Annelid coenoses of wetlands representing different decomposer communities

Annelid coenoses in wet soils reveal specific characteristics in relation to the prevailing complex of abiotic and biotic factors effective in these soils. Especially, the presence or lack of oxygen in the topsoil is of great influence for species composition and vertical distribution of annelids in wet soils. Some annelids, for example most of the smaller enchytraeids, avoid the anaerobic conditions by inhabiting only the uppermost layer of the soil. Others have developed a tolerance against low oxygen contents, either by physiological or by behavioural adaptation. In particular, some earthworm species are capable of penetrating anaerobic soil zones. Besides soil moisture conditions, base saturation and acidity are decisive for the species composition in soil. While some annelid species are comparatively indifferent to soil moisture and acidity, others tolerate only a rather narrow range of these parameters. For the latter, indicator values for soil reaction and soil moisture have been defined previously. Based on this knowledge the species composition found in a soil gives a differentiated picture of the prevailing living conditions. Furthermore, the occurrence of characteristic species allows us to determine the decomposer community for a given site. The information derived from determining the decomposer community integrates the influence of abiotic and biotic conditions fluctuating over time. The counteractions between water balance and decomposer community are discussed on the basis of data from various wetland habitats in Germany.