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Can Lumbricus terrestris be released in forest soils degraded by compaction? Preliminary results from laboratory and field experiments
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International audience. Compaction is an important and increasing threat for forest soils. In addition to preventive approaches, reme-diation solutions are needed. Among them, the release of anecic earthworms is thought to be a promisingapproach. However, most previous attempts in compacted forest soils failed to retrieve the introduced earth-worms. To gain more insight on the feasibility of releasing Lumbricus terrestris adults, we performed both alaboratory and a field study. Under laboratory conditions, the L. terrestris behavior was assessed in repacked soilcores with increasing soil bulk density (1.3, 1.4, 1.5 and 1.6 g cm 3 for a silt-loam soil). We found that burrowing(burrow volume, diameter and maximal burrow depth) as well as casting and feeding behavior were significantlyreduced ( 95%, 50% and 65%, respectively) at the highest bulk density compared to the lowest. For the fieldstudy, we released L. terrestris in a 10-year old experimental forest site in which two factors were studied: soilcompaction and liming. To prevent them from escaping, the earthworms were caged in PVC cylinders in com-pacted (or not) and limed (or not) plots. After six months, we assessed the burrowing behavior and litter con-sumption of the earthworms. L. terrestris showed a good survival rate (>52%), as assessed by surface activity, inall situations. Liming had no detectable effect whereas the increase in bulk density in compacted plots (from 1.29to 1.36 g cm 3) led to a significant decrease in the burrow volume. This suggests that, when forced to do so,L. terrestris is able settle in compacted and acidic soils and then perform its functional role (burrow creation andlitter burial).
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