Change search
ReferencesLink to record
Permanent link

Direct link
A 600 year long δ18O-record from cellulose of Breonadia salicina trees, South Africa
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
2008 (English)In: Dendrochronologia, no 26, 21-33 p.Article in journal (Refereed) Published
Abstract [en]

The oxygen isotope composition in cellulose was analysed along the growth axis of two 600-year-old Breonadia salicina trees (Matumi) from subtropical South Africa, with the aim of testing the isotope variations as a regional climate proxy. The visible tree rings in B. salicina are not annual and therefore radiocarbon analysis was applied to produce an age model for the isotope record, covering the time period between 1375 and 1995 AD. Before _1600 AD, a co-variation is evident between the variations in d18Ocellulose and previously published d13Ccellulose, indicating that a common factor is responsible for both the carbon and the oxygen isotope signals in the tree cellulose. Between _1600 and _1900 AD, the correlation between the isotope series weakens, concurrently with drastic changes in growth rates and average ring production rates. Possibly, this phase was a result of extreme changes in the growth environment, affecting the cellulose production rate, the source water d18O signal and the proportion of different types of oxygen isotope fractionation processes affecting the final isotope composition in the tree cellulose. We suggest that during the lifetime of the two B. salicina trees, different factors have governed the oxygen isotope signal in the cellulose. Both regional climate conditions and site-specific factors associated with the riparian growth environment have had an impact on the oxygen isotope variations in the two trees, clearly complicating the possibilities to utilise a d18Ocellulose record from this tree species for paleoclimatic reconstruction.

Place, publisher, year, edition, pages
2008. no 26, 21-33 p.
URN: urn:nbn:se:su:diva-24704ISI: 000259432000004OAI: diva2:198146
Part of urn:nbn:se:su:diva-7375Available from: 2011-01-17 Created: 2008-02-15 Last updated: 2011-01-17Bibliographically approved
In thesis
1. Late Quaternary climate and environmental change in the summer rainfall region of South Africa: A study using trees and wetland peat cores as natural archives
Open this publication in new window or tab >>Late Quaternary climate and environmental change in the summer rainfall region of South Africa: A study using trees and wetland peat cores as natural archives
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis contributes with information on past climate and environmental changes in South Africa’s summer rainfall region. The study is based on multi-proxy analyses on wetland peat cores and analyses of stable isotope composition (δ13C, δ18O) and wood anatomy in cross sections from subtropical trees (Breonadia salicina). The peat archive covers the last 16 ka (ka; 1000 cal yrs BP) and was analysed in terms of fossil pollen, charcoal, diatoms, phytoliths and stable isotope composition. The peat record infers relatively wet climate conditions at c. 13.7-12.8 ka, 10.5-9.5 ka and 2.5-0.5 ka, and drier conditions at c. 16-13.7 ka, 12.8-10.5 ka and during mid-Holocene. Tentatively, cooler late Pleistocene temperatures shifted towards warmer after c. 9.5 ka. The study of B. salicina demonstrates the paleo-climatic value of subtropical trees despite absence of annual tree rings. An age model was constructed from radiocarbon dating and calibration by wiggle matching. δ13C in B. salicina shows a co-variation with annual rainfall amounts, suggesting that it may be considered a regional climate-proxy. δ18O is mainly influenced by local factors, but acts as a useful complement when interpreting δ13C. Together with other regional, high-resolution records, the 600 year long δ13C-record suggests dry climate conditions in northern South Africa during the 1700s and mid-1500s AD. Inferred climate and environmental changes are suggested being a response to expansion, contraction and latitudinal shifts of the tropical, subtropical and mid-latitude atmospheric circulation cells. An observed inverse humidity pattern between southern and equatorial Africa suggests that ENSO-like teleconnections may be a possible forcing mechanism in a decadal to centennial time perspective.

Place, publisher, year, edition, pages
Stockholm: Institutionen för naturgeografi och kvartärgeologi, 2008. 108 p.
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 11
paleoclimate, Late Quaternary, pollen, stable isotopes, diatoms, phytoliths, dendroclimatology, South Africa
National Category
Physical Geography
Research subject
Physical Geography
urn:nbn:se:su:diva-7375 (URN)978-91-7155-581-6 (ISBN)
Public defence
2008-03-17, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 13:00
Available from: 2008-02-25 Created: 2008-02-15Bibliographically approved

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Norström, Elin
By organisation
Department of Physical Geography and Quaternary Geology (INK)

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 39 hits
ReferencesLink to record
Permanent link

Direct link