| Summary: | 碩士 === 中興大學 === 土壤環境科學系所 === 98 === To construct the food webs in the the Chijiwan Stream, C and N stable isotope of the dominant aquatic insects, periphytons, riparian vegetations, fine particular organic matter, and the Oncorhynchus masou formosanus were analyzed during two wet seasons ( Jul 2007 ~ Aug 2007 and 2008 ) and one dry one ( Dec 2006 ~ Feb 2007 ).
The C stable isotope analyses indicated C3 riparian vegetation had the lightest ratio ( -34.4 ~ -26.2 ‰ ), and C4 riparian vegetation was the heaviest one ( -14.8 ~ -12.5 ‰ ) in all our samples. The N stable isotope analyses indicated C3 riparian vegetation had the lightest ratio ( -5.6 ~ 5.7‰ ), and Oncorhynchus masou formosanus was the heaviest one ( 4.4 ~ 7.5‰ ) in all our samples. An “Isosource” packaged program was applied to predict the dominant function groups’s diet compositions of the food webs. Here, we predicted the results of this: First, the aquatic insects of the predator seem to be the dominant food ( 70 % ) of Oncorhynchus masou formosanus during the wet season and the aquatic insects of the collector seem to be the dominant food ( 40% ) of Oncorhynchus masou formosanus during the dry season. Second, C3 riparian vegetation seem to be the dominant food ( 50% ~ 95% ) of the aquatic insects.
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