Taxonomic and diet-based functional structure of carabid communities varies seasonally in cultivated fields

Agricultural intensification has altered the provision of natural bioregulation. We assessed the effects of five different crops under non-inversion tillage on the temporal dynamics of carabid assemblages. We evaluated how the taxonomic diversity, the composition, and the diet-based functional structure of communities varied over the spring period. Carabid assemblages were monitored over 4 years (from 2009 to 2012), in a total of 67 fields (each field followed one year) cropped with either winter oilseed rape, winter wheat, sugar beet, spring barley, or spring pea. We assigned a relative diet profile to each species accounting for more than 0.5 % of the total mean abundance-activity: granivorous, phytophagous, and zoophagous. The seasonal changes in species richness, abundance-activity, and evenness had the same dynamic in all crops. Despite differences in species identities between crops, the zoophagous and phytophagous diet profiles showed similar temporal dynamics in all crop types, suggesting a high functional equivalence among species present in cultivated fields. Zoophagous species were progressively replaced by primarily phytophagous species in all crops, while the increase in granivorous species was only observed in oilseed rape. Our results suggest that potential bioregulation do not significantly differ among crop types but vary along the spring season. Highlights We monitored carabid communities in five crop types under non-inversion tillage We observed similar seasonal increases in carabid abundance-activity and species richness in all crops during the spring period We observed similar trends in temporal changes in carnivorous and phytophagous diet profiles in all crops With seasonal changes, zoophagous species are progressively replaced by more phytophagous species Crop type is not the main factor driving temporal changes in diet-based structure of carabid assemblages