气候变化领域集成服务门户(CCPortal): The influence of crown and stem characteristics on timber quality in softwoods

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DOI	10.1016/j.foreco.2018.12.043
	The influence of crown and stem characteristics on timber quality in softwoods
	Krajnc L.; Farrelly N.; Harte A.M.
发表日期	2019
ISSN	0378-1127
起始页码	8
结束页码	17
卷号	435
英文摘要	The relationships between several crown and tree properties and timber quality were examined on three softwood species: Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), Norway spruce (Picea abies (L.) H. Karst) and Sitka spruce (Picea sitchensis (Bong.) Carr). Crown and stem characteristics were collected on 487 standing trees, and their acoustic velocity measured using a stress-wave device. Of the trees measured, 60 were chosen for further testing, stratified by crown social class and cut into structural sized boards (N = 1342). Each board was assessed with regard to knots using a grading X-ray machine, after which all boards were destructively tested in four-point bending and their mechanical properties (elastic modulus, bending strength and density) evaluated. To exclude the effect of branchiness across the crown social classes, mechanical properties were also examined on small clear samples cut from the undamaged section of the tested boards, a total of 1303 specimens were tested destructively in bending. Multi-level models based on Bayesian data analysis were used to evaluate the relationships between recorded characteristics, acoustic velocities and mechanical properties. Considerable differences in acoustic velocities were found between crown social classes, with suppressed trees having the highest velocities. This trend was also confirmed in mechanical properties of structural-sized boards and small clear specimens, suggesting that branchiness is not the primary cause of differences. Results indicate that slenderness affects both tree stiffness and the properties of sawn timber differently across the crown social classes. The relationship is negative in suppressed trees (increasing slenderness leads to a decrease in velocity or mechanical properties) and positive in dominant and co-dominant trees. The effect of crown projection area on either tree acoustic velocity or mechanical properties differs between social classes. In general, it was found to be positive, therefore an increase in crown projection area leads to an increase in either tree acoustic velocity or wood properties of timber. This trend is more evident in sawn timber than in acoustic velocities. The effects appear to be species dependant. No evidence was found of the effect of crown ratio, crown eccentricity or crown roundness on either the examined wood properties or acoustic velocities. Results confirm that there is a link between crown/stem development and timber quality. They indicate that in order to increase the overall quality of timber produced, the proportions of crown social classes in final stand composition should be adjusted with thinning. © 2018 Elsevier B.V.
英文关键词	Crown properties; Knottiness; Silviculture; Slenderness; Softwoods; Wood quality
语种	英语
scopus关键词	Acoustic wave velocity; Acoustic wave velocity measurement; Bending strength; Density (specific gravity); Grading; Mechanical properties; Plants (botany); Softwoods; Timber; Crown properties; Knottiness; Silviculture; Slenderness; Wood qualities; Forestry; biomechanics; canopy architecture; coniferous tree; silviculture; stand structure; stem; thinning; timber harvesting; wood quality; Bend Strength; Forestry; Mechanical Properties; Quality; Silviculture; Softwoods; Trees; Velocity; Picea abies; Picea sitchensis; Pseudotsuga; Pseudotsuga menziesii
来源期刊	Forest Ecology and Management
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/156198
作者单位	College of Engineering and Informatics & Ryan Institute, National University of Ireland Galway, Galway, Ireland; Forestry Development Department, Teagasc, Athenry, Ireland
推荐引用方式 GB/T 7714	Krajnc L.,Farrelly N.,Harte A.M.. The influence of crown and stem characteristics on timber quality in softwoods[J],2019,435.
APA	Krajnc L.,Farrelly N.,&Harte A.M..(2019).The influence of crown and stem characteristics on timber quality in softwoods.Forest Ecology and Management,435.
MLA	Krajnc L.,et al."The influence of crown and stem characteristics on timber quality in softwoods".Forest Ecology and Management 435(2019).