How does elevated tropospheric ozone exposure affect plant health over time?

随着时间的推移，对流层臭氧暴露增加如何影响植物健康？

• 批准号: 2439070
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2439070
• 关键词: How; does; elevated; tropospheric; ozone

Tropospheric ozone forms via photocatalysis of a free radical mechanism between NOx (NO and NO2) hydrocarbons and Volatile Organic Compounds (VOCs)1, resulting from industrial and transport pollution. Tropospheric ozone pollution has increased globally since 1950s2, and although ozone precursor emissions have plateaued in Europe and North America since the 1990s, long-range transport of ozone pollution produced in Asia and South America continues to raise European baselines3. Ozone exposure poses a major risk to both human4 and plant health5, as well as having a radiative forcing effect6.Ozone exposure causes oxidative stress in vegetation, leading to the increased release of VOCs by plants7 which in turn increase ozone production via a positive feedback effect8. Other key impacts of ozone on vegetation are early leaf drop (defoliation) and reduced growth. Ozone exposure affects critical growth stages, increases drought sensitivity and reduces the positive impact of nitrogen on root biomass accumulation9. At an ecosystem level, ozone exposure decreases primary productivity by limiting transpiration10 via stomatal closure. Ozone damage in forests can be monitored remotely via crown defoliation, discoloration and foliar injury.The Joint UK Land Environment Simulator (JULES) is a land surface model developed as a component of the Met Office and NERC Earth System Modelling Strategy. JULES currently uses the impact of stomatal conductance on growth as the single ozone linked parameter (ozone exposure reduces conductance), however the effects of ozone pollution on vegetation are complex11. The impact of chronic versus acute ozone exposure is poorly understood. Additionally, questions remain about long-term tree responses to changing ozone exposure. For example, to what degree do trees adapt to rising ozone baselines in terms of growth? There is debate as to whether ozone exposure limits plant CO2 uptake, or whether decreased stomatal flux under enhanced CO2 protects vegetation from ozone exposure.A better understanding of how changing ozone exposure affects vegetation in ecosystems would allow Earth system models, such as JULES, to better represent how plants respond to ozone fluxes across temporal and spatial scales. This improved representation of near surface ozone pollution would allow Earth system models to better predicts future carbon balances in a changing climate12.Chapter questions:1). What changes in global vegetation health can be attributed to ozone exposure via satellite data analysis?2). How does ozone exposure translate to physiological changes in trees? Do trees acclimate to chronic ozone exposure?3). How has changing ozone exposure over long time scales affected growth patterns in trees?4). How can the vegetation response to ozone in Earth System Models be improved to include longer term growth responses, as well as differences in susceptibility to ozone exposure potentially linked to past exposure?

对流层臭氧是通过工业和交通污染造成的 NOx（NO 和 NO2）碳氢化合物与挥发性有机化合物 (VOC)1 之间的自由基机制的光催化作用形成的。自 20 世纪 50 年代以来，全球对流层臭氧污染不断增加，尽管欧洲和北美的臭氧前体排放量自 20 世纪 90 年代以来已趋于稳定，但亚洲和南美洲产生的臭氧污染的长距离传输继续提高欧洲基线3。臭氧暴露对人类4和植物健康5构成重大风险，并具有辐射强迫效应6。臭氧暴露会导致植被氧化应激，导致植物释放挥发性有机化合物7增加，进而通过正反馈效应增加臭氧产量8 。臭氧对植被的其他主要影响是提前落叶（落叶）和生长减缓。臭氧暴露会影响关键的生长阶段，增加干旱敏感性并减少氮对根生物量积累的积极影响9。在生态系统层面，臭氧暴露通过气孔关闭限制蒸腾作用10，从而降低初级生产力。森林中的臭氧损害可以通过树冠落叶、变色和叶损伤进行远程监测。英国联合土地环境模拟器 (JULES) 是作为英国气象局和 NERC 地球系统建模战略的组成部分开发的陆地表面模型。 JULES 目前使用气孔导度对生长的影响作为单一臭氧相关参数（臭氧暴露会降低导度），但臭氧污染对植被的影响很复杂11。人们对慢性与急性臭氧暴露的影响知之甚少。此外，树木对臭氧暴露变化的长期反应仍然存在疑问。例如，树木在生长方面适应臭氧基线上升的程度如何？关于臭氧暴露是否会限制植物对二氧化碳的吸收，或者二氧化碳浓度增加时气孔通量的减少是否会保护植被免受臭氧暴露的影响，目前存在争议。更好地了解臭氧暴露的变化如何影响生态系统中的植被，将使地球系统模型（例如 JULES）能够更好地代表植物如何在时间和空间尺度上响应臭氧通量。这种近地表臭氧污染的改进表示将使地球系统模型能够更好地预测气候变化中的未来碳平衡12。章节问题：1)。通过卫星数据分析，全球植被健康的哪些变化可以归因于臭氧暴露？2)。臭氧暴露如何转化为树木的生理变化？树木能适应长期暴露在臭氧中吗？3)。长期变化的臭氧暴露如何影响树木的生长模式？4）。如何改进地球系统模型中植被对臭氧的响应，以包括长期生长响应，以及可能与过去暴露相关的对臭氧暴露的敏感性差异？