Seed predation reduces weed biomass and contributes to crop productivity in arable fields

Abstract: Weed seed predation is a widespread process that can contribute to the biological
control of weeds but we still lack empirical quantification of the effects of weed seed predators on weed dynamics. Besides, if weed dynamics are affected by seed predation, one can expect that seed predators will indirectly positively affect crop productivity, but such assessment has to our knowledge never been conducted. Here, we report on a highly replicated predator exclosure experiment that aimed to assess the impact of seed predators on the demography of nine weed species and on crop productivity. We demonstrate that across the 28 experimental fields, seed predation significantly reduced total weed biomass, compared to the reference where predators were excluded. Moreover, we show that in the absence of seed predators, the potential wheat crop yield is reduced by 80 % by weeds. The presence of seed predators strongly limits this drastic reduction, to 48 % with invertebrate seed predators to 56 % with both invertebrate and vertebrate seed predators.