Tree ring D/H ratio from Kenya, East Africa and its palaeoclimatic significance

Abstract

The D/H ratio of non-exchangeable hydrogen atoms in tree rings is a reliable record of the stable isotope ratio of source water used by a given tree during its growth. Depending on the site of growth, this source water has been shown to be the summer rains or groundwater or both. Because the isotope ratio of any of these source waters is influenced by climate, tree ring isotope data provide a fine climatic signature in most cases. However, isotope dendroclimate studies so far have been focused mainly in North America and to a lesser degree in Europe. We report here analysis of a record spanning 145 yr from a tree, Juniperus procera, from Kenya in East Africa. The D/H ratio correlates reasonably well with the recorded levels of the adjacent Lake Victoria and brings out interesting palaeoclimatic inferences from a region for which very little such data are available. Significantly, the relatively severe arid conditions around 1920s and the record rainfall around 1961 are reflected in the tree ring isotope ratio. This suggests that such tree ring isotope records could be used in the palaeoclimatic reconstruction of this area and could be applied to tropical environments.

Additional details