The effect of age and sample position on eucalypt tree-ring width series

In this study, we examine within-tree variance in proportionate tree-ring width (p_rw) and correlation between radii (r_wt), samples (r_bh), and trees (r_bt) in four eucalypt species common throughout eastern Victoria, Australia. In all species and sites studied, r _wt and r_bh differ significantly between cambial-age and sample-height classes. Differences between r_wt and r_bh are nonsignificant between tree-age or radial-azimuth classes. Significant differences in p_rw exist between cambial-age, tree-age, and sample-height classes and between radii on different compass bearings. Whilst differences in r_wt and r_bh between cambial-age classes appears to be the result of variation in mechanical demands with increasing stem size, stem deformation may account for differences between sample-height classes. Variation in p_rw appears to be due to stem geometry, stem eccentricities associated with root buttressing, and tree-age dependent variation in the rate of radial growth. No significant differences in rbt exist between sample-height classes. Analysis of the expressed population signal statistic indicates that site-level and species differences are far more significant than sample position on variance within tree-ring width series collected from eucalypts. We discuss the implications of the current work for eucalypt dendroclimatology.