Organic matter composition and the protist and nematode communities around anecic earthworm burrows
Andriuzzi, Walter S. | Ngo, Phuong-thi | Geisen, Stefan | Keith, Aidan M. | Dumack, Kenneth | Bolger, Thomas | Bonkowski, Michael | Brussaard, Lijbert | Faber, Jack H. | Chabbi, Abad | Rumpel, Cornelia | Schmidt, Olaf
By living in permanent burrows and incorporating organic detritus from the soil surface, anecic earthworms contribute to soil heterogeneity, but their impact is still under-studied in natural field conditions. We investigated the effects of the anecic earthworm Lumbricus centralis on fresh carbon (C) incorporation, soil organic matter composition, protists, and nematodes of a Cambisol under grassland. We used plant material labelled with stable isotope tracers to detect fresh C input around earthworm-occupied burrows or around burrows from which the earthworm had been removed. After 50 days, we sampled soil (0-10 cm depth) in concentric layers around the burrows, distinguishing between drilosphere (0-8 mm) and bulk soil (50-75 mm). L. centralis effectively incorporated fresh C into the drilosphere, and this shifted soil organic matter amount and chemistry: total soil sugar content was increased compared to unoccupied drilosphere and bulk soil, and the contribution of plant-derived sugars to soil organic matter was enhanced. Earthworms also shifted the spatial distribution of soil C towards the drilosphere. The total abundance of protists and nematodes was only slightly higher in earthworm-occupied drilosphere, but strong positive effects were found for some protist clades (e.g. Stenamoeba spp.). Additional data for the co-occurring anecic earthworm species Aporrectodea longa showed that it incorporated fresh C less than L. centralis, suggesting that the two species may have different effects on soil C distribution and organic matter quality.
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