The Occurrence of Resin Pockets in Sawlog Populations of Picea abies [L.] Karst. from Five Geographic Regions in Sweden
The occurrence of resin pockets in Picea abies [L.] Karst is described for five geographic regions in Sweden with extremes in temperature, windiness and humidity. Through systematic sampling at one measurement station per region, data were obtained from both ends of 1260 logs and a subsample of 3318 transverse sections from 166 logs. The average sum of lengths of resin pockets per unit volume of wood, for all five geographical regions, was estimated to be 9.8 ± 0.72 m m−3 when using data from a series of transverse sections. Measurements in field conditions underestimated the more precisely estimated mean value when using data from log ends (3.4 ± 0.56 m m−3), because small resin pockets were often missed out. An improved inspection of resin pockets is proposed to improve the precision of measurements based on log ends. The occurrence of resin pockets was less in butt logs than in upper logs (5.4 vs. 13.2 m m−3). The average width of resin pockets was 15.5 mm and average length 29 mm for the innerwood of butt logs, increasing to 21 mm and 42 mm, respectively, when moving to outerwood of upper logs. The dry geographic region had more resin pockets than the windy and humid region. It is therefore suggested that the effect of drought may have to be considered when predicting the occurrence of resin pockets in trees.