THE INFLUENCE OF SLUG (ARION RUFUS) MUCUS AND CAST MATERIAL ADDITION ON MICROBIAL BIOMASS, RESPIRATION, AND NUTRIENT CYCLING IN BEECH LEAF-LITTER

We investigated the effects of slug (Arion rufus L.) mucus and cast ma terial on litter decomposition, nutrient mobilization, and microbial a ctivity in two laboratory experiments: (1) Slug mucus and cast materia l was added to beech leaf litter (Fagus sylvatica L.), and leaching of N and P and CO2 production in microcosm systems were measured during 77 days of incubation; (2) mucus was added to beech leaf litter, and b asal respiration, microbial biomass (substrate-induced respiration), s pecific respiration (qO(2)), microbial growth ability after C, CN, CP, and CNP amendment, and lag time (time between CNP addition and start of exponential increase in respiration rate) were measured during 120 days of incubation. Leaching of N and P from beech leaf litter was sig nificantly increased in treatments with mucus or faecal material of A. rufus. Following day 3, slug mucus increased nitrification processes. Mucus addition to beech leaf litter also increased basal respiration and microbial biomass significantly. In contrast, specific respiration was not significantly affected by mucus addition, and generally decli ned until day 60 but then increased until day 120. Nutrient amendments indicated that between days 1 and 30, N was available for microbial g rowth in litter with mucus but not in control litter. Generally, the l ag time in beech leaf litter with added mucus was shorter than in cont rol litter. Lag times generally increased with age, indicating dominan ce of slow-growing microbial populations at later stages as a conseque nce of depletion of easily available C resources and nutrients. We con clude that C, N, and P cycling is accelerated by slug activity.