DYNAMIC INTERACTIONS BETWEEN FUNCTIONAL-GROUPS OF SOIL ARTHROPODS AND MICROORGANISMS DURING DECOMPOSITION OF CONIFEROUS LITTER IN MICROCOSM EXPERIMENTS

Using microcosms containing decomposing Pinus nigra litter, the effects of introducing two species of soil arthropods, the fungivorous collembolan Tomocerus minor and the detritivorous isopod Philoscia muscorum, have been studied. The effects of these animals on microbial respiration, on dehydrogenase and cellulase activity, and on the concentration of exchangeable macronutrients (Ca2+, Mg2+, K+, NOinf3sup-, NHinf4sup+, POinf4sup3-) were measured. Both species enhanced microbial activity and the concentration of exchangeable nitrate, ammonium, and phosphate. Ca2+ and Mg2+ concentrations were lowered in the microcosms with animals. The differences between the two species were mainly quantitative, and it appears that the effect of isopods is direct, whereas the collembolans show direct and indirect effects. Positive effects of the presence of animals were found when microbial activities or concentrations of exchangeable nutrients in microcosms without animals were low; negative effects were found when they were relatively high. Thus, soil arthropods have a buffering role in soil processes. These results ae discussed against a background of a supposed succession of sugar fungi/bacteria to more slowly growing decomposing fungi. © 1990 Springer-Verlag.