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題 名 | 疏伐與修枝作業對臺灣杉生長應力之效應=Effects of Thinning and Pruning on Growth Stress of Taiwania Cryptomerioides |
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作 者 | 黃彥三; 陳欣欣; 邱志明; 黃玲瓏; | 書刊名 | 中華林學季刊 |
卷 期 | 36:4=133 2003.12[民92.12] |
頁 次 | 頁361-370 |
分類號 | 436.18 |
關鍵詞 | 疏伐; 修枝; 生長應力; 應變規; Thinning; Pruning; Growth stress; Strain gauge; |
語 文 | 中文(Chinese) |
中文摘要 | 本計畫在探討臺灣杉造林木疏伐與修枝對樹幹生長應力之影響。就修枝與未修枝之臺灣杉各取二株加以伐採,造材成長1公尺原木,就樹幹表面利用應變規技術以切割法測定生長應變,另就胸高部位製成含髓心徑面板,測定不同距髓心位置之含水率、比重、靜曲彈性係數、破壞係數、殘留生長應變,並計算樹幹內部生長應力,探討修枝對生長應力之可能影響。試驗結果顯示,生長應力與樹高間並無明確關係。樹幹表面縱向應力呈現引張應力,而橫向(弦向)應力則呈現壓縮應力。樹幹內部縱向殘留應力呈V字型分布,靠髓心側為壓縮應力,靠邊材側呈現引張應力。對照組之縱向表面生長應變平均較疏伐修枝木大22%,橫向表面生長應變則大35%,顯示育林撫育作業可有效減低樹木生長應力,對林林資源的有效利用具正面義意義。橫向表面生長應變平均約為縱向表面生長應變絕對值之2倍,原木端面靠髓心有較大之殘留引張生長力,此等引張應力為導致伐木造材時端部心裂或環裂之成因。一般而言,樹幹外側與靠髓心部之含水率較高,比重亦有此現象。樹幹心材之彈性係數與破壞係數一般較邊材為低。 |
英文摘要 | We explored the effects of thinning and pruning on the growth stress in the trunk of Taiwania cryptomerioides. Two trees samples each from pruned and un-pruned stand were selected. Surface growth strains on the trunk were cut and measured every one meter apart from the base. In addition, the distribution f residual growth stress, moisture content, specific gravity, modulus of rupture and modulus of elasticity in the trunk were also measured. The results showed that the surface growth stress was tensile and the transverse (tangential) growth stress was compressive. The longitudinal residual growth stress distribution in trunk was V shape indicating tensile stress at the outside and compressive stress at the inside. On the average, longitudinal surface growth strain and transverse from the control were larger than those of thinning and pruning treatment 22% and 35%, respectively, the effectiveness of silvicultural practice on growth stress reduction could be observed. The value of transverse surface strain was about twice of that of longitudinal surface strain. The residual growth stress near the pith which may be the cause of heart shake and ring shake during the felling and cross cutting of trees. As a whole may be the cause of heart shake and ring shake during the felling and cross cutting of trees. As a whole specific gravity and moisture content were higher at the outside and near the center of trunk. The modulus of elasticity and the modulus of rupture of sapwood were higher than those of heartwood. |
本系統中英文摘要資訊取自各篇刊載內容。