Screening various variables of cellular anatomy in Scots Pines in Subarctic Finland for climatic signals

This exploratory study on Scots pine in subarctic Finland was aimed at identifying the climatic signal(s) ‘archived’ in cellular anatomy and tree-ring variables, such as diameter and wall thickness of tracheids, or early- and latewood width, respectively. For this purpose, these variables were measured in increment cores year by year from 1961–2008 and compared to each other. According to the low values of some statistical descriptors (e.g., expressed population signal and mean sensitivity) the cell-anatomical variables could, in fact, not be expected to be useful climatic proxies. Nevertheless, they turned out to significantly reflect other climatic signals than the tree-ring variables did. The tree-ring variables responded positively to temperature in July and August, whereas the cell-anatomical variables responded positively to temperature in December and January, prior to the growing season. These encouraging findings provide a strong rationale for further studies, and for enlarging the statistical sample size.