Application of the Minimum Blue-Intensity Technique to A Southern-Hemisphere Conifer

Abstract

Minimum blue-intensity (BI) appears to be a viable source of proxy-temperature data, but is yet to be applied to a Southern-Hemisphere species. Here, we apply the BI technique to Podocarpus lawrencei, a conifer endemic to the Australian Alps. We develop sample-preparation protocols and examine the climate sensitivity of resulting tree-ring width (TRW) and BI chronologies. We found that extractable resins were removed from P. lawrencei samples after 28 hours of Soxhlet extraction and a highly-significant negative correlation (r =-0.79, p<0.0001) exists between the resulting BI chronology and growing season (August-April) temperature maxima. The climate sensitivity of our BI data, combined with an apparent teleconnection with a previously-reported dataset, suggests that an unparalleled opportunity exists to develop a powerful proxy for growing-season temperatures in southeast Australia. © 2016 by The Tree-Ring Society.