Enhancing carabid beetle populations: insights from an agroecological experiment at landscape scale

Abstract: There is an important need to experiment agroecological farming at the landscape
scale in order to decipher and account for key ecological processes occurring at scales larger
than the field. This is especially relevant for understanding how mobile functional biodiversity delivering key services to agriculture can be enhanced. Such landscape-scale experimentation is the main aim of the INRAE CA-SYS platform created in 2018 where pesticide-free “naturebased” and highly diversified arable cropping systems are implemented and evaluated, on a spatially continuous block 125 ha of arable crops and ecological infrastructures (10 % of the area is planted with grass/flower strips and hedgerows). This innovative design was mobilized to explore the role of the spatial arrangement of contrasted cropping systems and flower strips on carabids. We found that no-till fields were the preferential overwintering habitat during carabid emergence peak. We also observed some redistribution of circulating carabids among habitats. The area of no-till fields within a 100 radius increased the abundance of circulating adults of most dominant carabid species, notably with tilled fields. The area of flower strips in the surroundings had a comparable positive effect for some species, suggesting that they can act as a temporary refuge and source.