A long-term biomonitoring programme has been established for many years in Baden-Wurttemberg, southern Germany, focussing mainly on environmental impacts of pollutants on vegetation and the analysis of heavy metals in litter, plant and animal tissue. The soil ecological research group at the Staatliches Museum fur Naturkunde, Karlsruhe have investigated the soil fauna at 11 selected forest sites within this programme with the specific objective of establishing a system of soil quality classification based on biological criteria. These sites represent different climatic and pedological regions as well as different levels of adverse environmental impact. Results relating to the incidence of predatory mesostigmatid mites in the study sites are reported here. Our methodology begins by ranking mesostigmatid mite taxa according to their life-history traits on an r/K-scale. A faunal maturity index, which expresses the proportion of species in a community with predominantly K attributes to those with more r attributes, can then be calculated for the fauna of any particular site. The less environmentally perturbed a soil is, the higher the value of this index. Comparative norms for the index in different forest types can be deduced by analysing published species lists from unperturbed sites. The index is a sensitive bioindication tool and a more integrative measure of the severity of environmental impact in forest ecosystems than is the more traditional measurement of heavy metal concentrations in soil Litter and earthworm tissues. (C) 1998 Elsevier Science B.V.
