Is cellulose extraction necessary for developing stable carbon and oxygen isotopes chronologies from Callitris glaucophylla?

We examined the necessity of extracting cellulose for the development of stable carbon and oxygen isotope chronologies from Callitris glaucophylla J. Thompson and L.A.S. Johnson (Cupressaceae). We compared relationships among isotopes of whole wood, cellulose and climate for the period 1979–1999 and using a moving interval technique with a 10-year window. Isotopes of whole wood and cellulose were significantly correlated and had similar relationships with climate when considered over the entire period. In general, variation in δ13C and δ18O was related to summer temperature relative humidity and rainfall. However, δ13C and δ18O of whole wood generally exhibited weaker and more variable correlations with climate through time than cellulose. In addition, isotopes of whole wood did not deviate from 1979 to 1999 mean values in the same way as isotopes of cellulose. The instability of whole wood–climate relationships may be due to the inclusion in whole wood of a climate signal from lignin that is more variable between tree rings than cellulose. Overall, it appears that C. glaucophylla at least whole wood does not record climate in the same way as cellulose and stable isotopes of cellulose provide a more temporally stable proxy of past climate. We suggest that when developing isotope chronologies for other species the suitability of whole wood vs. cellulose as a proxy for climate should be assessed with consideration of the temporal stability of their relationship with climate.