High-resolution studies of the Bølling-Allerød to the Younger Dryas transition in the Netherlands: implications for the reconstruction of vegetation changes and the potential role of (perma)frost in contemporary paludification

High-resolution studies of botanical microfossils and macroremains were performed on two Lateglacial sites in The Netherlands. Both sites showed a thin Sphagnum layer, formed during the transition from the relatively warm Bølling-Allerød interstadial to the cold Younger Dryas. Dendrochronological analyses revealed that pine trees survived into the Younger Dryas for decades without producing relevant amounts of pollen, demonstrating an asynchronicity between the decline of pine pollen and the actual death of the pine trees. We discuss possible causes for the sudden occurrence of Sphagnum following on the pine forest dieback and conclude that there may be a link with (perma)frost, causing perched water tables and inducing paludification. The formation of Sphagnum peat at the beginning of the Younger Dryas is not necessarily an indicator of wetter climate but could be an indication for a frozen subsoil inducing a (seasonal) perched groundwater table and cryopaludification.