Insight into the vegetation development of the Karkonosze Mountains (southwestern Poland) during the Late Vistulian and Holocene, based on data from glacial lakes

New palaeoecological records from two glacial lakes (the Mały Staw – 1183 m a.s.l. and the Wielki Staw – 1225 m a.s.l.) from the Polish Western Sudetes were obtained with the aim of better understanding the long-term vegetation development, the relationship between postglacial migration patterns, climate changes and human interference in mountainous areas, as well as to verify the local survival of some cold-adapted species during the Holocene maximum warming. Vegetation changes were reconstructed using pollen, spores and macrofossils. Several major stages of plant cover evolution over the last 12 000 years were identified. The end of the Late Vistulian (~12 100–11 700 cal BP) was documented for the first time in lake sediments from the region. During this period, the local vegetation was characterized by cold alpine meadows and patches of communities with shrubs (Betula nana, Alnus viridis, Salix, Juniperus, Ephedra) and trees growing at some distance from the lakes. In the Early Holocene, the expansion of boreal forests, consisting of Betula, Pinus sylvestris, as well as continental Larix and Pinus cembra, reached an altitude of ~1180 m a.s.l. An important discovery was the presence of Larix macrofossils in both studied profiles, which together with pollen evidence, confirmed its local persistence from the Early Holocene to the Middle Ages. It was also demonstrtaed that Betula nana, Selaginella selaginoides, Huperzia selago most probably persisted in the area from the Younger Dryas to at least the Middle Ages or even to the modern times, surviving through the Holocene climatic optimum. The increase in grassland representatives from ~4100 cal BP and the appearance of the cultivated plants (Triticum type pollen) from ~3300 cal BP, was due to the long-distance transport of pollen reflecting the development of agriculture and settlement outside the Karkonosze Mountains. It was not until the 10th century AD that the environment underwent a stronger anthropogenic transformation. Growing economic activities (e.g. metallurgy, mining of non-ferrous metal ores, glass production, forest industry) that developed, especially from the 12th century onwards required the supply of wood raw material. The development of agriculture in the region promoted the expansion of meadows and pastures and the greatest taxonomic diversity of herbaceous plants was recorded between the 13th and 15th centuries.