北大武山區植群多樣性之研究 Study on Vegetation Diversity of Peitawushan

Study on Vegetation Diversity of Peitawushan

研究生：廖家宏 Jia-Hong Liao

【摘要】

本研究旨在探討北大武山區之植群多樣性隨海拔梯度與坡向之植物多樣性變化，共設置35個0.05 ha樣區，同時觀測8項環境因子。共紀錄到596種維管束植物，其中包含27種稀有植物。經雙向指標種分析與降趨對應分析將所有研究樣區分出3種植群型與4種亞型，分別為厚葉柃木-鐵杉型；假長葉楠-長葉木薑子型，此型再細分出無脈木犀-假長葉楠亞型、台灣杜鵑亞型、瓊楠-豬腳楠亞型與台灣厚距花-阿里山千金榆亞型及黃肉樹-燈稱花型。以典型對應分析探討植物社會與環境因子之相關性，以海拔、地形位置、坡度、含石率與冠層覆蓋度為主要影響植物社會變化之因子。由物種反應曲線中發現主要優勢種在環境梯度上有比主要特徵種具有更高之耐性範圍。各植群型之α多樣性，在木本植物方面，均勻度指數、Shannon指數與Simpson指數皆以瓊楠-豬腳楠亞型最高，而種類豐富度與Avalanche指數則以台灣厚距花-阿里山千金榆亞型為最高；在草本植物方面，種類豐富度以瓊楠-豬腳楠亞型為最高；均勻度、Shannon指數及Simpson指數以無脈木犀-假長葉楠亞型為最高；而Avalanche指數則以台灣厚距花-阿里山千金榆亞型最高。南北向樣帶之植物社會結構中，南向樣帶草本植物在各海拔佔最高的比例，而北向樣帶各植物習性之變化則大於南向樣帶；在β多樣性上，南向樣帶之物種轉換率與海拔梯度相關，木本植物平均95%物種轉換需967 m，草本之轉換率與木本有相同的趨勢，在海拔1,359-1,457 m有較快速的物種轉換；而北向樣帶則與海拔梯度無密切相關，木本與草本之轉換率在1,560-1,650 m及1,650-1,740 m之間物種有較快的轉換率。

關鍵詞：雙向指標種分析、降趨對應分析、典型對應分析、α多樣性、β多樣性、物種轉換率

【Abstract】

The aims of this study were to investigate the vegetation diversity and plants diversity pattern along altitudinal gradient and aspects of Peitawushan. 35 plots of 0.05 ha were laid and 8 environmental factors were observed. There were 596 species of vascular plants, among which 27 were recognized as rare plants. Three vegetation types and four subtypes were identified using detrended correspondence analysis (DCA) and two-way indicator species analysis (TWINSPAN). The first vegetation type was Eurya glaberrima-Tsuga chinensis var. formosana type. The second vegetation type was Machilus japonica-Litsea acuminata type which could be further subdivided into Osmanthus enervis-Machilus japonica subtype, Rhododendron formosanum subtype, Beilschmiedia erythrophloia- Machilus thunbergii subtype, and Pachycentria formosana-Carpinus kawakamii subtype. The third vegetation type was Litsea hypophaea-Ilex asprella type. Canonical correspondence analysis (CCA) indicated that altitude, topographic position, slope, stone and coverage of canopy made significant contribution to the variation of vegetation composition. The species response curves showed that the dominant species had a wider range of tolerance along the environmental gradients than did characteristic species. For woody species, the Beilschmiedia erythrophloia-Machilus thunbergii subtype had the highest alpha diversity values as measured by evenness, Shannon and Simpson indices. Pachycentria formosana-Carpinus kawakamii subtype on the other hand had the highest values on the species richness and Avalanche index. For herbaceous plants, the Beilschmiedia erythrophloia-Machilus thunbergii subtype had the highest value on species richness, while the Osmanthus enervis-Machilus japonica subtype had the highest values on evenness index, Shannon index, and Simpson index, and the Pachycentria formosana-Carpinus kawakamii subtype had the highest values on Avalanche index. In terms of habit, the proportion of herbaceous plants in the southern transect was generally higher than that of the northern transect at the corresponding altitude. Concerning the beta diversity, the 95% turnover range for the woody species in the southern transect was calculated as 967 m. Both woody and herbaceous species showed the highest turnover ratios at elevation 1,359-1,457 m. For the northern transect, the change in species composition with altitude was less obvious. The highest turnover ratios of woody species and herbaceous species were observed at elevations 1,560-1,650 m and 1,650-1,740 m respectively.