雪山雪東線之不同海拔梯度的物種及生活型多樣性

Species and Life-form Diversity along the Altitudinal Gradient on the Mt. Shei Eastern Trail

臺灣面積雖小，但因地形起伏差異大，故而孕育多樣的物種。本研究為瞭解雪山雪東線不同海拔梯度之物種多樣性及生活型組成，調查自億年橋（1,682 m）沿步道至雪山主峰（3,886 m）共44 個10×25 m2 樣區。調查研究共記錄383種維管束植物，喬木層之α多樣性隨海拔梯度增加，呈現小幅上升後下降的趨勢；又地被層之α多樣性則隨海拔增加而降低，直至海拔2,500-3,000 m後再增加；其中喬木、地被層之均勻度沿海拔梯度皆無明顯變化。另β多樣性之Jaccard、Sørenson相似性指數則隨海拔梯度上升而遞增，顯示鄰近海拔之樣區間的物種組成相似性高。此外，生活型之豐多度沿海拔梯度增加而有逐漸降低的趨勢，且各植群型之生活型組成具明顯差異。是故藉由研究物種多樣性隨環境梯度之變化，可揭示物種多樣性與環境因子之關聯性；研究中發現高海拔之環境條件較為嚴苛，因而空間異質性較低，而不同植群於其生育地中具所仰賴之生存策略。 This study compiled 44 plots (each 10 × 25 m2) and recorded 383 species of vascular plant along the eastern trail of Mt. Shei from 1,682 m to 3,886 m. Overstory species richness and abundance generally increased along the altitudinal gradient until the peak appeared between 2,000 and 2,500 m and then declined along the altitudinal gradient. Understory species richness and abundance increased slightly at an altitude of 3,000 to 3,500 m. Overstory and understory evenness indices showed no obvious trends. Jaccard and Sørenson similarity indices decreased with an increase in the altitudinal gradient, This may be caused by environment factors and a decrease in spatial heterogeneity. Along the altitudinal distribution of sample plots, life form abundance clearly decreased. The vegetation distribution showed that the vegetation subtypes differed with the structure and composition of life forms. The structure of plant life-forms in the area may be based on plant survival strategies determined by their habitat.