Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Discussion papers
https://doi.org/10.5194/bg-2019-325
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-325
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 26 Aug 2019

Submitted as: research article | 26 Aug 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

High resolution 14C bomb-peak dating and climate response analyses of subseasonal stable isotope signals in wood of the African baobab – A case study from Oman

Franziska Slotta1,2, Lukas Wacker3, Frank Riedel1, Karl-Uwe Heußner4, Kai Hartmann1, and Gerhard Helle1,2 Franziska Slotta et al.
  • 1Freie Universität Berlin, Institute of Geological Sciences, Berlin, Germany
  • 2GFZ German Research Centre for Geosciences, Section 4.3 Climate Dynamics and Landscape Evolution, Potsdam, Germany
  • 3ETH Zürich, Laboratory of Ion Beam Physics, Zürich, Switzerland
  • 4Deutsches Archäologisches Institut, Scientific Department of the Head Office, Berlin, Germany

Abstract. The African baobab, Adansonia digitata, has great paleoclimatological potential because of its wide distributional range and millennial lifespan. However, dendroclimatological approaches are hampered by dating uncertainties due to its parenchyma-dominated wood anatomy. Here, securely-dated time series of annual wood increment growth and intra-ring stable isotopes of carbon and oxygen of cellulose for a baobab tree from Oman covering 1941 to 2005 were established. Precise dating with the bomb peak by highly resolved 14C measurements proved the annual character of the baobab's growth rings. But, F14C values of tree-ring cellulose were found up to 8.8 % lower than in the corresponding atmospheric CO2 for the period around the bomb peak. In conjunction with a considerable autocorrelation of the δ13C series this points to the incorporation of previous years' carbon significantly affecting the average age of derived wood. Terminal parenchyma bands, marking the tree-ring boundaries, were found to be significantly younger than their corresponding tree ring indicating that parenchyma tissue is alive for many years undergoing cell division, reorganization and potential growth. No autocorrelation was found in the δ18O series of tree-ring cellulose despite the huge water-storage potential of this stem-succulent tree species. Tree-ring width and stable isotope ratios have revealed significant climate sensitivity. δ18O was found to be a good climate proxy followed by tree-ring width and δ13C. Tree-ring width and intra-ring δ18Omin correlated well with each other and with precipitation amount for the period from pre-monsoon May to the end of the monsoon season in September/October. Intra-annual stable isotope courses were found rather similar for both δ13C and δ18O. Years with particularly low monsoon rain were reflected by increased stable isotope values in the mid-section of intra-annual courses. Distinct patterns with low subseasonal isotope values seem indicative for years with heavy rainfall events from pre-monsoonal cyclones. Rain events from post-monsoonal cyclones may also be recorded, however, only two years of observation prevent from a conclusive evaluation.

Franziska Slotta et al.
Interactive discussion
Status: open (until 07 Oct 2019)
Status: open (until 07 Oct 2019)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
[Subscribe to comment alert] Printer-friendly Version - Printer-friendly version Supplement - Supplement
Franziska Slotta et al.
Franziska Slotta et al.
Viewed  
Total article views: 230 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
177 51 2 230 0 0
  • HTML: 177
  • PDF: 51
  • XML: 2
  • Total: 230
  • BibTeX: 0
  • EndNote: 0
Views and downloads (calculated since 26 Aug 2019)
Cumulative views and downloads (calculated since 26 Aug 2019)
Viewed (geographical distribution)  
Total article views: 164 (including HTML, PDF, and XML) Thereof 164 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Cited  
Saved  
No saved metrics found.
Discussed  
No discussed metrics found.
Latest update: 19 Sep 2019
Publications Copernicus
Download
Short summary
The African baobab is a challenging climate- and environmental archive for its semi-arid habitat due to dating uncertainties and parenchyma-rich wood anatomy. Annually resolved F14C data of tree-ring cellulose (1941–2005) from a tree in Oman shows the annual character of the baobab's growth rings but were found up to 8.8 % lower than expected for 1964–1967. Sub-seasonal δ13C and δ18O patterns reveal years with low average monsoon rain as well as heavy rainfall events from pre-monsoonal cyclones.
The African baobab is a challenging climate- and environmental archive for its semi-arid habitat...
Citation