Ecophysiological strategies and functional trait syndromes as predictors for plant performance under different resource limitation in grassland

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European grasslands are exposed to changes in the strength and frequency of drought events and the availability of nitrogen (N) following changes in climate, N deposition and land-use. Current research shows that traits that allow plants to maintain a high level of performance under drought versus N limitation conditions are partly similar, partly contrasting. As an example, a high root to shoot ratio increases plant resistance to both drought and N limitation; but photosynthetic water use efficiency (WUE) should be as high as possible to improve drought resistance, whereas low WUE and high transpiration rates can facilitate N uptake in conditions of N limitation. Additionally, drought and N availability interact in their influence on plant performance via the coupling of water and N uptake. In this context, our understanding of optimal adaptations to co-limitation, and especially so under conditions of plant interspecific competition, is particularly poor. The next frontier is to i) identify trait syndromes that allow plants to maximize their resource use (acquisition and conservation) under conditions of drought and N co-limitation, ii) shed light on the physiological mechanisms that underlie them, and iii) estimate the potential for complementary resource use among plant competitors. Such knowledge is of major importance to predict the future of European grassland ecosystems.To meet these aims, three connected experiments are planned, of which two will take place at the Theoretical and Experimental Ecology Station (SETE), CNRS, Moulis, France, where the applicant will be hosted by Dr. Grégoire Freschet. These experiments will be conducted under close to natural conditions in greenhouses and include a full-factorial manipulation of water availability and nitrogen addition. The third experiment will be a satellite study during a secondment at the Ecotron facilities, Montpellier, France, and will be conducted in collaboration with Dr. Alexandru Milcu. It will examine ecophysiological mechanisms of water use and N uptake in very closely controlled environmental conditions.