Fire frequency and forest structure at a dry site between AD 440 and 1110 based on charcoal and pollen records from a laminated lake sediment in eastern Finland

The fire history of a dry Boreal forest site in eastern Finland before sett lement in the area was studied by means of charcoal and pollen analysis of annually laminated lake sediments. The average estimated local fire interva l of 70-80 years corresponds to values quoted in a few earlier Finnish stud ies based on annually laminated lake sediments from more mesic sites. The f ire interval is longer than expected from dendrochronological results obtai ned for dry sites in Fennoscandian forests, suggesting human influence duri ng the periods studied by the dendrochronological method. The high represen tation of Picea pollen preceding the period of slash-and-bum cultivation at this and some other dry sites suggests a mixed coniferous forest structure at dry forest sites before significant human influence. The charcoal influ x reflected estimated climatic shifts, suggesting that the fires increased during the warmer climatic periods. A small test comparing charcoal records on pollen slides with thin sections was included in this study. Large macr oscopic charcoal particles were so scarce in the sediment of Lake Laukunlam pi that two local fires discernible in the pollen and microscopic charcoal records could not be detected in the thin sections.