Średniowieczna historia roślinności rejonu Pasymia zapisana w osadach jeziorno-torfowiskowych

Abstract

Palynological analysis of sediments from the so-called PSM-II core extracted from a small peatbog on the Lake Kalwa peninsula, located a kilometre away from the Pasym stronghold, made it possible to determine changes in local vegetation, in particular woodland communities, within a 1000-year period (AD 550–1550). During this time the body of water in which deposition of sediments and subfossil plant remains had already begun, gradually became shallower and overgrown, eventually leading to the formation of a peatbog around AD 900. The results of this analysis clearly demonstrated that the lands around both the palynological and archaeological sites at Pasym had been densely forested, but that the composition and character of woodland communities had changed over time. From around AD 550–700/750 (Stage I of vegetation development) the region was dominated by pine forests associated with drier and poorer habitats, mixed coniferous forests and mixed deciduous woodland with abundant hazel growing in fresh or moist habitats with more fertile soil, which were probably subject to greater anthropogenic pressure from agriculture. Alder was predominant in periodically flooded wetland areas. From around AD 700/750–820 (Stage 2 of vegetation development) birch took on a more prominent role as a forest-forming species, helping create various types of communities. There were also changes in the relative numbers of tree species represented in mixed deciduous forests. Hornbeam became more abundant, whilst oak, hazel and lime decreased. Fields for cultivating crops (wheat and rye) were created in the vicinity of the site. Stage 3 of vegetation development, which occurred around AD 830–1450, was marked by the vigorous development of pine and mixed forests and woodland with a high percentage of birch, accompanied by a significant reduction in the coverage of alder woodlands and a drop in agricultural activity. The greatest prevalence of pine was noted during this period, as was a distinctive supra-regional trend, namely a dramatic reduction in alder, dated at other sites to c. AD 800–1000. Finally, stage 4 of vegetation development, dated to c. AD 1450–1550, was characterised by an even greater reduction in forested areas, with woodland clearance and exposure of surface soils associated with increased human activity. This process was conducive to the spread of photophilous herbaceous plants. Pollen from these species exceeded 20% thanks to the abundance of heather and meadow plants. Buckwheat appeared among cultivated crops alongside cereals, and possibly also hemp/hops. The sequence of changes in vegetation is largely consistent with that determined for Lake Łańskie, the nearest large lake in this region, though it differs slightly more from the record for Woryty, which is the type site for the central part of this mesoregion. In attempting to build a picture of the human impact on vegetation, the presence and change in number of palynological indicators of anthropogenic pressure was analysed, resulting in the identification of three phases associated with local human activity, dated respectively to c. AD 750–900, c. AD 1150–1300 and c. AD 1450–1550.