Landscape scale management affects weed richness but not weed abundance in winter wheat fields.

Summary

Farmland biodiversity provides ecological services that support food production, but the spatial scale(s) at which its management should be implemented is an acute question today. Effective management of weeds is a particularly hot issue as these plants can cause yield loss but support farmland biodiversity. In a general context of pesticide reduction, a clear understanding of how agricultural managements at different spatial scales interact with one another in shaping weed communities is required to develop sustainable weed management strategies. Here, we analyzed the contribution of potential drivers of weed species richness and weed abundance in 125 winter-wheat fields under a gradient of crop management intensity. We hypothesized that (i) local management practices in fields and (ii) the structure and composition of the landscape surrounding these fields would both explain the variations in weed richness and weed abundance observed within the study area. Linear mixed-effects models that included sequentially three sets of explanatory variables (farming system, local management practices, landscape structure and management) were applied and the relative performance of models was compared by AIC. Our analysis showed that weed species richness responded to factors acting at multiple spatial scales, with a predominant effect of landscape scale management, namely the proportion of organic farming within a 1 km radius. In contrast, weed abundance was difficult to predict and responded solely to few local management practices. As weed richness and abundance did not respond at the same spatial scales, we conclude that it may be possible to combine local and longer-term landscape management levers to deliver reduced weed infestation levels and enhanced arable biodiversity.