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 qCO 2 were not affected by earthworm density, but high earthworm density decreased MB in the F H layer primarily due to the reduction in OM in this layer.