思源埡口地區植群組成及多樣性

Composition and Diversity of Vegetation in Sihyuán Wùkǒu Area

思源埡口地區屬夏雨型氣侯的西北內陸區，且其南、北面分屬不同生態小區，蘊含豐富生物多樣性，係中央山脈保育廊道北端地景連結之重要區域。本研究共設置56個樣區，記錄145科440 屬898種植物，其中以薔薇科、菊科、蘭科等植物種類為最多。依相似度指數（SI）=20%所區分7類植群型中，思源埡口南、北面皆具之植群型為臺灣胡桃、日本楨楠－變葉新木薑子、長梗紫苧麻、柳杉等林型；而臺灣赤楊－臺灣二葉松林型僅於思源埡口南面，又臺灣扁柏林型、桂竹型則僅出現在思源埡口北面。此外，思源埡口北面之桂竹型屬演替中後期階段，且其豐多度較高。另思源埡口南、北面兼具之臺灣胡桃林型處於演替中前期階段；而日本楨楠－變葉新木薑子、長梗紫苧麻、柳杉、臺灣扁柏等林型符合幾何序列或截斷對數常態分布，顯示受到不同程度之干擾，其中日本楨楠林型－－變葉新木薑子林型的多樣性最高，長梗紫苧麻林型的豐富度亦高，柳杉林型之豐富度則較低。又思源埡口南面之臺灣赤楊－臺灣二葉松林型較符合幾何序列，部份符合對數序列、截斷對數常態分布或折枝模式，即呈現不同演替時序的發展。此等對該區之植群多樣性的深入探討，期能提供爾後相關生態監測與調查分析之參考。 The Sihyuán Wùkǒu area is located at the northwest inland region with the summer rain climate. It consists of different ecological subregions from the north and south side. Therefore, it has complicate biodiversity and stands on the important position to connect the northern landscape of the Central Mountain Range Conservation Corridor (CCC). It was recorded 145 families, 440 genera, and 898 species of vascular plants in the 56 surveyed plots. The species in Rosaceae, Compositae, and Orchidaceae were superior. There were 7 vegetation types classified by the similarity index (SI) of 20%. The Juglans cathayensis type, Machilus japonica-Neolitsea aciculata var. variabillima type, Oreocnide pedunculata type, and Cryptomeria japonica type arose on both the north and south sides. However, the Alnus formosanaPinus taiwanensis type only arose on the south side, and the Chamaecyparis formosensis type, Phyllostachys makinoi type only arose on the north side. Besides, the Phyllostachys makinoi type on the north side of the Sihyuán Wùkǒu was in the mid-late succession stage with superior richness. The Juglans cathayensis type on both sides was in the mid-early stage. Fitting in with the geometric series, or the truncated log normal distribution showed that the Machilus japonica-Neolitsea aciculata var. variabillima type, Oreocnide pedunculata type, Cryptomeria japonica type, and Chamaecyparis formosensis type suffered from different kinds of disturbance. The Machilus japonica-Neolitsea aciculata var. variabillima type had superlative diversity. The Oreocnide pedunculata type had superior abundance, but the Cryptomeria japonica type had inferior abundance. The Alnus formosana-Pinus taiwanensis type on the north side of the Sihyuán Wùkǒu pretty fitting in with the geometric series and partly fitting in with the logarithmic series, the truncated log normal distribution and the broken stick model showed that it was developing in several succession stages. These thorough discussion for the vegetation diversity in this area was expected to provide reference on the relative ecological monitoring and investigation in the future.