Organic matter composition and the protist and nematode communities around anecic earthworm burrows

Abstract

By living in permanent burrows and incorporating organic detritus from the soil surface, anecic earthworms contribute to soil heterogeneity, but their impact is still understudied 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.

Nitrogen Status and Dynamics in German Forest Soils

“…Nitrogen stock is one of the parameters with highest small-scale spatial variability. Next to the distribution of fine roots and earthworm activity (Meier and Leuschner 2010;Andriuzzi et al 2016), the spatial variability of litterfall, parent material, pH, and microclimate (Sabatini et al 2015), the distribution of stagnant conditions on the plot (Bekele et al 2013), and the presence of N fixing bacteria in the root system of a few tree species (Rodriguez et al 2011) were identified as causes for this variability. Mellert et al (2008) systematically investigated the variability of NFSI soil parameters on 33 Bavarian plots along a sampling grid of 3 m distance and discovered the least spatial autocorrelation in N stocks, while other parameters like pH or C/N ratio showed lower spatial variability on small scales.…”

Earthworms Building Up Soil Microbiota, a Review

“…This enrichment in organic matter mainly results from earthworm food choice (Curry and Schmidt, 2007), its digestion and excretion of intestinal or cutaneous mucus that can be cementing (Shipitalo and Le Bayon, 2004) or used as an energy source (Lavelle et al, 1995). Therefore, in addition to shaping soil structure, earthworms also have an important impact on soil organic matter dynamics and microorganisms in their gut, casts and drilosphere (Andriuzzi et al, 2016) and are also identified as biochemical (Lavelle et al, 2016) or autogenic ecosystem engineers (Lawton and Jones, 1995).…”

Towards an ecology of soil microplastics

“…These casts and burrows comprise a unique microhabitat that soil ecologists term the drilosphere (Andriuzzi, Bolger, & Schmidt, 2013;Sharma, Chandra, & Kanta, 2018). Drilosphere habitats have unique physicochemical properties (Görres & Amador, 2010;Görres, Savin, & Amadaor, 2001) and are hotspots of microbial and faunal activity (Andriuzzi et al, 2016;Nuutinen, Butt, Hyvälouma, Ketoja, & Mikola, 2017). By bringing these communities into close contact with microplastics, earthworms could enable microplastic effects on other soil organisms that would not otherwise occur, or alter the severity of microplastic exposure.…”