Forest fires can be reconstructed up to c 800 years back in time with tree rings. Many trees, especially Scots pine in our part of the world successfully survive forest fires but are often damaged basally. The damage, a “fire scar” is visible as an opening which is overgrown laterally from surviving cambium. The scar is perfectly dateable to exact year and approximate season within the vegetation period.
Fire scarred pines become heavily impregnated by resins and do not decompose as easily as undamaged trees. Therefore firescarred stumps snags and logs may present a perfect material for fire history reconstruction. In a northern Swedish study we sampled and dated fire-scarred wood over large areas and were able to reconstruct individual fire sizes over time. Fires in the 14th to the 17th century were often exceeding 5000 hectares in size, in a few cases single fires covered more than 20 000 hectares. Up until the mid 1800s fires burned approx. 1% of all swedish forests annually. Today 1/1000 of this will burn every year.