The role of soil fauna in crucial ecosystem services such as nutrient cycling remains poorly quantified, mainly because of the overly reductionistic approach adopted in most experimental studies. Given that increasing nitrogen inputs in various ecosystems influence the structure and functioning of soil microbes and the activity of fauna, we aimed to quantify the role of the entire soil nematode community in nutrient mineralization in an experimental set-up emulating nutrient-rich field conditions and accounting for crucial interactions amongst the soil microbial communities and plants. To this end, we reconstructed a complex soil foodweb in mesocosms that comprised largely undisturbed native microflora and the entire nematode community added into defaunated soil, planted with Lolium perenne as a model plant, and amended with fresh grass-clover residues. We determined N and P availability and plant uptake, plant biomass and abundance and structure of the microbial and nematode communities during a three-month incubation. The presence of nematodes significantly increased plant biomass production (+9%), net N (+25%) and net P (+23%) availability compared to their absence, demonstrating that nematodes link below- and above-ground processes, primarily through increasing nutrient availability. The experimental set-up presented allows to realistically quantify the crucial ecosystem services provided by the soil biota.

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Hirschmanniella mucronata populations isolated from two Cambodian provinces were characterised using morphological, morphometric and molecular criteria. Examination of 1024 specimens from 60 different paddy fields revealed high intraspecific variation in morphology and morphometrics, especially in tail terminus shape and stylet length. Sequence results confirmed that morphologically divergent individuals represent a single species, suggesting that neglecting morphological variation has led to an overestimation of Hirschmanniella diversity in former studies. Phylogenetic analysis of the SSU, D2-D3, LSU and ITS1-5.8S-ITS2 regions revealed three concordant clades, H. mucronata having a sister relationship with H. kwazuna and H. loofi. Plotting the diagnostic features, including tail terminus shape, stylet length and lip region morphology on the phylogenetic framework, revealed that none of them supported the clades and represented convergent features. All three molecular markers were able to discriminate all Hirschmanniella species, but the D2-D3 region was the easiest, fastest and most successful region to be amplified. Species delimitation and the diagnostic features of Hirschmanniella were re-evaluated. Hirschmanniella abnormalis and H. exacta are considered to be junior synonyms of H. oryzae and H. mannai a species inquirenda. Finally, a list of valid species with indication of synonyms and a polytomous key are provided

In terrestrial ecosystems decomposing cadavers act as resource patches affecting nutrient cycling and soil communities, but the effects on soil communities are not well known. In this study we investigated nematode community response to decomposing pig cadavers (Sus scrofa) over a one-year period. As nematodes play key roles in soil food webs and are known to respond to disturbances and nutrient enrichment, we hypothesised that they would respond to decomposing cadavers and that this response would change over time. We compared the temporal patterns of nematode density and community structure under pig cadavers, either placed directly on the ground or hung 1 m aboveground (for effects of cadaveric fluids only), with two controls, i.e., bare soil and bags filled with soil placed on the ground (fake pigsfor microclimatic effects only). In the control and fake pig treatments nematode densities, community patterns and maturity indices did not change significantly. In contrast, density increased significantly underneath the ground and hanging pigs two weeks after the beginning of the experiment, and nematode family richness, Simpson diversity and maturity index were significantly reduced in the cadaver treatments. Most nematode families responded negatively to cadavers with the notable exceptions of Rhabditidae, Neodiplogasteridae and Diplogasteroididae. The latter two were found exclusively underneath the decomposing cadavers and are promising bioindicators of vertebrate cadaver decomposition. Even though diversity, density and communities were recovering after one year, the impact of cadavers was still significant for the maturity index. These contrasting patterns illustrate how decomposing cadavers contribute to increasing local biodiversity and suggest that soil nematodes could be used as a tool to document the presence of a decomposing cadaver, or to estimate the time elapsed since death (post-mortem interval). Patterns should, however, be compared in different settings and seasons before such a tool can be validated.

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