Fire frequency during the Holocene in central Latvia, northeastern Europe

Fire is today a pan-European issue and is expected to be more salient because of climate and land use changes. Even though natural and anthropogenic fires have shaped forest composition and landscape characteristics since the last glacial retreat from northeastern Europe, fire frequency is an understudied topic. To address this issue, we analysed macroscopic charcoal (>160 μm) from two sediment sequences located in the central and littoral parts of Lake Bricu (central Latvia) revealing the fire frequency during the Holocene. The chronology of the analysed sediment sequences is based on spheroidal fly-ash carbonaceous particles and accelerator mass spectrometry radiocarbon dating. Macroscopic charcoal results were examined in detail using the CharAnalysis approach. The mean fire return interval for the entire Holocene was 372 years (261–494 years). Fire reconstructions revealed higher fire frequency during the early and late Holocene (cool climate), but lower frequency during the middle Holocene (warm climate). Although our study underlines that natural fire frequency might decrease during warmer climate, the anthropogenic fire use already has surpassed the baseline of natural fire frequency.