| Summary: | 碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 94 === Coast forest is an important natural environmental area. However, in the recent years, the needs of the public to develop the recreational area in the coast are increasing. Additionally, natural disturbance such as long-term Northeastern monsoon and typhoon cause the stand aging problems in partial area have caused unprecedented pressure to the coast forest in some areas. The previous studies only focused on the tree physiology and lacked doing research on the spatial and time change. Therefore, this research investigated the land use change in three different periods of the area from Sanjhan River to Chi-Shin Lake in Hualien , about 2,500 ha coastal area to probe into the role that the coast forest acting in the land use changing process. First of all, the aerial photographs of 1978, 1992 and 2002 were digitized and classified into 16 land use types. The layers were overlaid and the landscape index was applied to detect the changes. According to the result, from 1978 to 1992, the gaps of the pure Casuarina spp which were 4.4 ha, grew into 38.9 ha from 1992 to 2002 because of . The research is to comprehend the reason why the type of mixed Broad-Leaved Trees expanded. Consequently, I selected the coast forest in Deyan, which is approximately 20 ha as my study area and digitize the distribution of forest gap’s formation using the Remote Sensing measurement technology.Utilizing the different periods gap’s distribution map, I conducted vegetation investigation and analyzing to comprehended difference between gap distribution maps of different periods; on the other hands, vegetation spectral analysis was used to underatand the spectrum difference between all plots. The result shows that gap formed in three years was classified to be Murraya paniculata-Casuarina equisetifolia type, gap formed in five to seven years was Murraya paniculata- Macaranga tanarius-Casuarina equisetifolia type, when gap formed reach above seven years, vegetation type was Miscanthus floridulus-Macaranga tanarius-Broussonetia papyrifera. Accordingly, it can serve as an indicator species to estimate the gap formation in different periods. Additionally, in vegetation spectral analysis, NIR and NDVI showed a significant difference between different vegetation types. In this study area, the formation of gaps were found and the impact of frequency typhoons were higher than the recovery ability of Casuarina spp. stand. With this two reasons, the gap of coast forest expended and finally Casuarina spp.stand became to the Miscanthus floridulus-Macaranga tanarius-Broussonetia papyrifera type. If we use the Remote Sensing measurement technology to monitor the coast forest in other areas, the distribution and structures of the coast forests will be useful in decision of managing forests and replying conservation in the future.
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