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 c haracterised by severe acidity (pH < 3.0). To check leaf litter decay in th is environment, the first stages of leaf processing were studied under labo ratory conditions and leaf breakdown rates were determined in long-term exp eriments in situ. The laboratory experiments exhibited leaching of soluble compounds identical to leaching in neutral water. Microbial conditioning di ffered strongly in acidic waters from the neutral control. In the acidic wa ter intensive colonisation of leaves by fungi compensated for mass loss due to leaching. Phenols, known to inhibit fungal growth, could not be found i n the acidic water. The long-term litter bag experiments showed very low br eakdown rates (- k = 0.0014-0.0037 d(-1)). Absence of shredders and moderat e flow regime prevented fragmentation of leaves. Precipitation of ochre see med to inhibit colonisation by microbial decomposers and slow down leaf dec ay. The incomplete leaf breakdown will lead to a specific hyporheic environ ment with large interstices and rapid growing sediments. This has to be con sidered in restoration and management of streams of the post-mining landsca pe. (C) 2001 Elsevier Science B.V. All rights reserved.