Comparison of stable carbon isotope ratios in the whole wood, cellulose and lignin of oak tree-rings

The stable carbon isotope ratios (δ13C) of whole wood, cellulose and acid-insoluble lignin from annual latewood increments of Quercus robur L., from modern and sub-fossil wood, were measured and their potential use as palaeoenvironmental indicators examined. The resulting time series demonstrate a very high degree of coherence, with δ13C of cellulose isotopically enriched by approximately 3‰ compared to δ13C of lignin. The δ13C values of all three components are influenced by the climate of July and August. Modern whole wood retains the strongest climate signal, perhaps because its composition is closest to that of leaf sugars. In sub-fossil wood there is no evidence that differential decay leads to fractionation of carbon within either cellulose or lignin, but differential decay can alter the cellulose to lignin ratio.