應用Hegyi競爭指數規劃針闊葉混淆林林相改良之研究

Using Hegyi Competition Index to Plan the Timber Stand Improvement Operation in a Conifer-hard Wood Forest

本研究的目的在於探討以擇伐作業為基礎之林相改良方案，研究區域位於臺灣中部地區之惠蓀林場，林分為香杉（Cunninghamia lanceolata(Lamb.) Hook. var. konishii(Hay.) Fujita form. Konishii.）與闊葉混淆林，分別以胸高斷面積為基準，採用擇伐度為20%、40%及60%等不同方案進行林相改良方案之規劃，並考慮林木空間配置的排列，應用Hegyi競爭指數選取擇伐木。研究結果顯示株數、材積、樹冠競爭情形隨擇伐強度增加而有降低趨勢，而林木生長空間及孔隙率則隨擇伐強度增加而提升。另外本研究以Weibull機率密度模擬林分之直徑分布，發現各處理皆呈左偏歪之鐘型分布。經評估各方案後，以擇伐40%之林相改良效果較佳。 The purpose of this study was to plan timber stand improvement operation based on selection cutting. This study was conducted on a mixed Cunninghamia lanceolata (Cunninghamia lanceolata (Lamb.) Hook. var. konishii (Hay.) Fujita form. Konishii.) and hard wood forest in Hue-Sun Experimental Forest of central Taiwan. We designed different alternatives of selection cutting, i.e., selection cutting 20%, 40%, and 60%, respectively, based on basal area. We used the Hegyi competition index to select trees which should be cut that can consider spatial distribution. The result of this study showed the number, volume and crown competition declined while tree growth space and gap rate enhanced with increasing cutting rate. In addition, the Weibull function was used to model diameter distributions, and showed a left-skewed distribution for the all stands after treatments. Moreover, we found that the selection cutting 40% is suitable for timber stand improvement after evaluating different alternatives of selection cutting.

The purpose of this study was to plan timber stand improvement operation based on selection cutting. This study was conducted on a mixed Cunninghamia lanceolata (Cunninghamia lanceolata (Lamb.) Hook. var. konishii (Hay.) Fujita form. Konishii.) and hard wood forest in Hue-Sun Experimental Forest of central Taiwan. We designed different alternatives of selection cutting, i.e., selection cutting 20%, 40%, and 60%, respectively, based on basal area. We used the Hegyi competition index to select trees which should be cut that can consider spatial distribution. The result of this study showed the number, volume and crown competition declined while tree growth space and gap rate enhanced with increasing cutting rate. In addition, the Weibull function was used to model diameter distributions, and showed a left-skewed distribution for the all stands after treatments. Moreover, we found that the selection cutting 40% is suitable for timber stand improvement after evaluating different alternatives of selection cutting.