Holocene vegetation history and soil development reflected in the lake sediments of the Karkonosze Mountains (Poland)

A 11-m-long lake sediment core of a mountain lake situated at 1225 m a.s.l. in the Karkonosze Mountains (Poland) provided a unique, multi-proxy archive to reconstruct natural and human-induced environmental changes over the entire Holocene period. Pollen analyses allowed for the local and regional reconstruction of vegetation history. The chemical composition of the core and the determination of amorphous Fe and Al phases enabled to trace back soil formation in the surrounding catchment. About 11 ka ago, birch-pine and pine-birch communities started to develop in the Preboreal chronozone. Subsequently, the vegetation cover changed to Corylus–Picea–Abies + Fagus in the higher and middle mountain zones, and to Ulmus–Quercus–Carpinus in the mountain foreland and footslopes. The decline of forests that started in the 11th century because of clearing was accompanied by the expansion of grasses, both as pastures in the mountains and cereal crops in the foreland. At the same time, the mining and smelting gave rise to environmental pollution with heavy metals (Pb, Cu and Zn) at a regional scale. Combined geochemical and palynological data indicated relationships between vegetation type, sediment texture and its elemental composition. This relationship seemed to be linked to climatic conditions and surface erosion intensity. A first progressive soil-forming phase occurred from 10.9 until about 8.4 ka cal. BP. Rapid and strong soil erosion (regressive phase), related to rapid climate deterioration, occurred at about 8.4 ka cal. BP. Thereafter, continuous soil formation (progressive phase) and podzolization in the Boreal and Atlantic continued until about 1 ka BP when strong human impact (deforestation) led again to a regressive soil evolution