The aim of the project is to test the three following hypotheses:
The innovative character of the project consists in the coupling by mechanistic modelling of two unconnected experimental approaches: the study of plant diversity effects at equal management (Jena) and the study of management effects at identical initial diversity (ORE PCBB). The project is in charge of the diversity measurements planned for the ORE-PCBB, but not funded by another way, and will permit to complete the measurements at Jena (and funded otherwise) concerning biological diversity, particularly some plant-soil interactions (microbial communities linked to nitrogen cycle and root traits). Moreover, the Jena experiment will supply unique data to parameterise (with trait values which allow parameters calculation) the GEMINI model on the monocultures, and then to test it with the results obtain in the mixtures.
Simulating diversity dynamics in a managed grassland and its role for productivity and ecosystem functioning undergoes a mechanistic modelling approach which takes especially into account the disturbance regime (mowing, grazing) and phenotypic plasticity of plants. An individual-centred model will allow analysing the mechanistic basis of complementarity and dominance effects between plant species, or between functional types, as well as the role those species have for productivity and nitrogen-carbon cycles. This model also takes into account the aspects of competition between soil microbial groups of decomposers (Fontaine et al. 2004) as well as the role of root traits in these processes (Personeni & Loiseau 2004). It has already been successfully tested in the case of binary mixture of grasses and of grasses and legumes. Applied to grasslands, this approach is complementary to that used by generic models with theoretical aims and concerning the role of biodiversity in ecosystem functioning (Loreau 1998).