Autogenic succession, land-use change, and climatic influences on the Holocene development of a kettle hole mire in Northern Poland

We reconstructed the Holocene developmental history of a kettle-hole peatland in the Tuchola forest of Northern Poland, using pollen, testate amoebae and plant macrofossils indicators. Our aims were to determine the timing and pattern of autogenic succession and natural and anthropogenic influences on the peatland. Northern Poland is under mixed oceanic and continental climatic influences but has so far been less studied in a palaeoecological context than more oceanic regions of Europe. In the first terrestrial developmental phase of the mire, the testate amoebae-inferred depth to water table revealed two major dry shifts at ca 9400 (end of lake phase) and ca. 7100 cal. BP (a period of global cooling and dry shift in western Europe). Conditions became wetter again in two steps at ca. 6700 and ca. 5800 BP after a dry event at ca. 6100 BP. The timing of the wet shift at 5800 BP corresponds to wet periods in Western Europe. Peat accumulation rates were low (0.1 mm yr-1) between ca. 5600 and ca. 3000 BP when sedges dominated the peatland. In the last 2500 years surface moisture fluctuated with wet events at ca 2750-2400, and 2000 BP, and dry events at ca. 2250-2100 and 1450 BP. After 1450 BP a trend towards wetter conditions culminated at ca. 500 cal. BP, possibly caused by local deforestation. Over the mire history, pH (inferred from testate amoebae) was mostly low (around 5) with two short-lived shifts to alkaline conditions (7.5) at ca. 6100 and 1450 BP indicating a minerotrophic influence from surface runoff into the mire. Up to about 1000 BP the ecological shifts inferred from the three proxies agree with paleoclimatic records from Poland and Western Europe. After this date, however correlation is less clear suggesting an increasing local anthropogenic impact on the mire. This study confirms that kettle-hole peatlands can yield useful palaeo-environmental data as well as recording land-use change and calls for more comparable studies in regions are the interface between major climate influences.