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

摘要

This work reports the first high-precision C-14-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 C-14 time-scale for the Southern Hemisphere (SH). The tree rings analyzed here came from a single tree of Parana pine (Araucaria angustifolia) growing at 22 degrees 50'S, 46 degrees 04'W (Camanducaia, Minas Gerais, Brazil). A slight depletion of atmospheric C-14 after 1927 AD was observed, due to the Suess effect. Our C-14 results also showed the rise and rapid decrease of atmospheric C-14 concentrations associated with the detonation of nuclear weapons during the late 50s, and its subsequent uptake by other large C sinks. Current C-14 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/C-14 data with the SH Zone 1-2 compilation dataset shows this subtropical tree species' potential to refine the C-14 calibration curve. (C) 2014 Elsevier B.V. All rights reserved.