The effects of earthworm species on organic matter transformations and soil microbial communities are only partially related to their bioturbation activity

Résumé 0

This dataset was acquired to investigate the effects of earthworm species on soil bioturbation, biogeochemical transformations of soil organic matter, and soil microbial communities under controlled conditions. Six earthworm species (Lumbricus terrestris, Allolobophora chlorotica, Octolasion cyaneum, Octodrilus complanatus, Aporrectodea caliginosa meridionalis and Microscolex dubius) were incubated in soil cores with soil and alfalfa litter for 6 weeks, at 16 °C. The soil is a silty loam sampled in an agricultural plot in Estrées-Mons, northern France. Two series of soil cores were performed, including controls (3 with litter and without earthworm, 3 without litter and without earthworm per series). At the end of the incubation period, the entire cores were scanned using a medical scanner for bioturbation measurements. All images were processed the same way to compute the number of macropores (set of connected voxels), the volume of burrows (sum of all the macropore volume), the vertical barycentre of the burrow system (the centre of mass of the burrow system when only the vertical dimension is taken into account), the diameter (assessed as the median of the diameter of all vertical pores with a circularity > 0.8) and burrow system continuity (number of burrows whose vertical length was higher than 30% of the depth of the soil core). In cores with earthworms, the soil was sampled from three different compartments: surface casts, the drilosphere (i.e., soil surrounding burrows, up to 4 mm from the burrow walls), and surrounding bulk soil. In control cores without earthworms, the soil was sampled from three different depths: surface (0-2 cm from the soil surface), middle (8-12 cm) and bottom (18-22 cm). Biogeochemical measurements, performed on the different soil compartments, included : soil humidity, dissolved organic carbon (C), total C, total nitrogen (N), mineral N, organic N contents, C to N ratio, nitrate (NO3-) and ammonium (NH4+) contents at the time if sampling and after 8 days in incubation at 20°C, carbon dioxide (CO2) fluxes measured with Isotope-ratio mass spectrometry (IRMS) method after 46, 91, 136, and 181 hours of microcosm incubation at 20°C, CO2 fluxes measured with sodium hydroxide (NaOH) traps after 46, 94, 142, and 190 hours of microcosm incubation at 20°C. Microbiological measurements, performed on the different soil compartments, included: total DNA concentration in soil, 16S rRNA copy number, 18S rRNA copy number, bacterial operational taxonomic unit (OUT) composition, and Shannon index, calculated on bacterial OTU. This work was supported by the the AgroEcoSystem Division of INRAE through the funding of the “GloWorms” project.