Friday, January 24, 2014

University of Auckland Tree-Ring Lab

I had the opportunity to visit the University of Auckland, School of the Environment, Tree-Ring Lab prior to our post-conference tour. Gretel Boswijk, Anthony Fowler, and George Perry are the main researchers in this lab and they specialize in the Kauri long chronology that now extends back to 2500 BC and climate reconstruction. This is made from long living samples, archaeological wood, and sub-fossil wood buried in bogs (up to 2000 years in age). You can see their long chronology printed out and taped on the wall.

Drew Lorrey is another dendrochronologist in Auckland who co-lead our post conference tour. He has his own lab at the National Institute of Water and Atmospheric Research which is a Crown Research Institute established in 1992.
The Auckland Tree-Ring Lab mainly uses Hansen design measuring stages with linear encoders added by their physics mechanical group. They measure their samples and visually compare the line plots of ring width to determine a visual age. Then they use computer programs to examine the statistical match of the date which provides r values and t values for them to assess the quality of the match. They have mainly used Dendro for Windows developed by Ian Tyers in Sheffield, although this program is no longer supported. They have also used Baillie and Pilcher’s Cross73 and Martin Munro’s Cross84. They have traditionally plotted graphs on a printer to visually compare on a light table. They would annotate the graphs for questionable areas that needed to be checked on the wood. Now they use Corina which was developed by Peter Brewer and the Cornell lab (now at the Laboratory of Tree-Ring Research in Tucson) to visually match plots on the computer screen.  Corina also enables them to combine visual and statistical crossdating.  Gretel emphasized that all of this work brings them back to the wood to check the dating.  
A cartoon from the Nelson Newspaper where Gretel grew up published in 2012.

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