由於林分直徑分布狀況直接影響到林分的價格,使用全林分模式求其平均材積收穫到經濟價值並不適當,Weibull機率密度函數因具有容易求得各直徑級機率及曲線配置極具彈性之效果,甚適合處理直徑分布問題,所以為求算林木經濟價值甚為理想的方法,本研究之目的為應用Weibull函數於蓮華池杉木人工林分析各林齡直徑分布及其經濟價值。在8-20年生杉木人工林,每公頃林木的株數由83株至143株,隨年齡增加而遞減,Weibull函數之母數b、c值,b值為5.43到19.68,隨林齡增加而加大,顯示直徑的分布範圍隨林齡增加而擴大,c值為2.08到3.52,變化較小,但有隨林齡增加由正偏曲線趨向常態分布之現象,材積由8年生的87立方公尺/ha增加到20年生的197立方公尺/ha,其年生長率為0.07,而原木價由8年生的16.8萬元/ha到20年生的61.2萬元/ha,其年成長率為0.11。
The purpose of this study is to estimate the stand diameter distribution and economic value in china fir plantation of Lieu-Hua-Chih with Weibull probability density function. From 8-to-20 yeas-old stand, the parameter b of Weibull function was increased from 5.43 to 19.68. This showed that the range of diameter distribution increased with age. The parameter c was 2.08 to 3.52, which showed variation is small, nonetheless, the distribution curves gradully shifted from positively skewed to normal distribution with age. From 8-to-20 year-old stands, the timber volume was increased from 87m^3/ha to 197m^3/ha with annual growth rate of 7%, and the current timber value increased from NT$168,000/ha to NT$612,000/ha with annual growth rate of 11%.