fire prone periods to occur under a specific solar irradiance state over the same period. I concluded that low solar activity is positively correlated to high fire activity, whereas neutral solar activity is negatively correlated to high fire activity, as they differ ...