Forest ecosystems and their resilience to climate extremes across Europe

在过去的几十年里，欧洲森林通过从大气中吸收大量的二氧化碳并将其储存为木材，在减缓气候变化的速度方面发挥了重要作用。然而，越来越多的证据表明，这种碳汇现在正在减弱，这可能会对将全球变暖控制在2摄氏度以内的国际努力造成灾难性后果。最近森林碳汇强度的下降被认为至少部分与欧洲炎热干燥夏季的频率和强度增加有关-包括2003年，2010年和2018-19年破纪录的热浪。如果欧洲的森林要继续成为向低碳未来过渡的解决方案的一部分，我们迫切需要了解这些生态系统如何受到极端水资源压力的影响并从中恢复。Fortress项目的总体目标是生成第一个关于极端高温和干旱如何影响欧洲森林固碳和储存碳的能力的完整图片：从单个树苗的生长和生存，到整个景观的种群动态。该项目采用操纵性实验、树木年轮记录的长期回顾性分析、来自泛欧无线树木传感器网络的实时生态生理数据、尖端遥感和机器学习的独特组合，旨在：（i）揭示哪些欧洲树种对极端气候最有适应力以及原因;揭示气候如何在每日、季节、年度和数十年时间尺度上限制树木生长和用水;以及（iii）开发下一代早期预警信号，利用一系列数据预测树木因液压故障而死亡的风险，包括卫星图像。在这样做的过程中，Fortress项目将从根本上改变我们未来管理，监测和模拟欧洲森林生态系统的能力。

Over the past several decades European forest have played a major role in slowing the pace of climate change by sequestering vast amounts of CO2 from the atmosphere and storing it as wood. However, growing evidence suggests that this carbon sink is now weakening, with potentially disastrous consequences for international efforts to keep global warming within 2 degrees C. This recent dip in the strength of the forest carbon sink is thought to be linked, at least in part, to a rise in the frequency and intensity of hot dry summers in Europe - including the record-breaking heatwaves of 2003, 2010 and 2018-19. If Europe's forests are to continue being part of the solution for transitioning to a low-carbon future, we urgently need to understand how these ecosystems are impacted by and recover from periods of extreme water stress. The overarching goal of the FORTRESS project is to generate the first complete picture of how extreme heat and drought impact the ability of European forests to sequester and store carbon: from the growth and survival of individual tree seedlings, to population dynamics across entire landscapes. Using a unique combination of manipulative experiments, long-term retrospective analyses of tree ring records, real-time ecophysiological data from a pan-European wireless tree sensor network, cutting-edge remote sensing and machine learning, this project aims to: (i) reveal which European tree species are most resilient to climate extremes and why; (ii) uncover how climate constrains tree growth and water use at daily, seasonal, annual and multi-decadal time scales; and (iii) develop the next generation of early warning signals that predict a tree's risk of mortality from hydraulic failure using a range of data, including satellite imagery. In doing so, the FORTRESS project will radically transform our ability to manage, monitor and model Europe's forest ecosystems into the future.