Forest fire history in Norway: from fire‐disturbed pine forests to fire‐free spruce forests

I have used occurrence of macroscopic charcoal particles, pollen analyses and radiocarbon datings to examine local forest fire abundance in southern and central Norway. Peat cores, covering the last 1000 to 6000 yr, were sampled from 20 bog margin and swamp forest sites, and the charcoal records documented local fire occurrence in 10 of the sites. Forest fires have not occurred in the sites located in central Norway, whereas the fire occurrence in southern Norway showed large variation among the sites. However, forest fires ceased prior to the establishment of Norway spruce Picea abies in seven of the sites, whereas the establishment of spruce preceded the fire decline in three of the sites. Odds ratio calculations indicated that it is several hundred times more likely that fires occurred prior to, than after, the spruce establishment. Although time spans between fire decline and spruce establishment showed some variation, they did not increase along a gradient from east to west in Norway, suggesting that the establishment of spruce might have initiated a change from fire‐prone to fire‐free ecosystems.