Climate signal in Pericopsis elata tree rings d18O series and potential for precipitation reconstructions in the eastern Congo Basin

Résumé fourni par la source

it is unclear whether pronounced droughts reaching the most remote regions of the Congo Basin are within a historical norm or have occurred only in the last decades. There is a growing evidence that a number of species with anatomically distinct rings can be used for dendroclimatological studies in the Congo Basin, such as Afrormosia (Pericopsis elata) (PEEL). Annual growth increments, i.e. Tree-Ring Width (TRW), are often co-determined by many environmental factors and yield low potential for reconstructions. Earlier work has shown that δ18O measured in PEEL tree rings holds a precipitation amount effect. Here we focus on new P. elata isotope series to estimate the isotope-precipitation relationship at the annual-scale and discuss its potential for reconstructing precipitation variability back to 1850 AD. δ18O values yielded better sensitivity as well as coherence between trees compared to TRW. Lower δ18O values (28-29‰) after 1960 reflect the anomalously wetter conditions between 1950 and 1970 recorded in the Congo Basin and neighbouring areas. Higher δ18O values after 1970 are in agreement with the reduction in precipitation reflected in gauges and satellite data. Further comparisons with instrumental data and other proxies can refine a precipitation reconstruction currently extending to 1850 AD.

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