Larch forests of Middle Siberia: long-term trends in fire return intervals

Fire history within the northern larch forests of Central Siberia was studied (65 + A degrees N). Fires within this area are predominantly caused by lightning strikes rather than human activity. Mean fire return intervals (FRIs) were found to be 112 +/- A 49 years (based on firescars) and 106 +/- A 36 years (based on firescars and tree natality dates). FRIs were increased with latitude increase and observed to be about 80 years at 64A degrees N, about 200 years near the Arctic Circle and about 300 years nearby the northern range limit of larch stands (similar to 71A degrees A + N). Northward FRIs increase correlated with incoming solar radiation (r = -0.95). Post-Little Ice Age (LIA) warming (after 1850) caused approximately a doubling of fire events (in comparison with a similar period during LIA). The data obtained support a hypothesis of climate-induced fire frequency increase.