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

Abstract

Due 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.

Synergic hydraulic and nutritional feedback mechanisms control surface patchiness of biological soil crusts on tertiary sands at a post-mining site

“…Landscape reclamation, including soil, vegetation and ecosystem management is challenging, because the material dumped is tertiary carboniferous and pyritic sands which are often poor in nutrients, have a low water holding capacity, contain high amounts of potentially toxic elements and have an extremely low pH (Schaaf and Hüttl, 2005). In this context, new land surfaces in post-mining areas can be regarded as initial ecosystems comparable to newly created landscapes by volcanic activity, to glacier retreat areas in arctic or alpine environments, or to coastal and inland sand dunes (Schaaf et al, 2011).…”

Origin of Nitrogen in Reforested Lignite-Rich Mine Soils Revealed by Stable Isotope Analysis

“…These areas are predominantly restored by afforestation with pine after initial amelioration by addition of CaO and NPK fertilization . During the early stage of mine soil development the element budgets of these sites are controlled by pyrite oxidation releasing large amounts of iron and sulfuric acid, inducing enhanced weathering of primary minerals and precipitation of secondary minerals , .…”

Landscape Development From Point Zero

“…Without any further countermeasures, pyrite containing mine soils may show pH values below 3.0 (Schaaf and Hüttl 2005). This effect of AMD can be reduced by soil amelioration measures as shown below.…”

“…Thus, the application of alkaline substances in larger quantities is common practice for many sites in the Lusatian post-mining landscapes. Today, lime is used but in former decades fly ash obtained from coal combustion was frequently applied for alkalization of substrates (Schaaf and Hüttl 2005).…”