The steadily increasing global carbon dioxide concentration is further recognized through the decreasing trend of 13C/12C isotopic ratio in the annual rings of twentieth-century trees. The decrease is averaged to about 0.012 per mil per year which is attributed not only as due to anthropogenic fossil-fuel burning but also to the man’s impact on the land pattern.
Received: 1979-3-19
Revised: 1979-4-17
Published Online: 2014-6-2
Published in Print: 1979-8-1
© 1946 – 2014: Verlag der Zeitschrift für Naturforschung
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