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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]

Grasslands face more frequent and extreme droughts; yet, their responses to increasing drought intensity are poorly understood. Increasing drought intensity likely triggers abrupt shifts (thresholds) in grassland ecosystem functioning which can implicate recovery trajectories.Here, we determined how drought intensity affects plant productivity, and plant–soil carbon (C) and nitrogen (N) cycling. We exposed model grassland plant communities with contrasting resource acquisition strategies (a fast‐ vs a slow‐strategy plant community), to a gradient of drought intensity. The drought gradient ranged from well‐watered to severely water‐limited conditions. We identified thresholds of plant community productivity (above‐ground biomass) at peak drought and 2 months after re‐wetting, and measured net ecosystem exchange and ecosystem respiration of C throughout the drought and recovery phases. At peak drought and 1 week after re‐wetting, we traced recently acquired C from plants to the soil and into microbial biomass and fatty acids using 13C pulse labelling, and measured plant and soil N.At peak drought, slow‐strategy plant communities were more drought resistant than fast‐strategy communities, as the threshold in plant productivity occurred at a higher drought intensity for the slow‐ than the fast‐strategy community. Shortly after re‐wetting, microbial uptake of recent plant‐assimilated C increased with increasing past drought intensity, coinciding with an increase in soil N availability and leaf N. Threshold responses to drought intensity at peak drought translated into non‐linear recovery responses, with greater compensatory growth in the fast‐strategy community. At peak drought, increasing drought intensity reduced C uptake and increased relative C partitioning to leaves and microbial biomass. Upon re‐wetting, plant community strategy mediated drought intensity effects on plant and soil C and N dynamics and plant recovery trajectories. The fast‐strategy community recovered quickly, with higher leaf N than the slow community, while the slow community increased C allocation to microbial biomass.Synthesis. Our findings highlight that C and N dynamics in the plant–soil system display non‐linear responses to increasing drought intensity both during and after drought, which has implications for plant community recovery trajectories. [ABSTRACT FROM AUTHOR]

Flooding threatens the functioning of managed grasslands by decreasing primary productivity and increasing nitrogen losses, notably as the potent greenhouse gas nitrous oxide (N2O). Sowing species with traits that promote flood resilience and mitigate flood‐induced N2O emissions within these grasslands could safeguard their productivity while mitigating nitrogen losses.We tested how plant traits and resource acquisition strategies could predict flood resilience and N2O emissions of 12 common grassland species (eight grasses and four legumes) grown in field soil in monocultures in a 14‐week greenhouse experiment.We found that grasses were more resistant to flooding while legumes recovered better. Resource‐conservative grass species had higher resistance while resource‐acquisitive grasses species recovered better. Resilient grass and legume species lowered cumulative N2O emissions. Grasses with lower inherent leaf and root δ13C (and legumes with lower root δ13C) lowered cumulative N2O emissions during and after the flood.Our results highlight the differing responses of grasses with contrasting resource acquisition strategies, and of legumes to flooding. Combining grasses and legumes based on their traits and resource acquisition strategies could increase the flood resilience of managed grasslands, and their capability to mitigate flood‐induced N2O emissions. A free Plain Language Summary can be found within the Supporting Information of this article. [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]

Minimizing nitrogen (N) losses and increasing plant N uptake in agroecosystems is a major global challenge. Ecological concepts from (semi)natural grasslands suggest that manipulating plant community composition using plant species with different traits may represent a promising opportunity to face this challenge. Here, we translate these trait‐based concepts to agricultural systems in a field experiment, aiming to reveal the main determinants of how plant community composition regulates N‐cycling in intensively managed grasslands.We focused on key N pools (plant N from soil and from biological N‐fixation, soil mineral N and N2O emissions) as well as on biological drivers of N‐cycling in soil (abundance of N‐cycling microbial communities, earthworm populations and arbuscular mycorrhizal fungi), using three common grass and one legume species in monoculture, two‐ and four‐species mixtures. We hypothesized that: (a) plant species mixtures increase plant N uptake, reduce soil mineral N concentrations and N2O emissions and promote the abundance of biological N‐cyclers; (b) legume presence stimulates N pools, fluxes and biological N‐cycling activity, (c) but in combination with a grass with acquisitive traits, more N is retained in the plant community, while N2O emissions are reduced.We found that mixtures increased plant N and lowered the soil mineral N pool compared to monocultures. However, plant species identity played an overarching role: Legume presence increased N2O emissions, plant N pools, soil mineral N and the abundance of N‐cycling microbes and earthworms. Combining the legume with a grass with low leaf dry matter content and high root length density (and with high root biomass) reduced the higher soil mineral N and N2O emissions induced by the legume, while harnessing positive effects on plant N pools and biological N‐fixation.Synthesis and applications. Our results show the potential of plant community composition to steer N‐cycling in fertilized agroecosystems, paving the way for a more biologically based agriculture. Legumes will play a crucial role, but selecting an optimum companion species is key for the sustainability of the agroecosystem. [ABSTRACT FROM AUTHOR]

The increasing frequency of extreme weather events, such as floods, requires management strategies that promote resilience of grassland productivity. Mixtures of plant species may better resist and recover from flooding than monocultures, as they could combine species with stress‐coping and resource acquisition traits. This has not yet been tested in intensively managed grasslands despite its relevance for enhancing agroecosystem resilience.Using intact soil cores from an 18‐month‐old field experiment, we tested how 11 plant communities (Festuca arundinacea, Lolium perenne, Poa trivialis and Trifolium repens in monoculture, two‐ and four‐species mixtures) resist and recover from repeated flooding in a 4‐month greenhouse experiment.We found that plant community composition, not whether the community was a mixture or monoculture, influenced the community's resistance to flooding, although most communities were able to resist and recover from both floods.The plant community's position on the leaf economic spectrum in flooded conditions was related to its resistance to and recovery from flooding. Resistance to and recovery from a severe flood were related to flood‐induced intraspecific trait variation, causing a shift in the community's position on the leaf resource economic spectrum. In flooded conditions, resource‐conservative communities (characterized by low specific leaf area, low leaf nitrogen content and high leaf dry matter content) better resisted and recovered from flooding. The community's position on the root resource economic spectrum was less connected to the community's resistance and recovery.Synthesis and applications. Our study shows that in flooded conditions, resource‐conservative plant communities are more resilient to flooding than resource‐acquisitive communities in an intensively managed grassland. This suggests that plant community position on the leaf economic spectrum, as well as species' flood‐induced intraspecific variation, should be considered when designing grasslands to withstand increasing flood frequency and severity. [ABSTRACT FROM AUTHOR]

Highlights: [•] Red clover biomass was significantly greater when grown on biochar-amended soil. [•] An increase in K availability increased the competitive ability of red clover to grass and plantain. [•] This effect disappeared when N fertilisation was applied. [•] The liming effect of the biochar did not influence red clover growth or competitive ability. [Copyright &y& Elsevier]

Intensively managed grasslands are large sources of the potent greenhouse gas nitrous oxide (N 2 O) and important regulators of methane (CH 4) consumption and production. The predicted increase in flooding frequency and severity due to climate change could increase N 2 O emissions and shift grasslands from a net CH 4 sink to a source. Therefore, effective management strategies are critical for mitigating greenhouse gas emissions from flood-prone grasslands. We tested how repeated flooding affected the N 2 O and CH 4 emissions from 11 different plant communities (Festuca arundinacea, Lolium perenne, Poa trivialis, and Trifolium repens in monoculture, 2- and 4-species mixtures), using intact soil cores from an 18-month old grassland field experiment in a 4-month greenhouse experiment. To elucidate potential underlying mechanisms, we related plant functional traits to cumulative N 2 O and CH 4 emissions. We hypothesized that traits related with fast nitrogen uptake and growth would lower N 2 O and CH 4 emissions in ambient (non-flooded) conditions, and that traits related to tissue toughness would lower N 2 O and CH 4 emissions in flooded conditions. We found that flooding increased cumulative N 2 O emissions by 97 fold and cumulative CH 4 emissions by 1.6 fold on average. Plant community composition mediated the flood-induced increase in N 2 O emissions. In flooded conditions, increasing abundance of the grass F. arundinacea was related with lower N 2 O emissions; whereas increases in abundance of the legume T. repens resulted in higher N 2 O emissions. In non-flooded conditions, N 2 O emissions were not clearly mediated by plant traits related with nitrogen uptake or biomass production. In flooded conditions, plant communities with high root carbon to nitrogen ratio were related with lower cumulative N 2 O emissions, and a lower global warming potential (CO 2 equivalent of N 2 O and CH 4). We conclude that plant functional traits related to slower decomposition and nitrogen mineralization could play a significant role in mitigating N 2 O emissions in flooded grasslands. Unlabelled Image • Flooding increases N 2 O from managed grasslands • Plant community composition explains flood-induced N 2 O • Festuca arundinacea decreased, and Trifolium repens increased, flood-induced N 2 O • Higher root C:N is related to lower flood-induced N 2 O [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]