八通關地區草生地之植群變動與火災適存植群之研究

Abstract

八通關位於玉山國家公園境內，因其地處交通要衛而得名。該地區海拔2900公尺左右，屬一啞口地形。其氣候呈夏雨冬乾，乾濕季分明。植被景觀為由火災幹擾形成之玉山箭竹草原。 本區之植群處於演替序到之早期階段，其內核群〝變動（fluctuation）〞明顯。為瞭解其因應火災及微環境而變動之現狀，調查區內86個樣區及相關環境因數12種。經群團分析後得出四種變動型，代表植物（玉山箭竹、高山芒、紅毛杜鵑及馬醉木）在各型的相對優勢度與環境之幹濕有明頭閱係。玉山箭竹、高山名、紅毛杜鵑、馬醉木與二葉松分別具有適應火災的特殊生活型，可稱為火災適應植物（fire-adapted Plants)。 區內火災痕跡明顯，判斷其遷去發生不止一次火災，包括山屋附近的地表火及八通關西峰之樹冠火。另植被的演進及燃料循環皆影響火災類型。並推測火災發生的季節應為冬季，且由於受到風向及地形的限制，使火災跡地呈東西向。 木來本區若不再受到火災幹式採油樹擾，其植被應朝鐵杉森林或二葉松過渡森林演替。若無法排除大災之發生，則演替仍會停滯於草原之亞極盛相。

Pa—Tun—Kuan, located in Yu—Shan National Park, is famous for its main traffic passage. The altit?de of this area is about 2800 meters, and the topography is a saddle. Rainfall of the area is concentrated in summer, and there is a dry winter. The vegetion and landscape is Yushania grassland which was maintained by frequent fire disturbance. The plant communities of this area were in early successional stage , and there was anobvious fluctuation within the grassland vegetation. In order to realize its present situation of fluctuation caused by fire and microclimate, 86 sample stands were se— lectet and 12 environmemtal factors were observed. Four fluctuation types were revealed by cluster analysis. There was an obvious relationship between the relative dominance of the represented species in each types and the moisture condition in each types. Five species were observed to have special mophologically modifications and lifeforms to survived the frequent fires. Such plants were so called ‘fire—adaped plants’. The landscape of this area was obviously caused by fire, and more than once. The types of fire include ground fire and crown fire. The types of fire were also affected by the vegetation types and litter circulation. ccording to analysis of climatic and geographical factors, the fires happened in winter in most cases. Because of the wind blow and geographical limitation, the fire area shaped in east—west direction. The succession of vegetation will be Pinus forest then Tsuga forest when the affect of fire is excluded, otherwise the subclimax vegetation of the Yushania grassland will be maintained.