• Libocedrus Bidwillii Tree-Ring Chronologies in New Zealand

      Xiong, Limin; Palmer, Jonathan G.; Soil, Plant, and Ecological Sciences Division, Lincoln University, Canterbury, New Zealand (Tree-Ring Society, 2000)
      Twenty-three Libocedrus bidwillii (New Zealand cedar) tree-ring chronologies have been developed from New Zealand. This total consists of twelve new sites collected by the authors and eleven previously collected by others (five of which we have updated and six of which were not). Standardization of the tree-ring series from each site used a double detrending method (linear-exponential or linear regression or a horizontal detrending plus spline detrending fitted to 2/3 the length of each tree-ring series). ARSTAN modeling using the Aikaike Information Criterion (AIC) to determine the filter model removed all significant autocorrelations from the residual chronologies. The average chronology length is around 500 years, and the sites are spread over 8° of latitude (i.e.. 38°-46 °S) and nearly 10(X) m in elevation (i.e., 244-1220 m.a.s.1.). The species tends to grow slowly (mean ring-width 0.7 mm), and the tree rings have a high autocorrelation value (0.79). The average mean sensitivity was 0.17, and the average mean correlation between all radii within chronologies was 0.55. Comparison of the chronologies showed a highly consistent and significant pattern among most of the sites. There was a reduction in interchronology correlation with separation distance; however, there was no clear relationship, or an effect, due to elevation. The spatial extent and temporal length of the network of sites offers the most comprehensive opportunity for New Zealand climate reconstruction to date.
    • Variations of Radiocarbon in Tree Rings: Southern Hemisphere Offset Preliminary Results

      McCormac, F. G.; Hogg, A. G.; Higham, T. G.; Baillie, M. L.; Palmer, J. G.; Xiong, Limin; Pilcher, J. R.; Brown, David; Hoper, S. T. (Department of Geosciences, The University of Arizona, 1998-01-01)
      The Queen's University of Belfast, Northern Ireland and University of Waikato, Hamilton, New Zealand radiocarbon laboratories have undertaken a series of high-precision measurements on decadal samples of dendrochronologically dated oak (Quercus patrea) and cedar (Libocedrus bidwillii) from Great Britain and New Zealand, respectively. The results show a real atmospheric offset of 3.4 +/0.6% (27.2 +/4.7 14C yr) between the two locations for the interval AD 1725 to AD 1885, with the Southern Hemisphere being depleted in 4C. This result is less than the value currently used to correct Southern Hemisphere calibrations, possibly indicating a gradient in Delta-14C within the Southern Hemisphere.