Influence of silvicultural regime on wood structure characteristics and mechanical properties of clear wood in Pinus sylvestris

Abstract

The objective of the study presented here was to evaluate the influence of two contrasting silvicultural regimes on the structural characteristics and mechanical properties of different wood tissue types at different heights in Scots pine (Pinus sylvestris L.) trees, and reasons for these differences. Wood samples were taken from two stands (a dense 85-year-old stand established by direct seeding and a 56-year-old widely spaced stand established by planting, designated SDR and PWR, respectively in the boreal zone of Sweden). The wood properties associated with the examined silvicultural regimes differed, in terms of both structural characteristics (with up to fivefold differences between SDR and PWR) and mechanical properties (with up to almost threefold differences between SDR and PWR). Differences between the regimes were highest for stiffness, followed by strength and hardness properties and lowest for relative stiffness after 1000 h of loading (creep) (with higher parameter values for SDR than for PWR in each case). The rankings could be explained by differences among the mechanical properties in their sensitivity to maturation of wood characteristics. In conclusion, silvicultural regimes have great potential to regulate wood structural characteristics and mechanical properties, apparently due to the influences of the green crown and growth rate on the vascular cambium, the strength of which vary throughout the rotation period. A silvicultural regime could therefore be seen as a tool that can be used to select material qualities and to make wood a more homogenous material for engineers.