Myriapod and isopod communities in soils contaminated by heavy metals in northern France

Soil invertebrates suffer from contamination of the soil by heavy metals. W e have studied the effects of contamination by cadmium, zinc and lead on th eir communities in soils in northern France by comparing polluted land with non-contaminated sites. We have followed the seasonal variations and effec ts of soil properties. Saprophagous invertebrates (Diplopoda, Isopoda) and Chilopoda were sampled by pitfall-trapping from February to November in fai rly contaminated areas. In addition, a Berlese extraction of the litter in two very highly contaminated sites was conducted during autumn; animals wer e also trapped during June in the same locations. The most active period fo r myriapods was spring (April and May), whereas isopods were abundant from April to the end of summer. No clear relation was found relating dominant s pecies or number of myriapods or isopods to concentration of heavy metal in the little-contaminated soils. The dominant species seemed not to be relat ed to pollution but to vegetation or soil characteristics. In the most cont aminated sites, with metalliferous grassland and a thick undecomposed litte r layer, a threshold in contamination values seemed to be reached: no isopo ds or millipedes were found, but only Chilopoda and Symphyla.