Plant litter strengthens positive biodiversity–ecosystem functioning relationships over time.

Nitrogen (N) inputs from legume residues over the long-term contribute to improve soil N cycling and the productivity of succeeding plants in species-diverse ecosystems. Litter mixtures enhance soil fertility, thus enhancing biomass production, which in turn creates positive diversity–productivity feedback in the long-term. Positive effects of litter diversity on the composition and diversity of soil organisms increase over time. Residue-borne pathogens and pests gradually accumulate through litter input from monocultures, whereas diverse plant-litter mixtures reduce the incidence and spread of residue-borne pathogens and pests in the long-term. Plant litter can strengthen biodiversity–ecosystem functioning relationships in both natural and managed ecosystems. Appropriate management of residues from plant mixtures across multiple growing seasons can promote the sustainability of food production systems. Plant biodiversity–productivity relationships become stronger over time in grasslands, forests, and agroecosystems. Plant shoot and root litter is important in mediating these positive relationships, yet the functional role of plant litter remains overlooked in long-term experiments. We propose that plant litter strengthens biodiversity–ecosystem functioning relationships over time in four ways by providing decomposing detritus that releases nitrogen (N) over time for uptake by existing and succeeding plants, enhancing overall soil fertility, changing soil community composition, and reducing the impact of residue-borne pathogens and pests. We bring new insights into how diversity–productivity relationships may change over time and suggest that the diversification of crop residue retention through increased residue diversity from plant mixtures will improve the sustainability of food production systems. [ABSTRACT FROM AUTHOR]