ABSTRACT

Nitrogen contents and stable carbon isotope ratios of Zelkova serrata leaves collected from roadside trees in Toyama City, Japan were measured in order to judge the stress due to water availability and nutrient efficiency. Furthermore, the source of urban atmospheric CO₂ was examined from the isotopic discrimination between Zelkova serrata leaves and CO₂ in the ambient air based on the correlation between carbon isotope ratio and content of CO₂, since there was no stress associated with the roadside trees. The carbon isotope ratio of roadside tree leaves decreases with increasing traffic. This suggests that the atmospheric CO₂ in urban street is contaminated by exhaust gases of car.