Effect of early release from intense competition within high density natural regeneration on the properties of juvenile and mature wood of 40-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.)

Abstract

While numerous studies have considered the effects of initial planting spacing on wood properties, little is known about the properties of trees grown from dense natural regeneration and the effects of early release from competition. This study examined 40-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.) trees originating from regeneration with an initial density ∼27,000 stems ha−1. Treatments were a control of natural regeneration with no interventions and regeneration re-spaced to two metres (height ∼1.6 m). Density and strength measurements were made on the juvenile and mature wood. No differences were observed in density, modulus of elasticity (MOE) and modulus of rupture (MOR) between the juvenile and mature wood of the control trees. By contrast, the juvenile wood of re-spaced trees was less dense and had a lower MOE than the mature wood. The control trees revealed a uniformity of properties across the juvenile and mature wood zones, unlike the re-spaced treatment. Re-spaced trees appear to adapt to their new environment by producing more thin-walled conductive tissue and lowering overall cell wall density that continues from the juvenile to mature wood. Higher compression wood levels in the control trees are thought to be linked to stem slenderness.