Colonisation by enchytraeids as a suitable indicator of successful biological reclamation of post-mining technosols using alders

Abstract

Enchytraeids and earthworms were studied in a reclaimed sand mine, at a combustion waste disposal site and in natural forest stands in the Bieszczady Mountains. The study verifies the influence of three alder species (Alnus incana, A. viridis, A. glutinosa), reclaimed mine soil substrates (RMS) and combustion waste (CW) on annelid communities. Earthworms were absent in RMS and CW. Enchytraeid densities varied, from almost 2000 ind. m−2 (individuals per m2) to >9000 ind. m−2 in RMS and CW and to 30,000–60,000 ind. m−2 in natural forest soils. Soil properties strongly correlated with enchytraeid density were pH, silt content and organic carbon content. In total, eight genera and thirteen species were recorded. In combustion waste technosols, species tolerating dry conditions and high pH predominated (e.g. Henlea ventriculosa). In sand mine soils, species diversity was very low (Shannon index 0.16), but Hemifridericia bivesiculata was recorded, a species that was known within Europe only from Hungary. Alder trees, especially A. glutinosa, allowed enchytraeids to reach high population density. In soil afforested by A. glutinosa the succession stage was more advanced than in soil under A. incana because, in variants with A. glutinosa, more species classified as belonging to the transitional stage of succession (Fridericia spp.) or even preliminary climax stage of succession (Cognettia sphagnetorum), were recorded. In the variant with A. incana, Enchytraeus spp. predominated. These are considered pioneer species. The study of enchytraeids confirmed that alders should be recommended for biological reclamation.