Radial Variation in Tracheid Lengths in Dominant Trees of Selected Coniferous Species

The radial variation was examined for tracheid lengths of Norway spruce (Picea abies (L.) Karst.), European larch (Larix decidua Mill.), and Scots pine (Pinus sylvestris L.) wood from dominant trees coming from an even-aged stand, and growing under identical forest site and climatic conditions. The measurements were completed on macerated material. The variation of tracheid lengths in annual rings from the core to the bark was used for determination of the border between the juvenile and mature wood in the trunk cross-section. The boundary age between the juvenile and mature wood zones established for the examined species was comparable, as it was 25 annual rings for Scots pine and 29 for European larch and for Norway spruce. In the juvenile zone, the tracheid lengths increased 2.2-fold in Norway spruce wood, while in Scots pine and European larch wood it was approximately 1.7-fold. By contrast, in the mature wood zone the tracheid lengths was stabilized at a certain level, showing slight fluctuations. The differences in the tracheids length of early and late wood in the examined annual rings were also determined, and it was established that for the majority of annual rings they are statistically significant (p<0.05).