Article: Intra-tree variability in wood anatomy and its implications for fossil wood systematics and palaeoclimatic studies

The validity of using quantitative analyses of wood anatomical characters as systematic tools and as palaeoenvironmental proxies has been questioned on the basis that natural variability, and in particular intra-tree variability, tends to drown out the signal being sought. A detailed quantitative description of the wood anatomy of a balsam fir tree was undertaken along root-stump-trunk-branch transects to ascertain intra-tree variability, and to assess noise-to-signal ratio. Results demonstrate significant ontogenetic trends for anatomical parameters such as tracheid pit distribution, cross-field pit frequency, ray dimensions, ray spacing, tracheid diameter, mean ring width and mean sensitivity. However, although intra-tree variability is great, results suggest that fossil taxa nevertheless may be distinguished from one another on the basis of standard qualitative and quantitative procedures. With regard to palaeoenvironmental studies, results indicate that a significant, but not unrealistic, increase in sample size and an improved knowledge of specimen ontogeny is needed in the future if signals are to be distinguished from background intra-tree variability for some parameters.