Restoring for a resilient future: Woodland community assembly trajectories in the face of multiple stressors

生态系统恢复是国际上提出的一种基于自然的气候解决方案。英国的目标是到2035年每年种植5万公顷的树木。这种种植有多个目标：解决生物多样性丧失问题，增加碳储量并实现净零，以及支持相关的生态系统服务共同效益。恢复轨迹朝向这些目标的方向取决于多种压力因素，包括干旱和土地退化的遗产，例如可以阻止林地演替的优势植被。然而，一个重要的压力来源--地表臭氧--仍然被忽视。尽管这是臭氧引起的净初级生产力下降近50%的证据。这表明臭氧的存在可能会严重损害多个恢复目标，特别是净零点。我们知道，对于个别树木来说，臭氧会损害气孔控制，降低根冠比。这使得受臭氧影响的植物更容易受到干旱等压力因素的影响，并改变了水分和营养吸收的关系。然而，我们对臭氧与其他应激源结合时如何影响社区集会恢复轨迹的了解非常有限。我们假设，在多个应激源的背景下，最初的恢复轨迹将取决于所涉及物种的功能特征。这是因为环境过滤器(即不同的压力源)可以作用于功能特征的分布。同时，胁迫可以改变表观遗传学和基因表达，从而影响植物功能。这篇博士论文利用实验和尖端分析技术，提出了以下问题：在存在其他胁迫因素(干旱、杂草物种)的情况下，臭氧是否会在初始林地群落恢复轨迹中产生更大的差异？功能特征、生态生理学和表观遗传机制之间的关系能否解释不同的恢复轨迹？最终，回答这些基础科学问题将有助于为植树干预和建模计划提供信息，以确保在联合国生态系统恢复十年之后具有弹性的恢复轨迹。

Ecosystem restoration is proposed internationally as a nature-based climate solution. The UK aims to plant50,000 ha trees per year by 2035. This planting has multiple aims: addressing biodiversity loss, increasingcarbon storage and reaching Net Zero, and bolstering associated ecosystem service co-benefits. Thedirection that restoration trajectories take towards these aims depends upon multiple stressors, includingdrought and land degradation legacies, for instance dominant vegetation that can arrest woodlandsuccession. However, an important stressor - surface-level ozone - remains overlooked. This is despiteevidence of ozone-induced declines in net primary productivity of near 50%. This suggests that the presenceof ozone could seriously compromise multiple restoration goals, particularly Net Zero.We know, for individual trees, that ozone can impair stomatal control and reduce root-to-shoot ratios. Thismakes ozone-affected plants more susceptible to stressors such as drought, and alters water and nutrientuptake relationships. However, we have very limited knowledge of how ozone, when combined with otherstressors, influences community assembly restoration trajectories. We hypothesize that initial restorationtrajectories in the context of multiple stressors will depend on the functional traits of species involved. Thisis because environmental filters (i.e. different stressors) can act on the distribution of functional traits. Atthe same time, stress can alter epigenetics and gene expression with consequences for plant function.This PhD, using experiments and cutting-edge analytical techniques, asks:Does ozone create greater divergence in initial woodland community restoration trajectories in thepresence of additional stressors (drought, co-occurring weed species)?Can relationships among functional traits, ecophysiology and epigenetic mechanisms explaindivergent restoration trajectories?Ultimately, answering these fundamental science questions will help inform tree-planting interventions andmodelling initiatives to ensure resilient restoration trajectories beyond the UN Decade of EcosystemRestoration.