Vineyard Floor Management as a Multifunctional Strategy for Pollinator Communities and Grape Quality

In sustainable viticulture, inter-row vegetation management may improve biodiversity and influence grape quality, but the relationships among vegetation, pollinators, and grape quality remain insufficiently researched. A three-year study (2023–2025) was conducted in a vineyard in western Romania to evaluate the effects of inter-row management practices, including bare soil (BS), spontaneous vegetation (SV) and a multispecies cover crop mixture (CC), on vegetation traits, pollinator groups, grape yield and quality in four cultivars (‘Merlot’, ‘Pinot Noir’, ‘Sauvignon Blanc’ and ‘ Italian Riesling’). Vegetation cover, flower density and plant species richness were recorded; pollinators were sampled using transects and classified into five groups; grape quality parameters, phenolic compounds, and anthocyanins (red cultivars) were measured at harvest time. CC consistently had the highest vegetation cover, flower density and species richness, whereas BS had the lowest values. Plant Shannon diversity was strongly positively associated with total pollinator abundance (r = 0.962, R2 = 0.925, p < 0.001; n = 108 plot-year observations), indicating that it accounted for 92.5% of the observed variation. Inter-row management explained 76.5% of the variation in pollinator community composition (PERMANOVA, R2 = 0.765, p = 0.001). Mean grape yield and berry weight were higher under BS (3.14 kg vine−1 and 1.45 g, respectively) than under SV (2.69 kg vine−1 and 1.36 g) or CC (2.29 kg vine−1 and 1.29 g; p < 0.001). Total phenolic content was higher under CC than under BS in all four cultivars, although the magnitude of the difference depended on cultivar. In the two red cultivars, mean anthocyanin content was higher under CC (751 mg L−1) than under SV (672 mg L−1) or BS (621 mg L−1). Treatment differences in vegetation characteristics varied among years, while grape quality responses also differed among cultivars. Overall, the results indicate a trade-off between yield-related traits, which were associated with BS, and phenolic and anthocyanin accumulation, which were higher under CC. Multispecies cover crops may therefore offer ecological and compositional benefits, although their use should account for potential competition with grapevines for resources.