紅檜人工林不同林分密度生長與自我疏伐之研究

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，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。紅檜為台灣最重要之造林樹種，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，株行距為1×1 m^2，於林齡8年生時，林分已發生嚴重自我疏伐現象，此時每公頃約有7,800株，因此進行5種密度調整，每公頃分別保留10,000(對照區未疏伐8,608)、5,000、2,500、1,660及1,110株，林分經定期調查，至調整後22年，發現立木平均胸徑大小與保留株數多寡成反比，樹高亦有相同趨勢，惟不同密度生長或殘存株數大小差異之程度，有隨林齡之增加而減少，最後成一致軌跡變化之趨勢。又本試驗以密度調整後，藉由發生自我疏伐之樣區，求出林分最大密度或林分自我疏伐曲線ν＝ 6.12449×104ρ^(-1.70700)(式中ν及ρ分別代表單株材積及林分每公頃株數)，本研究結果可做為台灣北部紅檜人工林於不同林齡階段疏伐策略決定之重要資訊。

關鍵字

紅檜人工林；自我疏伐曲線；林分結構

並列摘要

The protection of ecological environments and conservation of natural resources are the current global trend on the earth. Therefore, the ban of natural forest cut is still a continuing tendency. Under the circumstances, it is important that sustainable and intensive management of man-made forest through silvicultural and genetic manipulations should render it to be the main emerging provider of forest product. Red cypress (Chamaecyparis formosensis) is the native species and has good wood properties which can serve as a excellent furniture lumber. The stand had undergone serious self-thinning at 8 yr of age, so stand densities were adjusted to 5000, 2500, 1660, and 1110 trees/ha, while the control plot had 8608 trees/ha. Mean DBH growth decreased with increasing retention of trees per hectare, and the mean height growth showed the same tendency when the plantation reached an age of 30 yr. Serious competition was occurring in the 10000 trees/ha, 5000 trees/ha, 2500 trees/ha, and 1660 trees/ha and mortality reached 80.9%, 69.9%, 36.8%, and 27.6% respectively. However, the above differences among different stand densities should decrease with increasing stand age, and then expected to level off to a constant trajectory. In this report, the full-density curve or self-thinning curve on mean stem volume, which shows the upper limit of stand density in regard to arbitrary stem volume, is expressed by the equation, ν＝6.12449×104ρ^(-1.70700), where V and ρ denote the mean stem volume per tree and stand density per hectare, respectively. The results of this study may serve as a useful reference for the thinning practices of red cypress plantations at difference stand age.

並列關鍵字

Red cypress plantations ； Self-thinning curve ； Stand structure

國際替代計量

紅檜人工林不同林分密度生長與自我疏伐之研究

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