Holocene wildfire regimes in western Siberia: interaction between peatland moisture conditions and the composition of plant functional types

Abstract. Wildfire is the most common disturbance type in boreal forests and can trigger significant changes forest composition. Waterlogging peatlands determines degree of tree cover depth burnt horizon associated with wildfires. However, interactions between peatland moisture, vegetation composition flammability, fire regime forested Eurasia remain largely unexplored, despite their huge extent regions. To address this knowledge gap, we reconstructed Holocene regime, composition, hydrology at two sites located predominantly light taiga (Pinus sylvestris Betula) interspersed dark communities sibirica, Picea obovata, Abies sibirica) western Siberia Tomsk Oblast, Russia. We found marked shifts past water levels over Holocene. The probability occurrence intensification frequency severity increased times low table (drier conditions), enhanced fuel dryness, an intermediate dark-to-light ratio. High level, thus wet peat surface conditions, prevented fires from spreading on surrounding forests. Deciduous trees (i.e. Sphagnum were more abundant under wetter conifers denser prevalent drier conditions. On a scale, severe recorded 7.5 4.5 ka proportion avoiders sibirica Rybnaya Ulukh–Chayakh) fire-resister community characterised by Pinus lower local level. Severe also occurred last 1.5 kyr declining abundance avoiders, expansion invaders (Betula), fluctuating tables. These findings suggest that frequent, high-severity lead to compositional structural when fail reach reproductive maturity events or where extensive gaps limit seed dispersal. This study shows prolonged periods synchronous activity across sites, particularly during early mid-Holocene, suggesting regional imprint centennial- millennial-scale climate variability wildfire activity. Humans may have affected Neolithic; however, increasing human presence region, Ulukh–Chayakh Mire 4 centuries, drastically ignitions compared natural background levels. Frequent warm dry spells predicted change scenarios for future will enhance drying convey competitive advantage conifer taxa. conditions probably exacerbate wildfire, disrupt conifers' successional pathway, accelerate towards deciduous broadleaf cover. Furthermore, climate–disturbance–fire feedbacks carbon balance affect overall resilience change.