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Resource‐use complementarity of producer species is often invoked to explain the generally positive diversity–productivity relationships. Additionally, multi‐trophic interactions that link processes across trophic levels have received increasing attention as a possible key driver. Given that both are integral to natural ecosystems, their interactive effect should be evident but has remained hidden. We address this issue by analysing diversity–productivity relationships in a simulation experiment of producer communities nested within complex food‐webs, manipulating resource‐use complementarity and multi‐trophic animal richness. We show that these two mechanisms interactively create diverse communities of complementary producer species. This shapes diversity–productivity relationships such that their joint contribution generally exceeds their individual effects. Specifically, multi‐trophic interactions in animal‐rich ecosystems facilitate producer coexistence by preventing competitive exclusion despite overlaps in resource‐use, which increases the realised complementarity. The interdependence of food‐webs and producer complementarity in creating biodiversity–productivity relationships highlights the importance to adopt a multi‐trophic perspective on biodiversity–ecosystem functioning relationships. [ABSTRACT FROM AUTHOR]

Aims: Previous cover crop studies mainly focused on the links between plant uptake and soil fertility, and there is a clear knowledge gap regarding the role of microbes in these processes. Our aim was then to better understand the effects of plant mixtures (versus monoculture) and the specific effects of each plant species on nitrogen (N) and phosphorus (P) partitioning between plant, soil, and more particularly microbial pools. Methods: Monocultures and mixtures composed of black oat, field pea and Indian mustard were grown during two months in a greenhouse. The concentrations of carbon (C), N and P were measured in both plant and microbial biomass at final harvest, together with soil available N and P. Results: Overall, our findings highlight stronger selection effect (i.e., presence of key species) rather than complementarity effects (i.e., species mixture) to affect the measured parameters. The presence of pea increased the biomass production of oat and mustard, as well as the nutrient concentration of oat, whereas pea P concentration decreased in presence of oat and mustard N and P concentrations were negatively impacted respectively by the presence of oat and pea. We also observed a strong competition between plants and microbes for both soil N and P. Conclusions: The oat-pea and the oat-pea-mustard mixtures represented the best compromise between biomass production, nutrient storage and biomass C:N ratio, thus insuring a good organic matter decomposition and nutrient provision for the following main crop. [ABSTRACT FROM AUTHOR]

Aims: Genotypic mixtures have been receiving a growing interest as genetic diversity could increase crop productivity. Resource-use complementarity is an expected key underlying mechanism, provided that varieties in the mixture differ in resource-related traits, notably root traits. We aimed at examining how trait differences and resource-use complementarity drive biomass production of genotypic mixtures.Methods: Four rice (Oryza sativa) genotypes including two Near-Isogenic Lines only differing in root depth were grown in monoculture and in two-way mixtures in pots under two levels of phosphorus supply. We analyzed the relative difference between mixture biomass and the best monoculture biomass in relation to between-genotype phenotypic distance on ten resource-related traits.Results: Mixtures never outperformed the best monoculture. However, relative mixture productivity increased with increasing between-genotype distance in biovolume, specific leaf area and top soil root biomass. This was mainly driven by a “selection effect”: trait differences led to competitive ability differences and the dominant genotypes tended to gain more in mixture than the subdominant genotypes lost compared to monoculture.Conclusions: Rather than trying to minimize competition through resource-use complementarity, we argue that promoting interactions between genotypes that have different competitive abilities may be a more promising approach to design productive crop mixtures. [ABSTRACT FROM AUTHOR]