The influence of heartwood extractives on wood density patterns in tree stems

Abstract Context: Wood density varies within stems from pith to bark and base to top. Wood density is the combination of cell walls and extractives, each factor controlling different wood properties. Understanding the distribution of heartwood extractives is critical for species grown for their heartwood. Aims: Heartwood compounds are resource intensive to quantify by chemical extraction and have been rarely considered in studies of within stem wood density patterns. The objective was to disentangle the contributions of cell walls and extractives to within stem density patterns without the need for extraction. Methods: By sampling Eucalyptus bosistoana F.Muell. and Eucalyptus globoidea Blakely trees across a wide age-range, wood density of heartwood and sapwood was measured for all within-stem positions. Statistical modelling allowed to quantify the contributions of cell walls and heartwood extractives to specie-specific within-stem density patterns. Results: Heartwood extractives had a significant effect on wood density for the two species. The within-stem patterns differed between species and were complex. Conclusion Strategically sampling wood density for a wide age-range of trees allows to deduce the complex specie-specific within stem patterns of heartwood extractives and cell walls, without the laborious task of wood extraction. This improves our understanding of wood quality.