Declining Trend in the13C/12C Ratio of Atmospheric Carbon Dioxide from Tree Rings of South AfricanWiddringtonia cedarbergensis

Abstract

Stable carbon isotope chronologies using tree ring wood cellulose have proved useful for developing hypotheses on climate and environment change. However, within both the Southern Hemisphere and Africa there has been very little tree-ring-based isotope research. Here we report the first high-resolution (annual)13C/12C chronology for both Africa and the Southern Hemisphere. The 77-yr stable carbon isotope chronology was developed from sixWiddringtonia cedarbergensistrees from a site in the Cedarberg Mountains, Western Cape Province, South Africa. The results indicate that13C/12C ratios are not different from 1900 to 1949. After 1949, however, values become significantly more negative to 1977. The isotopic record from the pooled trees at the Die Bos site does not correlate with rainfall. This correlation is not significant even when theWiddringtoniastable carbon isotope record is de-trended for the anthropogenic CO2contribution. TheWiddringtoniarecord does, however, correlate significantly with atmospheric13C/12C CO2values derived from ice core data, tree ring13C/12C chronologies from the Northern Hemisphere, and recent Southern Hemisphere records.