Theme: East-West Interdisciplinaty Boreal Forest Fire Experiment, Part 2 Moderator: J. G. Goldammer
Influence of Man on the Forest Fire Frequency in North Karelia, Finland, Evidenced by Fire Scars in Scots Pines
Lehtonen, Hannu, Huttunen, Pertti, Zetterberg, Pentti
The aims of this research were to determine how often forests have burnt in North Karelia during recent centuries and how man has affected the frequency of fires. Fire scars in living pines (Pinus sylvestris L.) and pine stumps dated by dendrochronology were used as evidence for past fires. The study area, Autiovaara, covers 300 ha and is part of Patvinsuo National Park in eastern Finland. The commonest forest site types are myrtillus and vaccinium types. Within the study area are large slash and burn cultivation areas. Thirty-seven samples were collected from Autiovaara.
The fire history chronology was established for a period of 582 years, 14121994. For this period a total of 37 different fire years were dated. For the whole study area the mean fire interval (MFI), which is the average number of years between consecutive fires, was 10.9 years. On sites beside a slash and burn cultivation area, the MFI was clearly shorter, 29 years, than on sites not bordering on a slash and burn cultivation area where the MFI was 54 years. The MFI was clearly shorter than that found in other studies made in boreal forests. The main reason for this is the human impact on the area. Forest fires became more common in the 17th century, and it seems that slash and burn cultivation increased in the 17th century. Forest fires decreased in the end of the 19th century and the explanation for this is the decreased use of fire for agricultural purposes.
The results of this study show that in the past forest fires introduced by man have had a substantial influence on successions of vegetation in the boreal forests of North Karelia. In the future the same method will be used on the other study areas, where forest site type or human impact is different. This study is part of the Assessment of Forest Biodiversity project.
Key words: fire history, fire interval, dendrochronology.
Correspondence: Hannu Lehtonen, Karelian Institute, Section of Ecology, University of Joensuu, P.O. Box 111, SF-80101 Joensuu, Finland