Matching Dendrochronological Dates with the Southern Hemisphere ¹⁴C Bomb Curve to Confirm Annual Tree Rings in Pseudolmedia rigida from Bolivia

Andreu Hayles, Laia; Santos, Guaciara M.; Herrera-Ramírez, David A.; Martin-Fernández, Javier; Ruiz Carrascal, Carlos Daniel; Boza-Espinoza, Tatiana E.; Fuentes, Alfredo F.; Jørgensen, Peter M.

This study used high-precision radiocarbon bomb-pulse dating of selected wood rings to provide an independent validation of the tree growth periodicity of Pseudolmedia rigida (Klotzsch & H. Karst.) Cuatrec. from the Moraceae family, collected in the Madidi National Park in Bolivia. ¹⁴C content was measured by accelerator mass spectrometry (AMS) in 10 samples from a single tree covering over 70 yr from 1939 to 2011. These preliminary calendar dates were determined by dendrochronological techniques and were also used to select the samples for ¹⁴C AMS. In order to validate these preliminary dates using the established Southern Hemisphere (SH) ¹⁴C atmospheric concentration data set, the targeted rings were selected to be formed during periods before and after the ¹⁴C bomb spike nuclear tests (i.e. 1950s–1960s). The excellent agreement of the dendrochronological dates and the ¹⁴C signatures in tree rings associated with the same dates provided by the bombpulse ¹⁴C atmospheric values for the SH (SHCal zone 1–2) confirms the annual periodicity of the observed growth layers, and thus the high potential of this species for tree-ring analysis. The lack of discrepancies between both data sets also suggests that there are no significant latitudinal differences between the ¹⁴C SHCal zone 1–2 curve and the ¹⁴C values obtained from the selected tree rings at this geographic location (14°33′S, 68°49′W) in South America. The annual resolution of P. rigida tree rings opens the possibility of broader applications of dendrochronological analysis for ecological and paleoclimatic studies in the Bolivian tropics, as well as the possibility of using wood samples from some tree species from this region to improve the quality of the bomb-pulse ¹⁴C SHCal curve at this latitude.


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Academic Units
Lamont-Doherty Earth Observatory
Biology and Paleo Environment
Tree Ring Lab
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December 12, 2016