EFFECTS OF 4 ECOLOGICAL CATEGORIES OF EARTHWORMS ON CARBON TRANSFER IN SOIL

A laboratory experiment was performed to determine the effects of 4 ec ological categories of earthworms on the transfer of organic carbon de rived from surface litter in different soil compartments (surface cast s, below-ground casts, burrow walls and surrounding soil). The earthwo rm species chosen were Eisenia andrei (epigeic), Lumbricus terrestris (epianecic), Aporrectodea giardi (anecic) and Aporrectodea caliginosa (endogeic). The earthworms were incubated with C-13-labelled litter in rebuilt soil columns for 246 days. At the end of the experiment, surf ace casts, below-ground casts and burrow walls were significantly enri ched with Litter C compared to the control soil and surrounding soil. Surface and below-ground casts were most enriched. About 50% of the to tal organic C in the surface casts of the epigeic and epianecic specie s was derived from the Litter compared with 40% in the casts of the an ecic and endogeic species. Below-ground casts, mainly produced in this study by L. terrestris and A. giardi, were on average enriched with 4 7.5% of litter C. The litter C enrichment of the burrow wall was high and constant whatever the depth (43.3% organic C derived from the litt er on an average) with L. terrestris, whereas it was lower and tended to decrease with soil depth with A. caliginosa and A. giardi. On the o ther hand, the intensive burrowing activity of the anecic and endogeic species led to an even distribution of the litter C in the soil colum n whereas with the epianecic species the distribution was more localiz ed. (C) 1998 Elsevier Science B.V.