HIGH-RESOLUTION DELTA-C-13 MEASUREMENTS OF OAK SHOW A PREVIOUSLY UNOBSERVED SPRING DEPLETION

We have subdivided single tree rings into between 24 and 35 contiguous samples and measured the deltaC-13 value for each. These high-resolution measurements show a previously unobserved spring depletion as part of a pattern of enrichment-depletion-enrichment-depletion through a single growing season as opposed to the depletion-enrichment-depletion cycle previously thought to exist. The earlywood/latewood transition does not coincide with identifiable isotopic boundaries and therefore is not a suitable demarcation point for sampling as part of palaeoclimatic study. Latewood and post spring depletion values of deltaC-13 were separately correlated with geophysical parameters. Post spring depletion wood yielded better correlations and is therefore more suitable for palaeoclimatic study.