Annual nature of the growth rings of Araucaria araucana confirmed by radiocarbon analysis

Abstract

During the late 1950s and early 1960s, thermonuclear tests added considerable amounts of 14C to the atmosphere. Since that time the amount has declined, which is owed to the exchange and dispersal of 14C into the Earth's carbon reservoirs, creating an isotopic chronometer (the 14C bomb peak) to all living organisms. In this study, we make use of this alternative radiometric method to compare dendrochronological ages with the 14C signature of wood samples, as a way to independently confirm the annual nature of the growth rings of Araucaria araucana trees growing in a northern Patagonia (38°52'S, 70° 34'W) site, represented by a forest of old living specimens of ca. 900 years. High precision 14C-AMS of selected tree-rings from two trees confirms the annual frequency of the ring formation against an existing dataset of atmospheric 14C values in the SH Zone 1-2, validating these tree specimens for further use on improving the temporal resolution of the 14C age calibration curve for the Southern Hemisphere.