Evaluation and valorisation of biodiversity and services provided by flower strips in field crops

Abstract

The collapse of biodiversity in agriculture, as well as increased resistance to plant protection products, means that agricultural systems must be rethought. To do this, it is necessary to improve the place given habitat and resource areas for functional biodiversity, such as by implementing flower strips. We present works analysing the synergies and antagonisms between the services provided by these strips on the multifunctionality of agricultural systems through the monitoring of a network of fields in around thirty farms by a multidisciplinary team made up of actors from research, development and agricultural advice. Composed of 42 different species, the strips established slowly and their composition begins to stabilise after three years, with perennial species succeeding annuals and flowering from March to October. The abundance of pollinators visiting the canopy is positively correlated with floral abundance. The plant-pollinator interaction networks highlight the adaptation of pollinator group visits to the available resource. The effects of flower strips on biodiversity depend on the type of cropping system in which they are sown and on the organism considered: the effects are positive on pollinators and on spiders in organic farming. In terms of regulation, the presence of a flower strip doubles the rate of parasitism of pollen beetles in fields without insecticides, and the parasitism of oilseed rape pests increases with the nectar resources provided by weeds. In faba bean crops, nectar resources provided by flowers increase aphid predators, but this does not translate into better aphid control. Determining the effects of flower strips and cropping systems is limited by numerous confounding effects, inter-annual variability and by a study time that is too short compared to the response time of biodiversity. The study should therefore be continued over the longer term.