Variation in Size and Shape of Pitch Pockets in Picea abies from Four Geographic Regions in Sweden

摘要

The variation of size and shape of pitch pockets in Picea abies (L.) Karst has been described for four geographic regions in Sweden. Logs were cross-cut in 40mm thick discs and thereafter each pitch pocket, visable in any of the cross-cuts, was uncovered and measured. The observed pitch pockets appeared in a wide range of different types. One type of pitch pockets is associated with knots. Other types are defined by rupture or not of the enclosing annual ring, by differences in the viscosity grade of the pitch and by differences of their size and shape. In all four regions pitch pocket width increased with distance from the pith. Significant differences in size of pitch pockets was found between the four regions. The paper discusses the factors be-hinds the variation in the appearence of the pitch pockets.