State of knowledge of earthworm communities in German soils as a basis for biological soil quality

Abstract

Within a project aiming to improve the preconditions for the protection of the habitat function of soils in Germany, the database Bo-Info was established, in which soil-biological data from permanent soil monitoring sites of several German states as well as from the literature was compiled. Soil-biological data _mce_on the occurrence and abundance of earthworms were analysed with respect to their distribution and relation to site (habitat type, land use) and soil properties (pH, texture, organic matter). Reliable data for earthworms were available from 294 sites. In total, 32 species (all species known to occur in Germany) were present in the database, 10 of which were very common. Ecological preferences regarding land use, pH, soil organic matter (SOM) and texture were derived for these 10 species. The occurrence of earthworms at the species and ecological-group level is determined by land use and soil pH value and less by soil texture. A clear distinction between epigeic species on the one hand and endogeic and anecic species on the other hand was found regarding SOM. Earthworm communities of habitat types representing the four major land use types (grassland, crop sites, deciduous and coniferous forests) clearly differed. Using three examples from different land use forms, typical species could be identified at the next sub division level of habitat types, provided a sufficient number of data was available. As a result, qualitative expectation (= reference) values (species richness and composition) are proposed for the most important habitat types (e.g. different types of crop sites, grassland and coniferous forests). Due to their ecological relevance, the use of earthworms for soil biological site classification and assessment is recommended.