What can element budgets of false-time series tell us about ecosystem development on post-lignite mining sites?

The post-lignite mining landscape in Lusatia, Germany, is dominated by sand y substrates of Tertiary and Quaternary sediments. Lignite and pyrite conte nts of varying amounts can result in extremely phytotoxic site conditions. To establish pine stands on these sites, large amounts of CaO were used for amelioration. The development of these ecosystems in 2-60-year-old pine st ands on two typical substrates in a 'false-time series' approach was studie d. Continuous measurements of weather data, soil tensions and soil water co ntents, together with regular sampling of rainwater and soil solutions at d ifferent soil depths, were used to calculate element fluxes through the eco systems and outputs from the soil. Soil solution compositions indicate very high spatial and temporal dynamics. Over time, sharp depth gradients are f ormed as a result of amelioration and due to soil forming processes. Acid p roduction by pyrite oxidation, weathering of primary minerals, precipitatio n of secondary salt and mineral phases, and leaching of salts down the prof ile are the dominating processes at the lignite and pyrite containing sites . These processes result in long-term soil and site conditions that are ver y different from pre-mining conditions or compared to non mined soils of th e region. Soil solutions are mainly composed of Ca,, Al,, Fc,, and SO,, dep ending on soil pH and pyrite content. The dynamics in lignite- and pyrite-f ree sands are much less pronounced and overall show much lower concentratio ns. The element outputs from the systems on pyritic substrates can reach ve ry high levels. (C) 2001 Elsevier Science B.V. All rights reserved.