Organic fields sustain weed metacommunity dynamics in farmland landscapes

Summary

Agro-ecosystems constitute essential habitat for many organisms. Agriculturalintensification, however, has caused a strong decline of farmland biodiversity.Organic farming (OF) is often presented as amore biodiversity-friendly practice,but the generality of the beneficial effects of OF is debated as the effects appearoften species- and context-dependent, and current research has highlightedtheneedtoquantify therelativeeffectsof local- and landscape-scalemanagementon farmland biodiversity. Yet very few studies have investigated the landscapeleveleffects of OF; that is to say, how the biodiversity of a field is affected by thepresence or density of organically farmed fields in the surrounding landscape.We addressed this issue using the metacommunity framework, with weedspecies richness in winter wheat within an intensively farmed landscapein France asmodel system.Controlling for the effects of local and landscape structure,we showed that OF leads to higher local weed diversity and that thepresence of OF in the landscape is associated with higher localweed biodiversityalso for conventionally farmed fields, and may reach a similar biodiversity levelto organic fields in field margins. Based on these results,we derive indications forimproving the sustainable management of farming systems.