福山地區維管束附生植物之物種組成及功能性狀在垂直方向的變化趨勢

Abstract

在森林中包括光度、相對濕度及溫度等環境因子都會隨高度改變，形成垂直的環境梯度。維管束附生植物因為生長在其他植物之上，面對從林下層到樹冠層的多樣微環境，因此適合用來研究垂直環境梯度對生物的影響。本研究針對在臺灣東北部福山試驗林的附生植物，以釐清附生植物的物種組成以及功能性狀是否會隨著高度改變。本研究選定24棵樣樹，在每棵樣樹上劃設5-6個垂直分區，並透過雙索攀樹技術，在各分區內設立樣區進行物種調查。除了記錄樣區內的物種及豐度，亦採集個體量測功能性狀，包括葉厚度、比葉面積、葉乾物質重、單位葉面積葉含水率以及葉綠素含量 (單位葉面積及單位葉質量) 。 研究結果顯示，樣區的物種組成會隨離地高度而改變。各物種會佔據不同的高度範圍，形成垂直分層分布。此外，對於單葉的附生植物物種來說，葉厚度以及單位葉面積葉含水率會隨高度上升而增加，比葉面積和單位葉質量的葉綠素含量則會隨高度上升而減少。本研究指出離地高度確實對附生植物的分布以及功能性狀都具有顯著的影響。

Vascular epiphytes grow on other plants, facing various micro-environments from dark and humid understory to bright and dry canopy. Therefore, it is quite suitable to use epiphytes to analyze the effects of vertical environmental gradients on organisms. I studied vascular epiphytes in Fushan Experimental Forest (located in northeastern Taiwan) in 2018 and aimed to determine whether species composition and several functional leaf traits of vascular epiphytes change along vertical environmental gradients. I used doubled rope techniques to climb up 24 sampled trees and surveyed the epiphytes on them. I set 5-6 vertical zones within each sampled tree based on height above ground, and set sampling plots within each zone, recorded all species that appeared in the plots and their abundance. I also collected some epiphyte individuals to measure functional traits including leaf thickness, specific leaf area, leaf dry matter content, leaf water content (per unit area) and leaf chlorophyll content (per unit area and per unit mass). The results show that epiphyte species composition changed significantly with height, and epiphyte species differentiated in their height distribution. Angle differences between aspects of plots and the south direction were also suggested to have effects on epiphyte species composition. Besides, several functional leaf traits show vertical trends. Leaf thickness and leaf water content (per unit area) of simple-leaved epiphytes significantly increased with height, while specific leaf area and chlorophyll content (per unit mass) decreased with height. This study reveals that height is an important factor which not only structures species composition but also creates vertical trends of several functional leaf traits.