C-14 CONCENTRATIONS IN TREE STEMS .1.

The C-14 concentrations in trees sampled at various latitudes were mea sured with a Tandetron Accelerator Mass Spectrometer at Nagoya Univers ity. The growing periods of the parts for C-14 measurements were estim ated by the relationship between meteorological conditions and the app earance of anatomical features of annual rings such as false rings, la tewood formation, and so on. The following results were obtained: 1. T he latitude dependence of the C-14 variation is found in tree stems as well as in the atmosphere. 2. The C-14 concentrations in tree stems a re almost equal to those in the atmosphere at the latitude where the t ree had grown and at the time when the sampled section is formed. Ther efore the C-14 concentrations in the atmosphere are estimated by those of the tree stems. 3. The time when the C-14 concentration in the tre e showed its maximum value has difference of 1-2 years with that of th e latitude where the tree had grown. 4. This phenomena seemed to be re lated closely with the mechanism of global mixing of (CO2)-C-14 produc ed by atmospheric nuclear weapon tests. This mechanism causes a time l ag of C-14 variation between northern and southern hemisphere.