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Evaluating the dendroclimatological potential of blue intensity on multiple conifer species from Australasia


Wilson, R and Allen, K and Baker, P and Blake, S and Boswijk, G and Buckley, B and Cook, E and D'Arrigo, R and Druckenbrod, D and Fowler, A and Grandjean, M and Krusic, P and Palmer, J, Evaluating the dendroclimatological potential of blue intensity on multiple conifer species from Australasia, Biogeosciences, 18, (24) pp. 1-41. ISSN 1726-4170 (2021) [Refereed Article]

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Author(s) 2021. This is an open access article under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License, (

DOI: doi:10.5194/bg-2021-119


We evaluate a range of blue intensity (BI) tree-ring parameters in eight conifer species (12 sites) from Tasmania and New Zealand for their dendroclimatic potential, and as surrogate wood anatomical proxies. Using a dataset of ca. 1015 trees per site, we measured earlywood maximum blue reflectance intensity (EWB), latewood minimum blue reflectance intensity (LWB) and the associated delta blue intensity (DB) parameter for dendrochronological analysis. No resin extraction was performed, impacting low frequency trends. Therefore, we focused only on the high frequency signal by detrending all tree-ring and climate data using a 20-year cubic smoothing spline. All BI parameters express low relative variance and weak signal strength compared to ring-width. Correlation analysis and principal component regression experiments identified a weak and variable climate response for most ring-width chronologies. However, for most sites, the EWB data, despite weak signal strength, expressed strong calibrations with summer temperatures. Significant correlations for LWB were also noted, but the sign of the relationship for most species is opposite to that reported for all conifer species in the Northern Hemisphere. DB performed well for the Tasmanian sites but explained minimal temperature variance in New Zealand. Using the full multi-species/parameter network, excellent summer temperature calibration was identified for both Tasmania and New Zealand ranging from 52 % to 78 % explained variance, with equally robust independent validation (Coefficient of Efficiency = 0.41 to 0.77). Comparison of the Tasmanian BI reconstruction with a wood anatomical reconstruction shows that these parameters record essentially the same strong high frequency summer temperature signal. Despite these excellent results, a substantial challenge exists with the capture of potential secular scale climate trends. Although DB, band-pass and other signal processing methods may help with this issue, substantially more experimentation is needed in conjunction with comparative analysis with ring density and quantitative WA measurements.

Item Details

Item Type:Refereed Article
Keywords:blue light intensity, Tasmania, New Zealand, conifers
Research Division:Earth Sciences
Research Group:Physical geography and environmental geoscience
Research Field:Palaeoclimatology
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Allen, K (Dr Kathy Allen)
ID Code:147768
Year Published:2021
Deposited By:Geography and Spatial Science
Deposited On:2021-11-15
Last Modified:2022-11-02
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