LUMBRICID ASSOCIATIONS ON A FORMER OPEN CLAY PIT AFTER RECULTIVATION WITH DIFFERENT TREE SPECIES

The earthworm fauna was recorded from a former open clay pit five and seven years after the area had been recultivated with various tree spe cies. The highest abundances (200-245 specimens/m(2)) and biomasses (4 6.8 to 48.4 g/m(2)) were found in the following stand types: mixed woo dland of balsam poplar (various sorts) and grey alder (Alnus incana (L .) MOENCH), mixed woodland of balsam poplar (Andoscoggin) and black al der (Alnus glutinosa (L.) GAERTN.), and a pure stand of black alder. C learly lower values were found in a plot with common oaks (Quercus rob ur L.) under a dense shelterwood of naturally regenerated willows (Sal ix spec), and a plot exclusively stocked with naturally regenerated wi llows. The rapid resettlement of the backfilled, compacted clay soil i s above all explained by the high pH-values found in the surface soil The differences between the studied plots regarding total abundance an d biomass might be explained by the different qualities and amounts of litter. The highest species diversity - expressed by the Shannon-inde x - and the highest proportion of endogeic species, particularly Aporr ectodea caliginosa Savigny 1826, were calculated for the two stands wi th a mixture of alder and balsam poplar. This result could have been c aused by the lack of parent soil bed and the particularly high pH-valu e of the soils found there.