Comparing recent and buried Chernozems/Phaeozems in Central Germany : soil transformation and human impact since 3.8 ka

Abstract

Chernozems and Phaeozems in Central Germany have been subject to both natural alterations and human influences for millennia. This study systematically compares a buried Early Bronze Age Chernozem, preserved under the Bornhöck burial mound, with a neighboring surface soil to analyze soil transformation and human impact over the past 3.8 ka. Our results indicate that, unlike in more humid Central European regions where former Chernozems/Phaeozems have been entirely transformed into Luvisols, soils in the study area have undergone slower alterations due to the dry regional climate and high carbonate content of the parent material. Key pedogenic processes include gradual decalcification, black carbon decomposition, and weak clay illuviation. Before and during the Early Bronze Age human impact was minimal, limited mainly to shallow plowing (<20 cm) and phosphorus enrichment from human and/or animal excrements. Especially since the industrialisation human impact strongly increased, what is evident in higher values of magnetic susceptibility, the enrichment of heavy metals and sulfur likely due to fly ash deposition from lignite-burning power plants, and shifts in the isotopic composition of soil organic matter from agricultural practices. The most pronounced human impact since that time has been secondary recalcification due to fly ash input, which halted the natural transformation of Chernozems/Phaeozems into Luvisols and modified soil biota conditions. Given ongoing climate change and increasing regional temperatures, decalcification of these secondary carbonates should strongly decelerate or even stop.