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Gebregeorgis EG, Robertson I, Koprowski M, Zhou LP, Gao P, Williams AP, Eshetu Z, Wils THG. Historical droughts recorded in extended Juniperus procera ring-width chronologies from the Ethiopian Highlands. Int J Biometeorol 2020; 64:739-753. [PMID: 32008098 PMCID: PMC7220890 DOI: 10.1007/s00484-020-01863-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 11/27/2019] [Accepted: 01/09/2020] [Indexed: 06/10/2023]
Abstract
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.
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Affiliation(s)
- E Gebrehiwot Gebregeorgis
- Department of Ecology and Biogeography, Faculty of Biology and Environment Protection, Nicolaus Copernicus University, Lwowska 1, 87-100, Torun, Poland.
- Department of Plant Biology and Biodiversity Management, Addis Ababa University, P.O.Box 3434, Addis Ababa, Ethiopia.
| | - I Robertson
- Department of Geography, College of Science, Swansea University, Singleton Campus, Swansea SA2 8PP, UK
| | - M Koprowski
- Department of Ecology and Biogeography, Faculty of Biology and Environment Protection, Nicolaus Copernicus University, Lwowska 1, 87-100, Torun, Poland
| | - L P Zhou
- Department of Geography, Peking University, Beijing, 100871, China
| | - P Gao
- Department of Geography, Peking University, Beijing, 100871, China
| | - A P Williams
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
| | - Z Eshetu
- Department of Earth Science, College of Life Science, Climate Science Center, Addis Ababa University, Addis Ababa, Ethiopia
| | - T H G Wils
- Department of Geography, School of Teacher Training for Secondary Education, Fontys University of Applied Sciences, Tilburg, The Netherlands
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