Dendroclimatic interpretation of tree-rings in Agathis australis (kauri). 1. Climate correlation functions and master chronology.

In this paper we analyse nine existing Agathis australis (kauri) chronologies for their response to climate, and compare our results with those of previous studies. We update the southernmost chronology, from Katikati, which now extends to the 1997 growth ring (1997-98 growing season in Southern Hemisphere). We also employ recent standardisation procedures that have been demonstrated to eliminate the chance of biasing the chronology indices. Climate correlation functions are generated for all nine kauri chronologies, by correlating chronology indices with meteorological datasets. In an earlier study only a 12 month response window was analysed, combined with lagging the growth year in order to account for prior-season growth response. Our expanded dendroclimatic response window covers the 21 months from May of the year of growth (t), back to the previous September (year t - I). There are consistent significant correlations with climate for all nine kauri sites, most pronounced in the form of a positive response in season t to precipitation in the previous season (t - 1), and an inverse response to temperature in the year of growth. The most robust climate signal comes from the Katikati chronology, which has been updated by 16 years to the 1997 growth ring. The additional years allow for more degrees of freedom and a better estimate of the climate correlation functions. Correlation and Principal Component Analyses validate the combining of eight of the nine chronologies into one regional time series. The results presented in this paper are encouraging for future dendroclimatic research with Agathis australis, towards the goal of long-term reconstruction of climate.