Variability of the wood fibre structure indices for silver birch (Betula pendula Roth.) in north-eastern Poland

The variation of the fibre structure indices was determined for silver birch. The examined trees came from north−eastern Poland, which is the largest source of raw material of this species. Wood samples were taken for measurement from trees aged 45 and 70 years that grew in the fresh deciduous forest habitat. Fibre structure indices measuring felting, flexibility, rigidity, rigidity according to Runkel as well as Mühlsteph's and compactness indices were selected as the basic fibre pulp properties and subjected to statistical analysis. A significant effect of the location and age of trees on all wood fibre structure indices except for the effect of age on the compactness index was found. The studies also showed a significant, simultaneous effect of tree location and age on the mean values of all analysed indices of silver birch wood fibre structure