Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy.
Sci Total Environ. 2021 Feb 20;756:143795. doi: 10.1016/j.scitotenv.2020.143795. Epub 2020 Nov 27.
Tropospheric ozone (O) levels are still elevated in many regions of the world including Northern Hemisphere forests areas, and are predicted to increase further due to anthropogenic activities and climate change. Oaks are major woody angiosperms in the Northern Hemisphere in terms of biodiversity, ecological dominance, and economic values. This meta-analysis shows overwhelming evidence of the O effects on 51 growth, anatomical, biomass, physiological and biochemical parameters of 14 deciduous or evergreen oak species distributed all around the Northern Hemisphere. Although no large impacts were observed on biomass, suggesting an O tolerance by oaks, some impairments were found at physiological level that might negatively affect carbon sequestration and water vapour transfer to the atmosphere. This outcome suggests the need to incorporate this phenomenon into future projection studies dealing with how atmospheric change and forest biomes will interact in effecting climatic change. Among the antioxidants used by oaks to respond to O, phenols seem to have a crucial role. Deciduous species resulted more affected by O than evergreen ones, as well as oaks native to Eurasia, in comparison with those from North-America. Experiments performed in less controlled environments showed more O deleterious effects, especially under higher AOT40 levels, but negative impacts were also reported for acute O exposures. Most of the reviewed studies with additional treatments to O exposure investigated the interaction(s) between O and drought, but the negative effects induced by drought seemed not to be exacerbated by the pollutant. However, more combined experiments on the impact of O and co-occurring stressors on woody species are necessary. Another major issue is the lack of experiments on adult trees. To better understand O impacts, and to reinforce the strength of O impact predictions, O controlled experiments on young individuals should be combined with long-term experiments on mature trees grown in open-air conditions.
对流层臭氧 (O) 水平在包括北半球森林地区在内的世界许多地区仍然很高，并且由于人为活动和气候变化，预计还会进一步增加。橡树在北半球的生物多样性、生态优势和经济价值方面是主要的木本被子植物。这项荟萃分析表明，臭氧对分布在北半球各地的 14 种落叶或常绿橡树物种的 51 个生长、解剖、生物量、生理和生化参数的影响具有压倒性的证据。虽然没有观察到对生物量的大影响，表明橡树对臭氧具有耐受性，但在生理水平上发现了一些损伤，这可能会对碳固存和水蒸气向大气的传输产生负面影响。这一结果表明，需要将这一现象纳入未来的研究中，研究大气变化和森林生物群系将如何相互作用，从而影响气候变化。在橡树用于应对 O 的抗氧化剂中，酚类似乎起着关键作用。与来自北美的橡树相比，落叶树种比常绿树种以及欧亚大陆的橡树受到 O 的影响更大。在控制条件较差的环境中进行的实验显示出更多的 O 有害影响，尤其是在 AOT40 水平较高的情况下，但也有报道称急性 O 暴露会产生负面影响。在对 O 暴露进行额外处理的审查研究中，大多数研究都调查了 O 与干旱之间的相互作用，但干旱引起的负面影响似乎没有因污染物而加剧。然而，对于木本物种的 O 和共同胁迫因素的综合实验仍然是必要的。另一个主要问题是缺乏对成年树木的实验。为了更好地了解 O 的影响，并加强 O 影响预测的力度，应该将对年轻个体的 O 控制实验与在开放条件下生长的成熟树木的长期实验相结合。
