A 200-year drought record for the east coast of Australia from subtropical Araucaria cunninghamii tree rings

Authors: Heather A Haines*, Chronos 14Carbon-Cycle Facility, UNSW, Jonathan G Palmer, Chronos 14Carbon-Cycle Facility, UNSW, Nathan B English, Central Queensland University, Quan Hua, Australian Nuclear Science and Technology Organization , Patricia Gadd, Australian Nuclear Science and Technology Organization, Justine Kemp, Australian Rivers Institute, Griffith University, Jon M Olley, Australian Rivers Institute, Griffith University
Topics: Geomorphology, Australia and New Zealand, Paleoenvironmental Change
Keywords: dendroclimatology, drought, Australia, subtropical forest
Session Type: Virtual Paper
Day: 4/9/2021
Start / End Time: 3:05 PM / 4:20 PM
Room: Virtual 30
Presentation File: No File Uploaded

In Australia the majority of tropical and subtropical regions lack any long-term instrumental climate records. Tree rings provide one of the few options for climate reconstructions yet very few dendrochronological investigations have been undertaken. Discouragingly early assessments of Australian species indicated most were not suitable for dendroclimatology. One exception noted were trees in the Araucariaceae family. This is a common tree family along the subtropical-tropical Australian east coast, the trees are longer lived than many other species in the region, contain growth rings which are annual in nature, and grows in response to climatic conditions.

Here we examine in detail tree-ring characteristics and growth response from a stand of Araucaria cunninghamii trees located in subtropical Southeast Queensland, Australia (a region known for experiencing extreme hydroclimatic events). Our assessment shows the presence of false, faint, locally absent, and pinching rings. By combining traditional dendrochronological analysis with more recent techniques such as age validation by bomb-pulse radiocarbon dating and density analysis, a robust ring-width chronology from 1805-2014 was developed. Dendrometers installed on four trees confirmed that tree growth was annual, that moisture sensitivity was driving growth, and that the strongest correlation to the tree-ring chronology was to drought conditions. The strength of this response was compared to both local and regional drought indices and the long-term drought conditions shown by the ANZDA. The combined analysis led to the development of a 200-year drought reconstruction for the region and demonstrates influences from both ENSO and the IPO.

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