HISTORY OF FOREST-FIRES IN EASTERN FINLAND FROM THE 15TH-CENTURY-AD -THE POSSIBLE EFFECTS OF SLASH-AND-BURN CULTIVATION

The history of forest fires in two areas in eastern Finland, Kitsi and Ahvenjarvi, both of about 150 ha, is studied by dendrochronological d ating of fire scars. Forty-nine samples were collected from Kitsi and 20 samples from Ahvenjarvi. The history of fires spans the period AD 1 403-1994 at Kitsi and 1359-1994 at Ahvenjarvi, within which a total of 23 fire years were dated for Kitsi and 22 for Ahvenjarvi. Over the 40 0-year period of Ao 1500-1900, fires occurred an average of once every 19.2 years in Kitsi and once every 20.6 years in Ahvenjarvi. The mean fire interval at Kitsi was 42.3 years and that at Ahvenjarvi 48.8 yea rs before Ao 1650 and 32.2 years after 1650. Forest fires increased to wards the end of the seventeenth century and decreased markedly after 1850. There were fewer fires for a time at the beginning of the eighte enth 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 infl uencing the vegetation dynamics of the boreal forests of North Karelia , and slash-and-bum cultivation has greatly affected the history of fi ns in the region.