In Ireland, most structural timber from Sitka spruce (Picea sitchensis[Bong.] Carr.) is machine graded into C16 strength class. However, timber from early thinnings is mostly used for non-structural applications. There is an increased demand for structural timber, and timber from young trees could contribute to wood supply. However, this timber has lower mechanical properties than mature timber. In order to pre-sort the resource for structural application of wood from thinning, the possibilities of acoustic and density (D) measurements on young trees and logs have been investigated. The stress wave velocity (SWV) and pin penetration depth (PD) were measured on standing trees, which were then felled and cut into 10-m-long logs and subsequently into 3-m-long logs. Fundamental frequency was measured on logs. Finally, the logs were processed into boards, which were tested in accordance with EN 408 to obtain modulus of elasticity (MOE) in bending, bending strength (BStr) and D. The results showed good relationships between timber properties and acoustic and D measurements. Models for predicting grade properties of timber from thinnings are presented. Pre-sorting of young Sitka spruce trees and logs helped obtain higher C16 yields.
Basic density is a fundamental wood property of pulp and sawn wood. An IML Resi PD 400 drilling resistance tool (IML System GmbH, Wiesloch, Germany) was used to evaluate the basic density of Eucalyptus nitens discs and the impact of needle friction on basic density prediction. To determine the accuracy of that prediction with the commonly used linear drill bit shaft friction correction and determine whether this correction is linear, 40 discs were drilled radially, then cut into segments which were measured for basic density. Drilling resistance had a strong relationship with basic density in the outer wood; it was weaker at the pith but this did not compromise prediction accuracy. When using a linear friction correction, the drilling resistance underpredicts basic density by 7.6% in the first 2–3 cm after stem entry, after which the prediction error ranged from 0.6–1.9%. The friction correction was found to be nonlinear, especially at the first few centimeters. To apply this friction correction, basic density values from the model should be added to predict basic density values until 2.9 cm from Resi entry point and after that subtracted to account for the drill bit shaft friction.
As Europe moves towards more sustainable construction, there is an increasing demand for structural timber. The purpose of this research is to explore new forestry management strategies, which will produce an optimum balance of the quantity and quality of structural timber over a minimum period of time. The focus is on timber from Sitka spruce, which is the most important Irish commercial forest tree species. Planting density is an important factor affecting both structural timber quantity and quality. Trees with wider spacing get more light and grow faster, which affects annual ring width and knot size. These, in turn, affect the bending strength, modulus of elasticity and density of timber, which are the grade determining properties according to EN 338:2003. The current standard planting density in Ireland is 2500 stems/ha and the timber produced meets the requirements for the C16 strength class. For Irish-grown Sitka spruce timber, modulus of elasticity is the critical grade determining property, which dictates the strength class. This study has two aims, first to explore the possibilities of improving the strength class by increasing the planting density and second, to explore the possibility of keeping the same class while increasing the quantity of structural timber by reducing the planting density. The effects of different planting densities, ranging from 1550 to 3700 stems per hectare, on the structural properties of Sitka spruce timber originated from a forest in County Leitrim are examined. Overall, 72 trees were felled and cut into logs. Logs were non-destructively tested using acoustic tools and subsequently processed into structural timber. The timber boards were then tested using three different types of strength graders in order to examine the difference in timber modulus of elasticity between different planting densities. The results showed statistically significant effects of different planting densities on the variation in timber modulus of elasticity.
Eucalypt plantations in Tasmania have been managed predominantly for fibre production, but there is also growing interest in the production of solid wood products. For solid wood production, stiffness and basic density are key wood properties as they define the suitability of the timber for particular products and ultimately value. To inform processing options available for targeting high value wood products there is a need to understand how wood properties vary within a tree and how thinning impacts wood quality to foster efficient processing. Three thinning trials of 20–22-year-old plantation grown Eucalyptus nitens were used to assess stiffness and basic density longitudinally from the base to 20 m height in the tree and radially at a fixed height of 2.5 m. Longitudinally and radially, wood properties varied more within the tree than the variation which arose as a result of thinning. Stiffness was lowest at the bottom of the tree irrespective of thinning treatment and the highest stiffness was located from 7.5 to 15 m height depending on thinning and site. Commercial thinning to 300 trees ha−1 had no effect on stiffness in the bottom of the tree but resulted in lower stiffness in the upper logs. Trees in thinned stands had slightly lower basic density and that reduction was consistent within the tree and across sites. Thinning resulted in significant radial change in wood properties and the thinning effect was apparent soon after the thinning treatment. The results demonstrate that thinning has an adverse impact on wood properties, but not to a degree that hinders the benefits thinning brings to maximizing wood growth. However, the high variation in wood quality within the tree suggests that it would be valuable segregating logs within a tree to maximize solid wood product value.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.