A 10 000 year local forest fire history in a dry heath forest site in eastern Finland, reconstructed from charcoal layer records of a small mire

Abstract

Local fire history covering the entire Holocene period at a dry forest site in North Karelia, eastern Finland (ca. 63°07' N, 30°44' E), was reconstructed on the basis of visible charcoal layers from peat deposits of a small mire basin. Seven points studied along a transect a few metres long provided a record of ancient local forest fires that had scarred the margin of the peat deposit. The charcoal layer records indicate a drastic increase in forest fires about 500 years ago compared with the earlier part of the Holocene period. During the past 500 years, human influence has been extensive in the area, and there have been 9 local fires during that period, while during the previous 9500 years there had been only 34 fires. Between the establishment of spruce (Picea abies (L.) Karst.) 6300 calendar years B.P. and the beginning of significant human influence, the site had burned over at a mean interval of 220–260 years. The data indicate a decrease in fire frequency associated with a warm climate between 9000 and 6300 calendar years BP. This suggests that climatic warming does not necessarily result in increased frequency of forest fires.