Radiocarbon adjustments to the dendrochronology of a yellowwood tree

Abstract

High-precision radiocarbon dating of a millennium-old yellowwood tree from the Midlands of Natal shows that the tree-rings do, in general, record annual growth, but that both missing and false rings occur. At two places along the transect of the trunk there are blocks of 19 and 143 missing rings, respectively, and during the time of most rapid growth some 20 false rings are identified. By matching the C-14 results to the radiocarbon calibration curve, an uncertainty of only two or three years is achieved in the dating. The data illustrate that the age of a tree can be determined accurately with radiocarbon, but this does require the analysis of several samples. The ring-width analysis shows periods of slower and more rapid growth over the centuries that are interpreted as reflecting changes in the precipitation rate in the summer rainfall region of South Africa. Five exceptionally narrow rings around 1820 suggest that five years of severe drought after two decades of very high rainfall may have been a contributing factor to the widespread tribal warfare and devastation that occurred at that time.