2005-2008年七家灣溪濱岸植群之生物多樣性研究

Biodiversity Investigation on Riparian Vegetations of Cijiawan Creek for the Years 2005-2008

七家灣溪是臺灣櫻花鈎吻鮭的重要棲地，為使其族群得以延續，保護森林溪流生態系乃是當務之急。而本研究為暸解其濱岸植群之組成與結構變化，於2005、2007-2008年進行喬木、地被層植物之監測調查。研究結果得知2005、2007-2008年之物種組成並無太大變化，其群團分析的結果相似；皆可分為蓪草─臺灣紫珠型，栓皮櫟－－化香樹型，臺灣二葉松－－臺灣赤楊亞型，臺灣二葉松－－栓皮櫟亞型，以及臺灣二葉松－－臺灣赤楊－－臺灣紫珠亞型等。此外，本研究以2005、2007-2008年之七家灣溪濱岸植群的植群調查資料，進行種豐富度指數分析比較，結果得知2005與2007-2008年間喬木層植物之多樣性無明顯變化；而以有勝溪測站之多樣性及均勻度最高，又觀魚台測站的多樣性較低，另高山溪測站較不均勻。另僅2005年乾季、2007年濕季之地被層的Shannon均勻度指數具顯著差異，即濕季的物種組成較為均勻；而相同季節於不同年度間，其植群的種豐富度指數則無顯著差異，此等顯示二年度間之地被層植物的多樣性變動不大。是故在現今武陵地區相關經營單位管理之下，2005-2008年七家灣溪濱岸植群多樣性維持穩定。

Cijiawan Creek is the only stream of Taiwan where the Formosan landlocked salmon Oncorhynchus masou formosanus inhabits. To preserve this precious but endangered species, it is urgent to protect its stream habitat and riparian forest ecosystem. We investigated the overstory and understory vegetations of the riparian zone in 2005 and 2007-2008. The results showed that the species compositions resulted from the matrix cluster analysis were similar between 2005 and 2007-2008. They were dividable into two types and three subtypes: the Tetrapanax papyriferus-Callicarpa formosana type, the Quercus variabilis-Platycarya strobilacea type, the Pinus taiwanensis-Alnus japonica subtype, the Pinus taiwanensis-Quercus variabilis subtype, and the Pinus taiwanensis-Alnus japonica-Callicarpa formosana subtype. The results of the species abundance index analysis also showed that there was no significant difference in the species diversity of the overstory between 2005 and 2007. The diversity and evenness indices were the highest at Yousheng Creek Station, while the lowest diversity at the Fish-watching Platform Station and the lowest evenness at the Gaoshan Creek Station. There was significant difference in the evenness indices of the understory between the dry season in 2005 and the wet season in 2007, indicating the species composition was evener in the wet season. The species abundance indices of the understoy were not significantly different in the same season among the different years. This meant that the diversities of the understories were fairly stable between the two years. Apparently, under the present management of the Wuling area authorities, the riparian vegetation diversity of Cijiawan Creek was fairy stable for the years 2005 to 2008.