Global warming and air pollution have been widely concerned in the world. It is indisputable that the regional increasing of air temperature and ozone (O₃) concentrations occurred frequently in past decades. Urban trees play important roles in decreasing environmental temperature and removing air pollutants. However, urban trees are often suffering from the impacts of abiotic factors such as heat wave and O₃ pollution, especially in summer in urban areas. By now, little information is known about the combined and interactive effects from air warming and elevated O₃ exposures on urban tree species. 

A research team led by Prof. Xingyuan He from the Institute of Applied Ecology (IAE) of the Chinese Academy of Sciences, along with their collaborators, reported that the significant interactive effects between increased air temperature and elevated O₃ on growth and physiological changes of urban tree species. 

The results showed that air warming of 2℃ alleviated the adverse effect of O₃ pollution on urban tree species by maintaining high antioxidative level and protecting photosynthetic apparatus by decreasing stomatal conductance.  

In addition, the species-specificity of urban trees was found in sensitivity to air warming and O₃, and the combination of the two factors. Researchers found that Ginkgo biloba was more sensitive than Populus alba ‘Berolinensis’ to both air warming and O₃, implying that G. biloba may be a good potential indicator species for regional warming and air pollution, particularly under environmental conditions as they co-occur in urban areas. 

The findings obtained may deepen our understanding of the physiological responses and ecological adaptations of urban tree species to multi-environmental factors, which will contribute to tree species selection and developing management strategies for urban forest under climate change. 

Their research paper "Experimental warming alleviates the adverse effects from tropospheric ozone on two urban tree species" was published online in Environmental Pollution. 

This research is financially supported by the National Natural Science Foundation of China.