Declining fires in Larix-dominated forests in northern Irkutsk district

To study the poorly known fire history of Larix-dominated forest in central Siberia, we collected samples from 200 trees in 46 systematically located study plots. Our study area stretches ∼90km from north to south along the River Nizhnyaya Tunguska in northern Irkustk district. Cross-dated tree-ring chronology for all samples combined extended from the year 1360 AD to the present and included 76 fire years and 88 separate fire events. Average fire cycle gradually lengthened from 52 years in the 18th century to 164 years in the 20th century. During the same time, the number of recorded fires decreased even more steeply, i.e. by more than 85%. Fires were more numerous but smaller in the past. Contrary to expectations, climate change in the 20th century has not resulted in increased forest fires in this region. Fire suppression may have contributed to the scarcity of fires since the 1950s. However, a significant decline in fires was evident earlier; therefore an additional explanation is required, a reduction in human-caused ignitions being likely in the light of historical accounts.