Diversity patterns and trait-specific variations in soil nematode communities associated with Solidago invasion

• Soil nematodes in relation to Solidago invasion were analyzed via DNA metabarcoding. • Nematode ASV richness and functional diversity were lower in invaded soils. • Unlike ASV richness, functional diversity of herbivores was higher in invaded soils. • Nematode community structure varied with invasion, season, and soil moisture. • Network complexity was lower in invaded soils, mainly due to fewer herbivore links. Plant invasions substantially alter both aboveground and belowground communities. Invasive species modify habitats, directly and indirectly affecting soil biota and functions. Soil nematodes, the most diverse and abundant faunal groups in the soil food web, play a crucial role in shaping plant-soil feedback mechanisms. Using a DNA metabarcoding approach, we conducted the first in-depth analysis to examine the relationship between nematode assemblages and the dominance of the aggressive exotic species, Canadian goldenrod ( Solidago canadensis ), by comparing invaded and uninvaded (control) plot pairs in a protected urban meadow over two consecutive growing seasons. In Solidago stands, nematode taxonomic diversity declined, particularly at the ASV level, with herbivores and fungivores contributing most to this decline. In contrast, bacterivore genus richness was higher in invaded soils compared to control soils. Although overall functional diversity declined, herbivorous nematodes were functionally more diverse in invaded soils. Community composition differed significantly between invaded and uninvaded soils, with influences from soil moisture and season. Bacterivore frequency (mainly enrichment opportunists) was higher, while herbivore frequency (particularly facultative endoparasites) was lower in invaded soils. These changes led to a simplification of network structure, reducing herbivore connections and increasing the roles of bacterivores and predator-omnivores. Our results suggest that the invasion strategy of S. canadensis relies mainly on two key plant-soil feedback mechanisms: (1) release from herbivory pressure, and (2) enhanced nutrient acquisition or supply via bacterial pathways. By integrating taxonomic, trait-based, and network approaches, this study highlights how plant invasions can reshape belowground biodiversity and alter ecosystem functioning.