臭氧污染对南方典型常绿与落叶树种的生态风险评估

中国臭氧污染呈快速上升和蔓延趋势，导致我国绝大多数森林长期暴露于高浓度的臭氧环境，尤其是城市森林。植被叶片气孔吸收是臭氧干沉降的主要通道，叶片N含量与气候因子对气孔导度有显著交互作用。考虑到常绿与落叶树种的叶片属性差异及其臭氧敏感性不同，本项目选择多种常见常绿和落叶树种，开展4个氮水平和5个臭氧浓度的室外控制试验，研究不同臭氧和氮素处理下气体交换参数、N素含量、生物量等动态变化及复合效应；基于田间观测数据，开展叶片N含量与气孔导度响应关系的参数化研究；发展Jarvis型气孔导度模型和吸收通量模型，建立不同植物功能类型的臭氧吸收通量-效应响应关系，并与浓度暴露指数AOT40的剂量响应关系进行比较，明确臭氧对城市树木的影响临界值；评估城市森林对臭氧吸收净化及臭氧对亚热带地区生物量的影响。研究结果对于森林的臭氧风险评估、绿化树种选择、提出臭氧污染防控方案和实现碳中和目标具有重要的科学和应用价值。

In recent years, ozone pollution has been rising and spreading rapidly in China, leading to most forest exposure to high ozone concentration, especially for urban forest.. Stomatal ozone uptake by plant leaves is the main pathway of ozone dry deposition, and there is a significant interaction between leaf N content and stomatal conductance. Considering the difference in leaf trait and ozone sensitivity between evergreen and deciduous tree species, this project will expose six common evergreen and deciduous tree species to different combinations of four soil nitrogen levels and five ozone levels, under field conditions, to study the dynamic changes and combined treatment effects on gas exchange parameters, leaf N and biomass. Based on the obtained data, a parameterization will be carried out to incorporate leaf N content into the stomatal conductance function. The Jarvis type stomatal conductance model and ozone flux model will be developed, flux response relationships will be established for evergreen species and deciduous species. Moreover, the ozone flux –response relationship and concentration-based AOT40 metric will be compared and the ozone critical value of ozone impact on urban trees will be determined. Based on the results above, the ozone uptake by urban forest will be finally quantified and effects of ozone on biomass of subtropical forest will be evaluated. The results of this study have important scientific and practical value for improving ozone risk assessment of urban forest, choosing urban greening tree species, putting forward ozone pollution prevention and control plans, and realizing carbon neutral goal.