Fire return intervals within the northern boundary of the larch forest in Central Siberia

A fire history of northern larch forests was studied. These larch forests are found near the northern limit of their range at similar to 71 degrees N, where fires are predominantly caused by lightning strikes rather than human activity. Fire-return intervals (FRIs) were calculated based on fire scars and dates of tree natality. Tree natality was used as an approximation of the date of the last fire. The average FRI was found to be 295 +/- 57 years, which is the longest reported for larch-dominated stands. Prior studies reported 80-90-year FRIs at 64 degrees N and similar to 200 years near the latitude of the Arctic Circle. Comparing data from fires that occurred in 1700-1849 (end of the Little Ice Age, LIA) and 1850-1999 (post-LIA warming) indicates approximately twice as many fires occurred during the latter period. This agrees with the hypothesis that observed climatic warming will result in an increase in fire frequency. Our results also indicate that fires that did not leave visible fire scars on the tree stem may be identified based on the date of growth release revealed from dendrochronology.