Tree-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.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/621340 |
| Date | 06 1900 |
| Creators | O'Donnell, Alison J., Allen, Kathryn J., Evans, Robert M., Cook, Edward R., Trouet, Valerie |
| Contributors | The Laboratory of Tree-Ring Research, University of Arizona |
| Publisher | Elsevier B.V. |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | Article |
| Rights | © 2016 Elsevier B.V. All rights reserved. |
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