Structural components influencing the permeability of ponded and unponded Sitka spruce*

Abstract

SUMMARYStudy of the gaseous permeability of wood stored in ponds to promote bacterial decomposition of the bordered pit membranes has shown that the pit aperture/pit cavity contributes to the total resistance to flow of liquids through both ponded and unponded wood. In ponded wood the contributions of the pit apertures/pit cavities ranged between 5% and 46% of the total resistance, the tracheid lumina making up the remaining 96–54%. This large variation is attributed to the presence of different proportions of earlywood and latewood in specimens tested. In air‐dried unponded wood, however, the pit membrane pores contribute an average of 81% of the total resistance to liquid flow, the tracheid lumina an average of 16%, and the pit aperture an average of only 3%. An implication of these results is that previously used analytical techniques for the determination of the radius and number of conducting flow paths in wood, based on the assumption that only two structural components offer resistance to flow, are not wholly satisfactory.