Effects of four ecological categories of earthworms on carbon transfer in soil

Abstract

A laboratory experiment was performed to determine the effects of 4 ecological categories of earthworms on the transfer of organic carbon derived from surface litter in different soil compartments (surface casts, below-ground casts, burrow walls and surrounding soil). The earthworm species chosen were Eisenia andrei (epigeic), Lumbricus terrestris (epianecic), Aporrectodea giardi (anecic) and Aporrectodea caliginosa (endogeic). The earthworms were incubated with 13 C -labelled litter in rebuilt soil columns for 246 days. At the end of the experiment, surface casts, below-ground casts and burrow walls were significantly enriched with litter C compared to the control soil and surrounding soil. Surface and below-ground casts were most enriched. About 50% of the total organic C in the surface casts of the epigeic and epianecic species was derived from the litter compared with 40% in the casts of the anecic and endogeic species. Below-ground casts, mainly produced in this study by L. terrestris and A. giardi, were on average enriched with 47.5% 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 litter 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 other hand, the intensive burrowing activity of the anecic and endogeic species led to an even distribution of the litter C in the soil column whereas with the epianecic species the distribution was more localized.