History of forest fires in eastern Finland from the fifteenth century AD - the possible effects of slash-and-burn cultivation

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Abstract
The history of forest fires in two areas in eastern Finland, Kitsi and Ahvenjärvi, both of about 150 ha, is studied by dendrochronological dating of fire scars. Forty-nine samples were collected from Kitsi and 20 samples from Ahvenjärvi. The history of fires spans the period AD 1403-1994 at Kitsi and 1359-1994 at Ahvenjärvi, within which a total of 23 fire years were dated for Kitsi and 22 for Ahvenjärvi. Over the 400- year period of AD 1500-1900, fires occurred an average of once every 19.2 years in Kitsi and once every 20.6 years in Ahvenjärvi. The mean fire interval at Kitsi was 42.3 years and that at Ahvenjärvi 48.8 years before AD 1650 and 32.2 years after 1650. Forest fires increased towards the end of the seventeenth century and decreased markedly after 1850. There were fewer fires for a time at the beginning of the eighteenth century, especially in Kitsi. The changes in the history of fires reflect changes in the population of North Karelia and the extent of slash-and-burn cultivation. Past forest fires were a major factor influencing the vegetation dynamics of the boreal forests of North Karelia, and slash-and-burn cultivation has greatly affected the history of fires in the region.