Invasive Robinia pseudoacacia vs native Quercus robur: do soil nematode communities vary in tree species-specific forests?

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Abstract Although invasive tree species pose a significant threat to biodiversity, their impact on soil micro- and mesofauna has not been sufficiently investigated yet. We investigated the influence of black locust Robinia pseudoacacia L., a naturalised exotic non-native species with invasive potential on soil Nematodes. Using a paired-vice approach, we analysed how nematode communities (diversity, genus richness, trophic and functional composition, structure), differ in pure black locust stands compared with those in native neighbouring native oak ( Quercus robur ) forest. The nematodes made up incredible communities in this study, both in abundance of individuals as well as taxa number, when a total of 107 nematode genera were recorded (102 genera in black locust and 105 genera in oak forests). Contrary to our expectation however, the structure of nematode communities in oak and in black locust stands did not differ in terms of total nematode abundance, genus richness, biomass, functional and trophic composition as well as alpha diversity. Nevertheless analyses of beta diversity revealed distinct differences in nematode community composition suggesting that the taxonomic composition of nematode assemblages differed between forest types. Bacterivorous nematodes prevailed, followed by plant parasites, omnivores, fungivores and predators in both invasive black locust and native oak forests without statistical differences (p > 0.05), except plant parasitic nematodes. Both Maturity indices (MI, MI2–5), Enrichment, Structure and Channel index did not show significant responses to black locust, except for the plant parasitic index (PPI), which was found to be higher in R. pseudoacacia forests. The analysis of nematode metabolic footprints showed that black locust increased the herbivore footprint but did not significantly influence enrichment, structure, composite, bacterivore, omnivore, predator and fungivore footprints. In conclusion, invasive black locust and native oak formed similar communities of soil nematodes and likewise regulated the soil food web mainly via a top-down effect.