Organic fields sustain weed metacommunity dynamics in farmland landscapes
Résumé
Agro-ecosystems constitute essential habitat for many organisms. Agricultural
intensification, 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 appear
often species- and context-dependent, and current research has highlighted
theneedtoquantify therelativeeffectsof local- and landscape-scalemanagement
on farmland biodiversity. Yet very few studies have investigated the landscapelevel
effects of OF; that is to say, how the biodiversity of a field is affected by the
presence or density of organically farmed fields in the surrounding landscape.
We addressed this issue using the metacommunity framework, with weed
species richness in winter wheat within an intensively farmed landscape
in France asmodel system.Controlling for the effects of local and landscape structure,
we showed that OF leads to higher local weed diversity and that the
presence of OF in the landscape is associated with higher localweed biodiversity
also for conventionally farmed fields, and may reach a similar biodiversity level
to organic fields in field margins. Based on these results,we derive indications for
improving the sustainable management of farming systems.