The belowground food web holds a big part of the associated biodiversity in forest ecosystems and plays a major role in essential ecosystem processes, e.g. litter decomposition and nutrient turnover. So far, important interactions between diversity and composition of above-and belowground food webs have been observed. However the effects of tree species diversity on the belowground food web are so far not conclusive. This study aims at elucidating the effect of tree species mixtures, species diversity and trait diversity on the composition of the earthworm communities in European forests. Experimental platforms of planted tree species diversity assemblages in Finland (Satakunta) and Germany (Biotree) are therefore intensively sampled for earthworms using the combined mustard extraction/hand sorting method. First results are reported and discussed and diversity effects are evaluated with overyielding tests.