EFFECTS OF PENTACHLOROPHENOL IN FOREST SOIL - A MICROCOSM EXPERIMENT FOR TESTING ECOSYSTEM RESPONSES TO ANTHROPOGENIC STRESS

Changes in the structure and function of a soil decomposer community a nd growth of birch (Betula pendula) due to chemical contamination were studied in laboratory microcosms. Sodium pentachlorophenate (PCP) was added to the humus layer of a simulated forest soil at three nominal concentrations (0, 50 and 500 mg kg(-1) dry mass). After two growing p eriods (48 weeks), there were more small soft-bodied mites, but less c ollembolans and microbial biomass, in the higher PCP concentration tre atment than in the other treatments. Number of enchytraeids were signi ficantly reduced and fungal-feeding nematodes became extinct in the so il with the higher PCP concentration. Soil respiration did not change due to PCP contamination. Diversity of soil fauna tended to decrease w ith increasing PCP concentration. Number of faunal taxa were not influ enced by PCP. Mainly due to reduction of enchytraeids, total animal bi omass was significantly lower in the higher PCP concentration treatmen t than in the other treatments. At week 8, leaching of nutrients was g reatest in the higher PCP concentration treatment. At the end of the e xperiment no significant changes in soil pH and NH4+-N content of the soil were found. Birch growth and N concentration of the leaves were r educed with the higher PCP concentration. We assume that direct toxici ty of PCP at the beginning of the experiment and changes in the decomp oser community structure (mainly reduction of enchytraeids and changes in microflora) due to PCP were responsible for the lowered primary pr oduction in the systems.