Developing tree-ring chronologies and climate reconstructions from moisture sensitive Araucariaceae trees in tropical and subtropical Australia

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Australasian Quaternary Association Inc.
Many parts of tropical and subtropical Australia lack both annually-resolved long-term instrumental climate data and proxy climate records. This limits our understanding of past climate patterns and impacts. There are however, remnant forest stands where dendroclimatology could be applied to extend the climate record. Tree species in these regions are known to be compromised by numerous ring anomalies and as such are understudied resulting in indistinct tree growth-climate relationships. Recent research of trees in the Araucariaceae family has attempted to address these issues with the goal being to develop long-term climate reconstructions across tropical and subtropical Australia. Araucariaceae trees are commonly found across northern and eastern Australia and are longer lived than many other local non-temperate species. They are known to produce growth rings that are mostly annual and their growth appears sensitive to climate, specifically to moisture conditions. Three Araucariaceae species, hoop pine (Araucaria cunninghamii), bunya pine (Araucaria bidwillii) and purple kauri pine (Agathis atropurpurea) have been studied at five locations within the rainforests of eastern Queensland. Ring anomalies including false, faint, locally absent, and pinching or wedging rings, were identified. This was done by applying bomb-pulse radiocarbon dating and Itrax radiographic analysis to hoop pine trees from subtropical Lamington and D’Aguilar National Parks respectively. Additionally, dendrometers were installed on trees of all three species so that the climate variables influencing seasonal growth could be identified. It was found that moisture conditions drive annual growth in Araucariaceae trees but that the onset and cessation of the growth season is dependent on temperature. Forest elevation also needs to be considered as the growth season length is longer at lower elevation and there is an influence of cloud cover seen in the north Queensland rainforest, which is close to a cloud forest classification. Annual growth was confirmed for all species through this analysis and the suitability for their use in climate reconstruction proven. Following this, a 164-year drought reconstruction for Southeast Queensland was developed using hoop pine trees from the subtropical rainforest of Lamington National Park. Additional work is continuing to further develop a network of long-term Queensland tree-ring climate records. © The Authors
Tree rings, Climates, Climate models, Moisture, Trees, Australia, Tropical regions, Forests, Climatic change, Queensland
Haines, H. A., English, N. B., Hua, Q., Olley, J. M., Gadd, P. S., Palmer, J. G., & Kemp, J. (2018). Developing tree-ring chronologies and climate reconstructions from moisture sensitive Araucariaceae trees in tropical and subtropical Australia. Paper presented at the AQUA Biennial Conference, Canberra, 10-14 December 2018. (pp. 85).