Influence of Pit Aspiration on Earlywood Permeability of Douglas-Fir

Sapwood earlywood longitudinal gas permeability is a sensitive barometer of the effect of seasoning conditions on pit aspiration. The proportion of aspirated pit pairs was quantitatively linked with longitudinal gas permeability and can be used to explain the earlywood permeability of a given sample. If comparable levels of pit aspiration are found in two samples differing in permeability, however, it may be necessary to examine other anatomical aspects of the wood being permeated. Permeability is a function of the number of open pits per tracheid, which, coupled with tracheid length, determines the probability of occurrence of a continuous flow path through the wood specimen being permeated. Percentage pit aspiration operates in conjunction with number of pits per tracheid to determine the number of open pits per tracheid. While the proportion of aspirated pits can be measured and related to permeability, it is suggested that tracheid length, total number of pits per tracheid, and number of tracheids per square millimeter also be evaluated in order to assess properly the effect of pit aspiration on permeability