台灣中部武陵地區防火樹種之篩選

Abstract

森林火災往往造成巨大損失，預防林火，設置永久防火線或防火林帶是值得重視的手段。在台灣中高海拔地區，火災常常造成資源的大量損失，因此在交通不便之中高海拔山區，建立防火林帶以防止火災之擴散為必要之作業。 本研究主要目的為測定武陵地區現有樹種之各項燃燒特性，實驗結果可供做防火林帶造林樹種之用，漸次取代目前中部高山地區台灣二葉松人工純林，減緩森林火災之發生。調查現有常綠性闊葉樹種包括：木荷 (Schima superba)、楊梅 (Myrica rubra)、狹葉櫟 (Cyclobalanopsis stenophylloides)、菱葉柃木 (Eurya gnaphalocarpa)、山肉桂 (Cinnamomum insularimontanum)、青剛櫟 (Cyclobalanopsis glauca)、高山莢蒾 (Viburnum propinquum)、大頭茶 (Gordonia axillaries)。落葉性闊葉樹種台灣赤楊 (Alnus formosana)、栓皮櫟 (Quercus variabilis) 、台灣紅榨槭 (Acer morrisonense)、楓香 (Liquidambar formosana)、青楓 (Acer serrulatum) 以及針葉樹種華山松 (Pinus armandii) 等。測定項目包括生立木葉片含水率、葉片分解重量留存率、葉片醇苯抽出物、葉片木質素含量及灰分含量等，並且用熱重量分析觀察各樹種之重量損失曲線。 試驗結果顯示含水率以菱葉柃木最高，最低為華山松；抽出物成分以楓香最高，最低為菱葉柃木；木質素含量最高為楊梅，最低為華山松；灰分含量最高為楓香，最低為楊梅。選擇防火樹種需考量各項因子，因此，利用主成分分析將樣區內的樹種重新排列，得到常綠性樹種排序為菱葉柃木、木荷、楊梅、山肉桂、大頭茶、高山莢蒾、青剛櫟、狹葉櫟；落葉性樹種排序為台灣紅榨槭、楓香、台灣赤楊、青楓、栓皮櫟。落葉性樹種在乾季時容易造成林地上燃料物累積，較不適合做為防火林帶，因此常綠性樹種菱葉柃木、木荷、楊梅為優良防火樹種。

Forest fires have always led to significant losses. Installing permanent firebreaks and fire preventive zone are important measures. Fire accidents often caused serious and significant losses at mid- and high-altitude regions of Taiwan. Creating fire-retarding forest belts to prevent the spread of forest fires at these altitudes is critical because transportation is difficult. We determined the combustibility of current tree species in the Wulin area. Our experimental results indicate that species selection when fire preventive zone to gradually replace current Pinus taiwanensis plantations in alpine areas in central Taiwan will decrease the spread of forest fires. We located the following evergreen broad-leaved tree species: Schima superba, Myrica rubra, Cyclobalanopsis stenophylloides, Eurya gnaphalocarpa, Cinnamomum insularimontanum, Cyclobalanopsis glauca, Viburnum propinquum, Gordonia axillaries. Additionally, we located the following broadleaved deciduous tree species: Alnus formosana, Quercus variabilis, Acer morrisonense, Liquidambar formosana, Acer serrulatum, and Pinus armandii. The determination items included moisture content of standing green leaves, weight retention (%) after leaf decomposition, alcohol-benzene extractives from leaves, lignin, and ash content in leaves. We also observed weight loss distribution using thermogravimetric analysis. The results indicated that E. gnaphalocarpa had the highest moisture content, while P. armandii had the low moisture content. For extractives, L. formosana had the highest and E. gnaphalocarpa had the smallest amount. M. rubra has the highest content of lignin, while P. armandii had the least. L. formosana had the most abundant ash content and M. rubra contained the least. Each element must be considered for selection based on fire-retarding properties. We re-arranged tree species in the sampling region in accordance with fire-retardant properties. For evergreen trees, the order was E. gnaphalocarpa, S. superba, M. rubra, C. insularimontanum, G. axillaries, V. propinquum, C. glauca, and C. stenophylloides. While among deciduous trees, the order is A. morrisonense, L. formosana, A. formosana, A. serrulatum, and Q. variabilis. Deciduous trees easily cause fuel accumulation in forests during dry seasons, which is not suitable for use in fire preventive zone. Therefore, evergreen trees such as E. gnaphalocarpa, S. superba, and M. rubra are ideal species for fire prevention.