非破壞性技術評估疏伐修枝處理對台灣杉造林木材質之影響

Study on evaluation of Taiwania trees quality grown with different thinning and pruning treatments using nondestructive techniques

林振榮(Cheng-Jung Lin)

指導教授 ： 王松永

國立臺灣大學/生物資源暨農學院/森林學研究所/博士(2004年)

https://doi.org/10.6342/NTU.2004.01134

摘要

木材是不可缺少的民生資材，在重視環境保護的趨勢下，將逐漸限制木材資源的使用，故造林木將成為木材供應的主要來源，而疏伐及修枝作業是森林經營中重要的措施，其對木材生產量及材質的轉變應予瞭解，近年來，非破壞性技術發展作為立木材質評估的方法之一，但目前材質評估效果有限，故本研究之目的在利用超音波法及鑽孔抵抗技術評估不同疏伐及修枝處理影響台灣杉造林木材質之效應，以提升應用該檢測技術與瞭解不同疏伐及修枝後造林木材質狀況。本研究之主要結果如下：
1.台灣杉縱向超音波速度(V)隨密度之增加而減少，徑向及弦向V在隨密度的增加而增加，動彈性係數(DMOE)在徑向及弦向隨密度的增加而增加，縱向則與密度無關。
2.台灣杉造林木V隨含水率(MC)的增加而有減少的趨勢，由V值算出之DMOE變化顯示，在纖維飽和點(FSP)以下時，DMOE值隨著含水率的增加而減少，而在FSP以上時則隨含水率的增加而增加，此趨勢維持常數變化的現象，為探討在FSP以上含水率對V值之影響，在此利用超音波技術求出自由水之有效率(k value)，台灣杉造林木縱向試材為0.58。再使用調整後有效密度及超音波速度去計算DMOE時，則在FSP以上時DMOE隨MC增加則可維持常數變化的結果。
3.為簡化在FSP以上時調整DMOE值的方式，經推算含水率(MC)及容積密度(BD)與V的關係迴歸式，再重新計算DMOE，可得到與前述K值調整相同效果，獲得對應DMOE。
4.不同疏伐修枝處理的台灣杉立木、氣乾鼓形材、實大樑、無缺點小試材，其超音波速度(V)、動彈性係數(DMOE)、靜曲彈性係數(MOE)、破壞強度(MOR)及密度值，在疏伐處理傾向為：未疏伐處理 > 中度疏伐 > 強度疏伐處理；而修枝處理傾向為：中度修枝 > 未修枝處理 > 強度修枝。由上述材質指標為觀點，台灣杉林木較佳的強度性質是在未疏伐及中度修枝處理中。經統計分析結果，超音波技術可以作為立木材質評估的方法。
5.應用鑽孔抵抗技術測定台灣杉造林木之鑽孔抵抗值與密度間存在線性關係，而在同一年輪內之早晚材境界密度值與平均最大密度及最小密度值，兩者具有顯著性正相關存在。鑽孔抵抗值(R)與含水率(MC)及容積密度數(BD)間，可以藉複迴歸方程式表示，此可作為高含水率時如立木時之校正。應用鑽孔抵抗技術評估年輪特性值，其結果在年輪寬方面，疏伐作業具有促進效應，修枝具有抑制效果之趨勢，故疏伐增加年輪寬而修枝將減少年輪寬趨勢，在密度方面則發現未疏伐及中度修枝處理有增大的趨勢，強度疏伐及強度修枝則發現有降低的傾向。另外不同疏伐及修枝處理台灣杉試材的管胞長度及微纖維傾斜角間沒有顯著性差異存在。

關鍵字

非破壞性試驗 ； 疏伐 ； 修枝

並列摘要

The effects of different thinning and pruning treatments on the wood properties of Taiwania (Taiwania cryptomerioides Hay) using the ultrasonic wave and drilling resistance methods were investigated, with the following results:
1.The ultrasonic wave velocity (V) in the longitudinal direction tended to decrease with increased density, but the V in the radial and tangential direction also tended to increase with increased density. The dynamic Young's modulus (DMOE) in the radial and tangential directions tended to increase with increased densities on the whole, while it was independent with density in the longitudinal direction.
2.The V in the longitudinal and radial direction tended to increase with decrease in Moisture content (MC). Above the fiber saturation point (FSP), DMOE values tended to decrease rapidly with decreasing MC; whereas below the FSP, the DMOE values tended to increase gradually with decreasing MC. The k values for the ultrasonic wave propagated through the longitudinal and radial direction of Taiwania plantation lumber were equivalent to 0.58 and 0.33 respectively. Using the effective density and ultrasonic wave velocity to calculate the longitudinal and radial DMOE, it was found that the DMOE tended to remain constant with MC during the MC reducing process from a water-saturated condition to FSP.
3.Moreover, V (in longitudinal direction) tended to decrease linearly with increasing bulk density (BD). On the contrary, V (in radial direction) tended to increase with increasing BD. However, the correlations between ultrasonic velocity, MC, and BD could be represented by polynomial regression model. K value for ultrasonic wave was affected by different density. The adjusted dynamic DMOE remain fairly constant above the FSP by simple method.
4.The average V, DMOE (standing tree, lumber, and specimen), modulus of elasticity (MOE), modulus of rupture (MOR), and density (lumber and specimen) in the thinning treatments showed a trend as follows: non-thinning > medium-thinning >heavy-thinning. This indicates that thinning reduces average bending properties. Then, the average V, DMOE, MOE, MOR, and density in the pruning treatments showed a trend as follows: medium-pruning > non-pruning > heavy-pruning. According to the tendency of results, the better average qualities of trees, lumbers and specimens occurred in the non-thinning and medium pruning treatment by ultrasonic-wave technique and static bending tests. Moreover, there were very significant positive relationships between density, V, DMOE, MOE, and MOR. Results of this study also demonstrate that the effect of silvicultural practices on wood properties can be identified with the ultrasonic-wave technique.
5.The drill resistance technique as applied to Taiwania plantation wood uses a liner relationship between the solid density and the drill resistance values. There is a positive significant relationship between the average Dmax+Dmin density (maximum and minimum densities) and the density boundary of early and late wood in a ring. The thinning caused wider annual rings than medium and non-thinning, pruning caused narrower annual rings than non-pruning, and that the thinning treatment affected annual rings more effectively than the pruning treatment. The average ring density in the thinning treatments showed a trend as follows: non-thinning > medium >heavy. This indicates that thinning reduces average ring density. The average ring density in the pruning treatments showed a trend as follows: medium > non-pruning > heavy. The drill resistance values tended to decrease with the decreasing of MC. Positive significant relationships were found among the MC, bulk density, and drill resistance values. In addition, no significant differences were shown for tracheid length and microfibril angle among the three thinning and pruning treatment specimens.

並列關鍵字

thinning, pruning ； nondestrutive test

參考文獻

23.Wang SY, Lin CJ, Chiu CM (2004) Evaluation of wood quality of Taiwania trees grown with different thinning and pruning treatments using the ultrasonic-wave method. Wood Fiber and Science (in print). [SCI]

27.邱志明、林振榮、唐盛林、湯適謙、羅卓振南 (2004) 不同藥劑塗布對櫸木之修枝傷口變色與腐朽之效應。台灣林業科學(in print)

3. 王松永、林振榮 (2001) 應用鑽孔抵抗技術評估台灣杉造林木之早晚材境界密度。台灣林業科學16(3)：196-200。

13.王松永、林振榮 (2001) 應用鑽孔抵抗技術評估台灣杉造林木之早晚材境界密度。台灣林業科學16(3)：196-200。

11.邱志明、羅卓振南、林振榮 (2000) 修枝度對台灣杉造林木製材品質之影響。台灣林業科學15(3)：399-410。