The non-native plant invader in the beech forest does not make nematode communities less structural

Abstract Invasive plants are capable of homogenizing the above and belowground biota and are together with climate change recognized as one of the biggest threats to global biodiversity. Soil nematode communities reflect the surroundings they inhabit and they are used as biological indicators of soil condition. In this study, we evaluated soil properties and nematode communities in the beech forest floor covered by dense vegetation of invasive Impatiens parviflora (small balsam) and compared them with uninvaded sites. We assumed that the invasion of I. parviflora could be influencing soil fauna through their litter and also could be changing several soil properties which consequently affect soil nematode communities. A total of 52 nematode species were found in the soil samples. The mean number of species varied from 18 to 31, but did not significantly differ between invaded and uninvaded plots across all sampling dates. Nevertheless, redundancy analysis indicated that the nematode community in plots with small balsam differed significantly from that in uninvaded plots, reflecting different proportions of genera in the two communities. Small balsam invasion significantly enhanced the relative abundance of bacterivores whereas the decreased abundance of plant parasites and root-fungal feeders, mainly in spring and summer sampling dates. Ordination of nematode species along the structure index and enrichment index trajectories revealed maturing food web, low to moderately disturbed in the I. parviflora invaded soils as well as uninvaded forest plots. Decomposition channels of soil food webs in both plots were balanced, fungal-bacterial mediated, nonetheless low values of channel index suggesting prevailing bacterial decomposition. Our study reveals, that expansion of I. parviflora moderates influenced composition of nematode communities, and the soil food web, increased soil nitrogen, carbon and C/N ratio, whereas did not modify soil acidity.