Origin, age and transformation of Chernozems in northern Central Europe – New data from Neolithic earthen barrows in SW Poland

Among the clay-illuviated soils, dominant in the loess belt in southern Poland, islands of chernozemic soils are distinguished by their spectacular agricultural productivity. However, those soils are not marked as Chernozems/Phaeozems in European and world soil maps due to their common excessive wetness and doubts regarding their origin. Well-preserved earthen barrows of the Funnel Beaker culture, discovered recently in Muszkowice (SW Poland) offer a unique possibility of pedo-archaeological reconstruction (the first of such in Poland) of the pre- and post-Neolithic development of soil cover in loess-dominated areas, and explanation of the existing differentiation of soil cover into neighbouring Chernozems and Retisols. The buried chernozemic soil (Phaeozem) in Muszkowice started to develop in the Late Pleistocene period (mean residence time of humus – 12,670–13,000 cal BP). Until the burial (ca. 5480–5310 cal BP), an at least 22-cm thick mollic horizon has developed, with secondary carbonates accumulation at ca 80 cm. The barrow mound soil, constructed entirely of initially humus-rich topsoil material, has transformed into Retisol with fully developed, thick eluvial and illuvial (argic) horizons, and still preserved a high content of humus in the barrow mound soil profile. Further, the surrounding soils are entirely altered into Retisols (with secondary carbonates starting at 135–160 cm). Taking into account the palynological reconstruction from the nearest pollen profile in the loess-covered area, a crucial importance of the open-canopy (mainly oak) forests is concluded for the persistence of Chernozems under a temperate (increasingly moist) climate from the Early Holocene to the Neolithic period. In turn, the close-canopy broadleaf forests (mainly beech) are considered to be responsible for the rapid transformation of Chernozems/Phaeozems into Retisols/Luvisols in the Late Holocene. Chernozems have persisted and probably even rejuvenated only in the areas of permanent settlement since the Neolithic until the present time, where human activity (farming, pasturing) has eliminated a continuous broadleaf/beech close-canopy forest cover.