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All living things, like humans, animals, plants, and even microbes, need to take up the same nutrient elements to live, most importantly nitrogen and phosphorus. Understanding the cycling of these elements through the ecosystem is one key to understanding why ecosystems work the way they do. One of the questions we are asking is if the diversity of organisms, like plants or insects, is related to these nutrient cycles. When plant communities are made up of many different plant species, they seem to make better use of the available soil nutrients than plant communities made up of fewer species. This may be because of something called complementarity, which means different plant species access the available nutrients in different ways, for example from different soil depths. In this article, we will describe the connections between plant biodiversity and soil nutrient cycling and discuss the implications for the functioning of the whole ecosystem.

Earth is home to over 350,000 vascular plant species that differ in their traits in innumerable ways. A key challenge is to predict how natural or anthropogenically driven changes in the identity, abundance and diversity of co-occurring plant species drive important ecosystem-level properties such as biomass production or carbon storage. Here, we analyse the extent to which 42 different ecosystem properties can be predicted by 41 plant traits in 78 experimentally manipulated grassland plots over 10 years. Despite the unprecedented number of traits analysed, the average percentage of variation in ecosystem properties jointly explained was only moderate (32.6%) within individual years, and even much lower (12.7%) across years. Most other studies linking ecosystem properties to plant traits analysed no more than six traits and, when including only six traits in our analysis, the average percentage of variation explained in across-year levels of ecosystem properties dropped to 4.8%. Furthermore, we found on average only 12.2% overlap in significant predictors among ecosystem properties, indicating that a small set of key traits able to explain multiple ecosystem properties does not exist. Our results therefore suggest that there are specific limits to the extent to which traits per se can predict the long-term functional consequences of biodiversity change, so that data on additional drivers, such as interacting abiotic factors, may be required to improve predictions of ecosystem property levels.

Earth is home to over 350,000 vascular plant species1 that differ in their traits in innumerable ways. Yet, a handful of functional traits can help explaining major differences among species in photosynthetic rate, growth rate, reproductive output and other aspects of plant performance2–6. A key challenge, coined “the Holy Grail” in ecology, is to upscale this understanding in order to predict how natural or anthropogenically driven changes in the identity and diversity of co-occurring plant species drive the functioning of ecosystems7, 8. Here, we analyze the extent to which 42 different ecosystem functions can be predicted by 41 plant traits in 78 experimentally manipulated grassland plots over 10 years. Despite the unprecedented number of traits analyzed, the average percentage of variation in ecosystem functioning that they jointly explained was only moderate (32.6%) within individual years, and even much lower (12.7%) across years. Most other studies linking ecosystem functioning to plant traits analyzed no more than six traits, and when including either only six random or the six most frequently studied traits in our analysis, the average percentage of explained variation in across-year ecosystem functioning dropped to 4.8%. Furthermore, different ecosystem functions were driven by different traits, with on average only 12.2% overlap in significant predictors. Thus, we did not find evidence for the existence of a small set of key traits able to explain variation in multiple ecosystem functions across years. Our results therefore suggest that there are strong limits in the extent to which we can predict the long-term functional consequences of the ongoing, rapid changes in the composition and diversity of plant communities that humanity is currently facing.

International audience; Concern about the functional consequences of unprecedented loss in biodiversity has prompted biodiversity-ecosystem functioning (BEF) research to become one of the most active fields of ecological research in the past 25 years. Hundreds of experiments have manipulated biodiversity as an independent variable and found compelling support that the functioning of ecosystems increases with the diversity of their ecological communities. This research has also identified some of the mechanisms underlying BEF relationships, some context-dependencies of the strength of relationships, as well as implications for various ecosystem services that mankind depends upon. In this paper, we argue that a multitrophic perspective of biotic interactions in random and non-random biodiversity change scenarios is key to advance future BEF research and to address some of its most important remaining challenges. We discuss that the study and the quantification of multitrophic interactions in space and time facilitates scaling up from small-scale biodiversity manipulations and ecosystem function assessments to management-relevant spatial scales across ecosystem boundaries. We specifically consider multitrophic conceptual frameworks to understand and predict the context-dependency of BEF relationships. Moreover, we highlight the importance of the eco-evolutionary underpinnings of multitrophic BEF relationships. We outline that FAIR data (meeting the standards of findability, accessibility, interoperability, and reusability) and reproducible processing will be key to advance this field of research by making it more integrative. Finally, we show how these BEF insights may be implemented for ecosystem management, society, and policy. Given that human well-being critically depends on the multiple services provided by diverse, multitrophic communities, integrating the approaches of evolutionary ecology, community ecology, and ecosystem ecology in future BEF research will be key to refine conservation targets and develop sustainable management strategies.

Soils are important for ecosystem functions and services. However, soil processes are complex and changes of solid phase soil properties, such as soil organic matter contents are slow. As a consequence, a comprehensive understanding of the role of soil in the biodiversity-ecosystem functioning (BEF) relationship is still lacking. Thus, long-term observations and experiments are needed in biodiversity research in order to better understand how biodiversity influences soil properties and thus the BEF relationships. To elucidate the integrated response of soil-related functions and processes to plant diversity, we reviewed literature on the water, nutrient and carbon cycles in biodiversity research with specific focus on the Jena Experiment. Furthermore, we took advantage of the long-term observations of water, nutrient and carbon dynamics gathered in the Jena Experiment to investigate changes of the plant diversity effect over time on theses cycles and the accompanying plant-microbial interactions. We found that soil organic carbon and soil nitrogen stocks in the top 15 cm constantly increased over time and that this increase was positively related to plant species richness. In contrast, the concentrations of the quantitatively most important nutrient ions nitrate and phosphate in soil solution decreased with time, likely because of the ongoing removal of nutrients by plant biomass harvest. We furthermore observed a shift in the microbial community composition, which was triggered by an increased availability of plant-derived carbon at higher plant species richness over time, suggesting that plant communities compensated for nutrient losses by stimulating the microbial nutrient cycling. In addition, water including dissolved nutrients and carbon percolated deeper in plots of higher plant diversity. Thereby, higher plant diversity spatially extended the nutrient cycling through the microbial communities to deeper soil layers from which nutrients are transferred to the topsoil by deep-rooting plants. Although microbial nutrient cycling cannot fully compensate for negative plant diversity effects on nutrient availability in soil solution, this suggests that over time the role of plant-derived inputs becomes increasingly important for ecosystem functioning. It furthermore implies that plant species richness tightens plant-microbial interactions, which in the long-term feed back on other ecosystem functions, such as productivity.