Processing of leaf litter in acid waters of the post-mining landscape in Lusatia, Germany

Most surface waters of the post-mining landscape in Lusatia, Germany, are characterised by severe acidity (pH<3.0). To check leaf litter decay in this environment, the first stages of leaf processing were studied under laboratory conditions and leaf breakdown rates were determined in long-term experiments in situ . The laboratory experiments exhibited leaching of soluble compounds identical to leaching in neutral water. Microbial conditioning differed strongly in acidic waters from the neutral control. In the acidic water intensive colonisation of leaves by fungi compensated for mass loss due to leaching. Phenols, known to inhibit fungal growth, could not be found in the acidic water. The long-term litter bag experiments showed very low breakdown rates (− k =0.0014–0.0037 d −1 ). Absence of shredders and moderate flow regime prevented fragmentation of leaves. Precipitation of ochre seemed to inhibit colonisation by microbial decomposers and slow down leaf decay. The incomplete leaf breakdown will lead to a specific hyporheic environment with large interstices and rapid growing sediments. This has to be considered in restoration and management of streams of the post-mining landscape.