Agricultural intensification reduces plant taxonomic and functional diversity across European arable systems.

1. Agricultural intensification is one of the main drivers of species loss
worldwide, but there is still a lack of information about its effect on
functional diversity of arable weeds communities. 2. Using a large scale
pan European study including 786 fields within 261 farms from eight
countries, we analysed differences in the taxonomic and functional
diversity of arable weeds assemblages across different levels of
agricultural intensification in. We estimated weed species frequency in
each field, and collected species’ traits (vegetative height, specific
leaf area and seed mass) from the TRY plant trait database. With this
information we estimated taxonomic (species richness), functional
composition (community weighted means) and functional diversity
(functional richness, evenness, divergence and redundancy). We used
indicators of agricultural management intensity at the individual field
scale (e.g. yield, inputs of nitrogen fertilizer and herbicides, frequency
of mechanical weed control practices) and at the landscape scale
surrounding the field (i.e. number of crop types, mean field size and
proportion of arable land cover within a radius of 500m from the sampling
points). 3. The effects of agricultural intensification on species and
functional richness at the field scale were stronger than those of
intensification at the landscape scale, and we did not observe evidence of
interacting effects between the two scales. Overall, assemblages in more
intensified areas had fewer species, a higher prevalence of species with
ruderal strategies (low stature, high leaf area, light seeds), and lower
functional redundancy. 4. Maintaining the diversity of Europe’s arable
weed communities requires some simple management interventions, for
example, reducing the high intensity of field-level agricultural
management across Europe, which could be complemented by interventions
that increase landscape complexity.