Substantial changes in land and forest management led to critical transitions in peatland functioning over the last 700 years

Over the last 300 years, many European forests have been progressively modified toward monoculture ecosystems, with preference given to coniferous forests. These forests, often dominated by Scots pine (Pinus sylvestris), are currently impacted by various disturbance factors, e.g., more frequent windthrows, droughts, fires and insect infestations. Peatlands located in these monocultures are also significantly impacted, enhancing their vulnerability to drying and burning. Here, we investigate how the functioning of a Sphagnum-dominated peatland has changed during the last ca. 700 years along with the introduction of new forest management strategies-modification of a mixed-forest complex into a Scots pine monoculture. Multi-proxy, high-resolution palaeoecological analyses include AMS radiocarbon dating, pollen and spores, plant macrofossils, testate amoebae and historical data. Direct peatland fire disturbance was reconstructed using a wide range of charcoal analyses: charcoal counts and morphological types to reconstruct past fire activity, and Raman spectroscopy to reconstruct past fire intensity. The results obtained confirm that introduction of new management techniques impacted the functioning of the peatland, leading to critical transitions in vegetation composition and hydrology. Detailed analyses of a distinct charcoal layer present in the peat show that increased fire activity as recorded by charcoal accumulation does not necessarily equate to burning intensity. Therefore, we recommend the use of charcoal-derived wildfire intensity reconstructions in tandem with charcoal abundance studies.