紅檜與台灣扁柏林分自我疏伐之初探

為反應生態環境保護與自然資源保育之世界潮流，天然林之繼續禁伐仍為必然之趨勢，在此情況下，透過育林技術，永續並集約經營現有人工林，使之成為林產物供應之主要來源，已成為林業經營上一項主要課題。紅檜與台灣扁柏均為台灣重要之鄉土樹種且材質優異，可做為優良之傢俱用材，紅檜試驗地位於太平山事業區20林班，造林時，栽植密度為10,000株 ha^(-1)，株行距為1×1 m，於林齡8年生時，林分已發生嚴重自我疏伐現象，因此進行5種密度調整，每公頃分別保留10,000(對照區未調整8608)、5000、2500、1660及1110株，台灣扁柏試驗地位于大溪事業區94林班，林分天然更新後，15年生時密度達11,200株 ha^(-1)，因此，同樣進行除伐之林分密度調整，每公頃留存5000、3300、2000株，另太平山事業區32林班32年生時，未干擾之對照區林分約1500～2000株。惟不同林分密度之存活株數達最大密度時，隨著林木生長株數會減少，最後成自我疏伐曲線一致軌跡變化之趨勢。又本試驗以密度調整後，藉由發生自我疏伐，枯死率達5%之樣區，視為林分最大密度或林分自我疏伐門檻，求出林分單木材積(ν)與每公頃密度(ρ)的廻歸式，紅檜為ν = 4.73544×10^4 ρ^(-1.67604)，台灣扁柏ν = 4.12392×10^5 ρ^(-2.12166)。達最大密度時，林分二次方根平均胸徑(QMD)和林分株數之關係為紅檜log QMD = 3.379-0.662 log ρ，台灣扁柏log QMD = 3.669-0.801 log ρ，台灣扁柏自我疏伐斜率及截距均大於紅檜，本研究結果可做為台灣北部檜木人工林決定不同生長階段或林齡，疏伐策略決定之重要資訊。

關鍵字

紅檜；台灣扁柏；林分結構；自我疏伐曲線

並列摘要

The protection of ecological environments and conservation of natural resources are current trends would wide. Therefore, the ban of natural forest cutting is still a continuing tendency. Under these circumstances, sustainable and intensive management of forest plantations through silvicul-tural practices should render them the main provider of forest products. Chamaecyparis formosensis (red false cypress) is a native species to Taiwan and has good wood properties which can serve as an excellent timber for furniture. The stand we investigated underwent serious self-thinning at 8 yr of age, and stand densities of treatment plots were while that of the control plot was 8606 trees ha^(-1) were adjusted to 5000, 2500, 1660, and 1110 trees ha^(-1), while Chamaecyparis obtusa var. formosana (yellow false cypress) sites were located at compartment no. 94 of Ta-Shi and no. 32 of the Tai-Ping-Shan working circle at Chi-lan Mt. in northern Taiwan. The former site was a naturally regenerated stand after site preparation. Stand density reached 11,200 trees ha^(-1) at 15 yr of age, due to serious competition. The stand densities for the treatment plots were adjusted to 5000, 3300, and 2000 trees ha^(-1). At the latter site, stand densities were 1500~2000 trees ha^(-1) at 32 yr old for non-thinned plots. However, the above different stand densities, while reaching maximum densities for both species, should decrease with increasing stand growth, and then are expected to level off to a constant trajectory. In this report, the mortality ratio reached 5%, and served as the full-density or self-thinning threshold. The relationship between the mean stem volume (ν) and stand density (ρ) for red cypress was: ν = 4.73544×10^4 ρ^(-1.67604); anf for yellow false cypress was: ν = 4.12392×10^5 ρ^(-2.12166). When reaching the maximum density, the quadratic mean diameter (QMD) and stand density (ρ) equations were: red false cypress QMD = 2.393×10^3ρ^(-0.662), and yellow false cypress QMD = 4.667×10^3 ρ-^(0.801). Results of this study can serve as a useful reference for thinning practices of Chamaecyparis plantations at difference stand growing stages or ages.

並列關鍵字

Chamaecyparis formosensis ； Chamaecyparis obtusa var. formosana ； stand structure ； self-thinning curve

國際替代計量

紅檜與台灣扁柏林分自我疏伐之初探

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