Acquisition of microbial communities and enhanced availability of soil nutrients by the isopod Porcellio scaber (Latr.) (Isopoda : Oniscidea)

In microcosm experiments Porcellio scaber increased litter disappearance of oak and alder litter. Alder litter disappeared at more than twice the rate of oak litter. Soil texture did not influence the disappearance of oak lit ter; however, disappearance of alder litter was enhanced on silt rather tha n on sand. P, scaber enhanced microbial communities (i.e. microbial respira tion and microbial biomass) on both silt and sand when feeding on either al der or oak. Overall, microbial respiration increased 10-fold when isopods f ed on oak litter on sand and 20-fold when isopods fed on alder litter on sa nd. On silt, the initially high microbial respiration remained constant whe n isopods fed on oak and doubled when they fed on alder litter. In all trea tments without P. scaber there was a decrease in microbial respiration over the 12-week experimental period. The availability of macronutrients (C-org , N-tot, P, K, Mg, Ca) in the topsoil was increased when P. scaber fed on a lder litter but less pronounced when P. scaber fed on oak litter. Using san d as a substrate, there was an apparent increase only for C-org, Mg and Ca; on silt, increases in C-org, N-tot and P were measured. Under field condit ions the contribution of P. scaber to nutrient fluxes will be higher on san d than on silt.