Empirical models for radial and tangential fibre width in tree rings of Norway spruce in north-western Europe

Abstract

Abstract Tracheid dimensions influence the quality of wood and that of pulp and paper. Both between- and within-ring variations are influenced by tree developmental stage, site, genetics, and forest management. To contribute to the knowledge in this regard, the radial and tangential tracheid dimensions on Norway spruce, defined as the lumens and double cell wall thickness, have been measured using a SilviScan device. Namely, 4947 annual rings from 35 trees from plantations in France, Norway, and Sweden were examined. Mixed-effects models were constructed concerning the radial and tangential tracheid widths for the total ring and in three within-ring compartments – earlywood (EW), transition wood (TW), and latewood (LW) – as functions of age, radius, height in the tree, and growth rate. Between-site and between-tree variations were also considered. The mean radial tracheid width was 34.2 μm (EW), 29.9 μm (TrW), and 22.1 μm (LW). The tangential tracheid width was on average 30.1 μm in all compartments. The radial and tangential tracheid widths in the rings and compartments increased from the pith to the bark and decreased with greater growth rates. Within a given ring, both properties decreased with height in the tree. The fixed part of the models of the radial tracheid width accounted for 68% (EW), 45% (TW), and 33% (LW) while for the models of the tangential fibre width it accounted for 42% of the variation in all compartments. Climate or hydraulic maintenance was hypothesised to be responsible for the variation of the radial tracheid width.