栽植密度對六龜地區台灣杉生長之影響

The Effect of Planting Density on the Growth of Taiwan-fir Plantations at Lu-Kuei Area

陳麗琴(Lih-Chin Chen) ； 黃進睦(Gin-Mu Hunag) ； 張添榮(Ten-Yong Chang) ； 洪富文(Fu-Wen Horng)

《台灣林業科學》 11卷1期 (1996/03) Pp. 1-11

https://doi.org/10.7075/TJFS.199603.0001

摘要

本研究的目的為應用Weibull機率密度函數及指數迴歸生長模式，探討六龜地區台灣杉人工林12年生以後，不同栽植密度不同林齡下之林分直徑分布結構及其生長情形，試驗地點為六龜地區台灣杉人工林七種不同栽植密度28年生之永久試驗樣區。各樣區所調查之每木胸徑資料經檢定均適合3因子Weibull函數模式，再經Q(A,PD)=α0e(上標α1/A+α2/PD^2)得栽植密度及林齡與Weibull函數母數a. b. c.值及存活株數的關係式，發現a與b值均隨栽植密度增加而減少，隨年齡增加而加大，c值則不受栽植密度影響，僅隨林齡增加而略為下降。經預測模式可發現密度愈大，同林齡之林分材積也愈高，但單株材積卻愈小，會形成此現象，主要是單株多寡足以影響林分材積，同時也預測了不同栽植密度不同林齡之林分直徑分布結構及其生長與收穫量，32年生林分從栽植密度為1111株/ha到4444株/ha，其收穫量分別從424.5立方公尺/ha到746.9立方公尺/ha，後者為前者的1.76倍，但栽植密度低的大徑木較多。由小到大的栽植密度之林分材積年生長率從12年生的16.2%-19.3%到32年生的2.35%-2.7%，而不論何種栽植密度下之林分生長或單株生長均以12-18年生最為旺盛，而栽植密度2000株/ha-2500株/ha以下的林分單位栽植密度所增加之生長量較高，又如每公頃栽植密度2000株林齡32年生之林分，胸徑20cm以下有460株，21-30cm之間有530株，31cm以上有138株，材積收穫量為644.l立方公尺/ha，平均年生長量為20.l立方公尺/ha。如果經營目標為收穫量最大，則需選擇栽植密度較高者，若考量林分品質或經濟價植，則大徑木的多寡及林分材積的大小是經營者同時需要考慮的；本文提供不同栽植密度不同林分大小徑級株數預測表，可供經營者依其目標選擇栽植距離之參考。

關鍵字

台灣杉 ； Weibull機率密度函數 ； 直徑分布 ； 栽植密度 ； 生長與收穫

並列摘要

Taiwan-fir (Taiwania cryptomerioides) is a mono species of Taiwania genus in Taiwan. Due to its fast growth and good wood quality Taiwan-fir has become an important species for middle elevation conifer plantations for past 20 years. At Lu-Kuei of Southern Taiwan, a density trial plantation baa been established for 28 years. The densities were 1111, 1333, 1600, 2000, 2500, 3333 and 4444 trees/ha with 3 replicates of 0.05ha pints for each density. The dbh of individual trees was measured at the age of 12, 15, 22, 25 and 28 years old. In this study, the Weibull probability density function and exponetial regression growth model were coed in analyze the density and the timber growth of this permanent trial plantation. The dbh data of the three plots for each density were lamped together to test its fitness fur the Weibull distribution function. The results indicated that the data of each density fitted a 3-parameter Weibull distribution function; and through the regression model of Q(A,PD)=α0e(superscript α1/A+α2/PD^2), the relationship of stand density and age and parameters of a, b, c of Weibull distribution and survival rates could be predicted. From rids prediction equation, it showed that the per unit volume growth increased with the increase of stand density at the same age, while the individual tree volume decreased with the higher stand densities. The 52 ye old stand volume growth would be 425 m^3/ha to 747m^3/ha with the planting density of 1111 trees/ha to 4444 trees/ha, and the dbh distribution with 2000 trees/ha at planting density would result in a stand of 460 trees of dbh ＜20cm, 530 trees/ha of dab between 21-30cm, 138 trees of dbh ＞31cm, and its mean annual increment being 21.1m^3/ha/year, and total volume growth 644 being m^3/ha. If the maximum volume in the management target, a higher planting density is recommended, However, if the timber quality or economic value in considered the timber (dbh) nine and economic value should be evaluated simultaneously. This study also tabulated the tree number for each dbh class at different planting density from 12 to 32 years old at Taiwania plantations for the choice of forest manager at Lu-Kuei and surrounding areas.

並列關鍵字

Taiwania cryptomerioides ； Weibull probability density function ； diameter distribution ； planting density ； growth and yield