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Productive grasslands in temperate regions have relied strongly on low plant diversity with high management intensity and fertiliser inputs. Increasing plant diversity can provide high yields of digestible forage for livestock production with lower environmental impacts, and thus represents a diversity‐dependent nature‐based solution that can deliver multiple ecosystem functions.Sharing lessons from the design of managed, productive grassland communities, we address the following questions: how can we identify combinations of plant species that best deliver a selected function or multiple functions? and; when is community composition more important than species richness?We describe approaches that separate plant diversity into its underlying components: species richness, composition and relative abundance. Disentangling these three components facilitates a more nuanced understanding of how diversity can contribute to the design of diversity‐dependent nature‐based solutions. [ABSTRACT FROM AUTHOR]

Plant diversity is an important driver of below‐ground ecosystem functions, such as root growth, soil organic matter (SOM) storage and microbial metabolism, mainly by influencing the interactions between plant roots and soil. Dissolved organic matter (DOM), as the most mobile form of SOM, plays a crucial role for a multitude of soil processes that are central for ecosystem functioning. Thus, DOM is likely to be an important mediator of plant diversity effects on soil processes. However, the relationships between plant diversity and DOM have not been studied so far.We investigated the mechanisms underlying plant diversity effects on concentrations of DOM using continuous soil water sampling across 6 years and 62 plant communities in a long‐term grassland biodiversity experiment in Jena, Germany. Furthermore, we investigated plant diversity effects on the molecular properties of DOM in a subset of the samples.Although DOM concentrations were highly variable over the course of the year with highest concentrations in summer and autumn, we found that DOM concentrations consistently increased with plant diversity across seasons. The positive plant diversity effect on DOM concentrations was mainly mediated by increased microbial activity and newly sequestered carbon in topsoil. However, the effect of soil microbial activity on DOM concentrations differed between seasons, indicating DOM consumption in winter and spring, and DOM production in summer and autumn. Furthermore, we found increased contents of small and easily decomposable DOM molecules reaching deeper soil layers with high plant diversity.Synthesis. Our findings suggest that plant diversity enhances the continuous downward transport of DOM in multiple ways. On the one hand, higher plant diversity results in higher DOM concentrations, on the other hand, this DOM is less degraded. This study indicates, for the first time, that higher plant diversity enhances the downward transport of dissolved molecules that likely stimulate soil development in deeper layers and therefore increase soil fertility. [ABSTRACT FROM AUTHOR]

Plant species richness positively affects plant productivity both above- and belowground. While this suggests that they are related at the community level, few studies have calculated above- and belowground overyielding simultaneously. It thus remains unknown whether above- and belowground overyielding are correlated. Moreover, it is unknown how belowground community level overyielding translates to the species level. We investigated above- and belowground overyielding in the Jena Trait-Based Biodiversity Experiment, at both the community and species level and across two 8-species pools. We found that above- and belowground overyielding were positively correlated at the community level and at the species level--for seven out of the 13 investigated species. Some plant species performed better in mixtures compared to monocultures and others performed worse, but the majority did so simultaneously above- and belowground. However, plants invested more in aboveground overyielding than belowground. Based on this disproportional investment in overyielding aboveground, we conclude that light was more limiting than belowground resources in the present study, which requires individual species to compete more for light than for belowground resources. [ABSTRACT FROM AUTHOR]