| Summary: | 碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 94 === To realize the relationship between physical environmental factors and the potential habitats of the Formosan landlocked salmon, a widespread field survey needs to be conducted. Through an extensive field investigation, fine quality environmental data can be obtained. However, the broader a research area is, the higher the costs involved would be. Therefore, it would be more effective in utilizing resources if we could assess the basic environmental conditions before conducting a field survey.
The main goal of this study is to formulate a framework for integrating topographic and precipitation information and then to build a model on how potential habitats of the Formosan landlocked salmon would change under different physical criteria. The study proceeds from estimating the precipitation models and then delineates and characterizes the stream system within the study area. Based on potential habitat limiting criteria extracted from literature and the stream characteristics generated by a digital elevation model (DEM) analysis program, the intrinsic potential habitats of the Formosan landlocked salmon are then determined.
The result indicated that the modeled stream characteristics coincided with the filed surveyed ones. The results also suggested that in order to obtain a distributional range resembling the historical one, the potential habitats for the species should be within 1,390 ~ 2,000 m in elevation, with a mean gradient less than 0.06 m m-1, and an annual discharge rate between 0.06 and 21 cms. These ranges are broader than the ones given in the current literature. In addition, the degrees of valley constraint (VWI) for the potential habitats should be between medium and high. This study suggested that the mean gradient is the main habitat-limiting factor for the Formosan landlocked salmon within the study area.
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