Influence of invasion by Sosnowsky's hogweed on nematode communities and microbial activity in forest and grassland ecosystems

This study determined the effect of the invasive plant Heracleum sosnowskyi on selected soil microbial properties and the taxonomic and trophic composition of soil nematode communities in the Serpukhov district of Moscow region, Russia. We compared invaded by H. sosnowskyi (at least twenty years) and uninvaded plots in two ecosystems, forest and grassland. Soil was sampled and analysed in the autumn and spring. The forest and grassland ecosystems had substantially different soil microbial and nematode communities, but both were considerably altered by invasion. The soil microbial properties differed among the investigated plots and season, but the differences were observed to be non-significant between the invaded and the uninvaded plots. By contrast, invasion significantly negatively affected total nematode abundance and altered nematode numbers and the generic composition of two trophic groups, herbivores and omnivores, in both seasons, but significantly only in the spring. The numbers of bacterivorous, fungivorous, and predaceous nematodes were not affected by H. sosnowskyi invasion. The channel index indicated that bacteria strongly contributed to decomposition in all plots (grassland and forest), regardless of invasion status. Enrichment and structure indices suggested that resource availability and ecosystem disturbance were higher in the invaded than the uninvaded plots, but significantly only in the spring. Our results thus indicated that invasion by H. sosnowskyi influenced several nematode communities parameters while others remained unaffected, regardless of habitat were invasion take place. © 2019 The Authors