Forests out of balance: The impacts of drought-induced tree mortality on carbon and water cycling

气候变化正在增加干旱事件的严重性和频率。对树木和森林特别有害的是干旱时期延长，同时伴随着热浪。据观察，这些所谓的热旱事件在包括中欧在内的世界许多地区引发了树木死亡。随着气候变化，大气中的二氧化碳浓度正在增加，这可能会减轻树木对干旱事件的生理反应。在这里，模型可以帮助解决多种环境变化的复杂性，但目前的模型发展缺乏树木导水率、光合作用、组织衰老和树木死亡之间的关键交互作用。因此，我们希望通过对几个树种的最先进的水力描述来增强基于过程的模型，这些描述将与其他关键的植物生理过程相联系。这将使我们能够研究干旱事件频率的增加将如何改变未来大气条件下的树木死亡率和森林碳吸收。对于跨尺度的参数化和评估，将使用从自己的叶片气体交换实验结果到来自遥感研究和森林监测网络的树木死亡数据的丰富数据。该项目的主要目的是评估欧洲森林在潜在的未来、更极端的气候条件下的碳汇潜力。

Climate change is increasing the severity and frequency of drought events. Particularly detrimental to trees and forests are prolonged drought periods alongside co-occurring heatwaves. These so-called hot drought events have been observed to trigger tree mortality in many regions world-wide, including Central Europe. Alongside climate change, atmospheric CO2 concentrations are increasing, which may potentially mitigate tree physiological responses to drought events. Here, models can help to tackle the complexity of multiple environmental change, but current model developments lack critical interactions between tree hydraulic conductivity, photosynthesis, tissue senescence and tree mortality. Therefore, we want to enhance a process-based model with a novel state-of-the-art hydraulic description for several tree species that will be linked to other critical plant physiological processes. This will allow us to address how an increased frequency of drought events will alter tree mortality rates and forest carbon uptake under future atmospheric conditions. For parametrization and evaluation across scales, a wealth of data will be used reaching from own experimental results of leaf gas-exchange to tree mortality data from remote sensing studies and forest monitoring networks. The main aim of the project is to assess the carbon sink potential of European forest stands under potential future, more extreme climate conditions.