Vineyard footprint on pollinators is mediated by flower vegetation, organic farming, seasonal and weather factors, a case study from North Italy

Intensive, industrialized agriculture is considered a major driver of pollinator decline and viticulture may play a relevant role in this context. A global priority is to find ways to decrease the agricultural impact on biodiversity and to undertake an ecological intensification of farms, especially for maintaining pollinator biodiversity. To recommend practical ways to support pollinators, we explored if they react to the intensive vineyard production in a valley in Northern Italy: we tested if environmental, weather and management parameters could be responsible for shaping pollinator abundance, diversity and functional trait distribution across different wine farms, sampled with observation plots and transect walks. Results demonstrated both some effects shared across pollinator groups and some idiosyncratic responses. Generally, management factors including the herbaceous vegetation cover, weed height and its flower diversity showed strong and positive linear relationships with the abundance (+13 % by unit) and diversity of pollinators (+15 % by unit), while organic farming was associated with a slight decline in the abundance of the overall pollinators (-10 % by unit) and of hoverflies and butterflies. Regarding the temporal and weather factors, pollinators decreased with wind intensity and seasonal progression, while a positive effect was found for intermediate values of air temperature and sampling hour, thus affecting insect activity. The community composition analysis showed that environmental and management factors translated in specific distributions of bee and hoverfly functional traits across sites. Farming practices allowing herbaceous cover, weed height and flower diversity are overwhelmingly important for pollinators to assure shelter and nutritional resources and should be systematically incorporated to mitigate vineyard impact. Furthermore, measures that support pollinators should also consider pollinator phenological dynamics associated with temporal and environmental parameters to accordingly modulate the time of agricultural treatment application. Overall, our study provides a knowledge basis for the development of pollinator-friendly vineyard practices to foster the ecological value of farms.