Variations in the stable carbon isotope ratios of Zelkova serrata

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 nutri-ent efficiency. Furthermore, the source of urban atmospheric CO2 was examined from the isotopic dis-crimination 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 atmos-pheric CO2 in urban street is contaminated by exhaust gases of car. exhibit more positive δ13C values under water stressed conditions, values changing by a much as 5.4‰. On the other hand, if there is no stress on urban roadside trees, the δ13C values of leaves are mainly controlled by those of atmospheric CO2. The aim of present study is to judge the stress due to water availability and nutrient efficiency from investigation of Zelkova serrata carbon iso-tope and nitrogen content at Sakuradori Street in Toyama City. We also would like to clarify the source of atmospheric CO2 from the isotopic dis-crimination between this plant and CO2 when there is no stress associated with Zelkova serrata