修枝度對台灣杉造林木製材品質之影響

Effects of Pruning on the Quality of Sawn Lumber from Taiwania Plantations

邱志明(Chih-Ming Chiu) ； 羅卓振南(Chen-Nan Lo-Cho) ； 林振榮(Cheng-Jung Lin)

《台灣林業科學》 15卷3期 (2000/09) Pp. 399-409

https://doi.org/10.7075/TJFS.200009.0399

摘要

台灣杉造林木於6年生時進行第一次修枝，至11年生再進行第二次修枝，24年生時，砍伐樣木發現不同程度修枝者，其原木品等及製材品等差異極大：以製材品等而言，B種修枝度的特等及一等材合計出現之頻度達到51.6%，C種（未修枝）則僅10.5%，而A種修枝度介於中間為36.1%，可見台灣杉修枝撫育之重要，將不同樹高之原木鋸製成弦面板材，均發現距髓心距離愈遠，板材品等愈佳，強度值也愈大且愈近基部品等亦愈高。以打音頻譜之非破壞性試驗所求得不同品等板材和由其製成之無缺點小試材兩者之動彈性係數，品等愈差者，兩者動彈性係數差愈大，成一指數曲線關係，不同修枝度之試材，若去除含節之所有缺點，製成無缺點小試材，所求得之靜力彎曲性質，MOR和MOE差異皆不顯著。

關鍵字

台灣杉造林木 ； 修枝 ； 製材 ； 品等 ； 打音

並列摘要

Pruning treatments were applied twice to Taiwania (Taiwania cryptomerioides) plantations when they were 6 and 11 yr old, and then 1 mean sample tree was cut from each plot when they reached the age of 24 yr. Results showed that there were very significant differences among the grades of logs and sawn lumber from plots with different pruning treatments. Concerning the grade of sawn lumber from plots of B-type (pruned up to 1/3 and 1/2 of tree height when 6 and 11 yr old, respectively), A-type (pruned up to 1/4 and 1/3 of tree height when 6 and 11 yr old, respectively), and C-type (unpruned) pruning treatments, the distribution percentages of excellent grade and no.1 (by CNS grading rules), were 51.6, 36.1, and 10.5%, respectively. Therefore, pruning practice is important to promote the grade of lumber from Taiwania plantations. There was a definite tendency of variation in mechanical properties and the grade of plain sawn lumber from different section heights of logs. The tendency initially showed lower values and lower grades, and then increased with distance from the pith and increased with distance from the apex. The dynamic modulus of elasticity (MOED) was obtained by a tap tone spectrum analysis system of nondestructive testing for sawn lumbers of various grades and small clear specimens. Results showed that the lower the grade the sawn lumber was, the larger the differences were in MOED for sawn lumber and small clear specimens. Moreover, the relationship between MOED of sawn lumber and small clear specimens was an exponential curve. No significant differences were found among the MOR and MOE of static bending properties of small clear specimens made from sawn lumber with all defects excluded from plots of various pruning treatments.

並列關鍵字

Taiwania plantations ； pruning ； sawn lumber ； grade ； tap tone