林下光環境與植群調查對瞭解林下稚樹生長與林分結構非常重要。本研究目的是利用位 於蓮華池試驗集水區的天然闊葉林與杉木人工林林分，以半球面影像分析林下光環境，並比較林 下光環境與植群多樣性指數之關係。試驗區設置20 m × 20 m樣區總共11處，分別為天然闊葉林7 處，杉木人工林4處。研究結果顯示，天然闊葉林與杉木人工林的樹冠孔隙率，平均值分別為12.1 ％及11.7 ％，特別是天然闊葉林第2、3、4及5樣區的樹冠孔隙率高於13 %以上。直射光及散射光 立地係數平均值在天然闊葉林分別15.6 ％及18.5 ％；在杉木人工林平均值分別為17.1％及21.3％。 從單因子變異數分析結果顯示天然闊葉林7個樣區間的樹冠孔隙率、直射光及散射光立地係數皆有 顯著的差異，而杉木人工林4個樣區間的樹冠孔隙率與直射光立地係數則不見顯著差異。天然闊葉 林林內光環境與林下植物的Simpson多樣性指數、Shannon多樣性指數、均勻度指數及物種豐富度 指數皆呈現負相關，顯示林下光環境指數值越低，物種多樣性與均勻性越高，杉木人工林則呈相 反之正相關趨勢。從杉木人工林林下植物的植群多樣性指數與林分密度分析顯示，杉木人工林林 分密度越高，物種多樣性與均勻性越低，且呈現顯著差異。此結果可能是因為杉木人工林曾經多 次清理地被層及疏伐，造成胸高直徑較小，優勢樹種較多，林分密度較高的現象。本研究結果可 以提供杉木人工林經營研究的參考。

Investigation on understory light environment and vegetation is very important for understanding seedling establishment and forest structures. The aim of this study was to analyze differences in understory light environment and vegetation diversity indices by hemispherical photography in natural broadleaf forests (NBF) and china-fir plantation forests (CPF) in Lien-hua-chih experimental watershed. We analyzed vegetation important indices and plant species in understory light environment including visible sky (VS), indirect site factor (ISF) and direct site factor (DSF). Eleven plots (20m×20m) were established with four plots in the CPF and seven plots in the NBF. The results showed that average VS values were 12.1 % in the NBF and 11.7 % in the CPF. Especially, the average VS values of No. 2, 3, 4 and 5 plots were over 13 % in the NBF. The average DSF and ISF values were 15.6 % and 18.5 % in the NBF, and 17.1 % and 21.3% in the CPF, respectively. The VS, ISF and DSF in the NBF from the seven plots were significant different by one-way ANOVA, but they were not significant different in the CPF. There were negative correlations between understory light environment and vegetation diversity indices (Simpson’s index of diversity, Shannon’s index of diversity, Evenness index and Species richness index) in the NBF indicating that index of understory light environment decreased with increasing diversity, evenness and species richness indices. According to the analyzed relationship between vegetation important indices and stand density, there were significant differences in the CPF indicating that stand density increased with decreasing diversity and evenness indices. The results might be due to the CPF having repeated removal of ground vegetation and thinning, which resulted in smaller diameter at breast height, dominant species and higher stand density. The results of this study can provide a reference for research in plantation management