Considering reversible variations in wood properties : possible applications in the choice of the tree-felling date ?

Traditional knowledge, in form of so-called rural rules, indicates that the date of tree felling has an important influence on wood quality. The main factor, after the season of the year, is said to be the position of the moon. The objective of the presented project was to study the variability of some user-related properties of wood, by analyzing measurable parameters. The material stems from four different Swiss sites and is representative of central European conditions. This part of the study involved 576trees - NorwaySpruce (Picea abies Karst.) and Sweet Chestnut(Castanea sativaMill.) - felled on 48 dates throughout the fall and spring of 2003-2004 (always on Mondays or Thursdays). Before the start of the experiment, one sample was taken on the same day from each of the tested trees, to serve as reference. Wood properties analyzed are: water-loss, shrinkage under controlled drying, air dry and oven dry density. Smaller series of samples were tested on hygroscopicity. The statistical analysis of the complete data series reveals(in addition to a seasonal trend)a generally weak, but highly significant role of the synodic and of the sidereal moon cycles, to a lesser extent of the tropical cycle. The lunar-related differences are more marked for the central 4 months of the trial. The results from this study bring some transparency and objectivity into a mainly unexplored field of traditional knowledge, a field subject to controversial discussions.Further research in chronobiology of wood could lead to an ecological technique enhancing specific wood properties.