The role of soil animals is in general poorly known. Several studies have shown that soil fauna may accelerate the decomposition rate and contribute to the release of plant nutrients, but there is a need for more exact quantitative knowledge in this field (e.g., Anderson et al. 1983; Seastedt 1984; Hagvar 1988; Abrahamsen 1990; Setala and Huhta 1990, 1991; Setala et al. 1990; Huhta et al. 1991).