臺東太麻里溪堤內洪氾區八種闊葉樹種造林之初期生長表現及施肥效應

Initial growth performance and fertilization effect among eight broad-leaved species on the floodplain of Taimali stream in Taitung

臺灣常因颱風帶來強降雨引發洪水及山崩，將中央山脈岩塊及礫石沖積至河川洪氾區，形成礫石含量高的貧瘠地，一般植物難以生長，屬於造林困難之不良環境，因多數洪氾區緊鄰城鄉地區，與當地居住環境及生活品質具有密切關係，有其必要進行復育造林之研究，提供洪氾區之造林技術。本研究選擇木麻黃、相思樹、臺灣欒樹、光蠟樹、欖仁、水黃皮、苦楝及黃槿等樹種於臺東太麻里溪堤內洪氾區進行造林試驗，試驗結果顯示八種造林樹種初期生長表現，對照組以木麻黃、相思樹及水黃皮的生長表現最佳，可為洪氾區內優先選擇的造林樹種。施肥試驗結果，施肥處理造林木的平均地徑淨生長為2.9 cm優於對照組2.0 cm，平均樹高淨生長為109.0 cm優於對照組66.0 cm，平均樹冠幅淨生長為105.0 cm優於對照組74.0 cm，以苦楝、欖仁、相思樹及黃槿的生長量增加最多，具有顯著差異。因此對於石礫含量高的貧瘠地，造林木可藉由適當的施肥，促進林木生長及提高適應逆境的能力。 Heavy rains during typhoon season are main factors that cause flood and landslide in Taiwan. Tremendous rocks erode from the Central Mountain Ridge and flow downstream, creating barren floodplains which fill with gravel that is inappropriate for afforestation. However, most of the floodplains in Taiwan are close to residential area and play important roles in the agricultural industry and water conservancy, it is important for us to construct afforestation techniques for barren floodplains. This study has focused on the initial growth performance of eight broad-leaved species, Casuarina equisetifolia, Acacia confusa, Koelreuteria henryi, Fraxinus griffi thii, Terminalia catappa, Millettia pinnata, Melia azedarach, and Hibiscus tiliaceus, on floodplains and compared their differences between fertilization treatments. The results showed that Casuarina equisetifolia, Acacia confusa and Millettia pinnata represent higher growth performances without fertilization, which could be practical tree species for floodplain afforestation. Furthermore, we found all species perform a significant growth increasement under fertilization treatment with 2.9 cm in ground diameter (2.0 cm in control), 109.0 cm in tree height (66.0 cm in control) and 105.0 cm in canopy diameter (74.0 cm in control). It also reveals that Melia azedarach, Terminalia catappa, Acacia confusa, and Hibiscus tiliaceus exhibit the highest growth performance with fertilization. We believe that to cultivate with appropriate fertilization is a prominent approach to promote growth and adaptability of afforestation on barren lands.