Historical droughts recorded in extended Juniperus procera ring-width chronologies from the Ethiopian Highlands

• Published in: International journal of biometeorology Vol. 64; no. 5; pp. 739 - 753
• Main Authors: Gebregeorgis, E. Gebrehiwot, Robertson, I., Koprowski, M., Zhou, L. P., Gao, P., Williams, A. P., Eshetu, Z., Wils, T. H. G.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2020; Springer Nature B.V
• Subjects: Animal Physiology; Annual precipitation; Biological and Medical Physics; Biophysics; Churches; Climate; Cores; Dental Porcelain; Drought; Droughts; Earth and Environmental Science; Environment; Environmental Health; Ethiopia; Hydroclimate; Image resolution; Juniperus; Mass spectrometry; Mass spectroscopy; Metal Ceramic Alloys; Meteorology; Original Paper; Plant Physiology; Titanium; Tree rings; Trees; Weather; Ethiopia; The Blue Nile River basin; Radiocarbon dating; Annual tree-rings; Pointer years; Tropical dendrochronology
• ISSN: 0020-7128; 1432-1254
• DOI: 10.1007/s00484-020-01863-7

In the Horn of Africa, little is known about temporal changes in hydroclimate owing to the influence of multiple weather systems, the complex terrain, and the sparse instrumental records. Absolutely dated tree-ring records offer the potential to extend our understanding of climate into the pre-instrumental era, but tree-ring studies in this region, and indeed all of tropical Africa, have been rare largely due to lack of an annual climate cycle that reliably produces annual tree-rings. In this study, 40 cores were obtained from 31 Juniperus procera trees growing in the grounds of Ethiopian Orthodox Tewahedo churches in the Gonder region of Ethiopia. The samples were cross-dated using a re-iterative process involving identifying anatomical features from high-resolution images. The tentative ring-width chronologies were revised after the determination of bomb-peak accelerator mass spectrometry radiocarbon dates. Individual series were significantly correlated to the respective master chronologies (r > 0.55; P  < 0.05), and expressed population signal values ranged from 0.55 to 0.92. Historical drought years were successfully traced in the chronologies by pointer year analysis. This study confirms that Juniperus procera growing in areas of unimodal precipitation exhibits annual tree-rings and offers the potential as an indirect measure of past climate.