Scenario for undirected progression of extremely acidic streams in the Lusatian post-mining landscape, Germany

The environment in former open-pit brown coal dumps differs from natural conditions. This paper gives the most likely scenario of the long-term progression of streams planned in the re-deposited lowlands in Lusatia, Germany. The scenario is based on observations of streams in old abandoned mines. The stream's progression is controlled by non-cohesive virgin soils, extremely acidic iron-rich water, specific stream and bank vegetation, and incomplete in-stream decay of plant litter and wood. The scenario differs from progression of natural streams. It is a sequence from an open-land stream to a woodland stream and finally to a wetland stream. Key processes responsible for these transitions are strong deposition of iron oxyhydroxides, incomplete decay of leaves and wood, and reduced vitality of riparian trees. Uncertainties of the scenario and management conflicts that may emerge from undirected stream progression are briefly discussed.