紅檜幼齡人工林密度試驗

Studies on Stand Density of Young Red Cypress (Chamaecyparis formosensis Matsum) Plantations

邱志明(Chih-Ming Chiu) ； 羅卓振南(Chen-Nan Lo-cho)

《台灣林業科學》 17卷2期 (2002/06) Pp. 205-217

https://doi.org/10.7075/TJFS.200206.0205

摘要

本文試驗地位於太平山事業區20林班，造林時，栽植密度爲10,000株/ha，株距爲1×1平方公尺，於林齡8年生時，林分已發生嚴重自我疏伐現象，此時7,800株/ha，因此進行5種密度調整，分別保留10,000（對照區未疏伐8,608）、5,000、2,500、1,660及1,110株/ha，林分調整後10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，林分8-18年生時，以保留2,500-1,660株/ha最佳，最能發揮林地生産力。至18年生時，10,000株/ha株數自我疏伐比率已達到59.3•，5,000株/ha者爲38.7•，2,500株/ha者爲4.3•，1,660及1,110株/ha則尚未發生自我疏伐現象，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，歷年之生長資料，求出紅檜幼齡林競爭密度效果及收穫密度效果實驗式，並藉發生自我疏作之樣區，求出林分最大密度或林分自我疏伐曲線ν＝93887.54ρ^(-1.755394)（式中ν及ρ分別代表單株材積及林分每公頌株數），本研究結果可供台灣大面積紅檜人工幼齡林疏伐撫育、密度控制之參據。

關鍵字

紅檜幼齡林 ； 林分密度生長 ； 競爭密度效果 ； 自我疏伐曲線

並列摘要

The study site for stand density of red cypress (Chamaecyparis formosensis Matsum) plantations is located in compartment no. 20, TaipingMt. Working Circle in the ChilanMt. area of northern Taiwan. The planted space was 1×1m^2. 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 18 yr. However, in a comparison of periodic annual increment at 10 yr after treatment, stand densities retaining 2500 and 1660 trees/ha showed the greatest increment in basal area and volume growth. Furthermore, serious competition was occurring in the control plot, and mortality reached about 59.3•because of the self-thinning effect. In addition, mortalities in plots with stand densities of 5000 and 2500 trees/ha were 38.7•and 4.3•after being treated, respectively, but no mortality was found in the plots with 1660 and 1110 trees/ha. However, the above differences between different stand densities should decrease with increasing stand age, and then expected to level off to a constant trajectory. In this report, the reciprocal equations of competition-density effect and yield-density effect were derived from the past 10 yr's growth data after treatment. Moreover, the full-density curve or self-thinning curve on mean stem volume, which shows the upper limit of stand density in regard to arbitrary mean stem volume, is expressed by the equation, ν=93887.54 ρ^(-1.755394), where ν 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 thinning practices of young red cypress plantations.

並列關鍵字

young red cypress plantations ； stand density ； growth ； competition density effect ； self-thinning curve