Annual growth rings in a sample of Paraná pine (Araucaria angustifolia): Toward improving the 14C calibration curve for the Southern Hemisphere

This work reports the first high-precision 14C-AMS dating of holocellulose from a Brazilian subtropical species for the period 1927–1997, with the goal to identify suitable Southern American tree species that will serve as benchmarks for improving the calibration of the 14C time-scale for the Southern Hemisphere (SH). The tree rings analyzed here came from a single tree of Paraná pine (Araucaria angustifolia) growing at 22°50′S, 46°04′W (Camanducaia, Minas Gerais, Brazil). A slight depletion of atmospheric 14C after 1927 AD was observed, due to the Suess effect. Our 14C results also showed the rise and rapid decrease of atmospheric 14C concentrations associated with the detonation of nuclear weapons during the late 50s, and its subsequent uptake by other large C sinks. Current 14C data can be used for the study of the global carbon cycle, forensic sciences applications, and the determination of the age and growth rate of tropical trees without annual ring patterns. The remarkable overall agreement of our tree-ring/14C data with the SH Zone 1–2 compilation dataset shows this subtropical tree species' potential to refine the 14C calibration curve.