Modelling biodiversity-ecosystem functioning relations in grasslands with special reference to mechanisms related to plasticity.

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Starting in February 2006, the modelling subproject TP15 of the Jena Experiment has been developing a mechanistic grassland model based on the GEMINI model (Soussana et al. 2000) as central tool for the analysis of biodiversity-ecosystem functioning relationships. During the initial 16 month the focus was on the development of a novel architectural and phenological model specifically designed for functional biodiversity research in grasslands. These activities of the first phase allow us now to represent phenotypic plasticity and to address its so far neglected role as important mechanism in the biodiversity-ecosystem functioning context. Here, we first develop a conceptual model that suggests (a) that different mechanisms leading to positive diversity-functioning relationships require different types of plasticity and (b) that the strength of the overall plasticity effect is modified by extent of plasticity, the functional diversity of the initial species composition and environmental heterogeneity. The hypotheses will be tested with two novel modelling approaches. The analysis of plasticity will be complemented by numerical experiments identifying parameter combinations that simultaneously optimize several ecosystem functions. In addition, this project will also contribute significantly to the modelling components within the projects on ‘Carbon Storage’ and ‘Nutrient Cycling’. In conclusion, this project will largely contribute to the overall data synthesis of biodiversity-ecosystem functioning relationships and at the same time to a better understanding of the underlying mechanisms.