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)

土地利用和降水是塑造全球草原群落多样性和生态系统功能的重要驱动力，也是全球变化的两个主要驱动力。生态系统将受到土壤养分变化（例如通过施肥）和更频繁和更严重的干旱事件的共同影响。这两个因素结合起来，可以起到相加作用，或相互作用，产生加速或抑制效应。因此，草地群落和生态系统对干旱的反应取决于养分状况。然而，我们缺乏对养分和干旱相互作用的机制的了解，因此目前无法预测在何种土地使用制度下草原对干旱更有弹性或更敏感。该项目的主要目的是通过在性状和整个植物性能水平上评估营养和干旱的综合影响，提高我们预测全球变化对草原后果的能力，在温室试验中，我们将对16个草地物种的可塑性进行比较，以评估干旱对草地群落组成和生产力的影响。营养素的综合套件20多个生理，形态和整个植物性状是相关的植物抗旱性。在一个普通的花园实验中，我们将量化营养和干旱（及其相互作用）对这些物种的全株干旱表现的综合影响。我们还将评估实验和自然干旱的影响，在不同梯度的养分供应和土地利用（特别是施肥）的探索。在性状、整株植物、群落和生态系统水平上直接联系数据，将增加我们对当前和未来条件下营养和干旱对草地综合影响的机械理解。这些结果将具有重要的应用和科学意义。

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.