SIGNAL STRENGTH AND CLIMATE RELATIONSHIPS IN C-13 C-12 RATIOS OF TREE-RING CELLULOSE FROM OAK IN EAST ENGLAND/

Annual oak (Quercus robur L.) latewood delta(13)C values are presented for the period 1895-1994 from two sites with different hydrological c haracteristics. Both ring width and delta(13)C indices record high-fre quency common forcing better than lower-frequency forcing. At both sit es the high-frequency variance in the delta(13)C indices of latewood c ellulose is highly correlated with combined July and August environmen tal variables. The association between the high-frequency variance in annual ring width indices and climate is not as strong. Higher correla tions with environmental variables were found for the high-frequency d elta(13)C indices at the dry site (Sandringham) than at the wet site ( Babingley), but the differences are not statistically significant. The se results illustrate the need for routine signal quantification in is otope records and hence a requirement for between-tree replication of isotope series in future studies. High-frequency (year-to-year) inters eries correlation is shown to be relatively strong, indicating that on ly small numbers of replicate series are needed to represent interannu al isotope variability accurately. However, common signal variance is diminished at lower (decadal and longer period) frequencies. This impl ies a need for increased sample replication in order to achieve chrono logy confidence equivalent to that routinely produced for simple ring width data. This work demonstrates that significant high-frequency cli mate signals are contained in isotopic measurements of trees whose rin g widths contain little or no such information.