DISTRIBUTION OF SOIL ANIMALS IN PATCHILY CONTAMINATED SOIL

Distribution of soil animals with respect to patchy chemical contamina tion was studied in microcosms containing reconstituted coniferous for est floor. Soil materials were defaunated and soil organisms were rein oculated into a mesh basket in the centre of each microcosm. Part of t he humus layer was contaminated with three concentrations of sodiumpen tachlorophenate (0, 50 or 500 mg PCP kg(-1) of dry humus) and put into mesh baskets (two per concentration) around the central patch. No dif ferences in dispersion ability from the reinoculated patch were found between microarthropod species. PCP decreased microbial biomass in the humus. Numbers of collembolans were significantly lower in the contam inated patches than in the clean ones. The same trend was observed in the numbers of other microarthropods (mainly oribatid mites). Microart hropods were found to move intensively in the microcosm and taxa compo sition in the patches were different between samplings. Although PCP r educed numbers of individuals it did not affect diversity of the micro arthropod community. Enchytraeids moved slowly from the central patch and number of individuals was lower in the most contaminated patches t han in the other patches. Specimens of Rhabditis spp. were the first n ematodes found in the surrounding patches. Later on other bacterial fe eding nematodes were dominant in the patches. Species of genus Acrobel oides were dominant nematodes in the highest PCP concentration. It can be concluded that despite relatively good mobility of the soil animal s, even small scale patchy contamination in the soil may have an influ ence on spatial distribution of the animals. Copyright (C) 1996 Elsevi er Science Ltd