新化林場人工林植群與物種多樣性調查

Vegetation and species diversity of the plantation in Xinhua Forest Station

新化林場為中興大學4個實驗林場之一，除提供作為森林學教育的教學與學生實習之用，亦是科學研究、水源涵養保護、森林環境教育與森林休閒活動的場域。本研究自2019年5月至同年11月於新化林場進行人工林植群調查，共設立54個15m×15m的樣區，記錄76科215屬244種維管束植物，其中有16種臺灣特有種；歸化種有55種，其中小花蔓澤蘭、紫花藿香薊、香澤蘭、南美蟛蜞菊、銀合歡、馬纓丹、大黍及野薑花等8種為文獻記載入侵能力較強的歸化植物。維管束植物清單中有超過1／5的種類為歸化植物，顯示研究區的人工林因人為擾動致使歸化植物容易進入林地。樣區之群聚分析結果顯示可分為I.大葉桃花心木型、II.黑板樹型、III.小葉桃花心木型、IV.馬尼拉欖仁型、V.臺灣櫸型、VI.玫瑰桉型、VII.印度紫檀型，以及VIII.荔枝型等8種林型。大葉桃花心木型佔林場面積最廣，林分胸高斷面積、林分密度指數與夏農指數的分析顯示，胸高斷面積與林分密度指數與夏農指數呈顯著負相關。降趨對應分析結果顯示，黑板樹型和大葉桃花心木型之地被組成較為相近，而玫瑰桉型和印度紫檀型之地被層組成與其他林型差異較大。典型對應分析顯示，海拔及坡度為人工林地被層組成分化的重要環境因子。新化林場的原生樹種有較高比例的陽性樹種與數量，應該為長期且頻繁人為擾動影響所致，建議可以適度引入一些鄰近地區演替後期的耐陰性樹種，以增加林場的物種多樣性。

Xinhua Forest Station is one of the four experimental forest stations owned by the National Chung-Hsing University. It provides rich resources for forest education, teaching, and student practice, and services such as water conservation and protection, environmental education, forest recreation as well as research collaboration. Plant resource and forest plantation surveys were conducted from May to November of 2019. There were 54 plots with a size of 15 m by 15 m for each plot. A total of 244 vascular plants from 215 genera and 76 families were identified. Among them, 55 naturalized species were detected, with seven having more invasive characteristics, they are Ageratum houstonianum, Mikania micrantha, Wedelia trilobata, Leucaena leucocephala, Lantana camara, Panicum maximum, and Hedychium coronarium. More than 20% of the total vascular plants were naturalized species, indicating that naturalized plants enter the artificial forest easily through the disturbances of forest management activities. The results of cluster analysis suggested that the forest plantations can be divided into the I. Swietenia macrophylla type, II. Alstonia scholaris type, III. Swietenia mahagoni type, IV. Terminalia calamansanai type, V. Zelkova serrate type, VI. Eucalyptus grandis type, VII. Pterocarpus indicus type, and VIII. Litchi chinensis type. Swietenia macrophylla plantation occupies the largest area of the Xinhua Forest Station. Furthermore, the results revealed that the Shannon index was significantly negatively correlated with stand basal area and stand density index, respectively. The results of descending correspondence analysis revealed that the understory composition of Alstonia scholaris and Swietenia macrophylla types were similar; however, the understory composition of Eucalyptus grandis and Pterocarpus indicus types differed from other forest types. The canonical correspondence analysis revealed that the altitude and slope are major environmental factors for differentiating plantation understory compositions. We also discovered that native tree species had a high proportion and abundance of pioneer trees, which could be attributed to frequent, long-term disturbance; therefore, it is recommended that some native shade-tolerant tree species of neighboring areas be introduced to enhance the species diversity at the Xinhua Forest Station.