Soil invertebrate biodiversity and functionality within the intensively farmed areas of the Po Valley

Although agricultural activities can strongly affect soil biodiversity and health, with consequences on the provisioning of soil biota-mediated functions, their specific impact on soil invertebrate communities is far from being fully elucidated. In this study, the invertebrate communities associated with the soils of six habitat types, including both semi-natural and cropping systems, of one of the most intensively farmed areas in Europe, the Po Valley (North Italy), were characterized using the eDNA metabarcoding approach. The aims were to examine the variation in the taxonomic and functional diversity among the habitats and evaluate the relation between the disturbance caused by the main agronomic practices adopted in the area and the community diversity. Overall, the invertebrate communities were found to substantially differ in terms of taxonomic and functional diversity between the six habitats considered. For example, cornfield and rice paddy showed the highest diversity of annelids and the lowest one of nematodes. Woodland was found to host the most unique soil fauna, while grassland shared the majority of its soil taxa with almost all the other habitat types. The trophic groups had significantly lower diversity in specific habitats (e.g., carnivores, herbivores, microbivores in cornfield) suggesting that biological soil quality and ecosystem services provision may vary among them. Concerning agronomic practices, it was not observed an inverse relation between diversity and the disturbance they cause. In detail, while tillage and insecticide use negatively affected invertebrate diversity as a whole, specific soil taxa and trophic groups were idiosyncratically affected by the different agronomic practices (e.g., pesticide and fertilizer use was related to an increase of annelid and bacterivore diversity). In this regard, the peak of diversity observed for specific taxonomic and functional groups might be attributed to an impaired community balance. Altogether, the results obtained contribute to a more comprehensive understanding of the intricate interplay between agricultural practices and soil invertebrate communities, with implications for the awareness of soil health, ecosystem services provision and biodiversity conservation in agroecosystems.