Earthworm Succession in Afforested Colliery Spoil Heaps in the Sokolov Region, Czech Republic



Earthworm communities were studied at six heap sites representing a chronosequence of Alnus glutinosa (black alder) stands (age 3–62 years) and compared with those on an unameliorated heap and in an alder stand (60 years old) on natural soil. Spoil heaps in the open-cast coal mining area near Sokolov (northwestern Bohemia) were mainly reclaimed using afforestation. No earthworms were found on the virgin heap. Young plots were colonized by euryecious epigeic earthworms (i.e., those living above soil surface), but higher proportions of endogeic species (i.e., soil dwellers), did not appear until after more than 30 years of succession. The density and biomass of earthworms increased from the youngest stand (67 individuals/m2; 5 g/m2) to the older ones (e.g., 407 ind/m2; 13 g/m2 in the 23-year-old stand). However, both parameters were low in the oldest stand (35 ind/m2; 3 g/m2), but this may have been the result of extensive soil disturbance. Earthworm populations were often higher in reclaimed sites than in the control alder stand (150 ind/m2; 7 g/m2). However, the community structures were different, with the control being dominated by the litter-feeding species, Dendrobaena vejdovskyi.