疏伐與修枝對臺灣杉人工林生長之影響

Effects of Thinning and Pruning on Taiwania (Taiwania cryptomerioides Hayata) Plantations

羅卓振南(Chen-Nan Lo-Cho) ； 鍾旭和(Hsu-Ho Chung) ； 邱志明(Chin-Ming Chiu) ； 周朝富(Chao-Fu Chou) ； 羅新興(Shin-Shing Lo)

《林業試驗所研究報告季刊》 6卷2期 (1991/06) Pp. 155-168

https://doi.org/10.7075/BTFRI.199106.0155

摘要

臺灣杉人工林應以長伐期為經營導向，並以生產高品質之大徑木為經營之目標，因此，中間撫育之施行，需以用途為導向。本研究乃就屏東林區管理處荖濃事業區第73林班，本所原實施修枝試驗之臺灣杉人工林，繼續進行疏伐試驗。試驗所擇之疏伐度係以每公頃胸高斷面積保留量為準，計分為四種：(A)弱度疏伐：保留量為51平方公尺/ha；(B)中度疏伐：保留量為46平方公尺/ha；(C)強度疏伐：保留量為41平方公尺/ha；對照區。疏伐木之選定，依照下層疏伐法的原則進行，於民國73年1月間（17年生）進行疏伐處理，並經過連續六年調查分析，其結果如下：
1.本研究結果顯示，中度疏伐和強度疏伐處理，可增進臺灣杉單株林木之胸徑和樹高生長，並提高林分斷面積和材積之生長量。此種效應於疏伐後第3年最為顯著，至第6年時，斷面積和材積的生長潛能，亦仍維持緩和上昇之趨勢。
2.臺灣杉若於11年生時修枝，對林木之胸徑、樹高、斷面積及材積生長均無顯著之影響，即使修枝高度達4.5m處亦然。
3.鬱閉林分經疏伐後，其樹冠幅和側枝節徑隨疏伐度之增加而增大，惟側枝節徑增幅不高，對林木品質之負面影響不大。
4.本試驗林分樹幹分叉之林木甚多，採用強度及中度之下層疏伐，可伐除此類幹形不良之樹木，並增加大徑木所佔的百分比，而有助於提高林分之經濟價值。
5.根據樹幹解析資料顯示，若臺灣杉人工林每公頃林分密度維持在1,600株左右時，則以14～18年生為實施流伐撫育最適之林齡。

關鍵字

臺灣杉 ； 疏伐 ； 修枝 ； 定期平均生長 ； 連年生長 ； 生長率

並列摘要

The present study was carried out in a 17-year-old Taiwain (Taiwania cryptomerioides Hayata) plantation located in Southern Taiwan. Four thinning treatments, based on the absolute basal area (BA) per hectare left after thinning namely: (A) light thinning with 51m^2/ha of BA retained, (B) intermediate thinning with 46m^2/ha of BA retained, (C) heavy thinning with 41m^2/ha of BA retained, and (D)no thinning. (i.e. the control were applied). After six years' continuous investigation and anlysis, the result can be summarized as follows:
1. Intermediate and heavy thinning significantly increased the D.B.H. and height growth of individual trees as well as the BA and volume growth of the plantations. These observed thinning effects were particularly evident during the third years after thinning.
2. Pruning, even up to 4.5m of the tree height, did not effect the increase of D.B.H., height, basbl aera and volume of 11-year-old Taiwania plantation.
3. Although the diameter of nodes and the width of crown increased with the intensity of thinning pure effects, however, did not result in lowering the wood qvality.
4. The removal of all deformed and over topped trees in intermediate and heavy thinning resulted in an increase of the percentage of large diameter trees, and, thus, increase the economic values of the plantation.
5. Results of stem analyses showed that, at stand density of 1,600 trees perhectare, the best time for thinning of Taiwania plantation would be at the age of 14-18 years old.

並列關鍵字

Taiwania cryptomerioides Hagata ； Thinning ； Pruning ； Periodic annual increment ； current annual increment ； gowth percentage