EXPLORING THE 14C BOMB PEAK WITH TREE RINGS OF TROPICAL SPECIES FROM THE AMAZON FOREST

In this work we explore the radiocarbon (C-14) signal as an independent tool to assess the year of formation of individual tree rings of tropical species in northern Brazil. Three different species were analyzed in this work: Dipteryx magnifica, Enterolobium maximum, and Hymenolobium petraeum. The studied samples are from the stem of only one individual of each species, all cut down in 2008 in Porto Trombetas, Para, Brazil. Individual tree rings were identified based on wood anatomy and they were counted from bark to pith. Several rings were selected for C-14 analysis in order to cover the overall shape of the C-14 atmospheric bomb peak (after 1955). The C-14 content was measured at Laboratory of Radiocarbon, Universidade Federal Fluminense (LAC-UFF). Results are compared with the Southern Hemisphere C-14 atmospheric calibration curves. For E. maximum and H. petraeum the C-14 signal exhibits an overall good match with the SH zone 3 and suggests annual seasonality in the growth-ring formation. These species offer suitable characteristics for dendrochronology. The D. magnifica shows mismatches in the C-14 measurements that are likely a result of difficulties in identifying ring boundaries with certainty. Additional techniques may be helpful to disentangle the origin of this discrepancy.