本研究擬以臺大實驗林溪頭營林區門田柳杉生長量長期試驗地歷年之調查成果，探討其生長量與二氧化碳貯存量之效應。該試驗地面積為0.153 公頃，從1927 年至2007 年共調查39 次；另於1928、1930 年進行兩次疏伐均為下層疏伐，疏伐指數分別為0.82、0.90，其材積收獲最多輪伐期為林齡38 年時。由林分結構及歷年株數與每公頃胸高斷面積總和得知，此林分已由成熟期漸進入衰老期之趨勢；另由林木性特值進行相關性分析結果，林木胸徑與樹高、胸徑斷面積有顯著正相關性，但株數與胸徑、樹高、胸徑斷面積成顯著負相關性，經卡方檢定(K-S test) 結果顯示均有顯著差異。本試驗地藉由碳吸存轉換模式推估出其碳貯存量，總計每公頃二氧化碳貯存量為159,262.697 噸/公頃，平均每年每公頃二氧化碳貯存量為1990.784 公噸/公頃。以造林所需成本做為造林對貯存二氧化碳之適應成本，貯存每公噸二氧化碳的成本為新台幣79.94 元，換算美金為2.76 美元，與國內外研究報告相比其每公噸二氧化碳的適應成本為低。此適應成本比直接利用化石燃料後再削減二氧化碳排放之減量更為經濟，顯示造林貯存碳的成本較低。

This study aims on the growth of Cryptomeria japonica D. Don and its benefit for the stock of carbon dioxide at the Men-tian permanent plot of NTUEF Xitou Tract. The plot area is 0.153 ha and 39 investigations had been done between 1927 and 2007. In addition, the plot had been
thinned at 1928 and 1930 using lower thinning with the thinning index 0.82 and 0.90, and the ideal rotation age with the highest timber yield is estimated to the age of 38 years. From the data of stand structure, number of trees and total basal area per ha, it shows that the stand has turned from mature to old age. DBH is positively correlated with tree height and basal area, while the tree number is negatively correlated with tree height, DBH and basal area. They all are significantly different by K-S test. The carbon stock is estimated by the transfer model of carbon sequestration. In total, the stock of carbon dioxide is 159,262.697 ton/ha and the annual average is 1990.784 ton/ha. The adaption cost for stock of carbon dioxide based on the cost of plantation is NT$79.94 (US$ 2.76). The adaption cost is comparatively lower than reviewed reports and references. It is more economic compared with reducing the emission of carbon dioxide after using fossil fuel directly.