增温和臭氧浓度上升对城市林木-香樟生长和气孔臭氧吸收的复合影响研究

With the rapid urbanization of our country, O3 pollution has become an increasing serious problem in many cities, where obvious degradation of urban forest caused by high level O3 has been observed. In the meantime, land surface temperature in urban area has increased greatly due to large emissions of greenhouse gases. Many cities have experienced extreme high temperature frequently in recent years. Temperature increases could cause great changes to plant physiology and further alter their responses to O3 stress. Clarifying the interactive effects of elevated temperature and O3 on plant growth is of great significance to O3 risk evaluation and plant protection, but few related researches have been carried out in our country. In this project, an environment with elevated temperature and O3 will be simulated using the open-top chamber system. The injury symptoms, stomatal characteristics, allocation of assimilation products and antioxidant capacity of Cinnamomum camphora cultivated in the chambers will be analyzed, and the influence mechanism of elevated temperature on plant O3 sensitivity will be revealed. Besides, based on the observed data of stomatal conductance (gs) and environmental variables, a set of model parameters for gs forecast of Cinnamomum camphora will be determined, through which the stomatal O3 flux can be calculated and compared among different treatments. Finally, the relationship between Cinnamomum camphora growth and stomatal O3 flux will be analyzed, and the stress risk of O3 pollution on Cinnamomum camphora will be assessed. Based on this project, a scientific basis could be provided to urban greening and O3 pollution control for the southern cities of our country.

近年来我国城市O3污染日益严重，高浓度O3已对城区林木生长造成严重威胁。与此同时，我国城市化增温效应明显，极端高温频繁发生于我国各大城市。气温升高可显著影响植物生理过程，进而改变其对O3胁迫的响应。鉴于国内有关增温对植物O3敏感性影响研究的缺乏，本项目拟以我国南方典型城市绿化林木-香樟为研究对象，利用开顶式熏气系统，模拟O3浓度和气温升高的生长环境，通过分析植株表观形态、气孔特征、同化产物分配和抗氧化参数的变化，揭示气温升高对香樟O3敏感性的影响机理。同时，利用气孔导度和环境因子实测数据，建立一套针对我国本土植物的气孔导度模拟参数，实现对其气孔O3吸收通量的计算和不同温度处理间通量差异的比较分析，并结合香樟生长损失数据，建立基于O3通量指标的剂量响应关系和风险评价方法，定量分析气温升高条件下O3污染对香樟个体的胁迫程度，为全球气候变化背景下我国南方城区的植被绿化和O3污染防控提供科学依据。

近年来我国城市O3污染日益严重，高浓度O3已对城区林木生长造成严重威胁。与此同时，我国城市化增温效应明显，极端高温频繁发生于我国各大城市。气温升高可显著影响植物生理过程，进而改变其对O3胁迫的响应。鉴于国内有关增温对植物O3敏感性影响研究的缺乏，本项目以我国南方典型城市绿化林木—香樟为研究对象，利用开顶式熏气系统，模拟O3浓度和气温升高的生长环境，主要研究了（1）大气O3浓度增加和气温升高对香樟个体形态、生理功能和同化产物分配的影响；（2）香樟气孔导度对不同环境因子的响应；（3）不同气温条件下，香樟气孔导度、气孔O3吸收通量的差异和O3通量—生物量关系；（4）不同温度下O3浓度指标和O3通量指标与植物生长损失的关系。基于本项研究发现：（1）香樟个体对O3具有极强的抗性，累积O3胁迫临界阈值（AOT40）非常高（>50 ppm h）；（2）O3处理和O3+增温复合处理显著影响了叶绿素a、叶绿素b和类胡萝卜素的含量，且O3和增温对香樟叶绿素含量具有明显的复合效应；（3）O3和增温两种处理对香樟叶片生理指标的影响存在一定的累加效应，该累加效应在丙二醛浓度变化上达到了显著水平；（4）O3和增温复合处理可导致叶片表面蜡质明显增厚；（5）O3和增温处理可明显降低香樟叶片气孔导度；（6）累积通量指标对O3处理下香樟生物量损失的拟合度较高，更适合用于评价O3污染对香樟生长胁迫的风险。本项研究初步揭示了O3胁迫和增温对香樟形态和生理过程的影响机理，明确了增温对香樟O3敏感性的影响过程，可为全球气候变化背景下我国南方城区的植被绿化和O3污染防控提供科学依据。