| Summary: | 碩士 === 環球科技大學 === 環境資源管理所 === 101 === Oncorhynchus formosanus is an endemic freshwater salmon fish to Taiwan. It was used to be widespread in the upper branches of Da-Chia Stream. But the habitats and population decreased day after the day owing to human, climatic, and environmental changes. It only exists in the Cijiawan Stream basin at present and faces the risk for extinction. To make a standard on releasing the salmons, the species and composition of the riparian vegetation in the upper Da-Chia Stream were monitored in this study to discuss the diversity changes.
There were 8 fixed stations, Luoyewei River Releasing Location (#201), Mt. Nanhu Entrance (#202), Shengguang (#203), Downriver Yusheng River (#204), Tollbooth by Yusheng River (#9), No. 2 River of Shijiawan River (#205), Upriver Shijiawan River (#10), and Downriver Shijiawan River (#11), and 2 potential releasing stations, Yicawan River (#301) and Leshan River (#302). 2 transect plots were set in every station.
There were 115 species, 91 genera, and 52 families of vascular plants recorded in October, 2012. There were 172 species, 127 genera, and 61 families in 2011. It exposed the huge disturbance from the flood in 2012. Besides, the species amount of Compositae was always the most in the 4 investigating seasons.
According to 65% of threshold limit value of similarity index on the understory, Diplazium dilatatum type, Eupatorium formosanum type, Artemisia indica type, Arundo formosana type, Miscanthus floridulus type, and Alnus formosana type, Acer serrulatum type, Nasturtium officinale type, Pilea rotundinucula type, and Sambucus chinensis type presented in both February and October in 2011-2012. The major component plants were C3 plants served as filtering aquatic insects’ food.
The overstory diversities of 2011 to February in 2012 were higher at the Station Tollbooth by Yusheng River (#9) and Station Luoyewei River Releasing Location (#201). However, the overstory diversity of October in 2012 was higher at the Station No. 2 River of Cijiawan River (#205).
As to the total species amount and species abundance indices of the understory, there were significant differences in stations (P<0.001), periods (P<0.001), and periods and stations (P<0.001). The diversities at the Station Luoyewei River Releasing Location (#201), the Station No. 2 River of Shijiawan River (#205), and the potential releasing location, Station Leshan River (#302) were higher from 2011 to February in 2012. While in October of 2012, the diversities at the Station Mt. Nanhu Entrance (#202), the Station No. 2 River of Shijiawan River (#205), and the Station Upriver Shijiawan River (#10) were higher. It was supposed that these stations maintained the species amounts better than others because less effects by flood.
This research comes to some immediate strategies:
1. Monitor the invasion potential of alien naturalized species.
2. Restore the Formosan landlocked salmon and their habitat in the whole section of Yusheng River.
3. Estimate the releasing location out of the area under Shei-Pa National Park Headquarters’control.
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