Taxonomic and functional characteristics of field edge weed communities along a gradient of crop management intensity

Abstract

The widespread loss of weed diversity and associated ecosystem functions is raising important concerns. Field edges could play a major role in the maintenance of weed functional diversity in arable landscapes as these habitats still harbour high weed diversity, owing to either a reduced farming management intensity and/or to a spillover of species from adjacent perennial field margins. Here, we investigated the taxonomic and functional characteristics of weed species recorded in surveys of field edges and their associated field cores over six consecutive years in 60 arable fields farmed with five crop management strategies. We found that field edges were richer, with species more functionally diverse and composition more stable over years than field core surveys. The distribution of individual functional traits differed between field edges and field cores, with higher values for seed mass and nitrophily (Ellenberg.N), and a wider distribution of specific leaf area values in field edges. The bimodal distribution of plant height and germination period observed in field edges became unimodal in field cores. Field edges harboured species with ecological strategies associated with field cores (ruderal species) plus a conservative strategy which could be explained by a spillover from the adjacent perennial field margins. Crop management strategies impacted field edge flora, though to a lesser extent than the field core flora whereas the functional differences between the field edge and the field core flora were less marked when crop management intensity was lower. These results indicate that field edges harbour a unique assemblage of species and highly contribute to the maintenance of weed diversity in arable landscapes. Future studies should thus focus on the importance of these specific functional traits to the agroecosystem functioning.