The role of nutrients for the variability of drought effects on community composition and productivity across land use gradients in grasslands: a trait-based approach (BETol 2)

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Land use and precipitation are important drivers for shaping community diversity, and ecosystem function in grasslands worldwide, and are two of the main global change drivers. Ecosystems will be exposed to a combination of changes of soil nutrients (e.g. through fertilization) and more frequent and intense drought events. In combination, both factors can act additively, or interact and result in accelerating or dampening effects. Consequently, grassland community and ecosystem responses to drought vary depending on nutrient regimes. However, we lack an understanding of the mechanisms underlying interactions of nutrients and drought, and are therefore currently unable to project under which land-use regimes grasslands are more resilient or sensitive to drought. The main aim of this project is to improve our capability of predicting consequences of global change for grasslands through assessing the combined effects of nutrients and drought at the trait and whole plant performance level, and integrating them with drought effects on community composition and productivity across land use gradients in grasslands.In a greenhouse experiment we will for 16 grassland species comparatively assess the plasticity in response to nutrients of a comprehensive suite of more than 20 physiological, morphological and whole plant traits that are relevant for plant drought resistance. In a common garden experiment, we will quantify the combined effects of nutrients and drought (and their interactions) for whole plant drought performance of these species. We will also assess the effects of experimental and natural drought across gradients of nutrient availability and land use (especially fertilization) in the Exploratories. Directly linking the data at the trait, whole plant, community and ecosystem level will increase our mechanistic understanding of combined nutrient and drought effects on grasslands under current and future conditions. The results will have important applied and scientific implications.