Correlation of carbon isotope ratios in the cellulose and wood extractives of Douglas-fir

Cellulose is usually isolated from the other components of plant material for analysis of carbon stable isotope ratios (δ13C). However, many studies have shown a strong correlation between whole-wood and cellulose δ13C values, prompting debate about the necessity of cellulose extraction for tree-ring studies. The δ13C values were measured in whole wood, extractive-free wood, purified cellulose, acetone/water-soluble extractives and hot water-soluble extractives of Douglas-fir sapwood. Cellulose and acetone/water-soluble extractives from heartwood from the same trees also were compared. Although the various materials showed different absolute δ13C values, the components of the same samples, including the extractives, were correlated. The correlations of carbon isotope ratios of cellulose, extractive-free wood and extractives, and the relatively low concentration of the extractives in the wood, suggests that extraction of purified cellulose from Douglas-fir wood samples may not be necessary for some tree-ring analyses.