Dissolved molecular signals as mediators of biodiversity effects

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It is generally accepted that the positive biodiversity-ecosystem functioning (BEF) relationship strengthens with time. This strengthening is supposed to be determined by i) the assembly of soil communities, such as microbial or faunal communities, and/or ii) the development of the plant communities. In both cases, interactions between plant communities and soil communities are altered. Most likely, these interactions and their alterations are mediated by the exchange of molecules. However, the question of how biodiversity affects the exchange of molecules and thus the mediation of interactions has rarely been considered in BEF research. Therefore, this project will analyse the interaction between plant and soil microbial communities and the soil matrix by using an advanced ultrahigh resolution mass spectrometric approach. We will analyse the molecular signatures of dissolved organic matter in order to better understand the positive BEF relationship in general and specifically its strengthening over time. We will compare the molecular signalling between plant communities and soil microbial communities that have different histories using a non-targeted approach of soil solution and soil extracts. Taking advantage of the Field Experiment, we will investigate the general effect of plant diversity on DOM composition under field conditions (WP1) and how it is affected by the soil history (WP2). The Ecotron Experiment, in which plants with different community histories are crossed with soils that have different histories, will enable us to assess the relative importance of plant vs. soil history on molecular DOM composition (WP3). Besides investigating the strengthening of the BEF relation over time on the basis of the molecular DOM composition, the temporal replicated DOM sampling in the Ecotron Experiment will allow to detect temporal shifts in the plant-microbe interaction. In close cooperation with the other subprojects, we will relate the DOM data to plant community properties, such as plant biomass production or plant defence traits, and to microbial-related variables like soil microbial activity, biomass, community structure and taxonomic composition of soil microbiota and fauna using uni- and multivariate statistics and network analyses. Together, these approaches will provide novel insights into the mechanisms of strengthening BEF relationships by exploring the molecular signals of plant-microbe interactions.