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Isotope composition of Zelkova serrata leaves as an indicator of atmospheric pollution in Japan

In spite of increasing concern regarding the effects of greenhouse gases, atmospheric CO2 concentration continues to increase, with current levels now as high as 370 ppm. This elevated CO2 concentration influences not only atmospheric characteristics, but also ground vegetation: leaf structure, chemical composition and carbon-isotope composition are all affected. It was with this in mind that we investigated the viability of coupling an isotopic and a botanical approach to determine leaf interaction in relation to atmospheric pollution levels. Results show that, among the botanical indexes considered, the most reliable proxy of atmospheric CO2 levels would appear to be leaf mass per area (LMA), which increases with pollution. Our study also shows that LMA determination coupled with carbon-isotope compositions is a sensitive tracer of the local pollution-level variations.