The impact of climate changes during the last 6000 years on a small peatland in North-Eastern Poland: A multi-proxy study

In this article, we focus on transformations of a small peatland, located in the remote area of north-eastern Poland, which originated through partial terrestrialisation of Lake Czarne during the last 6000 years. We investigated the changes in vegetation patterns and linked them to climate changes and a concurrent succession of forest in the surroundings of the basin. We applied pollen, non-pollen palynomorph (NPP), and plant macrofossil analysis, supplemented with geochemistry and 14C AMS dating. The transformation from poor fen to peat bog occurred within ca. 300 years (ca. 6000-5720 cal. BP). The hydrological changes on the peat bog, reconstructed qualitatively on the basis of selected NPPs (mostly HdV-10 and Archerella flavum), occur simultaneously to the widely recognised climatic events. During the cool and wet '5.2' and '4.2' climatic events the potential increases in the water table on the peat bog were identified. The subsequent period of dynamic fluctuations of the water table (ca. 3400 and 2350 cal. BP) was related to the gradual expansion of Betula on the mire. This period also partially overlapped with the '2.8' event that was responsible for water level fluctuations across Europe. The '1750-1350' cal. BP global cooling event also might have led to a potential wet shift ca. 1700-1600 cal. BP. Since ca. 1600 cal. BP the water level has significantly dropped and poor fen conditions were reestablished. This article shows the potential of NPPs in the qualitative detection of palaeohydrological events on the peat land. However, there is still a need to combine NPP data with quantitative reconstructions of water table changes to understand the complexity of relationships between climate changes and water table-vegetation responses.