Variability in climate historically influenced forest fire occurrence at multiple time scales in Fennoscandia

By compiling all available tree ring based fire history reconstructions, and a set of temperature and precipitation reconstructions, we analyzed how climate had influenced the occurrence of forest fires in Finland and the adjacent regions in western Russia. Our analyses were based on Bayesian scale-space methods, that made it possible to assess these fire-climate linkages over different time scales. In the analyses, we saw the well-documented relationship between fires and weather conditions during individual summers (high fire activity was related to dry summers). However, and somewhat surprisingly, fires and climate (summer temperature, and especially summer precipitation) were also very clearly related to one another at longer, approximately decadal, time scales. The result of this work, as a collaboration between our group, Department of Geosciences and Geography of University of Helsinki, and the Department of Mathematical Sciences at the University of Oulu, is now available in Ecological Monographs.

Historically, the synchrony of fire occurrence in different parts of the region was related to drought.

Biological “archives” carry reliable information of past temperatures for all four seasons in Finland

In a joint study with several research groups at the University of Helsinki and Aalto University, we compiled a collection of records on different biological and physical phenomena, to assess their reliability as an indicator of past temperatures for different seasons. This collection included different characteristics of tree rings, and plant and ice phenology. Our assessment showed how different combinations of these temperature indicators provided reliable information on the temperatures of all four seasons, as well as annual temperatures. See the full paper in Plos one.