Carbon sequestration-related traits of spontaneous flora under agroecological intensification in European cropping systems

Spontaneous flora is increasingly recognized as an important component of agroecosystem functioning. Plant functional traits may provide useful indicators of ecological processes potentially associated with soil carbon (C) sequestration, although these relationships remain indirect. This study investigated how agroecological intensification influences spontaneous flora diversity and soil C sequestration-related functional traits across seven European cropping systems. Vegetation surveys were conducted at minimum and maximum crop nutrient demand stages, and community-weighted means of canopy height, specific leaf area (SLA), grass-like morphology, support for arbuscular mycorrhizal fungi (SAM), and perenniality were calculated together with biodiversity indices. PCA, PERMANOVA, ANOVA/Kruskal–Wallis tests and Pearson correlations were used to evaluate the effects of management practices on community structure and functional traits. Responses to agroecological intensification were strongly context-dependent. In case studies with sufficiently rich spontaneous flora communities, management induced community reassembly, accompanied by shifts in functional traits. Among the practices evaluated, no-till promoted higher proportions of perennial, grass-like and SAM species, traits potentially related to ecological processes involved in belowground C inputs and soil C stabilization. In some case studies, it also favoured opportunistic high-SLA species associated with rapid resource acquisition and faster biomass turnover. Cover crops partly moderated the dominance of these acquisitive species, promoting more balanced communities. Across all case studies, community evenness was more strongly associated with the selected functional traits than species richness. The observed relationships should be interpreted as trait-based inferences, and direct measurements of soil C processes are required for validation.