Changes in structure, organic matter and microbial activity in pine forest soil following the introduction of Dendrobaena octaedra (Oligochaeta, Lumbricidae)

Epigeic earthworms [Dendrobaena octaedra (Savigny)] were introduced into intact litter-soil cores from a lodgepole pine forest. At three and six months following introduction of earthworms, changes in litter-soil structure, organic matter content (OM), basal respiration (BR) and microbial biomass (MB) were assessed. At six months 136 ± 173 and 430 ± 235 ind. m−2 of D. octaedra were present in the low and high earthworm density treatments, respectively. Initial effects were seen in the H horizon where organic and mineral material were mixed. In the high density cores after six months the F and H layers were indistinguishable, consisting entirely of casts. At six months OM decreased significantly in the H layer at both earthworm densities and OM was significantly lower in the high density cores. BR and qCO2 were not affected by earthworm density, but high earthworm density decreased MB in the FH layer primarily due to the reduction in OM in this layer.