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

随着气候、氮沉积和土地利用的变化，欧洲草原暴露在干旱事件的强度和频率以及氮素有效性的变化中。目前的研究表明，使植物在干旱和氮素限制条件下保持高水平表现的性状部分相似，部分相反。例如，较高的根冠比可以提高植物对干旱和氮素限制的抗性；但为了提高抗旱性，应尽可能提高光合作用水分利用效率，而在氮素限制条件下，低水分利用效率和高蒸腾速率可以促进氮素吸收。此外，干旱和氮素有效性通过水分和氮素吸收的耦合作用影响植物的表现。在这种背景下，我们对共同限制的最佳适应的理解尤其糟糕，特别是在植物种间竞争的条件下。下一个前沿是：1)识别使植物在干旱和氮素共同限制条件下最大限度地利用资源(获取和保存)的性状综合征；2)阐明它们背后的生理机制；3)估计植物竞争对手之间互补资源利用的潜力。这些知识对预测欧洲草原生态系统的未来非常重要。为了实现这些目标，计划进行三个相关的实验，其中两个将在法国穆利斯的CNRS理论和实验生态学站(SETE)进行，申请者将由Grégoire Freschet博士主持。这些实验将在温室中接近自然条件下进行，包括对水可获得性和氮素添加的全因素控制。第三个实验将是借调到法国蒙彼利埃的Ecotron设施进行的卫星研究，将与Alexandru Milcu博士合作进行。它将研究在非常严格控制的环境条件下水分利用和氮吸收的生态生理机制。

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.