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

Abstract

A fire history of northern larch forests was studied. These larch forests are found near the northern limit of their range at ~71°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°N and ~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.

Wildfires Dynamics in Siberian Larch Forests

“…This result is similar to observations within the North American portion of boreal forests [24,25], and supports the hypothesis of climate-driven increase of fire frequency in boreal forests with the possible turning of boreal forests from carbon sink to а carbon source. The fire return interval (we obtained earlier [6,20,21]) increased along the latitudinal gradient (Figure 6b). It varied from 80 years at 64˝N to about 200 years at the latitude of the Arctic Circle.…”

“…For example, the date of the first fire varied by up to 30 days. The fire return interval (we obtained earlier [6,20,21]) increased along the latitudinal gradient (Figure 6b). It varied from 80 years at 64° N to about 200 years at the latitude of the Arctic Circle.…”

“…Trees were sampled until at least 12 samples were collected. In this study we used earlier obtained data on FRI in northern larch forests [6,20,21] which were analyzed against insolation along the meridian. Test sites where FRI data were obtained are shown on Figure 1.…”

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

“…Combining the data from this study with previously published data (Kharuk et al 2008(Kharuk et al , 2011(Kharuk et al , 2013 Fig. 1) allowed consideration of the FRI dependence on latitude along a south to north transect.…”

“…The dominant species is L. gmelinii Rupr., which forms sparse stands (mean crown closure ≤0.3) with admixture of Betula pendula Roth. Ground cover is composed mostly of lichen and moss (Kharuk et al 2008(Kharuk et al , 2011(Kharuk et al , 2013. Within all sites fires are predominantly caused by lightning strikes rather than human activity.…”