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Free keywords:
plant succession, mid-dune reservoirs, paleoecology, climate change, Late Glacial
Abstract:
This study investigated the history of the development of six, paleo-lakes, which are at present filled with sediments, in a dune area in Central Poland, based on multiproxy paleoecological analyses and accelerator mass spectrometry radiocarbon dating. The aims of the paleoecological studies were: i) to determine the initial age of lakes development, ii) to reconstruct the local and regional plant succession, as well as iii) to reconstruct the environmental conditions during the initial stage of the development of lakes and peatlands. The obtained results indicated that: the former lakes in dune depressions were developed during the Bølling and Allerød when sparse vegetation allowed strong aeolian activity. Climate warming in Bølling led to the development of a denser plant cover, inhibition of sand transportation and the formation of mid-dune reservoirs with the accumulation of organic sediments. As indicated by 14 C dating, mid-dunes basins were formed between 14 686 ± 60 cal. yr BP and 13 421 ± 60 cal. yr BP. The results of the paleobotanical analysis suggested that the reservoirs were shallow, oligo-mesotrophic, inhabited by pioneer calcicole vascular plant species such as: Chara sp., Hippuris vulgaris , Potamogeton natans , Potamogeton fresii , Potamogeton alpinus and Potamogeton filiformis , and mosses such as: Pseudocalliergon trifarium , Calliergon sp. and Calliergonella cordifolium . The area next to the reservoirs was covered with sparse pine forests combined with birch, which is typical of the Late Glacial period. The open areas were dominated by psammophilic and steppe vegetation, including Poaceae, Artemisia and Hippophae rhamnoides . Geochemical analysis revealed that Ca 2+ and Fe 3+ were in high concentrations, which could have influenced the presence of taxa preferring soil with high Ca 2+ content. The accumulation of calcium in sediments confirms that the reservoirs were fed by groundwater originating from the progressive degradation of permafrost associated with thermal changes.
