352 years long fire history of a Siberian boreal forest and its primary driving factor

Fire is a major disturbance agent in the boreal forest, affecting the structure, dynamics and biogeochemical cycles in this biome. In the Asian section of boreal forest, the records of long-term fire history are few that limits our understanding of factors forcing regional fire dynamics. We presented an annually-resolved 352 year (1666-2017) fire chronology based on fire scars of Scots pine (Pines sylvestris L.) and Siberian larch (Larix sibirica Ledeb) from the Transbaikal area in the southeastern Siberia. Fire activity showed an increasing trend from 1720 to 1929 (R-2 = 0.80, P < 0.0001), and a significant decreasing trend from 1920 to 2010 (R-2 = 0.62, P < 0.001). We assessed the potential relationships between drought (as represented by the Palmer Drought Severity Index, PDSI, and the Monthly Drought Code, MDC), ocean-atmosphere circulation and forest fire by Superposed epoch analyses, cross-wavelet analysis and Granger causality analysis. Increased fire activity was associated with stronger drought from previous winter to current summer of fire event years and positive Arctic Oscillation (AO) before and during major fire season (February and April to May), as revealed by superposed epoch analysis. Granger causality pointed to the significant role of drought in driving forest fires. Our findings provide insights into the climate drivers of forest fire activity and its prediction in the Transbaikal region.

Automated summary

The study reveals a changing trend in fire activity in the Transbaikal region of southeastern Siberia, with significant relationships to climate factors such as drought and Arctic Oscillation. Granger causality analysis highlights the important role of drought in driving forest fires.