| Summary: | 碩士 === 國立臺灣大學 === 森林學研究所 === 90 === Water-conservation protection forest, designated for conserving water and protecting watershed, is one of the most important parts of protection forests management. The objective of this study is to investigate the current status of a water-conservation protection forest, the Four-Animal-Mountain area, and to evaluate if the original objective of water conservation can be achieved. Photo base maps obtained in 1974, 1984 and 1994 were used to establish a geographic database of the protection forest. According with the protection forest, watersheds of different stream orders were extracted by using digital terrain model (DTM). These watersheds were used as the study sites, and the landscape changes and landscape structure within these sites was analyzed based on landscape ecology. The condition of the protection forest was analyzed using spatial analysis techniques, and the issues of expanding or reducing the protected area were considered based on relevant laws of protection forests.
The results of landscape structure analysis indicate that the study sites have higher diversity and evenness index as compared to the original area of protection forest. The overall landscape changes show that the stream networks tend to reduce and the function of water conservation diminish as well. In addition, the forest lands were gradually replaced by man-made landscape types such as building structures and graveyards. This study divided the study site into two regions based on 55% slope. The results show that the landscape changes, landscape structure and diversity in the regions with slope above 55% are more simple, and the forest lands will dominate these regions in the future. For the regions with slope under 55%, the diversity is higher and the evenness index is increasing, representing more complicated land uses in these regions. The riparian area, defined as the 50m buffer zone along the streams, has increasing diversity and evenness index. Which indicates that the water body will be replaced by the other landscape types, and the function of the protection forest is decreasing. To achieve the water resource conservation objective, the riparian zones need to be included into the protection forest.
In summary, it is suggested that the regions with slope above 55% and the riparian zones should be designated as protection forest. For the regions within the protection forest with slope under 55%, man-made landscape types such as building structures, graveyards, and roads, which have existed prior to 1984 can be lifted according to the regulations of protection forest. For the other regions with slope under 55%, either within the protection forest or not, their current status need not be changed.
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