The impact of a copper gradient on a microarthropod field community

In order to evaluate the power of laboratory toxicity tests to predict the situation in the field, soil microarthropods were studied at the population and community levels in a copper contaminated field, and data were compared to the outcome of single species laboratory tests in the same soil type from a companion study. In addition to copper, the influence of several soil characteristics and plant cover data on soil microarthropod abundance and distribution was tested. Total microarthropod abundance was highest at intermediate copper concentrations, and linearly related to grass biomass. For single species populations no clear picture of abundance in relation to soil copper was seen. Two collembolan species, Folsomia quadrioculata and Folsomia fimetaria, were among the most sensitive. The Shannon-Wiener index of biodiversity decreased linearly with increasing soil copper concentrations. The application of multivariate statistics showed copper to be the parameter best fitting the distribution of microarthropod species in the field. A distinction could be made between sampling points with 50-199 mg Cu/kg soil and those with higher copper concentrations. The species composition of the microarthropod community was not correlated with plant species diversity or total grass biomass, but was affected by a nearby row of tall trees. Community analysis of field data proved as sensitive as laboratory testing, and seemed superior to single species field population data concerning detection of copper effects on soil microarthropods.