新化林場大葉桃花心木人工林直徑分布量化及碳吸存能力評估

Quantifying diameter distribution and assessing carbon storage capacity of a mahogany (Swietenia macrophylla) plantation in Hsinhua Forest Station

本研究的目的在於量化大葉桃花心木人工林之林分直徑分布及評估碳貯存量，研究區域位於臺灣南部的新化林場，隸屬於國立中興大學，該林分於1975年開始栽植，為監測林分的發展，本研究於2019年開始設置3個永久樣區，並於2019及2020年進行兩次調查，調查時林分的林齡分別為44及45年生。本研究採用胸高直徑建立樹高曲線式用以預測單木樹高，並應用Weibull機率密度函數量化林分直徑分布，所得之Weibull函數a、b和c參數值分別為12.5、20.69和1.81，經Kolmogorov-Smirnov適合度測驗結果顯示Weibull函數可有效模擬林分之直徑分布。林分於45年生時之材積量及碳貯存量分別為436.9 m3 ha-1和235.6 Mg ha-1。此外，在二次調查期間不論材積或碳貯存量皆呈現連年生長量大於平均生長量，亦即此林分在材積生長和碳貯存能力仍具有很大的潛力，本研究所得之結果可提供大葉桃花心木人工林經營之重要資訊。

The purpose of this study was to quantify diameter distribution and to assess carbon storage capacity of a mahogany (Swietenia macrophylla) plantation established in 1975. The plantation is located at the Hsinhua Forest Station of National Chung Hsing University, south Taiwan. To monitor stand development, 3 permanent plots were installed in 2019 and surveyed in 2019 and 2020 when the stand ages were 44 and 45 years old, respectively. The tree height equation was built based on diameter at breast height for predicting individual tree height. The Weibull probability density function was employed to quantify diameter distribution and the parameters a, b and c were predicted to be 12.5, 20.69 and 1.81, respectively. The result showed that the Weibull function was suitable for quantifying diameter distribution by the Kolmogorov-Smirnov test. Moreover, volume and carbon storage at 45 years old were estimated to be 436.9 m3 ha-1 and 235.6 Mg ha-1, respectively. We also found that the current annual increment was higher than the mean annual increment in volume and carbon storage during the two survey periods, indicated that this stand still had potential in the increment of volume and carbon storage. Our findings provide important information for mahogany plantation management.