Palaeoenvironmental changes recorded in a fluviogenic peatland, inferred from subfossil Scots pine (Pinus sylvestris) dendrochronology and peat analysis: the Mosty site (Bia3a Nida River floodplain, southern Poland)

Abstract

The Mosty site, located in an abandoned meander of the Bia3a Nida River (southern Poland) includes fluviogenic peat 1.54 m thick, with a record of palaeoclimatic changes since the Boreal phase (9258 cal BP). During exploitation of peat and sand, numerous subfossil tree trunks, mainly Scots pine (Pinus sylvestris L.), were extracted from the deposits. Reconstruction of palaeoenvironmental changes on the basis of peat multiproxy analysis of lithology, plant tissues, pollen and non-pollen palynomorphs and geochemistry, together numerous radiocarbon dates and dendrochronological analysis of subfossil wood, indicates flood-derived clastic sediment input to the peatland at ~8.2 ka BP, at 6.8–5.3 ka BP, to lesser extent after 4.2 ka and ~2.8 ka BP, and since 1.522 ka BP. A sedimentary hiatus was probably related to the strong cooling and drying of the climate at ~4.2 ka, which caused a break in peat sedimentation. The oldest single pine tree trunks dated by 14C at 10,198–9757 and 9426–9128 cal yrs BP grew as pine forest on the Bia3a Nida floodplain before the beginning of accumulation of the Mosty peatland deposits. A younger, single subfossil tree trunk (2964–2632 cal BP) grew in bog pine woodland on the peatland (above the hiatus) and fell during climate deterioration at ~2.8 ka. On the basis of the wiggle matching method, two bog pine floating chronologies were developed for the periods 1360–1187 (modelled age cal BP) and 1158–976 (mod. cal BP). The pine dying-off phase coincided with a significant increase in climate humidity in the 5th and 6th centuries AD, which included several fluctuations. The pine floating chronologies indicate the occurrence of alternating germination and dying-off tree phases. The beginning of colonization of the peatland by bog pines occurred during climatic drying, whereas the tree dying-off phases (deforestation) in peatlands took place during the climate humidity growth.