Responses of plants, earthworms, spiders and bees to geographic location, agricultural management and surrounding landscape in European arable fields

Farmland species provide key ecological services that support agricultural production, but are under threat from agricultural intensification and mechanization. In order to design effective measures to mitigate agricultural impact, simultaneous investigations of different taxonomic groups across several regions are required. Therefore, four contrasting taxonomic groups were investigated: plants, earthworms, spiders and bees (wild bees and bumblebees), which represent different trophic levels and provide different ecological services. To better understand underlying patterns, three community measurements for each taxonomic group were considered: abundance, species richness and species composition. In four European regions, ten potential environmental drivers of the four taxonomic groups were tested and assigned to three groups of drivers: geographic location (farm, region), agricultural management (crop type, mineral nitrogen input, organic nitrogen input, mechanical field operations and pesticide applications) and surrounding landscape in a 250 m buffer zone (diversity of habitats in the surroundings, proportion of arable fields and proportion of non-productive, non-woody habitats). First, the variation in abundance, species richness and species composition from 167 arable sites was partitioned to compare the relative contribution of the three groups of drivers (geographic location, agricultural management and surrounding landscape). Second, generalized linear mixed-effects models were applied to estimate the effect of the individual explanatory variables on abundance and species richness. Our analysis showed a dominant effect of geographic location in all four taxonomic groups and a strong influence of agricultural management on plants, spiders and bees. The effect of the surrounding landscape was of minor importance and inconsistent in our data. We conclude that in European arable fields, the avoidance of mineral nitrogen and pesticides is beneficial for biodiversity, and that species protection measures should take into account regional characteristics and the community structure of the investigated taxonomic groups.