Reconstruction of central Siberian fire history using lake sediments
Wildfires are an important ecological disturbance with the power to shape ecosystems and considered a dominant driver of change in the world’s boreal zone. The vast forests of the boreal account for roughly a quarter of all global biomass and house enormous amounts of carbon above and below ground. These forests are also subject to change. Increased tree mortality, altered species composition, permafrost degradation and the transition towards acting as a net carbon source are some of the con-sequences thought to be linked to an increase in global temperatures. Fire plays an important role in all those aspects, yet for most of Siberia, long-term fire regimes remain poorly understood. This thesis attempts to start filling a pronounced gap in the global distribution of fire history reconstructions based on sedimentary charcoal. From a sediment core of Lake Khamra (SW Yakutia, Russia), a continuously sampled, high-resolution record of macroscopic charcoal particles was created, spanning the last c. 2000 years. The mean fire return interval ranges between c. 70 - 80 years. Fire activity decreases after a maximum around c. 750 CE. Despite a slight increase in fire frequency within recent centuries, charcoal accumulation since the 20th century is among the lowest of the record. Larger charcoal particles seem to indicate fires directly at the lake’s shore. No clear fire impact on XRF-derived soil geochemistry was found. However, different charcoal morphotypes show promising contrasting patterns when cor-related with the reconstructed vegetation. This thesis highlights both the challenges and the great potential of fire reconstructions in the Siberian boreal forest.
Helmholtz Research Programs > PACES II (2014-2020) > TOPIC 3: The earth system from a polar perspective > WP 3.1: Circumpolar climate variability and global teleconnections at seasonal to orbital time scales