Anomalous tree-ring identification facilitated by AMS 14C analysis in subtropical and tropical Australian Araucariaceae samples enables development of a long-term, high-resolution climate reconstruction

In Australia the majority of tropical and subtropical regions lack long-term instrumental climate records. Paleoclimate reconstructions from tree rings provide one alternative but very few dendrochronological investigations have so far been undertaken. Early assessments of mainland Australian tree species were discouraging due to the high prevalence of anomalous ring boundaries. Some species, however, were seen as more favourable than others including those in the Araucariaceae family which is common along the subtropical-tropical Australian east coast. These trees are longer lived than many other species in the region and contain growth rings known to be annual in nature and responsive to climatic conditions. There is however, a heavy prevalence of anomalous ring boundaries in species from this family which must be accounted for when dating these species. Here we describe the tree-ring characteristics and growth response from two stands of Hoop pine (Araucaria cunninghamii) trees located in subtropical and tropical Queensland, Australia (regions known for experiencing extreme hydroclimatic events). Confirmation of annual growth driven by moisture sensitivity was determined using radius dendrometers on four trees in Lamington National Park (c. 28º S). Tree cores were collected from both the Lamington stand as well as a stand at Hidden Valley near Paluma, Queensland (c. 19º S). Ring-width assessment showed the presence of false, faint, locally absent, and wedging rings in both sites. Results of bomb-pulse radiocarbon dating of selected single tree rings demonstrated that trees from this species can fall into one of three categories: A – those with locally-absent rings around the circumference of the trees, B – those where false rings were observed, and C – those with many wedging and locally-absent rings. Only trees in the first two categories were able to be included in the master chronologies. Traditional dendrochronological analysis with age validation by bomb-pulse radiocarbon dating allowed for a robust ring-width chronology from 1805-2014 CE to be developed for the Lamington National Park site. Growth-climate analysis of the master tree-ring chronology determined that the strongest environmental correlation was to wet season drought conditions. The strength of this response was compared to local and regional drought indices as well as to a long-term drought reconstruction. The combined analysis led to the development of a 200-year drought reconstruction for the region which shows influences from both the El Niño Southern Oscillation and the Interdecadal Pacific Oscillation. © The Authors

Keywords

Mass spectroscopy, Accelerators, Australia, Tropical regions, Climates, Trees, Pines, Queensland, Southern Oscillation

Citation

Haines, H., Palmer, J., Hua, Q., English., N., Hiscock, W., Turney, C., Marjo, C., Gadd, P., Kemp, J., & Olley, J. (2021). Anomalous tree-ring identification facilitated by AMS 14C analysis in subtropical and tropical Australian Araucariaceae samples enables development of a long-term, high-resolution climate reconstruction. Anomalous tree-ring identification facilitated by AMS 14C analysis in subtropical and tropical Australian Araucariaceae samples enables development of a long-term, high-resolution climate reconstruction. Paper presented to the 15th International Conference on Accelerator Mass Spectrometry. ANSTO Sydney, Australia. November 15th – 19th. (pp. 28). Retrieved from: https://ams15sydney.com/wp-content/uploads/2021/11/AMS-15-Full-Program-and-Abstract-Book-R-1.pdf

URI

https://ams15sydney.com/wp-content/uploads/2021/11/AMS-15-Full-Program-and-Abstract-Book-R-1.pdf
https://apo.ansto.gov.au/dspace/handle/10238/14406

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