Effects of macro-decomposers on litter decomposition and soil properties in alpine pastureland: A mesocosm experiment

To analyse decomposition dynamics on abandoned alpine pastureland where organic material accumulates on the soil surface a mesocosm experiment was conducted. Twelve treatments were set up in a two-factorial design analysing food preferences (grass or dwarf shrub litter) of primary (Lumbricus rubellus, Dendrobaena octaedra, Cylindroiulus fulviceps) and secondary macro-decomposers (Octolasion lacteum, Enantiulus nanus), and their effect on decomposition processes, soil and microbial parameters (pH, soil organic matter content, C/N ratio, soil aggregate stability, basal respiration, microbial biomass).The primary decomposers L. rubellus and C. fulviceps strongly increased decomposition, while secondary decomposers and the presence of both a primary and a secondary decomposer had no or even negative effects on litter breakdown. Surprisingly, L. rubellus and C. fulviceps preferentially fed on dwarf shrub litter which we assumed to be of low food quality. It is concluded that factors other than the quality of the litter material are responsible for the reduced litter decomposition on abandoned alpine pastureland.Most soil parameters (pH, soil organic matter content, C/N ratio, basal respiration) were only slightly affected by the presence of decomposer species. Effects of interactions between earthworms significantly increased soil aggregate stability by 10–15% and microbial biomass by up to 121%. On the other hand the presence of millipedes significantly decreased soil aggregate stability and microbial biomass. Although most soil chemical and microbial parameters were only slightly affected by the presence of soil animals, presumably due to the short incubation time, statistical analyses showed the presence of macro-decomposers to be an important factor for litter decomposition.