Interactions between earthworm species in artificial soil cores assessed through the 3D reconstruction of the burrow systems

The aim of this study was to determine the impact of the interactions betwe en different earthworm species on the individual burrowing activity and esp ecially on the characteristics of burrow systems. Towards this end, individ uals of different earthworm species (Lumbricus terrestris, Aporrectodea gia rdi, A. caliginosa) were inoculated as single or paired species treatments into artificially packed soil columns. After 8 months, the soil columns wer e scanned by X-ray computed tomography. Three-dimensional skeletons of the burrow systems were then computed to characterise the burrow systems (burro w number, total and mean burrowed length, segment distribution in relation to depth, and rate of branching). Pronounced differences between species were found. L. terrestris built a pe rmanent burrow system characterised by low burrowed length, few connections and low rate of branching. On the contrary, A. giardi and A. caliginosa du g temporary burrow systems. The burrow system of A. giardi was the most int erconnected and showed the highest total and mean burrowed lengths. Differences observed between single and paired species treatments mainly co ncerned tl;e distribution of the burrow system in relation to soil depth in the core and total burrowed length. The burrow system of L. terrestris was much less deep and showed a higher length when the species was incubated t ogether with A. caliginosa. The burrow system of A. caliginosa was much dee per when the worm was cultivated with A. giardi. Differences in the rate of branching were also shown in paired species treatments compared to single species treatments. (C) 2001 Elsevier Science B.V. All rights reserved.