除伐與修枝對檜木天然更新林之效應

Effects of Cleaning and Pruning on Natural-regenerated Cypress Stands

羅卓振南(Chen-Nan Locho) ； 邱志明(Chi-Ming Chiu) ； 陳燕章(Yen-Chang Chen)

《台灣林業科學》 14卷3期 (1999/09) Pp. 315-321

https://doi.org/10.7075/TJFS.199909.0315

摘要

本研究探討除伐及修枝對檜木天然下種更新林分之效應，期能加速其成林，並誘導使其與上層林木構成健壯之異齡林。供試林分為大溪事業區第94林班，該試驗地面積計8.2ha，15年前曾實施單株擇伐天然下種更新，更新情況相當良好。除伐方式計分為保留2000株／ha；保留3300株／ha及未除伐之對照區。修枝處理則分為修枝至1/2樹高及未修枝之對照區。經處理5年後之研究結果顯示，除伐前胸徑級之株數分佈成倒J字型，除伐後則接近常態分佈。每公頃保留2000株和3300株更新林木者，可增進其胸徑和樹高生長，惟林分胸高斷面積和材積生長則無顯著差異。而修枝高度達樹高之1/2處，對林木生長並無不良影響，修枝後5年傷口癒合率可達98%，顯示修枝確有助無節材生產；惟至目前為止，經修枝處理之立木，其樹幹完滿程度並無明顯之變化。林內之相對光度均值，保留2000株／ha、3300株／ha者分別約為41％和39%，在未除伐之對照區為20%，且未除伐之對照區，在試驗5年期間，有7.3％更新林木相繼自然枯死。

關鍵字

檜木林 ； 稚樹 ； 除伐 ； 修枝

並列摘要

Cleaning and pruning were practiced on natural-seeding-regenerated cypress stands to study if the treatments could accelerate young trees to grow with the upper-layer trees and develop into well-constructed uneven-aged stands. The tested 8.2-ha cypress stands were located at Compartment No. 94, Tahsi Working Circle in northern Taiwan. These well-regenerated stands were treated with a single-tree selection method 15 yr ago. Cleaning treatments included (1) retaining 2,000 and (2) 3,300 trees/ha after cleaning, and (3) no cleaning. Pruning treatments were (1) trees pruned up to 1/2 of their heights and (2) no pruning. The results, 5 yr after treatment, showed that there were no significant differences in the growth of basal area at breast height and volume of different cleaning- treated stands. However, the DBH and tree height growth of stands retaining 2,000 and 3,300 trees/ha after cleaning were significantly increased. The DBH distribution curve of these stands before and after cleaning were an inverted S-shape and normal. Cypress trees could be pruned up to 1/2 of their heights without affecting the growth of stands. The occlusion percentage of branches 5 yr after pruning was 98%, and this proved that pruning could increase the production of clear logs. Nevertheless, pruning had no significant effects on the form factor or form quotient of retained trees after cleaning. The mean relative light intensities in stands retaining 2,000 and 3,300 trees/ha after cleaning were 41% and 39%, respectively. The control stand without cleaning with a low relative light intensity of 20% showed a mortality of 7.3% for naturally regenerated young trees.

並列關鍵字

cypress stands ； saplings ； cleaning ； pruning