New insights into the mid-late Holocene environmental history in the E Baltic – multi-proxy data from Aukštumala raised bog, W Lithuania

Abstract

This study reconstructs vegetation and environmental changes in western Lithuania during the Middle and Late Holocene, based on multi-proxy analyses of the Aukštumala raised bog in the Nemunas Delta. Two parallel sediment cores were investigated using pollen, plant macrofossils, radiocarbon dating, loss-on-ignition (LOI), magnetic susceptibility, and geochemical analyses. Seven main stages of environmental development were identified and interpreted in a regional and broader Holocene context. Sedimentation began around 6000 cal yr BP, when coniferous forests dominated in relatively dry conditions. A short-lived presence of aquatic plants at ∼5400 cal yr BP indicates temporary open-water habitats. Between 5000 and 4300 cal yr BP, conifers declined while birch expanded, suggesting a more open landscape and reduced wetland cover. Around 4400 cal yr BP, rising water levels and cooler conditions promoted vegetation typical of raised bogs. From 4300 to 3200 cal yr BP, lowered water tables together with the dominance of peat-forming plants indicate a cooler, wetter phase. Between 3200 and 2700 cal yr BP, one core records the transition from an intermediate-type bog to a raised bog, while the other reflects open-basin conditions with abundant wetland taxa. From 2700 to 2100 cal yr BP, birch forests spread, landscapes became more open, and water levels rose around 2400 cal yr BP. After 2100 cal yr BP, the peatland gradually transformed into a raised bog, with increasing Sphagnum, expansion of ericaceous vegetation, and evidence of local fires, reflecting unstable hydrological conditions. These results provide new insights into long-term ecosystem dynamics and their links to Holocene climate variability in the southeastern Baltic region.