Minna Väliranta, Ülle Sillasoo, Tiina, Ronkainen, Eeva-Stiina Tuittila
Proceedings of the 14th International Peat Congress
bog, fire, vegetation-recovery
Väliranta et al 2012: Late Holocene Fire History and Vegetation Recovery in Two Raised Bogs and a Glance to Modern Bog Fire Patt
Theme I. Inventory, stratigraphy and conservation of mires and peatlands
Macroscopic charcoal, plant macrofossils and radiocarbon dating were used to examine one bog section from Finland and one from Estonia. During the last 5000 years, both peatlands have experienced several fire events. A typical pre-fire vegetation community consisted of hummock Sphagna, often accompanied by Calluna vulgaris. Only the most severe fires resulted in a dramatic change in the vegetation composition. The recovery time of dry microtopes following severe combustion sometimes took up to 350 years. The results suggest that fires have been a regular phenomenon in boreal bogs. In order to better understand bog fire dynamics we surveyed modern fire pattern on a boreal bog that contained drainage-affected and unmanaged parts. Throughout the bog, dry hummock surfaces provided spreading routes for fire while hollows stayed intact. The drained part was combusted more severely than the pristine part. Our conclusion is that artificially lowered water levels increased the impact of fire. Possible implication for future is that in a warmer climate with prolonged extreme dry seasons, bogs are likely to become more vulnerable to fires.