Wood density provides new opportunities for reconstructing past temperature variability from southeastern Australian trees
AffiliationThe Laboratory of Tree-Ring Research, University of Arizona
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CitationO'Donnell, Alison J., Kathryn J. Allen, Robert M. Evans, Edward R. Cook, Valerie Trouet, and Patrick J. Baker. "Wood density provides new opportunities for reconstructing past temperature variability from southeastern Australian trees." Global and Planetary Change 141 (2016): 1-11.
JournalGlobal and Planetary Change
Rights© 2016 Elsevier B.V. All rights reserved.
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AbstractTree-ring based climate reconstructions have been critical for understanding past variability and recent trends in climate worldwide, but they are scarce in Australia. This is particularly the case for temperature: only one tree-ring width based temperature reconstruction – based on Huon Pine trees from Mt Read, Tasmania – exists for Australia. Here, we investigate whether additional tree- ring parameters derived from Athrotaxis cupressoides trees growing in the same region have potential to provide robust proxy records of past temperature variability. We measured wood properties, including tree-ring width (TRW), mean density, mean cell wall thickness (CWT), and tracheid radial diameter (TRD) of annual growth rings in Athrotaxis cupressoides, a long-lived, high-elevation conifer in central Tasmania, Australia. Mean density and CWT were strongly and negatively correlated with summer temperatures. In contrast, the summer temperature signal in TRW was weakly positive. The strongest climate signal in any of the tree-ring parameters was maximum temperature in January (mid-summer; JanTmax) and we chose this as the target climate variable for reconstruction. The model that explained most of the variance in JanTmax was based on TRW and mean density as predictors. TRW and mean density provided complementary proxies with mean density showing greater high-frequency (inter-annual to multi-year) variability and TRW showing more low-frequency (decadal to centennial-scale) variability. The final reconstruction model is robust, explaining 55% of the variance in JanTmax, and was used to reconstruct JanTmax for the last five centuries (1530–2010 C.E.). The reconstruction suggests that the most recent 60 years have been warmer than average in the context of the last ca. 500 years. This unusually warm period is likely linked to a coincident increase in the intensity of the subtropical ridge and dominance of the positive phase of the Southern Annular Mode in summer, which weaken the influence of the band of prevailing westerly winds and storms on Tasmanian climate. Our findings indicate that wood properties, such as mean density, are likely to provide significant contributions toward the development of robust climate reconstructions in the Southern Hemisphere and thus toward an improved understanding of past climate in Australasia.
NoteAvailable online 10 April 2016. 24 month embargo.
VersionFinal accepted manuscript
SponsorsThis research was funded by an Australian Research Council Discovery Project grant (DP120104320 to PJB). We are grateful to Michael Goddard for assistance in preparing core samples for analysis, Scott Nicholls for assistance in preparing and analysing samples, and the participants of the Dendroclimatology Masterclass as part of WorldDendro2014: Anders Brundin, Binod Dawadi, Nathan English, Maarit Kalela-Brundin, Robert Kennedy, Kathelyn Paredes, and Meritxell Ramirez-Olle. We are also grateful to Wasyl Drosdowsky for providing the STR intensity index data and Martin Visbeck for providing the monthly instrument-based reconstruction of the SAM. LamontDoherty Earth Observatory Contribution No. 7991.