Soil chemistry and tree nutrition of post‐lignite‐mining sites

Abstract

AbstractDue to the mixture of different geological overburden sediments during the mining process in the Lusatian lignite district (E Germany), soils developing on mine spoils show special characteristics that are very different from naturally developed soils of the surrounding region. In this context, high contents of lignitic fragments and pyrite dominate the early stages of pedogenesis. Amelioration measures utilizing large amounts of fly ash additionally alters top soil properties. A chronosequence approach was used to study soil development at sites afforested with pine over a period of 60 y. In the ameliorated top layers, pH values are clearly elevated, whereas the unameliorated subsoils remain very acid (pH 2.5–2.9). Total carbon stores of the soils are very high. Geogenic organic‐matter contents increase the CEC of the sandy substrates considerably. Secondary minerals such as gypsum govern soil‐solution composition revealing distinct depth gradients. Low pH and extremely high ion concentrations are found especially in the subsoils. Eventually these high values decrease mainly due to completed pyrite oxidation, leaching of soluble phases, and precipitation of secondary minerals. Despite unfavorable soil chemical conditions, the growth and nutritional status of the pine stands at these mine sites is surprisingly good. The content of lignitic fragments and secondary minerals in the soils seems to play an important role for the element cycling and nutritional status of the established forest ecosystems. However, the impact of disturbance provoked by mining operations presents a long‐term effect. The chronosequence sites studied show clear effects of disturbance even after several decades.