SURFACE CAST PRODUCTION BY THE EARTHWORM APORRECTODEA-NOCTURNA IN A PRE-ALPINE MEADOW IN SWITZERLAND

Field and laboratory experiments were carried out to describe the effe cts of Aporrectodea nocturna on soil characteristics in a pre-alpine m eadow and to support the development of a model of cast production. In the pre-alpine meadow, increased cast production, first observed abou t 20 years ago around a newly planted hedge, was recorded to a distanc e of maximal 170 m from the hedge. Numbers of A. nocturna between 130 and 165 m from the hedge decreased from 164 to 16 individuals m(-2). I n the same area cast production steadily decreased from about 1.5 kg m (-2) week(-1) to nil, the plant community structure changed and the mi crobial biomass decreased, but the root biomass and the moisture conte nt did not change. Laboratory experiments demonstrated that high cast production was not a specific feature of the A. nocturna population no r of the soil in the meadow. Diapause of A. nocturna was terminated in the laboratory during September. A model of cast production potential by the earthworm A. nocturna was established using laboratory determi nations of the relationships with body weight, temperature, acid water potential. The model was shown to predict cast production in the fiel d given the assumption that the water potential was 0 MPa. According t o the model, 81% of surface cast production was by juveniles, and 19% by adults of A. nocturna.