SOIL PROCESSES AS INFLUENCED BY HEAVY-METALS AND THE COMPOSITION OF SOIL FAUNA

1. The effects of heavy metals (Cu and Ni) on soil processes were stud ied experimentally in forest microcosms as a function of the presence of different groups of soil fauna (nematodes, microarthropods and ench ytraeids). 2. The soil respiration rate was measured at intervals and water leachates were analysed twice for mineral-N. At the end of the e xperiment, the mass loss of birch leaf litter was determined. 3. The s oil respiration and nitrification rates were significantly affected by heavy metals, with lower rates observed in the contaminated soil (200 + 100 mg kg(-1) Cu + Ni). In contrast, concentrations of ammonium-N w ere higher in the leachate from the contaminated soil compared to the control soil. There were, however, no significant differences in litte r mass-loss among metal concentrations. 4. The soil respiration rate w as affected only slightly by the composition of the fauna, whilst ther e were significant differences in the amounts of mineral-N leached fro m microcosms representing different faunal assemblages. 5. Microcosms containing the enchytraeid Cognettia sphagnetorum (Enchytraeidae) rele ased significantly more mineral-N than all the other units in both con trol and contaminated soils, showing the integral role of enchytraeids in N-dynamics.